Educational Linkage Approach In Cultural Heritage Prof. Mustafa Erdik – BU – Bogazici University...

Educational Linkage Approach In Cultural Heritage

Prof. Mustafa Erdik – BU – Bogazici University of IstanbulProf. Mustafa Erdik – BU – Bogazici University of Istanbul

Educational Educational ToolkitToolkit

Knowing the built heritage

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22Basic Basic CourCourssee

Teaching Material Teaching Material

TopicTopic 22..7.7.11

Earthquake response of historical structures


Copyright ©ELAICH Beneficiaries 2009-2012This material is an integral part of the “ELAICH – educational toolkit” and developed as part of the project ELAICH – Educational Linkage Approach in Cultural Heritage within the framework of EuroMed Cultural Heritage 4 Programme under grant agreement ENPI 150583. All rights reserved to the ELAICH Beneficiaries. This material, in its entirety only, may be used in "fair use" only as part of the ELAICH – educational toolkit for the educational purposes by non-profit educational establishments or in self-education, by any means at all times and on any downloads, copies and or, adaptations, clearly indicating “©ELAICH Beneficiaries 2009-2011” and making reference to these terms. Use of the material amounting to a distortion or mutilation of the material or is otherwise prejudicial to the honor or reputation of ELAICH Beneficiaries 2009-2011 is forbidden. Use of parts of the material is strictly forbidden. No part of this material may be: (1) used other than intended (2) copied, reproduced or distributed in any physical or electronic form (3) reproduced in any publication of any kind (4) used as part of any other teaching material in any framework; unless prior written permission of the ELAICH Beneficiaries has been obtained.

DisclaimerThis document has been produced with the financial assistance of the European Union. The contents of this document are the sole responsibility of the ELAICH Consortium and can under no circumstances be regarded as reflecting the position of the European Union.



Abstract The current presentation examines the basic steps in studying the earthquake response of historical structures. Initially, an empirical assessment of structural performance is accomplished followed by and analytical assessment. In order to improve the earthquake performance of historic structures, stabilization and retorfit are typically implemented. The next step is to install a structural strong motion network which will provide data for the dynamic response of the real historic structure. These data, after they are analyzed and interpreted, provide the basis for the comparison of data obtained by testing models of the structure on shake table.

The above five steps form an integrated methodology for studying the earthquake response of historic structures.


Content


Table of contents of this presentation Methodology for the Investigation of Earthquake Response of Historical

Structures Vibration surveys Finite Element Modeling Basic Properties of Materials Used in Numerical Modeling Stabilization and Retrofit (Improvement of Earthquake Performance) Monitoring the structure Dynamic response of Hagia Sophia Modeling the dynamic response of a real structure



Prof. Mustafa Erdik– Topic 2.7.1: Earthquake response of historical structures

1. Empirical Assessment of Structural Performance

2. Analytical Assessment of Structural Performance

3. Stabilization and Retrofit (Improvement of Earthquake Performance)

4. Use of Structural Strong Motion Networks: Data, Analysis, Interpretation

5. Shake Table Testing of Models

Methodology for the Investigation of Earthquake Response of Historical Structures


Ambient vibration Ambient Vibration testing is an important element of structural studies of complex systems. The results provide clues about the linear dynamic characteristics of the structure, which in turn help to calibrate the numerical structural models.Low amplitude vibrations emanating from daily-life sources such as traffic, human noise, wind etc. are measured by sensitive sensors. The testing system usually consists of an array of interconnected seismometers, which are placed in such a way throughout a building, to give the optimum information for its dynamic structural response. Laser displacement measuring systems also exist.

Forced vibration Testing is based on assessing the dynamic properties of a building by producing man-made vibrations. The source of vibration is usually a unit with a rotating mass that is mounted on the top of a structure during testing

Vibration Surveys



Hagia Sophia Ambient Vibration Survey



Full Finite Element Model of Hagia Sophia

Finite Element Modeling

Finite Element Modeling (FEM) allows the study of the behavior of the monument under various dynamic and static loading scenarios.

FEM describes the building with a network of nodes and bars that correspond to the architecture of the structure



General Isometric View of Hagia Sophia Finite Element Model

X Y

Z

GENERAL 3-DIMENSIONAL VIEW WITH SHADING (FROM SOUTH-EAST)

Position Type of Element Shape of Element

Piers, arches, pendantives Solid Hexa/Pentahedral Small and semi-domes Shell Quadrilateral /Triangular

Columns, beams Linear Frame Total number of elements 4000

Total number of nodes 7000

Finite Element Modeling



Various Views of FEM of Hagia Sophia

XY

Z

X Y

Z

X

Y

Z XYZ

VIEW FROM EAST VIEW FROM NORTH

VIEW FROM TOP3D-VIEW FROMSOUTH-WEST



Position of material types Modulus of

elasticity (kPa) Poisson Ratio

Mass (t/m3)

Thickness (m)

Main buttress (inner-outer piers) 8500000 0.20 2.0

Small piers 9000000 0.18 1.8

North-south arches 3000000 0.20 1.7

East-west arches (small) 4000000 0.18 1.8

Pandantives 3000000 0.16 1.7

Main dome 3000000 0.20 1.8

East-west small domes 3000000 0.18 1.8 0.375

East-west semi-domes 3000000 0.18 1.8 0.70

Mihrap dome 3000000 0.18 1.8 0.50

Windows under the N and S arches 3000000 0.11 1.75 0.80

Beams and columns 10000000 0.20 2.0

Basic Properties of Materials Used in Numerical Modeling of Hagia Sophia



MATERIAL ASSIGNMENTS

1

2

3

4

5

6

7

8

9

stone (E=10m)

stone (E=10m)

br-mortar(E= 2m)

br-mortar(E= 1m)

br-mortar(E= 3m)

br-mortar(E= 2m)

br-mortar(E= 3m)

br-mortar(E= 3m)

br-mortar(E= 2m)

E=ELASTICITY MODULUS

UNIT=(MILION kN/m2)

DIFFERENT MATERIAL PROPERTIESSHOWN BY DIFFERENT COLOURS

Basic Properties of Materials Used in Numerical Modeling of Hagia Sophia



In interventions the priority should be given to retrofit schemes that conform to the original construction techniques and materials. In new or innovative techniques, their compatibility, durability and reversibility need to be ensured prior to their adoption.

There should be compliance between the engineering and the architectural approach for the retrofitting/repair techniques.

The protection of historical buildings from earthquakes and other natural causes should follow the principles of Carta di Veneza (1964), where the rules of engagement for structural intervention has been defined order to keep the authentic value of the edifice.

Damage in historical structures can result from external loading (earthquakes, settlements), removal and/or change of structural elements or simply by the decay of material properties.

Stabilization and Retrofit (Improvement of Earthquake Performance)



Earthquakes can cause direct damage and amplify existing damage from past earthquakes and settlements.

Remedial and retrofit measures for earthquake action should ensure continuity of structural elements within the structure and improvement

of structural performance (seismic capacity)

Strengthening the material (grout or epoxy injections)Strengthening structural elements (jacketing of columns, steel braces, post tensioning, abutments, buttresses etc)Strengthening of the whole structure (i.e. addition of ring elements and chains around the building, improving connection between walls and floors)

The retrofit techniques should be selected on the basis structural engineering and material sciences supported by historical analysis. Any intervention should be

reversible and as little intrusive as possible.




Most of the damage to masonry structures is caused by lateral loads (i.e. earthquakes) especially for tall edifices with vaults and arches.

Vertical loads causing stresses comparable to the compressive strength of the masonry can create vertical cracks in the walls.

Lateral loads can cause diagonal tension cracks in the walls.

The use of ring beams and exterior gravity walls (‘counterfort’) were the main choices for retrofitting of old masonry structures.

Another traditional technique to increase the strength of masonry walls is to strengthen the connection between different structural elements with reinforced injections or with stiffening elements (i.e. longitudinal and/or transverse reinforcing elements and tie bars).




The structural performance of arches and vaults are controlled by the quality of the springers.

Differential settlement and movement of springers leads to formation of hinges and eventual collapse in strong earthquakes.

The use of tie bars at the springing level and/or external buttresses are the most common protective retrofit measures.

Horizontal tie bars, vertical post tensioning and diaphragms can be used to improve the earthquake performance of tall historical structures such as towers and minarets.




Retrofit Proposal for Hagia Sophia

Existing information regarding historical partial collapses, as well as locations of stress concentrations from linear analysis; and yield propagation and numerical collapse scenarios from the non-linear transient dynamic analysis provide relevant evidence that the detachment of the eastern and western semidomes from the eastern and western main arches constitute the most important collapse mechanism in Hagia Sophia in the event of a large earthquake.

One possible preventive action against this mechanism is to install tension links by means of suitable anchorages is proposed to avoid detachment and to ensure a uniform dynamic behavior of semi-domes and the eastern and western main arches.




E-W Section of the eastern portion of Hagia Sophia showing the anchorage bars between eastern main arch and the eastern

semidome.




Strong Motion Monitoring Systems

Real-time vibrational characteristics of historical buildings

Projections regarding their future earthquake performance under a possible major earthquake.

Strong motion network measures absolute accelerations at the sensor locations.

Yield information about the modal shapes of vibration, modal frequencies and modal damping ratios.

Data provided by strong motion networks are used in structural system identification.

Spectral and parametric system identification techniques.

GPS (Global Positioning System) technology has potential for long-period historical structures such as towers

Monitoring the structure



Hagia Sophia Strong Motion Recording Array

Monitoring the structure



Accelerations recorded by the Hagia Sophia array during the 12 November 1999 Düzce earthquake

Dynamic response of Hagia Sophia



First mode of vibration of Hagia Sophia. Dominant sense of vibration EW

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1di

spla

cem

ent

(cm

)

Top of NW Main Pier

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

Crown of N Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

Top of NE Main Pier

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

disp

lace

men

t (c

m)

Crown of W Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

Crown of E Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

disp

lace

men

t (c

m)

displacement (cm)

Top of SW Main Pier

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

displacement (cm)

Crown of S Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

displacement (cm)

Top of SE Main Pier

N

S

W E




Second mode of vibration of Hagia Sophia. Dominant sense of vibration NS

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1di

spla

cem

ent

(cm

)

Top of NW Main Pier

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

Crown of N Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

Top of NE Main Pier

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

disp

lace

men

t (c

m)

Crown of W Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

Crown of E Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

disp

lace

men

t (c

m)

displacement (cm)

Top of SW Main Pier

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

displacement (cm)

Crown of S Main Arch

-0.1 0 0.1

-0.1

-0.05

0

0.05

0.1

displacement (cm)

Top of SE Main Pier

E

N

S

W




Shake Table, Pseudo Dynamic and Cyclic Tests

Shake table tests are performed on models of the historical structures.

Test helps to understand the response of the structural system to earthquake with different amplitude and frequency characteristics, to investigate the vulnerabilities of the system and to understand the collapse patterns.

Shake tables are also effectively used in understanding and testing of methods for earthquake strengthening.

Modeling the dynamic response of a real structure



Shake-table testing of the model of the Hagia Irene case study




Shake-table testing of the model of the Hagia Irene case study




Finite Element Model of Hagia Irene




2.5.1. Earthquake response of historical structuresFinite Element Model and shake table test of Hagia Irene



Shake-table testing of the model of the St. Nikita church (Gavrilovic, 2001)




Palazzo Geraci in Palermo-Large Scale Model for Pseudo Dynamic Testing

(ELSA, http://tintin.jrc.it/hdocs)



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