Abstracts
SERIES Concluding Workshop -
Joint with US-NEES
“Earthquake Engineering Research
Infrastructures”
JRC-Ispra, May 28-30, 2013
In memory of Prof. Roy Severn
SERIES Concluding WS – Joint with US-NEES: Abstracts
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Contents
Session 1: Hybrid Testing
Towards faster computations and accurate execution of real-time hybrid simulation
Mosalam KM, Günay S 2
Robust integrated actuator control strategy for real time hybrid simulation
Ou G, Dyke SJ, Wu B 3
Real-time earthquake simulationusing force controlled actuators
Nakata N, Krug E 4
Numerical tools for the reduction of complex dynamic models
Abbiati G, Bursi OS, Cazzador E, Mei Z 5
A support platform for distributed hybrid testing
Lamata Martinez I, Obón Santacana F, Williams MS, Blakeborough A, Dorka UE 6
Monolithic time-integration algorithms for Hamiltonian systems suitable for real-time hybrid simulations
Abbiati G, Bonelli A, Bursi OS, Reza MS 7
Pseudo-dynamic testing with non-linear substructuring of a reinforced concrete bridge based on system
identification and model updating techniques
Abbiati G, Bursi OS, Cazzador E, Mei Z, Paolacci F, Pegon P 8
Assessment of the seismic behaviour of a retrofitted old RC highway bridge through PsD testing
Bursi OS, Ceravolo R, Di Sarno L, Erdik M, Paolacci F, Sartori M, Pegon P 9
Pseudo-dynamic testing of a piping system based on model reduction techniques
Reza MS, Abbiati G, Bonelli A, Bursi OS 10
Advanced Hybrid Simulation Frameworks for Civil Structures
Phillips BM, Spencer BF Jr. 11
Geographically distributed continuous hybrid simulation tests using shaking tables
Obón Santacana F, Dorka UE 12
Dynamic substructuring for soil structure interaction using a shaking table
Tang Z, Dietz M, Li Z, Taylor C 13
Real-time hybrid testing for soil-structure interaction: An adaptive signal processing framework
Dertimanis VK, Mouzakis HP, Psycharis IN 14
Towards an implementation of the FHT technique for SSI systems using nonlinear macroelements
Chatzigogos CT, Dietz M, Pecker A, Tang Z 15
Session 2: SERIES Transnational Access to Centrifuge Facilities
Centrifuge modeling of dynamic behavior of box-shaped underground structures in sand
Ülgen D, Sağlam S, Özkan MY, Chazelas J-L 17
Investigation of the seismic behaviour of shallow rectangular underground structures in soft soils using
centrifuge experiments
Tsinidis G, Rovithis E, Pitilakis K, Chazelas J-L 18
Investigation of several aspects affecting the seismic behaviour of shallow rectangular underground structures
in soft soils
Tsinidis G, Heron C, Madabhushi SPG, Pitilakis K, Stringer M 19
Experimental verification of shallow foundation performance under earthquake-induced liquefaction
Karamitros DK, Cilingir U, Bouckovalas GD, Madabhushi SPG, Papadimitriou AG, Haigh SK 20
Centrifuge modelling of the performance of liquefaction mitigation measures for shallow foundations
Marques A, Coelho P, Haigh SK, Madabhushi SPG 21
Centrifuge modeling of pairs of flexible retaining walls in saturated sand under seismic actions
Aversa S, De Sanctis L, Maiorano RMS, Tricarico M, Viggiani G, Conti R, Madabhushi SPG, Stringer M, Heron C
22
Experimental and numerical investigations of nonlinearity in soils using advanced laboratory-scaled models: An
application to the Rome historical centre
Bozzano F, Bretschneider A, Giacomi AC, Martino S, Scarascia Mugnozza G, Escoffier S, Lenti L, Chazelas J-L, Favraud C, Macé D 23
SERIES Concluding WS – Joint with US-NEES: Abstracts
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Session 3: US-NEES developments
The George E. Brown, Jr., Network for Earthquake Engineering Simulation (NEES): Accelerating improvements
in seismic design and performance by serving as a global collaboratory for discovery and innovation
Ramirez J 25
Promoting re-use of Earthquake Engineering data through the NEEShub
Browning J 26
Re-use of experimental earthquake data for research: Three illustrative examples
Van de Lindt JW 27
Communicating earthquake engineering:The education, outreach, and training activities of the George E.
Brown, Jr. Network for Earthquake Engineering Simulations
Fossum B 28
Damping estimation from seismic records
Bernal D 29
Session 4: SERIES Networking Activities: Distributed Database and Qualification of Research
Infrastructures
A faceted lightweight ontology for earthquake engineering research projects and experiments
Hasan MR, Farazi F, Bursi OS, Reza MS 31
The SERIES Distributed Database: Architecture and implementation
Lamata Martinez I, Ioannidis I, Fidas C, Williams M, Pegon P 32
The SERIES Distributed Database: Exchange format, local DBs and central portal interface
Bosi A, Bousias S, Chazelas J-L, Dietz M, Hasan MR, Madabhusi SPG, Prota A, Blakeborough T, Pegon P
33
Qualification of seismic research testing facilities in Europe
Zola M, Taucer F 34
Session 5: SERIES Transnational Access to Shaking Table Facilities on masonry, RC and steel
structures
Full scale testing of modern unreinforced thermal insulation clay block masonry houses
Lu S, Jäger A, Mendes L, Candeias P, Campos Costa A, Coelho E, Degée H, Mordant C, Sendova V,
Rakicevic ZT, Tomazevic M 36
Assessment of innovative solutions for non-load bearing masonry enclosures
Leite J, Lourenço PB, Vintzileou E, Palieraki V, Correia AA, Candeias P, Campos Costa A, Coelho E 37
Seismic behaviour of L- and T-shaped unreinforced masonry shear walls
Mordant C, Dietz M, Vasseur L, Degée H 38
Shake table testing of a half scaled RC-URM walls structure
Tondelli M, Petry S, Lanese I, Beyer K, Peloso S 39
Experimental and numerical investigation of torsionally irregular RC shear wall buildings with Rutherma
breakers
Yakut A, Le Maoult A, Richard B, Ragueneau F, Atanasiu GM, Scheer S, Diler S 40
Assessment of the seismic response of concentrically-braced steel frames
Broderick BM, Hunt A, Mongabure P, LeMaoult A, Goggins JM, Salawdeh S, O’Reilly G, Beg D, Moze P, Sinur F,
Elghazouli AY, Plumier A 41
Session 6: SERIES Transnational Access to Shaking Table Facilities on wood structures / General on
Experimental facilities
Seismic performance of laminated wood frames with moment connections under seismic loads:Experimental
investigation
Kasal B, Heiduschke A, Pospisil S, Urushadze S, Zembaty Z 43
Investigation of seismic performance of multi-storey timber buildings
Piazza M, Tomasi R, Campos Costa A, Candeias P 44
SERIES Concluding WS – Joint with US-NEES: Abstracts
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Experimental study on seismic performances of precast concrete shear wall with joint connecting beam
Lu X, Wang D, Zhao B 45
Full-scale pseudodynamic testing of the SAFECAST three-storey precast concrete building
Bournas D, Negro P, Molina F-J 46
Experimental earthquake engineering research in LNEC: Contribution to global seismic performance assessment of structures
Coelho E, Campos Costa A, Candeias P, Mendes L, Correia A 47
Session 7: Analytical and Experimental work on soil structure interaction, wave propagation and
field testing, including SERIES Transnational Access to Shaking Table Facilities
Large-scale Laboratory Experiments of landslide generated Tsunamis in the NEES Tsunami wave basin half a
century after the Vajont Dam disaster
Fritz H, McFall BC, Mohammed F 49
Caisson foundations subjected to seismic faulting: Reduced-scale physical modelling
Anastasopoulos I, Zarzouras O, Georgarakos T, Drossos V, Gazetas G 50
Effect of soil structure interaction on higher modes participation
Mirfattah SA, Mirfattah SK 51
Estimation of soil structure interaction effects, considering the frequency content of the motion
Mirfattah SH, Mirfattah SA 52
Development of new infinite element for numerical simulation of wave propagation in soil media
Sesov V, Edip K, Cvetanovska J 53
Design and construction of laminar container for 1-g shaking table tests
Sesov V, Cvetanovska J, Edip K, Rakicevic ZT 54
Analysis of the dynamic behavior of squat silos containing grain-like material subjected to shaking table tests
Foti D, Ivorra S, Trombetti T, Silvestri S, Gasparini G 55
Study of multi-building interactions and site-city effect through an idealized experimental model
Schwan L, Boutin C, Dietz M, Padron LA, Bard PY, Castellaro S, Ibraim E, Maeso O, Aznárez JJ, Taylor C
56
EuroProteas: A full-scale experimental facility for soil-foundation-structure interaction studies
Pitilakis D, Rovithis E, Anastasiadis A, Pitilakis K 57
Session 8: Analytical and Experimental Techniques / SERIES Transnational Access to Reaction Wall
Facility
In-situ seismic performance tests of a scoured bridge
Chang K-C 59
Validation of a visual deformation measurement system
Binbir E, Demir C, Ispir M, Ilki A 60
Development of wireless sensors for shake table and full scale testing and health monitoring of structures
Rakicevic ZT, Markovski I, Filipovski D, Micajkov S, Garevski M 61
Recent advances in seismic design of RC tall buildings using ultra-high-strength materials in Taiwan
Hwang S-J 62
Refined and simplified numerical models of an isolated old highway bridge for PsD tests
Paolacci F, Alessandri S, Mohamad A, Corritore D, Derisi R 63
Full-scale experimental validation of dual eccentrically braced frame with removable links
Stratan A, Dubina D, Ioan A, Taucer F, Poljansek M 64
Session 1 – Hybrid Testing
1
Hybrid Testing
Session 1
Tuesday, 28 May 2013
Session 1 – Hybrid Testing
2
TOWARDS FASTER COMPUTATIONS AND ACCURATE EXECUTION OF
REAL-TIME HYBRID SIMULATION
Khalid M. Mosalam and Selim Günay
University of California, Berkeley, USA
This paper reports three recent developments aimed towards faster computations and more
accurate execution of real-time hybrid simulations (RTHS). These developments were
conducted at the University of California, Berkeley as part of nees@berkeley site
development for an NSF-funded early–concept grant for exploratory research (EAGER)
project, namely “Next Generation Hybrid Simulation – Evaluation and Theory”.
The first of these developments is a standalone RTHS system which can accommodate
integration time steps as small as 1 milisecond. This fast execution time of an integration time
step is realized by a combination of the computation power introduced by a digital signal
processor (DSP) card, the physical data transfer between the computational platform and the
controller and the real-time compatible PID control technology of the controller and the
servo-hydraulic system. The fast execution feature eliminates errors that would be introduced
by the application of a predictor-corrector smoothing technique. Applications of the
developed RTHS system in testing porcelain and polymer composite insulator posts for high
voltage electrical switches are presented and discussed.
The second development is the use of an efficient equation solver in RTHS which decreases
computation time. This efficient solver, which decreases the computation time by factorizing
the Jacobian of the system of linear algebraic equations only once in the beginning of the
simulation, is especially beneficial in RTHS which involves analytical substructures with
large number of degrees of freedom. Applications of this development for multi-story multi-
bay framed structures with both linear and nonlinear constitutive relationships are presented.
The third development is a novel use of a three-variable control (TVC) for RTHS on a
shaking table configuration. Although the TVC, which employs velocity and acceleration
control in addition to the usual displacement control, is nowadays used in conventional
shaking table tests, this development is one of the very first applications of TVC in RTHS. It
is demonstrated that the TVC enhances the acceleration tracking in high frequencies, while
still eliminating the time delay between the command and feedback displacement signals.
Accordingly, adopting the TVC enhances the performance and reduces the errors in RTHS.
Session 1 – Hybrid Testing
3
ROBUST INTEGRATED ACTUATOR CONTROL STRATEGY
FOR REAL TIME HYBRID SIMULATION
G. Ou1, S. J. Dyke
1, B. Wu
2
1 Purdue University, USA
2 Harbin Institute of Technology, P.R. China
Real time hybrid simulation (RTHS) is able to perform substructure test in real time scale and
includes rate dependent feature in consideration. One major challenge for RTHS is that it
requires accurate and prompt execution of boundary condition that is calculated from
numerical substructure. In most cases, traditional PID control induces large time lag between
desired command and response which may cause system instability and further the failure of
the test. Many control strategies for servo hydraulic actuator-structure system have been
proposed recently to compensate such time lag and other system dynamics. This paper
introduces a new integrated control strategy into RTHS.
The new proposed Robust Integrated Actuator Control (RIAC) algorithm integrates three key
control components; first is the loop shaping feedback control based on H-∞ optimization,
second one is a pure delay feed-forward block for control performance enhancement and an
additional Kalman filter for feedback estimation and noise reduction. The combination of the
aforementioned blocks provides flexible performance based controller design according to
different evaluation criterion.
RIAC has been tested for displacement tracking on different actuator setups and proved to
work effectively. The efficacy of the proposed strategy is demonstrated through RTHS of a
3DOF steel structure with equipped magnetorheological (MR) damper. The experimental
components herein is the MR damper attached to a large scale actuator has maximum force
capacity of 2500KN, the numerical substructure is the rest of the steel structure.
Session 1 – Hybrid Testing
4
REAL-TIME EARTHQUAKE SIMULATION
USING FORCE CONTROLLED ACTUATORS
Narutoshi Nakata, Erin Krug
Johns Hopkins University, USA
This paper reports experimental real-time earthquake simulations using force controlled
hydraulic actuators. The method presented here is often referred to as effective force test
(EFT) method. An experimental setup consisting of a two-degrees-of freedom structure and
two hydraulic actuators at the Johns Hopkins University is utilized for implementation,
verification and validation of multidegrees-of-freedom EFT. Force feedback controller design
and experimental results are presented and performance and limitations of EFT are discussed.
The idea of the EFT method is to impose a loading to structures that is equivalent to a
reference ground motion using force-controlled hydraulic actuators.
Experimental results in harmonic simulation tests proved that the centralized decoupling loop
shaping force feedback controller was able to independently control forces in the two
actuators without interaction. Experimental results in earthquake simulation tests showed that
the dynamic forces were accurately controlled to provide tracking while maintaining
robustness. In summary, this paper experimentally proves that MDOF-EFT is feasible with a
centralized decoupling loop shaping force feedback controller.
Session 1 – Hybrid Testing
5
NUMERICAL TOOLS FOR THE REDUCTION OF
COMPLEX DYNAMIC MODELS
G. Abbiati1, O.S. Bursi
1, E. Cazzador
1, Z. Mei
1,2
1University of Trento, Italy
2Harbin Institute of Technology, China
Over the last decade, Real-Time (RT) and Pseudo-Dynamic (PsD) testing with Dynamic
Substructuring (DS) have gained significant popularity due to their versatility in testing
several types of linear and nonlinear structural systems. Nonetheless, despite the continuous
increase of computing power, implementation issues relevant to the typical solution time of
the Numerical Substructure (NS) make complex Finite Element (FE) models not suitable for
testing purposes. Moreover, time integration algorithms characterized by a deterministic
convergence time are crucial for real-time machines, whereby hybrid simulation code is
executed. As a consequence, optimal NSs capable of reproducing the behaviour of complex
dynamic linear/nonlinear systems must be tailored to ensure robustness to hybrid simulation.
In this perspective, a set of numerical tools devoted to the reduction of parts of NS models is
presented. With regard to the linear case, MatLAB implementations of well-known reduction
methods such as Guyan, System Equivalent Reduction-Expansion Process (SEREP), and
Craig-Bampton are provided. With respect to the nonlinear case, state space models can
finely synthetize complex systems. Nonetheless, the identification of the parameters of such
models is a quite non-trivial task. When the trial and error strategy fails, an optimization-
based approach must be adopted. The tool we are proposing herein sets the optimum problem
in the time-frequency domain. In particular, the minimization of a certain penalty function
forces the Short Time Fourier Transform (STFT) of the response of a simplified state space
model to match the STFT of the response of the reference model being reduced. The model
reduction of piers belonging to the fiber-based FE model of an old reinforce concrete viaduct
is presented as an application example. In particular, in order to simulate the typical
hysteretic behaviour of each single pier, the 3-DoFs linear model obtained from the dynamic
substructuring is combined with a Bouc-Wen spring in series with a slip-lock element. The
optimal tuning of the resulting state space model is done by means of the proposed tool and
comparisons are performed with the reference fiber-based FE model.
Session 1 – Hybrid Testing
6
A SUPPORT PLATFORM FOR DISTRIBUTED HYBRID TESTING
Ignacio Lamata Martinez1, Ferran Obon Santacana
2, Martin S. Williams
1,
Anthony Blakeborough1, Uwe E. Dorka
2
1 University of Oxford, Department of Engineering Science 2 University of Kassel, Institute of Structural Engineering
Large-scale testing continues to play an important role in earthquake engineering, generating
research results that lead to improved safety and security of European society. Distributed
hybrid testing offers a promising approach to use resources from geographically separate
laboratories in a highly efficient way, to perform more complex, larger-scale tests than are
possible in most individual laboratories. The method involves splitting a structure into a set
of substructures (some tested physically, some modelled numerically) located in different
laboratories. Simulation of the full structural response involves simultaneous testing of the
substructures with feedback of data between them, requiring fast communication through
computer networks. To handle systems involving rate dependence, there is a desire for test
speed to approach real time.
Organizing and planning distributed experiments entails much more complexity than is
involved in a single-laboratory hybrid test, besides the difficulty of tracing errors caused by
the distributed environment. This points to the importance of a platform to support the testing
activities.
This platform has been achieved by means of a specification called Celestina, created at the
University of Oxford. Celestina provides a framework for conducting the experiment
workflow. It provides a specification for the services to be implemented, under three main
headings of networking, test definition and experiment execution, and supports the actual
data exchange during a test. It does not force any particular implementation, which can be
independently developed and implemented under this framework, and nor does it restrict the
actual method of data exchange.
In this article we discuss the design and conception of the specification as well as one
implementation that has been validated through a series of substructured “numerical
experiments” in partnership with the University of Kassel. In a typical substructured test,
nodes at Oxford and Kassell were used to simulate the response of a 33-DOF steel frame
fitted with a TMD, with both nodes conducting testing (in simulation) according to
instructions from a Celestina-based program running in Oxford.
Session 1 – Hybrid Testing
7
MONOLITHIC TIME-INTEGRATION ALGORITHMS FOR HAMILTONIAN
SYSTEMS SUITABLE FOR REAL-TIME HYBRID SIMULATIONS
G. Abbiati, A. Bonelli, O.S. Bursi, Md S. Reza
University of Trento, Italy
In recent years, hybrid simulation techniques like Real-Time (RT) and Pseudo-Dynamic
(PsD) testing with Dynamic Substructuring (DS) became more and more popular to study in
depth the performance of structures subject to dynamic loads. With regard to relevant time-
stepping methods, they can be broadly classified into monolithic and partitioned. According
to the RTDS philosophy, in the monolithic approach, just the Numerical Substructure (NS) is
integrated whilst the remainder part, i.e. the Physical Substructure (PS), is considered as a
black box. Since common differential models aimed at simulate nonlinearities in the NS
make use of state space formulations based on extended state vectors, e.g. the Bouc-Wen
model, time integration algorithms conceived for Hamiltonian systems are preferable. In this
perspective, we provide the Simulink implementations of two time integration algorithms
belonging to the monolithic class and tailored to first order systems: i) the linearly implicit
Rosenbrock-based L-Stable Real-Time compatible (LSRT) algorithm with two stages; ii) the
Modified Generalized- (MG- ) method. For a proper selection of the parameters both the
algorithms are characterized by second order accuracy and linear stability. In particular, the
MG- allows for user controlled algorithmic damping. In order to validate the
implementations, RTDS experiments on a full-scale industrial piping system are presented.
Session 1 – Hybrid Testing
8
PSEUDO-DYNAMIC TESTING WITH NON-LINEAR SUBSTRUCTURING OF A
REINFORCED CONCRETE BRIDGE BASED ON SYSTEM IDENTIFICATION
AND MODEL UPDATING TECHNIQUES
G. Abbiati1, O.S. Bursi
1, E. Cazzador
1, Z. Mei
1,2, F. Paolacci
3 & P. Pegon
4
1University of Trento, Italy;
2Harbin Institute of Technology, China
3University of Roma Tre, Italy;
4Joint Research Centre, Italy
The seismic performance assessment and retrofit of a concrete bridge by means of a testing
program was conceived within the RETRO research activity funded by the SERIES project.
The old 400m span Rio Torto viaduct, under-designed with respect to the seismic load, is
considered as Case Study. The installation of a couple of isolation devices -one per column-
for each pier portal frame interposed between the cap beam and the deck was proposed to
achieve the Eurocode 8 seismic-performance requirements. A software framework devoted to
test the effectiveness of the seismic retrofit of the bridge through a set of hybrid simulations
is presented. In particular, two of the twelve piers - Physical Substructures (PSs) - will be
loaded through dynamic actuators, whilst the remaining ten piers and the deck as well -
Numerical Substructures (NSs) - are numerically modelled and solved. A refined Finite
Element (FE) fiber model of the bridge is implemented in the well-known OpenSEES
software to support the pseudo-dynamic test design. Time history analyses conducted on the
reference model highlighted appreciable nonlinearities of the pier dynamic responses already
under the Serviceability Limit State. As a consequence, a NS capable of reproducing this
nonlinear behaviour during hybrid simulations is deemed necessary. Nonetheless,
implementation issues relevant to the typical execution time of the NS - few milliseconds or
controller time steps - make complex FE fiber models unsuitable for testing purposes. A
rigorous nonlinear dynamic reduction of numerical piers was conceived as an extension of
the Craig-Bampton method; thus, the 3-DoFs model resulting from the linear dynamic
substructuring of each single pier is endowed with a simplified Bouc-Wen spring in series
with a slip spring. Since moment resisting reinforced concrete piers develop a ductile
response by activating different yielding mechanisms at different excitation levels, a test
procedure aimed at propagating damage from physical to numerical piers is devised: in order
to match the dynamic response of the reference OpenSEES model, at each run, a priori
unknown nonlinear parameters characterising the 3-DoFs reduced piers will be tuned by
means of a robust time-frequency approach. The constitutive laws of fiber-based beam
elements of the reference model will be updated from experimental measurements obtained
during the previous test. Lastly, the selected continuous time testing strategy together with a
complex NS forced the adoption of a time integrator which allows for subcycling; for this
purpose, the parallel partitioned PM algorithm is proposed and its experimental
implementation to the Rio Torto case study is presented.
Session 1 – Hybrid Testing
9
ASSESSMENT OF THE SEISMIC BEHAVIOUR OF A RETROFITTED OLD RC
HIGHWAY BRIDGE THROUGH PSD TESTING
O.S. Bursi1 , R. Ceravolo
2, L. Di Sarno
3, M. Erdik
4, F.Paolacci
5,
M. Sartori6, P. Pegon
7
1University of Trento, Italy;
2Politecnico di Torino, Italy
3University of Sannio, Italy;
4Koeri, Boğaziçi University, Turkey
5University Roma Tre, Italy;
6Alga Spa, Italy;
7Joint Research Center, Italy
The seismic vulnerability assessment of existing and new lifeline systems, especially
transportation systems, is becoming of paramount importance in resilient social communities.
Transportation systems were built worldwide mainly in the late 60s and early 70s; they were
designed for gravity loads and were often equipped with plain steel bars. As a consequence
most bridges are not detailed for seismic loads and hence their structural performance is
generally inadequate under earthquake ground motions. The existing state-of-art in the field
of seismic performance of existing bridges is scarce. It is therefore urgent to propose reliable
procedures for assessing the seismic vulnerability of existing bridge structures. The aim is to
provide comprehensive guidelines for the seismic assessment and retrofit of existing bridges.
The “Retro” Transnational Access project funded by the European Commission within the
Series-project aims at studying the seismic behaviour of existing reinforced concrete (RC)
bridges and the effectiveness of innovative retrofitting systems. The research activity focuses
on experimental and numerical investigations of old bridges, designed mainly for gravity
loads. To this aim, the seismic vulnerability of an existing Italian viaduct with portal frame
piers (Rio Torto Viaduct) is evaluated and an isolation system is designed using both
yielding-based and friction-based bearings. An experimental test campaign is being
performed at ELSA Laboratory of JRC (Ispra, Italy). Two specimens (scale 1:2.5), with two
(total height is 6.8 m) and three (total height is 11.2 m) transverse girders, one-bay reinforced
concrete frame are being built and tested using the pseudo-dynamic test technique with sub-
structuring. The modelling of the entire viaduct is considered along with the non-linear
behaviour of each pier, due to bending, shear on the transverse beams and strain penetration
effect at the column bases. During the test the following configurations are considered: 1)
retrofitted viaduct using Friction Bearings, and 2) the “as-built” viaduct imposing a medium
damage level. For each phase of the experimental campaign a proper dynamic identification
is performed. Natural records selected on the basis of a specific hazard analysis are used
during the tests. The comprehensive numerical investigations and the first results of the PsD
campaign have shown the high vulnerability of the sample bridge; a passive protection
system is thus deemed necessary. The isolation systems have been designed and
characterized, whereas the isolated configuration of bridge will be tested soon.
Session 1 – Hybrid Testing
10
PSEUDO-DYNAMIC TESTING OF A PIPING SYSTEM
BASED ON MODEL REDUCTION TECHNIQUES
Md. S. Reza, Giuseppe Abbiati, Alessio Bonelli, Oreste S. Bursi
University of Trento, Italy
Over the last three decades, Pseudo-Dynamic Testing (PDT) with Dynamic Substructuring
(DS) has gained significant popularity due to its applicability in testing several types of
nonlinear structures/systems. In a PDT with DS, a heterogeneous model of the emulated
system is created by combining a Physical Substructure (PS) with a Numerical Substructure
(NS) that describes the remainder of the system. However, until today, a major drawback of
this method has been considered its inadequacy to test a system containing distributed
masses. With an intention to overcome this limitation, this paper presents an extension of the
PDT with DS technique by enabling its application to structures having distributed masses. In
this respect, we describe the implementation of the PDT with DS on a typical petrochemical
piping system. Some challenges faced during the implementation are shown and strategies
adopted to overcome these problems are described. In greater detail, we show the
substructuring technique used and how we minimized relevant errors generated owing to this
substructuring. We discuss a number of model reduction techniques adopted for the reduction
of the PS and the earthquake forces to the coupling nodes. Moreover, a stability analysis of
the coupled system is proposed. Finally, experimental results are presented and the reliability
of the pseudo-dynamic testing technique is discussed for this application.
Session 1 – Hybrid Testing
11
ADVANCED HYBRID SIMULATION FRAMEWORKS
FOR CIVIL STRUCTURES
Brian M. Phillips1 and B.F. Spencer, Jr.
2
1University of Maryland;
2University of Illinois
Hybrid simulation is a cost effective alternative for the experimental evaluation of civil
structures. It combines experimental testing and numerical simulation with the dynamic
behavior of the structure represented numerically. Through substructuring, the total structure
can be partitioned into experimental and numerical substructures to represent the complete
dynamic behavior of the system. The component of interest, experiencing damage or other
complex nonlinear behavior, can be experimentally represented while the more easily
modeled components represented numerically. Substructuring also allows for multiple
platforms to independently represent each component. With multiple independent platforms,
a framework is required to coordinate the reliable exchange of information during the hybrid
simulation. This paper will review both traditional hybrid simulation and recent advanced in
real-time hybrid simulation (RTHS). UI-SimCor is software developed at the Univ. of Illinois
NEES facility to coordinate multiple platforms during traditional hybrid simulation. The
hybrid simulation framework incorporating UI-SimCor software as the coordinator is split
into three categories: (1) experimental modules consisting of servo-hydraulic systems,
specimens, sensors, and data acquisition systems; (2) computational modules consisting of
numerical simulation software, and (3) observer modules to coordinate with outside networks
and allow for geographically distributed hybrid simulation. The UI-SimCor software and
framework has proven successful for the hybrid simulation of curved bridges under complex
seismic loading, semi-rigid steel frames, and multiple education and outreach programs as
well as the geographically distributed hybrid simulation of a bridge focused on soil-structure-
foundation interaction. When the dynamic response of the experimental component is
deemed significant and difficult to represent numerically, the experimental component must
be tested in real-time. This necessitates the entire hybrid simulation to be run in real-time
(i.e., RTHS). The coordination of hybrid simulation components becomes time sensitive and
the computational side of the RTHS must be designed for real-time performance. In lieu of a
flexible framework such as provided by UI-SimCor, application specific coordination is
typically developed with only the necessary components included. Dedicated real-time digital
signal processors are used for numerical integration and actuator control. The interface
between experimental and numerical components, namely servo-hydraulic system, is also
designed for speed. However, these actuators contribute most significantly to the time lag in
the RTHS loop of action and reaction. Actuator control techniques must be developed to
compensate for these actuator dynamics such that they do not influence the results of the
RTHS. A framework for RTHS has been developed at the University of Illinois incorporating
high-performance hardware and software. To provide accurate tracking of the desired
trajectories, a model-based actuator control technique is incorporated in the framework. The
framework has proven successful at testing multi-degree-of-freedom systems with an MR
damper as the experimental component. Furthermore, the technique has been extended to
include multi-actuator systems for the testing of complex experimental components.
Session 1 – Hybrid Testing
12
GEOGRAPHICALLY DISTRIBUTED CONTINUOUS HYBRID SIMULATION
Ferran Obón Santacana and Uwe E. Dorka
University of Kassel, Germany
One of the tasks within the FP7 SERIES Project was the creation of a European Platform for
Geographically Distributed Tests. This platform was envisioned to be able to deal with
different protocols and algorithms so that its users and facilities were not restricted to one
specific protocol. The platform should also prove the possibility of performing
geographically continuous distributed tests since up to now the distributed tests between two
different countries that have been performed were stop and go. However, though the use of
an efficient sub-structure algorithm, continuous tests can be performed using standard
network connections.
With that in mind several activities were performed at the University of Kassel that involved
not only European partners, like the University of Oxford, but also other facilities and
networks around the world, namely: the University of California at Berkeley, the Hybrid
Simulation Testing Center (HYSTEC) in South Korea and the National Center for Research
on Earthquake Engineering (NCREE) in Taiwan. With each partner continuous time-scaled
hybrid simulation tests with a non-linear sub-structure were performed exploring the different
available protocols. In addition to such experiments, the possibility to carry out continuous
sub-structure testing with large numerical models (with the order of a thousand degrees of
freedom) using the Linux Cluster at the University of Kassel was studied proving the
extensibility of the platform to large and complex numerical models.
Session 1 – Hybrid Testing
13
DYNAMIC SUBSTRUCTURING FOR SOIL STRUCTURE INTERACTION
USING A SHAKING TABLE
Zhenyun Tang1, Matthew Dietz
2, Zhenbao Li
3, Colin Taylor
2
1 Kyoto University, Japan
2 University of Bristol, UK
3 University of Technology, Beijing, China
The experimental investigation of soil-structure interaction phenomena is typically performed
on a shaking table with a model foundation-structure system embedded in a soil container. As
the size and power of the shaking table limits the size of the specimen, only small scale
models can be tested using this method. A novel structural testing method to overcome this
disadvantage is supplied by the real-time dynamic substructuring. This paper develops a real-
time substructuring testing system for the seismic simulation of soil-structure interaction
using a shaking table. The soil-foundation system was modelled numerically, the
superstructure was modelled physically, and the shaking table was used to reproduce the
interface response. A new model-based control strategy called Full-State Compensation via
Simulation (FSCS) is used to compensate for the dynamics of shaking table that is a
conjunction of Inverse Dynamics Compensation via Simulation and full-state feedback. The
results from an entirely physical test are compared to those from a real-time dynamic
substructuring test in order to verify the validity of this method.
Session 1 – Hybrid Testing
14
REAL-TIME HYBRID TESTING FOR SOIL-STRUCTURE INTERACTION:
AN ADAPTIVE SIGNAL PROCESSING FRAMEWORK
Vasileios K. Dertimanis, Harris P. Mouzakis, Ioannis N. Psycharis
National Technical University of Athens, Greece
This study investigates the problem of conducting real – time hybrid tests for soil – structure
interaction using shaking tables. To this, a novel framework was formulated on the basis of
adaptive signal processing and parameter estimation methods. The former were utilized in
order to compensate the dynamics of the shaking table, while the latter were used for the
compensation of the total transfer delay.
Specifically, an adaptive inverse control scheme was designed and placed between the
numerical substructure and the transfer system, aiming at “canceling” the dynamics of the
shaking table. It follows that the cascade of the adaptive controller and the shaking table
becomes a delayed unit impulse response. To compensate this delay, a multi – step ahead
predictor was estimated by performing parametric and non – parametric identification on the
specimen (physical substructure).
The applied methodology is characterized by two additional innovative features: (1) it
replaces the traditional displacement command to the physical substructure by the
acceleration one. This allows a wider response spectrum to be actually implemented to the
specimen; and (2) it replaces the traditional load cell sensor for force feedback by an
accelerometer that is placed on the specimen mass.
The method was applied to a simple, linear SDOF structure (physical model) on a
horizontally deformable soil, reducing, thus, the SSI problem to two – DOF. Two specimens
were tested, with periods of 0.5 s and 0.2 s, both having a specimen – to – foundation mass
ratio equal to 4. While the results of this implementation scheme were promising, the
corresponding adaptation process requires further investigation, in order to avoid effects that
alter its performance.
Session 1 – Hybrid Testing
15
TOWARDS AN IMPLEMENTATION OF THE FHT TECHNIQUE FOR SSI
SYSTEMS USING NONLINEAR MACROELEMENTS
Charisis T. Chatzigogos1, Matt Dietz
2, Alain Pecker
1, Zhenyun Tang
2,3
1Géodynamique et Structure, France
2University of Bristol, UK 3Kyoto University, Japan
Joint Research Activity 3 of SERIES has been concerned with experimental and theoretical
investigations of interacting soil-structure systems under earthquake loading. In one of the
subtasks of this activity, the University of Bristol and Géodynamique & Structure (GDS)
have collaborated towards an implementation of the first variant of the Fast Hybrid Testing
technique using nonlinear foundation macroelements as the numerical substructure.
Efforts towards this goal have been twofold: regarding shaking table control, research at the
Univ. of Bristol has been principally concerned with the development of a novel controller
for shaking table sub-structuring capable of dealing with issues of shaking table dynamics
such as phase lag and magnitude error within a frequency range of interest. The developed
novel controller, called Full State Compensation via Simulation (FSCS), has been based on
inverse dynamics compensation and full-states feedback control techniques and has been
shown to exhibit enhanced stability and accuracy properties with respect to conventional
compensation controllers. The controller has thus been introduced in an integrated single
degree-of-freedom shaking table sub-structuring test system allowing for real-time sub-
structuring, particularly adapted for high-frequency, low-damping substructures and high-
magnitude excitation frequencies. In a parallel activity, GDS has been focusing on the
development of a nonlinear dynamic macroelement for shallow foundations. The scope has
been to propose a formulation encompassing the main sources of nonlinear behavior at the
soil-foundation interface (in particular soil plasticity, foundation uplifting and relative sliding
along the interface), which will be general enough to be used for different soil types and
shallow foundation geometries. Introduction of the foundation macroelement can be thought
of as a degree-of-freedom condensation procedure, in which the entire foundation and soil
domain are replaced by a link element with three (2D kinematics) or six (3D kinematics)
degrees-of-freedom. The interest in using macroelements in FHT is that a quasi-simultaneous
resolution of the nonlinear constitutive behavior of the numerical substructure can be
achieved, respecting the inherent constraints of real-time sub-structuring testing.
The two developments have been brought together in a realization of the first variant of the
FHT technique, in which the superstructure is modeled physically on the shaking table
whereas the foundation and soil substructure are modeled numerically. Using the novel FSCS
controller for the shaking table dynamics and introducing the foundation macroelement as the
numerical sub-structure, it has been feasible to test single degree-of-freedom model structures
under pure seismic loading and obtain qualitative features of non-linear SSI such as wide
force-displacement loops at the foundation level and residual foundation displacements at the
end of the excitation.
Session 2 – SERIES TA to Centrifuge Facilities
16
SERIES Transnational Access to
Centrifuge Facilities
Session 2
Tuesday, 28 May 2013
Session 2 – SERIES TA to Centrifuge Facilities
17
CENTRIFUGE MODELING OF DYNAMIC BEHAVIOR OF BOX SHAPED
UNDERGROUND STRUCTURES IN SAND
Deniz Ülgen1, Selman Sağlam
2,M. Yener Özkan
3, Jean Louis Chazelas
4
1Mugla Univrsity (MSKÜ), Turkey
2Adnan Menderes University in Aydin (ADU), Turkey 3Middle East Technical University (METU), Turkey
4IFSTTAR, Division Reconnaissance et Mécanique des Sols, France
Seismic safety of underground facilities such as pipelines, culverts, subways and tunnels
becomes an essential requirement for continuing economic and social development. Many
engineers earlier thought that the underground structures had been inherently safe against
earthquakes, but then, especially after the failure of some underground facilities during 1995
Kobe, Japan, 1999 Kocaeli, Turkey and 1999 Chi Chi, Taiwan earthquakes the safety
evaluation of the underground structures become a major concern of the engineers.
This research aims to investigate the dynamic response of box shaped underground structures
buried in dry sand. For this purpose, a series of centrifuge tests are carried out under
harmonic sinusoidal motions by considering the nonlinear behavior of both structure and
surrounding soil. The dynamic earth pressure is one of the most important parameters in the
seismic design of culverts. However, there is no an established methodology clarifying the
mechanism and evaluations of the dynamic earth pressures. Hence, response acceleration in
the ground, dynamic strains of the buried models and dynamic soil pressures acting on the
buried model are examined with special reference to the dynamic soil structure interaction.
Specific variables considered in this study are input motion characteristics and rigidities of
buried box structures. Three different models are used in the tests with varying rigidities.
Results of the experiments are evaluated in order to make an assessment on load transfer
mechanism between the soil and buried structure under different motions. Furthermore, the
findings of this study are compared with the predictions of closed-form solutions
recommended by Penzien (2000) and Huo et al. (2006).
Session 2 – SERIES TA to Centrifuge Facilities
18
INVESTIGATION OF THE SEISMIC BEHAVIOUR OF SHALLOW
RECTANGULAR UNDERGROUND STRUCTURES IN SOFT SOILS
USING CENTRIFUGE EXPERIMENTS
Grigorios Tsinidis1, Emmanouil Rovithis
2, Kyriazis Pitilakis
3, Jean‐Louis Chazelas
4
1Aristotle University of Thessaloniki, Greece
2Earthquake Planning and Protection Organization, Greece
3 Aristotle University of Thessaloniki, Greece
4IFSTTAR, Division Reconnaissance et Mécanique des Sols, France
Seismic response of underground structures is explored by means of well‐documented
experimental data as part of a Transnational Access action offered by the SERIES research
project (TA Project: DRESBUS II). For this reason, a series of centrifuge tests were
performed at the geotechnical centrifuge facility of IFSTTAR in Nantes focusing on
rectangular model tunnels in dry and saturated sands and excited under a centrifugal
acceleration of 40g. The testing program aimed at investigating the seismic behaviour of
rectangular tunnels as affected by soil‐structure relative flexibility and soiltunnel interface
characteristics. Both rigid and flexible structures with smooth or rough interfaces were tested
covering a wide range of soil‐tunnel configurations. Numerical analyses of the observed
tunnel behaviour were undertaken by means of the general FE platform ABAQUS and
compared to the experimental data. The effect of salient model parameters such as the
seismic earth pressures and the shear stresses around the tunnel are discussed. The above
study is foreseen to shed some light on a set of important but unresolved issues within
seismic design of underground structures.
Session 2 – SERIES TA to Centrifuge Facilities
19
INVESTIGATION OF SEVERAL ASPECTS AFFECTING THE SEISMIC
BEHAVIOUR OF SHALLOW RECTANGULAR UNDERGROUND STRUCTURES
IN SOFT SOILS
Tsinidis, G.1, Heron, C.
2, Madabhushi S.P.G.
1, Pitilakis, K.
1 & Stringer, M.
1
1Aristotle University of Thessaloniki, Greece
2University of Cambridge, UK
Extended underground structures (i.e. tunnels, subways, underground parking lots etc.)
constitute significant components of the transportation networks and the built environment.
During past earthquakes several cases of extensive damage and even collapse have been
reported for these types of structures, with that of the Daikai subway station in Kobe that
collapsed during the major 1995 Hyogoken‐Nambu earthquake, being the most interesting.
The specific features of underground structures make their seismic behavior very distinct
from aboveground structures. There is a lack of knowledge regarding several crucial issues
affecting this behavior (i.e. dynamic earth pressures on the side‐walls of a totally embedded
structure, seismic shear stresses around the structure‟s perimeter etc.), thus making seismic
design very tricky. Actually, for the evaluation of the seismic response of underground
structures, several methods may be found in the literature, based on different levels of
complexity. The results of these methods may substantially deviate, even under the same
assumptions, indicating the lack of knowledge regarding the phenomenon. To this end, a set
of three dynamic centrifuge tests have been performed at the University of Cambridge
(UCAM) jointly with Aristotle University of Thessaloniki (AUTH) on square tunnel models
embedded in dry sand. The tests were carried out at the geotechnical centrifuge facility of
UCAM, within the Transnational Access Activities of SERIES (TA project: TUNNELSEIS).
Two tunnel‐models were studied; a “rigid” and a “flexible” one, the latter deformed during
swing up and collapsed during an earthquake. The produced experimental data is used to
better understand the seismic behavior of non‐circular embedded structures. The data
obtained will be also used to validate advance numerical models and to improve the design
methods. The test set ups and the experimental procedure are briefly presented along with
representative experimental data. Among the main results we observed:
An important effect of the acceleration wave field on the tunnel response.
Presence of complex deformation modes for the rigid tunnel (rocking vibration),
usually precluded in the simplified design methods (pure racking deformation
assumption).
Residual values for the earth pressures on the sidewalls of the tunnels, caused by the
soil plastic deformations and the soil densification.
Residual values for the internal forces (both in terms of axial forces and bending
moments), caused by the soil plastic deformations, the soil densification and, to some
extent, due to small amounts of sliding on the soil‐tunnel interface.
Session 2 – SERIES TA to Centrifuge Facilities
20
EXPERIMENTAL VERIFICATION OF SHALLOW FOUNDATION
PERFORMANCE UNDER EARTHQUAKE-INDUCED LIQUEFACTION
Karamitros D.K.1, Cilingir U.
2, Bouckovalas G.D.
1, Madabhushi S.P.G.
2,
Papadimitriou A.G.3, Haigh S.K.
2
1National Technical University of Athens (NTUA), Greece
2University of Cambridge (UCAM), UK 3University of Thessaly (UTh), Greece
The seismic performance of a square footing, resting on an over-consolidated clay crust,
overlying a liquefiable sand layer, is examined herein, through the performance of a series of
three centrifuge experiments, conducted at the Schofield Centre of Cambridge University
Engineering Department (CUED). The scope of these experiments is to verify the beneficial
effect of the existence of a surficial non-liquefiable layer (over-consolidated clay crust) on
the response of the footing. In addition, these experiments aim at exploring whether this non-
liquefiable layer allows for a viable performance-based design methodology for shallow
foundations, without the need of implementing any soil treatment on the underlying
liquefiable sand. For this purpose, different thicknesses H of the clay crust were
parametrically used, varying from H=0.65 to 1.50B, with B being the footing‟s width (equal
to 3m in prototype scale).
Each test was performed in three stages:
a) The centrifugal acceleration was raised to 50g, in steps of 10g, allowing adequate
time for the consolidation of the clay layer.
b) Twenty (20) uniform cycles of harmonic excitation, with a peak acceleration of
amax=0.25g were applied at the base of the equivalent-shear-beam container. During this
stage, excess pore pressures were developed in the sand layer, resulting in the accumulation
of seismic settlements of the footing.
c) Immediately after the end of shaking and before the dissipation of excess pore
pressures, a hydraulic piston was used to increase foundation contact pressure, until bearing
capacity failure, in order to measure the (degraded) post-shaking bearing capacity. It should
be underlined that there are no published experimental data, regarding the liquefaction-
induced degradation of bearing capacity of shallow foundations and this is first time such a
study was attempted anywhere in the world.
Following a presentation of the testing configuration and the mechanical properties of the two
soil layers (clay crust and sand) in this paper, the experimental results are presented and
critically evaluated. The basic mechanisms of foundation performance are analyzed, during
as well as following shaking, while emphasis is given to the effect of non-liquefiable clay
layer thickness H on the accumulation of foundation settlements.
Session 2 – SERIES TA to Centrifuge Facilities
21
CENTRIFUGE MODELLING OF THE PERFORMANCE OF LIQUEFACTION
MITIGATION MEASURES FOR SHALLOW FOUNDATIONS
Andreia Marques1, Paulo Coelho
1, Stuart Haigh
2, Gopal Madabhushi
2
1University of Coimbra, Portugal 2University of Cambridge, UK
Earthquake-induced liquefaction is a major concern for structures built on saturated deposits
of cohesionless soils in seismically active regions, as it often causes failure of critical
structures and can lead to severe human and economic losses. Destructive consequences of
this phenomenon were continue to be witnessed from 1964 Alaskan and Niigata earthquakes
to more recent 2011 Tohuku earthquake and 2012 New Zealand earthquakes. During the past
decades, intensive efforts have been made to understand the mechanism of liquefaction and to
develop liquefaction resistance measures to enhance the performance of foundations during a
given seismic event. Centrifuge modelling has been proving its merits as a research tool to
facilitate progress in this field.
An on-going investigation at the Schofield Centre of Department of Engineering, University
of Cambridge, UK, focuses on the performance of shallow foundations susceptible to seismic
liquefaction, which is a particularly important research topic with large practical interest.
Three centrifuge modelling experiments were carried out to investigate the magnitude of
liquefaction effects on shallow foundations, under different conditions, and to assess the
performance of innovative mitigation techniques for this problem. This paper will present a
detailed analysis of the different results obtained during the tests and compare the influence
of the bearing pressures imposed on the ground by two different footings and the
performance of different mitigation techniques. A narrow densified zone under the footing
and an hybrid technique using densification and high-capacity vertical drains will be
considered in detail. The excess pore pressure measured during and after the seismic event
will be presented and discussed to evaluate and compare the results obtained in the different
situations considered in the modelling. Also, the accelerations measured at different positions
in the liquefiable soil and in the structures tested will be presented to better understand the
effects of using a densified zone, combined or not with vertical drains. Finally, the
settlements of the footings obtained in every case under study will be presented and
discussed, not only during the seismic event but also in the post-seismic phase, to investigate
the importance of consolidation settlements caused after soil liquefaction.
Clarification of the issues herein identified is a fundamental requirement to better understand,
predict and enhance the behaviour of shallow foundations built on liquefiable ground, which
can actively contribute to develop innovative liquefaction resistance measures that offer
improved cost-benefit ratios.
Session 2 – SERIES TA to Centrifuge Facilities
22
CENTRIFUGE MODELING OF PAIRS OF FLEXIBLE RETAINING WALLS IN
SATURATED SAND UNDER SEISMIC ACTIONS
(TA PROJECT: PROPWALL)
Stefano Aversa1, Luca de Sanctis
1, Rosa Maria Stefania Maiorano
1,
Michele Tricarico1, Giulia Viggiani
2, Riccardo Conti
2, Gopal Madabhushi
3, Mark Stringer
3,
Charles Heron3
1Università degli Studi di Napoli “Parthenope”, Italy 2Università degli Studi di Roma Tor Vergata, Italy
3University of Cambridge, UK
The centrifuge tests carried out under the research project PROPWALL at the Schofield
Center of the Cambridge University Engineering Department are presented and discussed.
The tests were carried out on flexible retaining walls embedded in saturated sand excited by a
train of quasi-sinusoidal waves. The piezometric head of the porosity fluid, methyl cellulose,
was at dredge level. Two tests were carried out on pairs of flexible retaining walls with one
level of support near the top, while the remaining two tests were performed on cantilevered
walls. The experimental equipment, the model preparation and the monitoring devices are
described in detail. The results are presented in terms of accelerations, deflections, bending
moments and excess pore pressures, as monitored through the devices installed on the walls
and within the soil mass. A preliminary interpretation of the observed behaviour is also given.
Session 2 – SERIES TA to Centrifuge Facilities
23
EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF NONLINEARITY IN
SOILS USING ADVANCED LABORATORY-SCALED MODELS:
AN APPLICATION TO THE ROME HISTORICAL CENTRE
(TA PROJECT: ENINALS)
F. Bozzano1, A. Bretschneider
1, A.C. Giacomi
1, S. Martino
1, G. Scarascia Mugnozza
1, S.
Escoffier2, L. Lenti
2, J-L. Chazelas
2, C. Favraud
2, D. Macé
2
1 “Sapienza” University of Rome, Italy
2 IFSTTAR, France
The SERIES TA project “Experimental and Numerical Investigations of Nonlinearity in soils
using Advanced Laboratory-Scaled models” (ENINALS) was focused on the centrifuge
modeling of seismically-induced strains vs. stratigraphic features. These last ones were
specifically referred to the presence, thickness and location of clay levels representing the
alluvial deposits of the Tiber River in Rome historical centre, which is exposed to Mw>6
earthquakes from the Central Apennine chain with epicentral distances shorter than 100 km.
Several studies have been focused on the amplification effects of the Tiber alluvial deposits
in Rome historical centre. Moving from this consolidated knowledge, the main goal of
ENINALS was to investigate possible non-linearity effects associated with the worst seismic
actions in Rome and, namely, related to the stratigraphic juxtaposition of more deformable
clayey-silts, and of stiffer sands or sandy-silts. A laboratory-scaled centrifuge modeling with
a dynamic action was associated to the numerical simulation of non linearity by 1D-3C
approaches. 4 samples were tested at reduced scale in the centrifuge, representing two
homogeneous soil columns (clayey and sandy column respectively) and two heterogeneous
soil columns, including a clay level between two sand beds representing a 5m and a 10m clay
layer respectively. The applied dynamic input represents the maximum expected seismic
action in Rome. It was reproduced at the shaking device as: i) a natural time history, ii) an
equivalent sinusoidal signal and iii) a multifrequential equivalent signal derived by the
recently proposed LEMA_DES approach. The effects of nonlinearity due to seismic shaking
in the considered heterogeneous soil columns was also simulated by the 1D-3C finite
difference numerical code SWAP, implemented by IFSTTAR. The strain effects obtained for
the homogeneous and for the heterogeneous soil columns were compared and a Shear Strain
Concentration Index (SSCI) was computed to define a differential strain rate. Findings show
i) a main role of soil heterogeneity in conditioning the shear strains and their distribution
along the vertical soil profiles and ii) drive to a quantitative approach to evaluate the
reliability of 1D vs. 2D-3D conceptual modeling in complex geological setting, as in the case
of alluvial valleys filled by heterogeneous soils.
Session 3 – US-NEES Developments
24
US-NEES Developments
Session 3
Wednesday, 29 May 2013
Session 3 – US-NEES Developments
25
THE GEORGE E. BROWN, JR., NETWORK FOR EARTHQUAKE ENGINEERING
SIMULATION (NEES): ACCELERATING IMPROVEMENTS IN SEISMIC DESIGN
AND PERFORMANCE BY SERVING AS A GLOBAL COLLABORATORY
FOR DISCOVERY AND INNOVATION
Julio Ramirez
Purdue University, USA
The George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) is a
network of 14 shared-use laboratories (https://nees.org/sites-mainpage/laboratories)
connected by a cyberinfrastructure that fosters collaboration in research and education
(https://nees.org/).
In the 9th year of official operations, over 400 multi-year, multi-investigator projects have
gone through NEES, yielding many advances in earthquake engineering and a wealth of
valuable experimental data. At the core of the NEES cyberinfrastructure is the NEES
platform for collaboration, NEEShub, providing convenient access to tens of thousands of
users from over 190 countries to the NEES central data repository (Project Warehouse). The
NEEShub hosts tools for data visualization, analysis, hybrid simulation, education, and
collaboration. In this paper a small sample of the many research, outreach, information
technology, and educational accomplishments of NEES are described. These examples
illustrate the impact of the efforts of the NEES community towards improving the resilience
of our society against earthquakes and tsunamis.
Session 3 – US-NEES Developments
26
PROMOTING RE-USE OF EARTHQUAKE ENGINEERING DATA
THROUGH THE NEESHUB
JoAnn Browning
University of Kansas, USA
Over the past several decades, the civil engineering profession has amassed vast amounts of
quantitative data obtained from numerical and physical simulations of seismic events. But the
bulk of the information lives only in printed media that are difficult and time consuming to
use. And much of the generated data are not available in journals because page limits have
forced researchers to leave out everything but the most pertinent facts. Further, the limited
data that are available in digital format are cumbersome to use because formats vary from
source to source.
The result is an inefficient method for studying the behavior of structures and soils, with
these common challenges:
Data pertaining to a common design or evaluation issue have to be compiled through
time‐consuming searches, requiring researchers to explore the ever-increasing
numbers of journals almost one by one;
Researchers may need to request additional data from publication authors;
Data plots and tables from publications must be digitized, essentially using manual
processes; and
Engineers with similar project needs must endeavor to collect and analyze the same
sets of data.
For the past 10 years, the George E. Brown Jr., Network for Earthquake Engineering
Simulation (NEES) has helped to bring data sets to the larger community. NEES‟ objective is
to assist researchers, practicing engineers, and code and guideline developers as they work on
innovations for minimizing damage caused by earthquakes or tsunamis. NEES operations are
managed by the NEES Community and Communications (NEEScomm) Center, which
manages the NEES cyberinfrastructure (hosted on NEEShub) and a nationwide network of 14
laboratories (www.nees.org/sites-mainpage) that are available to researchers from U.S.
universities and firms. Research at the NEES facilities is funded by the NSF; by other federal,
state, and local agencies; by private industry; and under the partnerships that NEES has
cultivated with investigators, research facilities, and agencies in Japan, Taiwan, Canada, and
China. To date, almost 400 multi‐year, multi‐investigator projects have been completed or are
in progress at NEES sites. The research data has become available in a digital medium, but
there is still a challenge to promote easy re-use of the data.
NEES has developed a number of initiatives through the NEEShub to help promote data re-
use in its most efficient formats. This presentation focuses on several of these initiatives,
including: establishment of DOI‟s for easy reference and promotion of datasets, NEEShub
Databases, visualization tools, and new data search mechanisms.
Session 3 – US-NEES Developments
27
RE-USE OF EXPERIMENTAL EARTHQUAKE DATA FOR RESEARCH:
THREE ILLUSTRATIVE EXAMPLES
John W. van de Lindt
Colorado State University, USA
One of the key contributions of the George E. Brown Network for Earthquake Engineering
Simulation (NEES) lies in the data archival process, particularly the ability of earthquake
engineering researchers to utilize experimental data for research beyond the original intent of
the experiment. Although this seems straightforward in concept, the ability to utilize
experimental data based on only what is archived presents a number of challenges. For
successful data re-use the following are key: (1) data specific to the purpose of the new study
must be available; (2) the needed accuracy which may not be the accuracy utilized in the
original experiment must be available and be able to be identified; and (3) the ability to
properly cite a journal paper or report from the original experiment should be readily
identifiable. In this presentation, three illustrative examples that re-use data from NEES
experiments in 2006, 2007, and 2009, focusing on a wood building shake table test, a steel
moment frame shake table collapse test, and reversed cyclic tests on reinforced masonry
shear- and transverse-walls, are applied to current or recent research studies. The first
examples on a wood and steel building utilize the global hysteresis to develop collapse
models for aftershock studies, while the latter example calibrates a system level masonry
model for use in seismic fragility development. In the wood example, the data from a two-
story light-frame wood building tested at NEES@UB in 2006 was utilized to develop a
global hysteretic model with one-degree-of-freedom at each story. The collapse model
developed was used to assess aftershock risk of a typical light-frame wood building with
future integration into a performance-based seismic design framework. The steel moment
frame test data was used for a similar purpose but to model typical steel frame buildings. The
reinforce masonry wall data was used to calibrate both shear wall and transverse wall
hysteretic models to implement them into SAPWood, a software package developed within
an earlier NEES project. Finally, both challenges and successes of using data from these three
experimental programs will be presented.
Session 3 – US-NEES Developments
28
COMMUNICATING EARTHQUAKE ENGINEERING: THE EDUCATION,
OUTREACH, AND TRAINING ACTIVITIES OF THE GEORGE E. BROWN, JR.
NETWORK FOR EARTHQUAKE ENGINEERING SIMULATIONS
Barbara Fossum
Purdue University, USA
The goal of broadening participation of underrepresented groups in engineering has long been
a priority at the National Science Foundation, and is repeatedly referenced in major policy
documents. Underrepresented groups in engineering are currently defined as women,
Hispanics, African Americans, Pacific Islanders and Native Americans. The NEES network
is committed to increasing the diversity of the network across all areas. Additionally the
network is inspiring and preparing the next generation of earthquake engineers through
programs involving Research Experience for Undergraduates. In collaboration with the
National Science Foundation (NSF), the Research Experience for Undergraduates (REU)
program is a six-week, hands-on, paid research experience for undergraduate students.
During this period, students perform research with NEES scientists, participate in education
workshops, attend scientific lectures, and develop new skills and interests in earthquake
engineering.
This talk will provide an overview of some of the programs implemented at NEES for
educating the next generation of earthquake engineers and increasing awareness of the NEES
network. Specific examples include opportunities for increasing the participation of
underrepresented groups, outreach to K-12 education, research opportunities for
undergraduate students and transferring research results to the practicing engineering
community. Participation of minority serving institutions will also be discussed.
Session 3 – US-NEES Developments
29
DAMPING ESTIMATION FROM SEISMIC RECORDS
Dionisio Bernal
Northeastern University, USA
Extraction of damping ratios from input-output measurements is a standard problem in
identification and exact results are obtained by all theoretically consistent algorithms when
the data generating system is viscously damped, linear, time invariant and the input-output
records are noise free. In practice, however, these assumptions are never entirely satisfied
and, as a consequence, identified damping ratios are random variables. In the particular case
of seismic analysis it is well known that identified damping values have relatively high
variance and it is shown here that this is a consequence of the low Fisher information
contained in the response; a significant contributor being the relatively short durations of
seismic signals. Notwithstanding the difficulties, values for damping are needed to formulate
predictive models and expressions to estimate the expected value for buildings have been
proposed through the years. Although not explicitly stated in most cases, these expressions
are based on analyses that reflect dissipation within the structure, as well as energy loss
through the soil structure interface. This paper summarizes recent work on characterizing the
uncertainty in the estimation of damping, discusses the issue associated with isolating
structural characteristics from those of the structure-soil system, and presents some new
statistical expressions for expected value of the first mode damping ratio derived from
analysis of a large collection of seismic responses.
Session 4 – SERIES Networking Activities: DDB & Qualification of RI
30
SERIES Networking Activities:
Distributed Database and Qualification of Research
Infrastructures
Session 4
Wednesday, 29 May 2013
Session 4 – SERIES Networking Activities: DDB & Qualification of RI
31
A FACETED LIGHTWEIGHT ONTOLOGY FOR EARTHQUAKE ENGINEERING
RESEARCH PROJECTS AND EXPERIMENTS
Md. Rashedul Hasan, Feroz Farazi, Oreste S. Bursi, Md. Shahin Reza
University of Trento, Italy
With the invention of the Semantic Web, computing paradigm is experiencing a shift from
databases to Knowledge Bases (KB), in which ontologies play a major role in enabling
reasoning power that can make implicit facts explicit to produce better results for users. In
addition, KB‐based systems provide mechanism to manage information and semantics thereof
that can make systems semantically interoperable and as such can exchange and share data
between them. To overcome the interoperability issues and to exploit the benefits offered by
the state of the art technologies, we moved to the KB based system. Essentially, we have
developed an earthquake engineering ontology using a faceted approach with a focus on
research project management and experiments. Following the validation of the ontology by a
domain expert, it was published in the knowledge representation language RDF and
integrated to the generic ontology WordNet. The experimental data coming from, inter alia,
cyclic and pseudo‐dynamic tests were also published in RDF. We used Jena, OWLIM and
Sesame tools for publishing, storage and management, respectively. Finally, integrating the
tools, ontologies and data, we developed a system to evaluate the effectiveness of the
approach and in fact we found quite convincing and satisfactory results.
Session 4 – SERIES Networking Activities: DDB & Qualification of RI
32
THE SERIES DISTRIBUTED DATABASE:
ARCHITECTURE AND IMPLEMENTATION
I.L. Martinez1, I. Ioannidis
2, C. Fidas
2, M. Williams
1, P. Pegon
3
1University of Oxford, UK
2University of Patras, Greece
3Joint Research Centre, Italy
The European scientific community is currently highly fragmented, with each laboratory
holding experimental data, stored in some cases in a non-structured way. As a consequence,
the dissemination and use of experimental results outside of the laboratory where they are
produced can be problematic. This leads to wasteful duplication of tests and ultimately limits
the impact of earthquake engineering research on practice, innovation and earthquake risk
mitigation. One part of the SERIES Networking Activities aim at facilitating the exchange of
data and data communication among research infrastructures in Europe providing access to
data by means of a distributed database. The scope was not to build a central database where
local databases would either migrate or merge, but instead to provide centralised access to
database nodes that are distributed over a network that are able to dialog with a central portal
in a uniform manner. To this end, database nodes use Web Services, to cast their data into a
uniform standard format for uploading and downloading. The paper concentrates on the
architecture and the implementation of the Distributed Database.
Session 4 – SERIES Networking Activities: DDB & Qualification of RI
33
THE SERIES DISTRIBUTED DATABASE: EXCHANGE FORMAT,
LOCAL DBS AND CENTRAL PORTAL INTERFACE
A. Bosi1, S. Bousias
2, J.L. Chazelas
3, M. Dietz
4, M.R. Hasan
5, S.P.G. Madabhusi
6,
A. Prota7, T. Blakeborough
8, P. Pegon
9
1Vienna Consulting Engineers, Austria;
2University of Patras, Greece
3IFSTTAR, France;
4University of Bristol, UK
5University of Trento, Italy;
6University of Cambridge, UK
7University of Naples, Italy;
8University of Oxford, UK
9Joint Research Center, Italy
The European scientific community is currently highly fragmented, with each laboratory
holding experimental data, stored in some cases in a non-structured way. As a consequence,
the dissemination and use of experimental results outside of the laboratory where they are
produced can be problematic. This leads to wasteful duplication of tests and ultimately limits
the impact of earthquake engineering research on practice, innovation and earthquake risk
mitigation. One part of the SERIES Networking Activities aim at facilitating the exchange of
data and data communication among research infrastructures in Europe providing access to
data by means of a distributed database.
From the User point of view, the approach is based on a scheme for the data to be exchanged
(Exchange Data Format), local databases (one prototype DB is currently deployed at various
SERIES places), interface and tools allowing populating the local DBs and a Central Portal
giving access to the SERIES data. The paper presents and discusses all these aspects.
Session 4 – SERIES Networking Activities: DDB & Qualification of RI
34
QUALIFICATION OF SEISMIC RESEARCH TESTING FACILITIES
IN EUROPE
Maurizio Zola1, Fabio Taucer
2
1Consultants of P&P LMC, Italy
2JRC, Italy
The qualification of large research seismic testing facilities in Europe was one of the main
goals of the SERIES Project. SERIES‟s Networking Activity 2 aimed at creating the
conditions leading to the qualification of Structural Testing Laboratories specialising in
earthquake engineering and equipped for large scale testing. The activities in NA2 were
aimed to address the assessment criteria for technical competence of the research
laboratories, based on repeatability and reproducibility of the testing activities.The NA2
activity was broken down in four Tasks: i) Evaluation and impact of qualification of
experimental facilities in Europe; ii) Assessment of testing procedures and standards
requirements; iii) Criteria for instrumentation and equipment management; iv) Development
and implementation of a Common Protocol for qualification.
The emergence of performance based engineering (PBE) approaches in earthquake
engineering offers an opportunity to rethink laboratory test approaches by tailoring the test
program to achieve performance outcomes that are explicitly defined for the particular test
specimen. To implement the Qualification a Draft Common Protocol covering the
Management and Technical General Requirements with a check list for the audits was
produced; moreover Specific Technical Requirements for Shaking Table Testing, Reaction
Wall Testing, On-site Testing, Data Acquisition and Processing were identified and specified
in four technical annexes to the Common Protocol.
Thus the qualification of the research testing facilities may be achieved:
• by the certification of the Management System after ISO 9001 for the Research
Engineering Activities;
• by the accreditation of the Laboratory after ISO/IEC 17025 for the Measurement
Activities;
• by the accreditation of the Laboratory after ISO/IEC 17025 with flexible scope for the
Research Testing Activities.
As far as the accreditation of the Research Testing Activities after ISO/IEC 17025 with
flexible scope the Laboratory (Supplier of tests) should receive a Testing Specification issued
by the Research Engineer (Customer) and the Specific Technical Requirements (Annexes to
the Common Protocol) should be applied. This proposal for the qualification of large research
infrastructures was presented to the Laboratory Committee of EA in Oslo and to the 1st
ERNCIP Conference in Ispra.
Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures
35
SERIES Transnational Access to Shaking Table
Facilities on masonry, RC and steel structures
Session 5
Wednesday, 29 May 2013
Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures
36
FULL SCALE TESTING OF MODERN UNREINFORCED THERMAL
INSULATION CLAY BLOCK MASONRY HOUSES
S. Lu, A. Jäger1, L. Mendes
2, P. Candeias
2, A. C. Costa
2, E. Coelho
2, H. Degée
3, C.
Mordant3, V. Sendova
4, Z. Rakicevic
4, M. Tomazevic
5
1Wienerberger AG, Austria;
2LNEC, Portugal
3University of Liege, Belgium
4IZIIS, SS "Cyril and Methodius" University, R. Macedonia
5Slovenian National Building and Civil Engineering Institute, Slovenia
In the scope of the SERIES project Transnational Access activities, Laboratório Nacional de
Engenharia Civil (LNEC) has provided access to its 3-D shaking table to the international
construction company Wienerberger AG and to a group of European experts, in order to
perform full-scale seismic tests on an industrial solution for buildings, using modern
unreinforced thermal insulation clays block masonry.
This solution represents a very common construction method in Europe that still lacks
seismic vulnerability assessment, because most results available were carried out on cyclic
shear tests, thus the effective three-dimensional dynamic response under seismic events still
requires experimental validation.
Consequently, two full-scale mock-ups adopting different geometries were tested on the 3-D
shaking table using a series of seismic records with increasing intensity.
This paper presents the most relevant results regarding the structural response of the
specimens, e.g. the dynamic response evolution, the collapse mechanism identified and the
maximum drift values measured. The paper closes with the main conclusions extracted from
this work and with the tasks identified for future work.
Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures
37
ASSESSMENT OF INNOVATIVE SOLUTIONS FOR NON-LOAD BEARING
MASONRY ENCLOSURES
João Leite1, Paulo B Lourenço
1, Elizabeth Vintzileou
2, VasilikiPalieraki
2, António A.
Correia3, Paulo Candeias
3, Alfredo Campos Costa
3, Ema Coelho
3
1University of Minho, Portugal
2National Technical University of Athens, Greece
3LNEC, Portugal
This paper presents the results of the SERIES TA project “Masonry Enclosures”. The project
addresses the seismic performance of masonry enclosures in European countries with
moderate and high seismicity based on the experimental evaluation of the seismic response of
reinforced concrete (RC) frames with innovative solutions for masonry infill walls,
considering both the in-plane and out-of-plane behaviour of the enclosures. The recent
L‟Aquila earthquake of 2009 has underlined that the current masonry infill solutions are not
effective, as illustrated by the considerable in-plane damage and out-of-plane collapses
throughout the affected areas. Eurocode 8 addresses this issue by imposing the use of
reinforced infill solutions but fails to give design and detailing methodologies.
With the above in mind, a shake table experimental research programme was devised in order
to investigate the seismic behaviour of reinforced infill walls and how they affect the global
structural response.
The first phase of the research activity involved the seismic testing at the LNEC of a two-
storey RC infilled frame building designed to the Eurocodes and built at a 1:1.5 scale. These
frames were filled with single leaf clay bricks and reinforced plaster was placed on both sides
of the infill walls and anchored to the RC frame and masonry units. From these tests it was
possible to assess the evolution of the seismic behaviour of infills and their influence on the
RC structure through several acceleration inputs of increasing amplitude, associated to
cumulative damage limit states.
The second part of the project comprises the dynamic testing of a closed RC plane frame with
external dimensions of 6.50mx3.25m and structural elements with 0.50mx0.30m cross-
sectional dimensions. This plane frame will be tested simultaneously for in-plane and out-of-
plane dynamic actions, representing the response of a frame panel in a typical RC building at
different levels. Both motions should match a given floor response spectra, of narrow band
frequency content.
This unique testing setup was specifically designed for this test and is mainly composed of a
stiff steel caisson three-dimensional frame which moves rigidly with the shaking table. It is
fixed to the upper beam in the transversal direction, while a system of rollers allows for an
independent motion in the longitudinal direction.
Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures
38
SEISMIC BEHAVIOUR OF L- AND T-SHAPED UNREINFORCED MASONRY
SHEAR WALLS
C. Mordant1, M. Dietz
2, L. Vasseur
1, H. Degée
1
1University of Liège, Belgium
2University of Bristol, UK
The contribution describes the results of the second phase of the SERIES project TA5 carried
out at EQUALS laboratory of University of Bristol. The experimental tests aim at
investigating (i) the influence of walls perpendicular to the seismic action ("flange-like"
behaviour) and (ii) the frame effect in load-bearing masonry structures subjected to
earthquake action. Two specimens are tested. The first specimen is made of two T-shaped
walls connected by a lintel to build up a frame. The two piers are designed so that the main
axis of the first one is perpendicular to the main axis of the second one. Thus, global torsional
effects are expected. The second specimen is a frame with two L-shaped walls as piers. The
structural system is globally symmetrical, but the connection of the "flange" (wall
perpendicular to the plan of the frame) to the "shear wall" (wall in the plan of the frame) is
different for both piers. In the first pier, flange and shear wall are glued, whereas they are
built in the second one. Different load cases are considered (gravity load acting on the flange
and/or on the shear wall). Results of the experimental tests evidence the contribution of the
link between piers and highlight a significant rocking behaviour. Depending on its position
and on the loading configuration, the flange is likely to increase the stability of the frame. It
is also showed that the torsional effects and the type of connection largely influence the
collapse mechanism. Additionally, identification of natural modes and damping ratios are
used to calibrate predictive models.
Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures
39
SHAKE TABLE TESTING OF A HALF SCALED RC-URM WALLS STRUCTURE
Marco Tondelli1, Sarah Petry
1, Igor Lanese
2, Katrin Beyer
1, Simone Peloso
2
1École Polytechnique Fédérale de Lausanne, Switzerland
2EUCENTRE, Italy
With the introduction of higher seismic design forces in the Swiss loading standard of 2003
most unreinforced masonry (URM) buildings failed to satisfy the seismic design check. For
this reason, in new construction projects, a number of URM walls are nowadays replaced by
reinforced concrete (RC) walls. The lateral bracing system of the resulting structure consists
therefore of URM walls and some RC walls which are coupled by RC slabs and masonry
spandrels. The same situation characterises a number of seismically retrofitted URM building
across Europe in which RC walls are added to the original structure to improve its behaviour.
Within the framework of the FP7-SERIES project, a four-storey RC-URM wall structures
was tested on the shake table at the EUCENTRE TREES Lab (Laboratory for Training and
Research in Earthquake Engineering and Engineering Seismology) in Pavia (Italy). The test
was conducted at half-scale and is part of a larger research initiative on mixed RC-URM wall
systems initiated at EPFL (École Polytechnique Fédérale de Lausanne). The key objective of
the testing campaign was to gain insights into the dynamic behaviour of mixed RC-URM
wall structures and to provide input for the definition of a performance-based design
approach of such mixed structural system.
Multiple shaking at increasing intensity was used to test the dynamic behaviour of the
examined building. The final shaking induced damage corresponding to the collapse
prevention limit state. Furthermore, random noise vibration tests were performed to monitor
the elongation of the natural periods induced by the damage progression.
The paper presents details on the structural system and the selected ground motion, the test
set-up and the instrumentation. Additionally, initial results of the shake table test are
presented with a first interpretation of the shown structural behaviour.
Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures
40
EXPERIMENTAL AND NUMERICAL INVESTIGATION OF TORSIONALLY
IRREGULAR RC SHEAR WALL BUILDINGS WITH RUTHERMA BREAKERS
A. Yakut1, A. Le Maoult
2, B. Richard
2, F. Ragueneau
3, G.M. Atanasiu
4,
S. Scheer5, S. Diler
5
1Middle East Technical University, Turkey
2CEA/Saclay, France;
3ENS Cachan, LMT, France
4Technical University of Iasi, Romania
5SCHÖCK Company, Germany
Seismic response of reinforced concrete shear wall buildings with irregularities has not been
studied in detail and thus requires detailed experimental as well as numerical investigations.
Therefore, a challenging model building having irregularly placed shear walls in plan has
been designed and tested on the AZALEE shaking table at the TAMARIS laboratory in
CEA/Saclay. This research project, called ENISTAT, has been granted under SERIES
projects via Transnational Access to CEA/Saclay facility in France. The project has three
main objectives: 1) Study the behaviour of the mock-up under increasing bi-directional
horizontal synthetic earthquake records; 2) Attempt to evaluate the experimental results using
modern experimental techniques for data acquisition; 3) Implement & monitor performance
of a new structural element that allows for wall-slab connection to reduce the thermal energy
loss. The specimen has been designed professionally in conformity with Eurocode 8 and
constructed at EMSI Laboratory – CEA Saclay. Rutherma elements were used only at the
second floor level as a connection member between the shear walls and the slab. The model
building has been instrumented to get measurements of accelerations, displacements and
strains at various critical locations. To determine relative movement of the second floor slab
with respect to walls due to presence of Rutherma members, relative displacement readings in
the three principal directions were made at five different locations. Prior to testing, numerical
analyses have been carried out to determine the test sequence and application of ground
motion records. Five tests have been performed under a selected synthetic ground motion
record which is scaled to achieve different PGA levels. The ground motion records were
obtained artificially such that they conform with the design spectrum defined in Eurocode 8.
After initial low level tests, seismic tests having PGA‟s of 0.1g, 0.2 g, 0.4g, 0.6g and 0.8g
were applied consecutively. Before each tests low level white noise tests were performed to
determine frequencies of the mock-up. During the first three tests, i.e. up to 0.4 g, no
significant damage has been observed in the structural members except minor hairline cracks
on the spandrel beams. At 0.6g test, more cracks in beams were observed without any major
crack in walls. Strain measurements in Rutherma steel sections indicated that the strains were
within the elastic range. During the 0.8g test, separation of the shear wall member on the
flexible side from the foundation was observed. After the test, major cracks that are mainly
confined on that side in the first floor were observed. No damage on the Rutherma breakers
was observed.
Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures
41
ASSESSMENT OF THE SEISMIC RESPONSE OF CONCENTRICALLY-BRACED
STEEL FRAMES (TA PROJECT: BRACED)
B.M. Broderick1, A. Hunt
1, P. Mongabure
2, A. Le Maoult
2, J.M. Goggins
3, S. Salawdeh
3, G.
O‟Reilly3, D. Beg
4, P. Moze
4, F. Sinur
4, A.Y. Elghazouli
5, A. Plumier
6
1Trinity College Dublin, Ireland;
2CEA/Saclay, France;
3 NUI Galway, Ireland
4University of Ljubljana, Slovenia;
5Imperial College London, UK;
6University of Liege, Belgium
The seismic response of concentrically braced frames (CBFs) is affected by the reduced
ductility capacity of hollow section bracing members under low cycle fatigue conditions.
Seismic response assessment also needs to account for the role of the gusset-plate
connections commonly used in CBFs, which influence local ductility demand in the bracing
members. The SERIES TA project BRACED investigates this behaviour in full scale seismic
tests, the results of which are used to validate recently-developed models for the ductility
capacity of hollow section bracing members and recent proposals for the improved detailing
of gusset plate connections. The experimental and numerical studies identify active yield
mechanisms and failure modes in member/connection combinations and provide essential
data on the earthquake response of European CBFs.
The central element of the integrated experimental and numerical research programme is a
series of shake table experiments on full-scale model single-storey CBFs on the Azalee
shaking table at CEA Saclay. The model braced frame is 2955 mm high and 4900 mm wide
and carries a mass of 44 tonnes. The brace member and connection details are varied between
experiments to investigate a range of global and local member slenderness representative of
those found in European buildings. In each experiment, three separate tests are performed
with table excitations scaled to produce elastic response, brace buckling/yielding and brace
fracture. The experimental programme involving 12 independent experiments is supported by
correlative pre-test predictions and post-test simulations using pushover and time-history
analysis.
The experimental programme builds on a previous test programme completed under the
Ecoleader programme at NTUA Athens, but with the test models designed to evaluate the
ultimate earthquake response of CBFs with realistic brace members and connections. In
particular, the relative strengths of the brace members and gusset plate connections are varied
between experiments.
The principal outcomes of the test programme include measurements of the displacement
ductility capacity of the brace specimens; an evaluation of the influence of gusset plate
detailing on system ductility and frame stiffness; observations on the evolution of response
frequency with displacement amplitude; assessment of the contributions of brace and
connection yielding to overall inelastic deformation in CBFs; and measurements of
equivalent viscous damping in CBFs.
Session 6 – SERIES TA to Shaking Table Facilities on wood structures / Experimental Facilities
42
SERIES Transnational Access to Shaking Table
Facilities on wood structures / General on
experimental facilities
Session 6
Wednesday, 29 May 2013
Session 6 – SERIES TA to Shaking Table Facilities on wood structures / Experimental Facilities
43
SEISMIC PERFORMANCE OF LAMINATED WOOD FRAMES WITH MOMENT
CONNECTIONS UNDER SEISMIC LOADS:EXPERIMENTAL INVESTIGATION
B. Kasal1, A. Heiduschke
2, S. Pospisil
3, S. Urushadze
3, Z. Zembaty
4
1TU Braunschweig/Fraunhofer WKI, Germany
2 HESS Timber, LLC, Germany
3ITAM Prague, Czech Republic
4University Opole, Poland
Laminated wood frames (LWF) offer alternative solutions for mid-rise structures (defined
here as structures of up to about 8 floors high) traditionally built of reinforced concrete (RC)
or steel. The laminated wood can be manufactured to relatively large cross sections and
acceptable load capacities. Previous studies showed that laminated wood frames can resist
large seismic loads mainly due to their energy dissipation capacity (Heiduschke, A., B. Kasal,
and P. Haller 2009; Kasal, B., I. Pospisil, I. Jirovsky, M. Drdacky, A.Heiduschke, P. Haller
2004). The experiments, described in these papers also showed that the laminated wood
frames will undergo relatively large drifts, which under existing drift design limitations
represents a drawback that needs to be addressed either technically or in the code. While the
frames tested and reported in the above literature had nonlinear, dowel-bearing type
connections capable of moment transfer in one direction, they required bracing between the
bays and light decks were used to supply additional torsional stiffness. Such construction is
possible but limits the flexibility (bracing must be always present) and presents a design
challenges due to the large stiffness differences in two principal directions of the frame. This
paper describes the experimental program that studied the seismic behavior of three-story
LWB with spatial (3-dimensional) moment connections. The 3-D moment connections are
not common in wood structures due to difficulties in their design and manufacturing. The
connection between beams and columns is always facilitated through some kind of steel
hardware that must be effectively connected with wood. These connections cannot be
produced and designed as rigid due to the low dowel-bearing strength of wood and exhibit
typical stress-softening behavior that was studied for decades and large body of literature
exists to describe the behavior of joints under cyclic loads. It has been generally accepted that
results of slow cyclic load (about 0.5-1.0 Hz) can be used in subsequent prediction of a
timber joint behavior under more rapidly varying load (such as seismic event) although some
load rate dependency of a connection stiffness and capacity has been reported. In this work,
we have used slow cyclic load to evaluate the properties of 3-D moment connections and
used this information for design and construction of experimental frames loaded by a seismic
forces using shake tables. The methodology, instrumentation and main experimental results
of the research programs are presented.
Session 6 – SERIES TA to Shaking Table Facilities on wood structures / Experimental Facilities
44
INVESTIGATION OF SEISMIC PERFORMANCE OF MULTI-STOREY TIMBER
BUILDINGS (TA PROJECT: TIMBER BUILDINGS)
Maurizio Piazza1, Roberto Tomasi
1, Alfredo Campos Costa
2, Paulo Candeias
2
1University of Trento, Italy
2LNEC, Portugal
The paper describes the research activities for Transnational Access to Earthquake
Engineering Research Centre (NESDE) at LNEC (Laboratório Nacional de Engenharia Civil,
Lisboa, Portugal), within the framework of the SERIES Project. The aim is to verify, through
full-scale shaking table tests, the effects of earthquakes on some timber buildings
characterized by the same geometry (three stories houses, 7 m x 5 m in plan), designed
according to the state of the art of the timber engineering, but built through three different
timber systems: platform frame system (PF), log house system (LH), cross laminated system
(CLT). The project involves University of Trento, as Lead User of Transnational Access Use,
University of Minho and University of Graz, and different industrial partners. The specimens
have been accurately designed taking into account all the critical point of the different
construction systems (connection details, the presence of openings in walls and in floors, the
effect of non-structural elements etc.), and taking advantages of previous research
experiences of each of the team involved in the project. The LH and the two PF structures
were tested in May and June 2012, the CLT building was tested on February 2013.
The seismic behaviour of these typologies can be very different, being associated to many
factors such as the plane and elevation regularity, the type and the number of connection
systems etc. There are aspects so far not sufficiently investigated, such as:
- the deformability of the decks and walls (the relative stiffness significantly influences the
distribution of horizontal loads on the walls);
- the presence of openings in the panels; Standards, generally, only suggest empirical
factors in order to reduce resistance, or recommend not to consider as structural resisting
elements the panels containing openings;
- the influence of non-structural elements on the building behaviour.
At European level, there is still a lack of design provisions. Just as an example, the CLT and
LH construction systems in Eurocode 5 and Eurocode 8 have not specific design rules, while
regarding the structural material (such as the cross laminated panels in CLT system), due to
the absence of a specific technical Standard for the production, only specific technical
approvals must be considered.
The paper illustrates the assumptions, the facts and the present state of this on-going research
on earthquake resistant timber houses.
Session 6 – SERIES TA to Shaking Table Facilities on wood structures / Experimental Facilities
45
EXPERIMENTAL STUDY ON SEISMIC PERFORMANCES OF PRECAST
CONCRETE SHEAR WALL WITH JOINT CONNECTING BEAM
Xilin Lu1, Dun Wang
2, Bin Zhao
3
1Tongji University, Shanghai, China
Structural connection is the major feature of precast concrete shear wall distinguished from
monolithic shear wall and it plays an important role in seismic performances of precast
concrete shear wall. Different from widely used technologies such as mechanic sleeve
connection and sleeve-mortar splicing connection, joint connecting beam that is composed of
staggered splicing rectangular steel loops protruding from wall panel, assembly of
longitudinal steel bars and stirrups as well as concrete-casting is adopted as an alternative to
connect reinforcements of precast concrete shear wall. This paper is concerned with location
and height of the joint connecting beam on performances of slender precast concrete shear
wall with constant axial loading under quasi-static test and comparisons are made with that of
monolithic shear wall. The destruction of test specimen configuration, the top lateral loading-
displacement hysteretic curve, shear bearing capacity, deformation, energy dissipation
capacity, strength reduction, stiffness degradation, reinforcement strain, as well as concrete
strain were analyzed. Test results show that shear bearing capacity of precast concrete shear
wall with joint connecting beam is a little smaller than that of monolithic shear wall; the
failure mode, stiffness and the energy dissipation capacity of the precast shear wall specimen
are nearly the same or better than those of the monolithic shear wall specimen. It is indicated
that concept and detailing of the joint connecting beam is feasible and applicable to precast
concrete shear wall structure, which has the advantages of with no welding, no costly
mechanic sleeves and speeding up construction progress and application of precast concrete
structure. In the end, recommendations on the structural design are proposed for further
application of precast concrete shear wall with joint connecting beam.
Session 6 – SERIES TA to Shaking Table Facilities on wood structures / Experimental Facilities
46
FULL-SCALE PSEUDODYNAMIC TESTING OF THE SAFECAST
THREE-STOREY PRECAST CONCRETE BUILDING
Bournas D.1, Negro P.
2, Molina F-J.
2
1University of Nottingham, UK
2JRC, Italy
In the framework of the SAFECAST Project, a full-scale three-storey precast building was
subjected to a series of pseudodynamic (PsD) tests in the European Laboratory for Structural
Assessment (ELSA). The mock-up was constructed in such a way that four different
structural configurations could be investigated experimentally. Therefore, the behaviour of
various parameters like the types of mechanical connections (traditional as well as
innovative) and the presence or absence of shear walls along with the framed structure were
investigated. The first PsD tests were conducted on a dual frame-wall precast system, where
two precast shear wall units were connected to the mock up. The first test structure sustained
the maximum earthquake for which it had been designed with small horizontal deformations.
In the second layout, the shear walls were disconnected from the structure, to test the building
in its most typical configuration, namely with hinged beam-column connections by means of
dowel bars (shear connectors). This configuration was quite flexible and suffered large
deformations under the design level earthquake. An innovative connection system, embedded
in the precast elements, was then activated to create emulative beam-column connections in
the last two structural configurations. In particular, in the third layout the connectors were
restrained only at the top floor, whereas in the fourth layout the connection system was
activated in all beam-column joints. The PsD test results showed that, when activated at all
the floors, the proposed connection system is quite effective as a means of implementing dry
precast (quasi) emulative moment-resisting frames.
Session 6 – SERIES TA to Shaking Table Facilities on wood structures / Experimental Facilities
47
EXPERIMENTAL EARTHQUAKE ENGINEERING RESEARCH IN LNEC
CONTRIBUTION TO GLOBAL SEISMIC PERFORMANCE ASSESSMENT OF
STRUCTURES
E. Coelho, A. Campos Costa, P. Candeias, L. Mendes, A. Correia
Laboratório Nacional de Engenharia Civil (LNEC), Portugal
LNEC has a long experience in all fields of earthquake engineering and has been one of the
main European institutions developing research & technology activities in several topics of
this engineering science, such as seismic testing, structural monitoring, hazard analysis and
risk assessment, numerical modelling, development of codes and consultancy.
In the experimental field, LNEC holds a facility of excellence at European level for
earthquake engineering research. Apart from the incorporation of significant material
resources resulting from the dimension of the facility, an interdisciplinary team is responsible
for the assessment of experimental programs, integrating specialists in all fields of earthquake
engineering. This allows the use of more appropriate approaches in seismic testing within a
comprehensive framework for seismic performance assessment. The experimental facility
operates since 1996 and, due to its characteristics, has been from the beginning included in
the European group of large-scale facilities in earthquake engineering, within the “Training
and Mobility of Researchers programme” of the European commission (4th
FP), later
continued through European consortia for earthquake and dynamic experimental research
within “Improving Human Potential programme” (5th
FP). Presently the LNEC facility holds
one of the four largest European shake tables and integrates the strong European 23-
consortium SERIES, “Seismic engineering research infrastructures for European Synergies”
of the 7th
Framework Programme, as one of the European world class research
complementary infrastructures providing access to external research groups. Therefore, a
significant portion of the experimental work carried out at LNEC results from the fruitful
links established with European institutions.
Apart from European collaborations and the 16-year important European funding, several
studies with national funding have been developed at the LNEC experimental facility for
seismic testing, in collaboration with Portuguese research institutions. Additionally several
shake table tests have been performed in cooperation with the Portuguese industry, both to
study the adequacy of the seismic behaviour of specific types of precast reinforced concrete
construction systems for use in substations, and to investigate the behaviour of electrical and
mechanical equipment subjected to dynamic ground input motions.
LNEC has also been actively involved in the continued development and implementation of
experiments dealing with identification and dynamic characterization of structures, in the
framework of consultancy studies for the seismic assessment of existing structures. While
describing the significant legacy of LNEC in the fields of seismic testing and global seismic
performance approaches, particular relevance is given to the participation and main outcomes
of the SERIES‟ transnational access, networking and joint research activities. Finally, some
ambitious plans on future directions for seismic research and testing at LNEC are outlined.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
48
Analytical and Experimental work on soil structure
interaction, wave propagation and field testing
including SERIES Transnational Access to
Shaking Table Facilities
Session 7
Thursday, 30 May 2013
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
49
LARGE-SCALE LABORATORY EXPERIMENTS OF LANDSLIDE GENERATED
TSUNAMIS IN THE NEES TSUNAMI WAVE BASIN HALF A CENTURY AFTER
THE VAJONT DAM DISASTER
Hermann M. Fritz, Brian C. McFall, and Fahad Mohammed
Georgia Institute of Technology, USA
The 50th
anniversary of the Vajont disaster highlights an extreme landslide tsunami in a
narrowly confined reservoir behind a 265.5 m high double curved arch dam. A maximum
water depth of 250 m was reached by early September 1963 during the third filling attempt of
the reservoir, but as creeping on the southern flank increased a third reservoir draw down was
initiated. By October 9, 1963 the water depth was lowered to 240 m as the southern flank of
Vajont reservoir catastrophically collapsed on a length of more than 2 km. The lateral
spreading of the surge overtopped the dam crest and sent a flood wave into the Piave Valley
resulting in 2000 fatalities. The wave runup in direct prolongation of slide axis reached the
lowest houses of Casso 270 m above reservoir level before impact corresponding to the
second largest tsunami runup in recorded history behind only the 1958 Lituya Bay, Alaska
landslide tsunami with 524 m runup.
Landslide tsunami hazards exist even in areas not exposed to tectonic tsunamis. Source and
runup scenarios based on real world events are physically modeled in the three dimensional
tsunami wave basin (TWB) of the Network for Earthquake Engineering Simulation (NEES)
at Oregon State University (OSU). A novel pneumatic landslide tsunami generator (LTG)
was deployed to simulate landslides with varying geometry and kinematics. The LTG
consists of a sliding box filled with up to 1,350 kg of naturally rounded river gravel which is
accelerated by means of four pneumatic pistons down the 2H: 1V slope, launching the
granular landslide towards the water at velocities of up to 5 m/s. Topographical and
bathymetric features can greatly affect wave characteristics and runup heights. Landslide
tsunamis are studied in different topographic and bathymetric configurations: far field
propagation and runup, a narrow fjord and curved headland configurations, and a conical
island setting representing landslides off an island or a volcanic flank collapse. Water surface
elevations were measured using an array of resistance wave gauges. The granulate landslide
shape and front velocity were measured using above and underwater cameras. Three-
dimensional landslide surfaces with surface velocities were reconstruction using a stereo
particle image velocimetry (PIV) setup. The speckled pattern on the surface of the granular
landslide allows for cross-correlation based PIV analysis. Wave runup was measured with
resistance wave gauges along the slope and verified with video image processing. The
measured landslide and tsunami data serve to validate and advance 3-dimensional numerical
landslide tsunami and prediction models.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
50
CAISSON FOUNDATIONS SUBJECTED TO SEISMIC FAULTING:
REDUCED-SCALE PHYSICAL MODELLING
I. Anastasopoulos, O. Zarzouras, T. Georgarakos, V. Drossos, and G. Gazetas
National Technical University of Athens, Greece
As part of the SERIES project, the Laboratory of Soil Mechanics of the National Technical
University of Athens conducted a series of physical model tests to investigate fault rupture
propagation through sand and its interaction with embedded caisson foundations. Besides
from being typical for bridge structures, the choice of embedded caisson foundations offers
the possibility of observing strongly nonlinear phenomena, such as the diversion and
bifurcation of the fault rupture path. A series of reduced-scale experiments were conducted,
investigating: (a) the style of dip-slip faulting (normal or reverse), and (b) the position of the
foundation relative to the fault rupture. The “bedrock” is subjected to movement due to fault
rupture of vertical offset h at a dip angle α = 45o. The displacements of the foundation, Δx,
Δz, and the rotation θ, as well as the deformation of the soil mass were recorded during the
experiments through image analysis and laser scanning of the soil surface. In the first case,
high-resolution digital cameras were utilized to capture images of the deformed soil during
the test, which were processed through image analysis software. In the latter case, a novel
technique was developed and applied through a custom system, designed and constructed in-
house. After each displacement increment, the ground surface was scanned with 8 laser
displacement transducers, travelling along the specimen at a constant speed, producing a
digital relief of the deformed surface. It is shown that the foundation acts as a kinematic
constraint, altering substantially fault rupture path. The horizontal and vertical movement and
the rotation of the caisson are a function of its position relative to the fault rupture.
Depending on the latter, a variety of interesting interaction mechanisms develop, such as
bifurcation of the rupture path and diffusion of plastic deformation. The conducted
experiments are in good qualitative agreement with similar centrifuge model tests, confirming
the validity of the experimental procedure, and enriching the experimental dataset on this
important research topic.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
51
EFFECT OF SOIL STRUCTURE INTERACTION ON HIGHER MODES
PARTICIPATION
Seyed Abolfazl Mirfattah1, Seyed Kazem Mirfattah
2
1UME School, IUSS Pavia, Italy 2Azad University of Yazd, Iran
Higher modes effects have been usually a concern in designing structures against earthquake
actions since they can alter the internal forces and location of plastic hinges. On the other
hand soil structure interaction (SSI) affects the modal properties of the system. In this study
the effect of SSI on modal participation factor and modal properties of a simple multi degree
of freedom system is investigated. In order to simulate soil structure interaction a direct
method is used and a rigorous finite element model of soil half space is presented. The role of
SSI on amplification or attenuation of higher modes motions is examined. The results show a
dramatic change in the participation of higher modes due to soil, foundation and structure
interaction.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
52
ESTIMATION OF SOIL STRUCTURE INTERACTION EFFECTS, CONSIDERING
THE FREQUENCY CONTENT OF THE MOTION
Seyed Hosein Mirfattah, Seyed Ali Mirfattah
JAHAD NASR Consultant Engineering Group, Yazd, Iran
In substructure method used in soil-structure interaction (SSI) analysis, interaction between
soil and foundation is modeled via spring and dashpot elements. Mechanical properties of
these elements depend on soil characteristics, foundation properties and also frequency of
motion. Therefore the response of the whole system is also frequency dependant. In this study
a number of structures are considered as simplified lumped mass SDOF systems and
equivalent spring and dashpot properties are calculated according to foundation impedance
by program DYNA. Circular foundations on soft soil (ground type D) are considered. Then
sensitivity of SSI effects on the response, to excitation frequencies in form of harmonic
motions and real ground motions are studied. Results show when the excitation frequency is
below a certain threshold, dramatic increase in maximum drift in short period systems and
considerable even in long period ones is observed this threshold is fundamental natural
frequency of the whole SSI system.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
53
DEVELOPMENT OF NEW INFINITE ELEMENT FOR NUMERICAL
SIMULATION OF WAVE PROPAGATION IN SOIL MEDIA
Vlatko Sesov, Kemal Edip and Julijana Cvetanovska
IZIIS, University Ss. Cyril and Methodius, R. Macedonia
Numerical simulation of geo-dynamical problems such as propagation of waves in soil media
still pretends to be huge challenge for geotechnical research community. Modeling of soil
geometry as unbounded space have been subject of investigation by many researchers
[Bettess, 1980; Marques and Owen, 1984; Akiyoshi 1998; Pastor 1999]. In simulating
unbounded domains, infinite elements are very useful tool to describe the far field behavior,
whereas the near field is described through conventional finite elements. The spatial
discretization of the far domain is considered using the infinite elements.
This paper presents work that has been done on developing the new infinite element which
can be applied on saturated media subjected to dynamic loading. The basic idea consists of
mapping an infinite region into a finite one. This technique needs appropriate mapping
functions by which a domain, unbounded in one direction, is transformed into a bounded one.
These mapping functions are obtained as a product of standard shape functions for finite
direction and special mapping functions for the infinite direction. The simulation of wave
propagation into infinity is realized in the time domain. However, in dynamical applications,
some additional effects must be taken into account. In fact, when body waves approach the
interface between the FE and the IE domains, they partially reflect back to the near field as
the quasi-static infinite elements cannot capture the dynamic wave pattern in the far field. To
overcome this, the waves are absorbed by adding a layer of viscous damping which basically
belongs to the absorbing boundaries class. The idea of adding a layer of viscous damping
originates from the work by Lysmer and Kuhlemeyer [1969], in which velocity and
parameter dependent damping forces are introduced to get rid of artificial wave reflections.
Newly infinite element of five nodes has been developed and implemented in ANSYS, using
the user programmable features, UPF. An absorbing layer has been added to the infinite
element by considering the wave velocities in the damping matrix. The matrices
corresponding to the mapped infinite elements is very similar to the one used for the standard
finite elements. The only adjustment concerns the existence of mapping functions different
from the shape functions.
Results from performed analytical investigation on one dimensional wave propagation
problems using Heaviside step function and impulse functions and two dimensional wave
propagation in a circular quarter space emphasized some of the key issues regarding the soil
behavior during the wave propagation.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
54
DESIGN AND CONSTRUCTION OF LAMINAR CONTAINER
FOR 1-G SHAKING TABLE TESTS
Vlatko Sesov, Julijana Cvetanovska, Kemal Edip and Zoran Rakicevic
IZIIS, University Ss. Cyril and Methodius, R. Macedonia
Investigation in the field of earthquake geotechnical engineering involve different
methodologies and approaches such as dynamic soil element tests, reduced scaled models,
numerical and analytical models and full scaled field tests. If done properly, scaled model
tests can be advantageous for seismic studies due to their ability to give more realistic
information about ground acceleration amplification, variation of pore pressures in the soil
medium, nonlinear behavior of soil, occurrence of failure, and soil structure interaction
phenomena.
This paper describes the process in design, fabrication and commissioning of a laminar shear
box for use in seismic geotechnical studies. A laminar box is a container which allows
„friction-free‟ horizontal movement of soil model and it is placed on a shaking table platform
to simulate wave propagation during earthquakes through a soil layer of finite thickness. The
laminar box described in this paper is built with dimensions 2 x 1 m (plan view) and 1.5 m in
height. It is designed to be used for shaking table tests on wide range of geotechnical
problems. The numerical analysis and preliminary calculations have been conducted to study
the performance of the laminar box in order to fulfill the design criteria are also taken into
consideration. Important aspects for the experimental setup of liquefaction studies,
characterization of investigated sand, model preparation, and soil properties are pointed out.
Special type of „contact-elements‟ are installed between laminar rings which significantly
improve the free deformability of ground model subjected to seismic loading. Amplification,
liquefaction and cyclic mobility phenomenon, excess pore water pressure generation and
dissipation rates, and further soil-structure interaction investigations can be performed using
such experimental tool. Intensive shaking table testing at the Geotechnical Laboratory in
IZIIS are performing in order to verify the technical characteristics of the laminar box. The
construction of such laminar box is expected to improve the research capabilities of European
research area (ERA) in the field of earthquake geotechnical engineering.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
55
ANALYSIS OF THE DYNAMIC BEHAVIOR OF SQUAT SILOS CONTAINING
GRAIN-LIKE MATERIAL SUBJECTED TO SHAKING TABLE TESTS
Dora Foti1, Salvador Ivorra
2, Tomaso Trombetti
3, Stefano Silvestri
3, Giada Gasparini
3
1Technical University of Bari (Italy)
2University of Alicante (Spain) 3University of Bologna (Italy)
This paper reports the outcomes of a series of shaking table tests performed at EQUALS lab
of Bristol University in the framework of SERIES project. The experimental test campaign
was devoted to the evaluation of the effective behaviour of grain in flat-bottom silos full of
grain during an earthquake. This research work starts from all the same basic assumptions of
Eurocode 8 except for the one regarding the horizontal shear forces among consecutive
grains. Only this difference leads to a new physically-based evaluation of the effective mass
of the grain, which horizontally pushes on the silo walls. The analyses are developed by
simulating the earthquake ground motion with time constant vertical and horizontal
accelerations and are carried out by means of simple dynamic equilibrium equations that take
into consideration the specific mutual actions developing in the ensiled grain. The findings
indicate that, in case of squat silos (characterized by low, but usual, height/diameter
slenderness ratios), the portion of the grain mass that interacts with the silo walls turns out to
be noticeably lower than the total mass of the grain in the silo and the effective mass adopted
by Eurocode 8.
Two series of tests have been performed with two different heights of the ensiled material to
simulate a silo more or less squat silo. The ensiled material has been modeled with ballotini
glass. In the paper, the silo model for the first and second test is presented, and then the
dynamic behavior of the structure is described with reference to the two series of shaking
table tests. The results indicate that, in the case of squat silos the portion of grain mass that
interacts with the silo walls turns out to be noticeably lower than the total mass of the grain in
the silo.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
56
STUDY OF MULTI-BUILDING INTERACTIONS AND SITE-CITY EFFECT
THROUGH AN IDEALIZED EXPERIMENTAL MODEL
Logan Schwan1, Claude Boutin
1, Matt Dietz
2, Luis A. Padron
3, Pierre-Yves Bard
4, Silvia
Castellaro5, Erdin Ibraim
2, Orlando Maeso
3, Juan J. Aznárez
3, Colin Taylor
2
1University of Lyon, France;
2University of Bristol, UK
3Universidad de Las Palmas de Gran Canaria, Spain
4ISTerre / IFSTTAR, University of Grenoble, France
5University of Bologna, Italy
Seismic risk may be a strong concern for cities as they concentrate population, real estate
and/or strategic public services. The common earthquake engineering practice does usually
consider the substratum, but disregards the resonant „surstratum‟ made up by the city itself.
However numerical and analytical models suggest that global soil-structure interactions, i.e.
Site-City effect, can occur and be significant, especially when the fundamental frequencies of
the soil and of the heaviest buildings coincide.
The aim of the present SERIES-SMISCE study is to investigate experimentally this
phenomenon and to compare the resulting data with two models. In the theoretical model
derived by homogenization [Boutin et al. (2006)], the city is shown to act as a frequency-
dependent analytical surface impedance. The numerical model consists in a 2D, hybrid BEM-
FEM approach that describes the layer by boundary elements and the structures by finite
elements. Experimentally, the site-city interaction is studied through an idealized specimen.
A polyurethane foam block with metric dimensions stands for the soil layer and 37 parallel
vertical aluminium sheets stand for the buildings. The buildings can bend and resonate with
out-of-plane excitation, but remain quasi-static with in-plane excitation. It enables to point
out the differences between resonant and inert masses. The specimen is designed to provide a
good matching between the fundamental frequencies of the foam block and of the aluminium
resonators. The whole is attached to the shaking table of Earthquake and Large Structures
Laboratory (EQUALS), and excited with a series of signals.
While excited in the non-resonant direction, the system acts classically as a layer with added
inert mass on the top surface. While excited in the resonant direction, global interactions (i)
split the resonance peak into two peaks that favours beatings; (ii) reduce significantly both
surface and the resonators‟ motions at their common fundamental frequency; (iii) decrease
the amplitude of the resonance peaks; (iv) induce longer signals with slower decreasing
codas. Another unconventional phenomenon is a depolarization effect. These specific
features have been recovered by both analytical and numerical models giving (i) a qualitative
and quantitative agreement with experimental results and (ii) a quasi-perfect agreement with
one another.
Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing
57
EUROPROTEAS: A FULL-SCALE EXPERIMENTAL FACILITY FOR
SOIL-FOUNDATION-STRUCTURE INTERACTION STUDIES
Dimitris Pitilakis1, Emmanuil Rovithis
2, Anastasios Anastasiadis
1,
Kyriazis Pitilakis1
1Aristotle University Thessaloniki
2Institute of Engineering Seismology & Earthquake Engineering (ITSAK), Greece
We present the experimental campaign to study soil-foundation-structure interaction and
wave propagation in soil media due to structural oscillation that took place in the
experimental facility of Euroseistest in Greece. The tests series were performed in the
framework of the on-going European project “Seismic Engineering Research Infrastructures
for European Synergies, SERIES” by means of a real-scale simplified model structure, called
EuroProteas, built in Euroseistest site. A particularly stiff structure founded on soft soil was
designed to mobilize soil-foundation-structure interaction effects. The structure‟s outer
dimensions are 3x3x5m having reconfigurable mass and stiffness properties. Two distinct
reinforced concrete slabs of 9t mass each form the superstructure mass, whereas a similar
R/C slab is employed as the surface foundation of the structure. Superstructure loads are
transferred to the foundation soil though four steel columns, interconnected in all four sides
with removable steel bracing system. Provisions for mounting an eccentric mass vibrator
were made on both the foundation and the roof slab. Provisions were also made for pull-out
experiments by a wire rope securely connected to the roof slab. Two boreholes (one at the
geometrical center of the surface foundation slab and one at 0.5m away from the foundation
side) and two trenches in two perpendicular directions allow for dense instrumentation for the
response recording.
In the framework of SERIES, six experimental campaigns took place: three pull-out (free-
vibration) and three forced-vibration sets of tests. Pull-out was performed with a 1t
counterweight and the total pull-out force exceeded 15kN. Forced-vibration tests were
performed using an eccentric mass vibrator, with sine sweeps in the range between 1Hz and
10Hz, and total force exceeding 20kN. The vibrator was placed both on the foundation and
the top of the structure.
Soil and structural response under free and forced vibration was recorded in a dense 3D array
of more than 60 recording devices (accelerometers, seismometers, shape acceleration arrays).
Instrumentation in the soil covered a volume of 9x9x12m around and beneath the foundation.
In this paper we present the recorded response from selected tests, highlighting soil-
foundation-structure effects in the structure and in the soil. We also present some preliminary
comparisons between the recorded response and numerical 2D and 3D simulations of the
experiments.
Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility
58
Analytical and Experimental Techniques / SERIES
Transnational Access to Reaction Wall Facility
Session 8
Thursday, 30 May 2013
Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility
59
IN-SITU SEISMIC PERFORMANCE TESTS OF A SCOURED BRIDGE
Kuo-Chun CHANG
National Center for Research on Earthquake Engineering, Taiwan
This paper presents a series of in-situ seismic performance tests of a bridge before its
demolition due to accumulated souring-induced problem. The tested bridge has two identical
parallel lanes, while right lane was constructed in 1961 with pier walls, and left lane in 1995
with circular columns, respectively. Each lane consists of seven 38 m-long simply-supported
PC I-girders. The experiment program includes three cyclical loading tests and one pseudo-
dynamic test. As a strong reaction wall system, the pier wall and two supplemental steel A-
shape frames were integrated to employ two hydraulic oil jacks, so as to apply lateral force
on the column and push column to the target displacements. The column is 180cm in
diameter and 1030cm in height, reinforced with 30-D32 longitudinal reinforcing bars and
transversely reinforced with D16 perimeter hoops spaced 20 cm apart. P3 column represents
a benchmark specimen with no scouring, while P4 is exposed up to 33 percent of the length
of the caisson foundation. Similar to P3 fixed on the ground, P2 is subjected to a code-
compatible ground acceleration of 0.32g first and then followed by a pushover test. Though
given two different exposed length of caisson foundation, it is due to gravel material of
ground, which is similar to a fixed-base condition, that each column behaved ductile and
achieved maximum lateral force of 1000kN at 5% drift ratio with buckling of longitudinal
reinforcements and separation of lateral reinforcements. However, the axial load verified by
the system identification showed a relative small value about 0.05 f'cAg, as a result to explain
why the failure of bridge column was flexural-dominate, even the design details didn't
satisfied with the current seismic design detail requirements.
Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility
60
VALIDATION OF A VISUAL DEFORMATION MEASUREMENT SYSTEM
Binbir E., Demir C., Ispir M., Ilki A.
Istanbul Technical University, Turkey
The pilot studies on visual deformation measurement systems at Structural and Earthquake
Engineering Laboratory of Istanbul Technical University (ITU) dates back to 2002. At that
time visual measurements were made with the support of geomatics department of Civil
Engineering Faculty of ITU.
Usage of conventional measuring devices to obtain deformations has some drawbacks such
as; a) deformations over a small part of test specimen can be measured, b) installation of
measuring devices may take notable time, c) during the installation of the devices, specimens
can be damaged due to various attachments, d) for data acquisition, a data logger is generally
required, e) the measurement devices may be out of order during the test, due to the excessive
damage of the specimen, f) due to the nature of the applied load and/or the characteristics of
specimens, the specimen can fail suddenly causing damage of the measurement devices.
Considering these drawbacks, a visual deformation measurement system is developed at the
Structural and Earthquake Engineering Laboratory of ITU within Series Project. The visual
measurement system consists of hardware and software components. Hardware components
include high-resolution camera, lens, metric calibration plate, and I/O card (USB). Software
component includes a graphic interface for measurement preparation and related modules and
measurement/reporting modules. The capability of the visual system is limited from several
aspects. The displacements can be tracked in 2D. The system is calibrated for two camera-to-
specimen distances (1.5 and 2.5 m) and operates with a precision less than 0.1 mm.
In order to validate the displacement measurements of the visual system, the measurements
obtained using this system are compared with the measurements of the conventional
displacement transducers. The validation study is conducted using the deformation data
obtained from the tests of the short columns confined with FRP sheets. This comparison
showed that the visual system measurements are in good agreement with the conventional
measurements.
Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility
61
DEVELOPMENT OF WIRELESS SENSORS FOR SHAKE TABLE AND FULL
SCALE TESTING AND HEALTH MONITORING OF STRUCTURES
Zoran T. Rakicevic, Igor Markovski, Dejan Filipovski, Slobodan Micajkov,
Mihail Garevski
IZIIS-SS “Cyril and Methodius” University, R. Macedonia
The application of wireless technology to testing and monitoring of civil structures has been
gaining considerable interest over the past decade or two.
Wireless sensors are not sensors by themselves, but rather are autonomous data acquisition
nodes to which traditional structural sensors (e.g. accelerometers) can be attached. Wireless
sensors are best viewed as a platform in which mobile computing and wireless
communication elements converge with the sensing transducer. With wireless sensors rapidly
evolving in multiple engineering disciplines, there currently exist a large number of different
academic and commercial wireless sensor platforms.
At IZIIS, within the framework of the SERIES project, two types of wireless sensors have
been developed. The first one MIMRACS (Micro Integrated Measuring, Recording And
Communication System) sensor presents an intelligent self-controlled high integrated
GPS/GPRS/WEB based micro processing digital 3D measurement device, with a possibility
for power independence appropriate for measuring, storing and transferring data with an
exact time of their appearance.
given. It has 3 MEMS Model 3028 piezoresistive accelerometers, one for each orthogonal
axis, microprocessor, 24-bit A/D converter, programmable amplifiers, programmable trigger
(x+y+z), inclinometer, gyroscope, GPS/GPRS/GSM modules, Flash memory, USB
communication and power supply.
The other type is developed on the similar platform as MIMRACS, with a difference that it is
more compact and lighter, has one MEMS Model 3028 piezoresistive accelerometer and uses
a ZigBee module and protocol for wireless communication.
Both developed sensors are suitable for laboratory testing (shake table testing) and full scale
measurements (ambient and force vibration) of structures, as well as health monitoring of
structures. The MIMRACS sensor can, also, be used as standalone seismic station in a
network for monitoring and recording of strong motion data.
Both sensors have been tested in laboratory condition by shake table - standalone testing and
testing on models, while recorded signals are compared to traditional wired accelerometers.
The comparison results showed very good correlation.
In this paper, both developed wireless sensors will be presented in detail, their hardware and
software, as well as comparison results from various conducted tests.
A short review of the world‟s wireless sensor development will also be given.
Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility
62
RECENT ADVANCES IN SEISMIC DESIGN OF RC TALL BUILDINGS USING
ULTRA-HIGH-STRENGTH MATERIALS IN TAIWAN
Shyh-Jiann Hwang
National Taiwan University
Metropolis renewal is an urgent need for Taiwan due to its high population density in urban
areas. Constructing the high-rise residential buildings has become a necessity for urban
renewal. The use of ultra-high-strength materials for the high-rise RC buildings can provide a
rational solution for this demand. However, the seismic attacks do pose a serious thread for
these high-rise RC buildings. Japan had launched the New RC Project since 1988. Recently, a
59-story RC building had been successfully constructed in Japan. This clearly indicates that
Japan had established a good technology of the high-rise RC buildings for Taiwan to follow
and to start its own. Since 2008, Taiwan started its research programs on the seismic design
of RC buildings using ultra-high-strength materials. This speech reviews existing research on
RC structures using ultra-high-strength materials in Taiwan to identify findings that may be
immediately useful to the structural engineers in government and private practice who are
working on high-rise RC building.
Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility
63
REFINED AND SIMPLIFIED NUMERICAL MODELS OF AN ISOLATED OLD
HIGHWAY BRIDGE FOR PSD TESTS
F.Paolacci1, S.Alessandri
1, A. Mohamad
1, D. Corritore
1, R. Derisi
2
1University Roma Tre, Rome, Italy
2University of Naples, Naples, Italy
RETRO project aims at studying the seismic behaviour of existing R.C. bridges and the
effectiveness of innovative retrofitting systems. The research program focuses on old bridges,
not properly designed for seismic action. In particular the seismic vulnerability of an old-
Italian viaduct with portal frame piers will be evaluated. A proper isolation system will be
designed using Slide Spherical Bearings. On the basis of a previous experimental campaign
consisted of cyclically imposed displacements on 1:4 reduced scale models of a reinforced
concrete portal frame pier, belonging to a typical old highway viaduct, a new experimental
activity has been proposed.
In particular, two specimens (scale 1:2.5), 2-floors and 3-floors one-bay reinforced concrete
frame respectively, will be realized and tested using the PsD technique with sub-structuring,
including the modeling of the entire viaduct. During the test, different configurations will be
considered including retrofitted viaduct using Spherical Sliding Bearings and “as-built”
viaduct.
The aim of the proposed experimental activity is: (i) Increasing the knowledge on the non-
linear behaviour of portal frame piers in presence of plain steel bars on which few studies are
realized; (ii) Employment of large-scale experimental test for the seismic assessment of
existing bridges; (iii) Study of the effectiveness of traditional and innovative seismic isolation
systems (FP isolators).
In this paper the non-linear response of the viaduct in “as-built” and “isolated” configurations
are analyzed through a non-linear model developed using the "NL platform OpenSees". The
response of a refined model that takes into account the main non-linear phenomena of the
viaduct (strain penetration of plain bars, shear deformation of transverse beams, flexural
deformations of columns and beams) is analyzed. The aim of the simulations is to evaluate
the seismic response of the entire bridges. In addition the effectiveness of the adopted
isolation systems is analyzed and discussed. The results are used to simulate the seismic
response of the viaduct in the isolated configuration.
The response is carried out using two accelerograms, as in PsD test campaign. Two signals
recorded during the Emilia earthquake in 2012 have been adopted; one for slight damage
condition and the other for Ultimate limit state condition. Because of the complexity of the
refined model, a simplified model is also proposed. It is composed of an elastic beam (the
deck) connected to non-linear springs, which are calibrated using the non-linear cyclic
response of each pier. A comparison between refined and simplified models is shown and
some conclusions on the usability of the simplified one are carried out.
Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility
64
FULL-SCALE EXPERIMENTAL VALIDATION OF DUAL ECCENTRICALLY
BRACED FRAME WITH REMOVABLE LINKS
(TA PROJECT: DUAREM)
Aurel Stratan1, Dan Dubina
1, Adriana Ioan
1, Fabio Taucer
2, Martin Poljansek
2
1“Politehnica” University of Timisoara, Romania
2JRC, Italy
Conventional seismic design philosophy is based on dissipative structural response, which
implicitly accepts damage of the structure under the design earthquake and leads to
significant economic losses. Repair of the structure is often impeded by the permanent
(residual) drifts of the structure. The repair costs and downtime of a structure hit by an
earthquake can be significantly reduced by adopting removable dissipative members and
providing the structure with re-centring capability. These two concepts were implemented in
a dual structure, obtained by combining steel eccentrically braced frames (with removable
bolted links) and moment resisting frames. The bolted links provide the energy dissipation
capacity and are easily replaceable, while the more flexible moment resisting frames provide
the necessary re-centring capability. The solution will be validated by full-scale pseudo-
dynamic test of a three-storey model of a steel structure with re-centring capability at the
European Laboratory for Structural Assessment (ELSA) at the Joint Research Centre in Ispra
within the framework of Transnational Access of the SERIES Project financed by the
European Commission.
The general set-up of the experimental mock-up, instrumentation, and the test sequence are
described. Pre-test numerical simulations were performed in order to assess the response of
the structure under different levels of the seismic input, as well as to establish the optimal
sequence of link removal and replacement. Moreover, due to concerns about the safety of
link removal through oxy-fuel cutting as results of sudden release of forces, a set of dampers
was installed with a temporary bracing system. Numerical simulations were used to provide
the optimal damper properties that would prevent vibrations in the worst scenario of sudden
release of forces during link removal.