Hazard Mitigation Of Civil Infrastructure

INTERACTION OF RC FRAMES AND INFILL MASONRY WALLS UNDER SEISMIC

LOADS

Luis Omar Rubio The University of Texas at Arlington

Hazard

• Earthquakes

Hazard Mitigation

• Use & understand the interaction between

Reinforced Concrete (RC) frames and masonry infill

walls

• Masonry walls may change the stiffness and

consequently, the period of the structure

• It is necessary to take into account their effect to

correctly design the structure

• Obtain the interaction through Pushover Analysis

Background: RC Frames

• Many countries, like Spain, use abundant of

masonry infill walls in their buildings

• RC frame building with masonry walls are generally

taken as an aesthetic component only due to

calculation complications

• Many studies have shown that masonry infill walls

help with increasing the structure’s stiffness, but also

• Complications when it is partially filled or with

different size openings: soft story, short column

• Further research is needed to fully understand the

interaction between RC frames and infill walls

Introduction

• Dr. Pallarés Rubio is currently researching the

interaction between RC frames and infill masonry

walls

• Both theoretical and experimental models are

being used to analyze the ultimate capacity and

possible failure modes o Theoretical: Non-linear Static Pushover Analysis through SAP2000

o Experimental: 5mX3m frames subjected to a constant horizontal

load

Introduction

• My Part in the Project o Working only with theoretical models

o Creating and running frame models on SAP2000

o Data Analysis

My Objectives

• Model concrete frame

• Define sections

• Find stiffness of the different types of frames o Without equivalent strut

o With equivalent strut

• Compare results

Background: Pushover Analysis

• An analysis in which assesses seismic vulnerability of

existing structures

• A static non-linear analysis under permanent

vertical loads and gradually increasing lateral loads

until a certain displacement or failure

• A method to observe the successive damage states

of a building

• A plot of total base shear versus top displacement

in a structure is obtained (would indicate any

premature failure or weakness)

2-D Concrete Frame Model

• 3 different types of

beams

• 2 different types of

columns

• Pinned end

connections

Cross-Sections

• Beam • Type 1

• Type 2

• Type 3

• Column • Type 1

• Type 2

SAP2000 & Challenges

• A civil engineering based software which analyzes

buildings or any other structural system

• Defining the materials o Strut to be equal as masonry infill properties

• Modeling the frame and members o Strut to act as a masonry infill wall

• The analysis o Having to go find the results

The Procedure

The Procedure

Analysis

• Model information

• Software plots the base shear vs displacement

• Modal analysis is obtained: T (period)

• Show weakest/failure point through T (period) and

data tables of capacity spectrum

Load Case Relative Distance Load Case Relative Distance For node 15 (m)

1.1 DEAD 0.05-0.95 PUSH 0.05-0.95 RUN 0.3

1.2 DEAD 0.05-0.95 PUSH 0.05-0.95 RUN 0.3

Analysis Modal

Hinges

ColumnBeamControl Displacement

Concrete Frame-Stiffness with and without Masonry Infill Wall

Analysis

• Force – Deformation

Curve

• Method for Equivalent

Strut

• Stiffness

Equivalent Strut for modeling Masonry Infill

• Estimating the width of

the strut using Paulay &

Priestley formula

approach

• Estimating the relative

stiffness of the masonry

infill wall using Benjamin

formula approach

• Estimating shear

modulus of the

masonry infill wall

Equivalent Strut for modeling Masonry Infill

• Assumptions and Parameters of Masonry Infill o Cross-section area of gantry, Ac: 0.09 m2

o Modulus of Elasticity of concrete, Ec: 31000 MPA

o Moment of Inertia of column, Ic: 6.750 x 10-4 in4

o Poisson ratio of masonry infill, v: 0.25

o Young’s Modulus of Elasticity of masonry infill, Em: 2500 Mpa

o Shear Modulus of masonry infill, Gm: 1000 Mpa

o Thickness of masonry infill wall, t: 0.1 m

• Width of Strut and Stiffness of Masonry Infill Wall o w = 1.3551m

o K = 2147.33 KN/m

Results

2-D RC Model Frame without Masonry Infill Wall

Results

2-D RC Model Frame with Masonry Infill Wall

Results

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

-0.1 0.0 0.1 0.1 0.2 0.2 0.3 0.3 0.4

Bas

e R

eac

tio

n F

orc

e, K

N

Displacement, m

Resultant Base Shear vs Monitored Displacement

1.1: Without Masonry Infill Wall

1.2: With Masonry Infill Wall

*The stiffness is the slope of the linear part of the curve starting at zero

Comparison

Without Masonry Infill wall With Masonry Infill Wall

• T = 0.127 seconds

• K = 10231.6 KN/m

• T = 0.0597 seconds

• K = 51563.9 KN/m

Conclusion

• Including the masonry infill wall dramatically

increased the stiffness of the structure

• Further research is still needed to fully understand

the interaction of RC frames with masonry infill walls

• Special thanks to Dr. Pallarés Rubio and the rest of

the UPV staff for everything they have done for me

and for making this internship such a wonderful

experience

References • Pradhan, Prachand Man. "Equivalent Strut Width for Partial Infilled Frames." JCE Journal of Civil Engineering

Research 2.5 (2012): 42-48. Web.

• ., Mohammad H. Jinya, and V. R. Patel. "Analysis Of RC Frame With And Without Masonry Infill Wall With

Different Stiffness With Outer Central Opening." International Journal of Research in Engineering

and Technology IJRET 03.06 (2014): 76-82. Web.

• "Structural Software for Analysis and Design | SAP2000." Computers and Structures, Inc. N.p., n.d. Web. 13 July

2016. <https://www.csiamerica.com/products/sap2000>.

• ComputersNstructures. "SAP2000 - 21 Static Pushover Analysis: Watch & Learn." YouTube. YouTube, 12

Aug. 2011. Web. 13 July 2016. <https://www.youtube.com/watch?v=CzqZVDse-eI>.

• CARLOSCORDOVA1. "ANALISIS ESTATICO NO LINEAL "PUSHOVER" POR EL M.Sc. ING. CARLOS

CORDOVA." YouTube. YouTube, 03 Jan. 2011. Web. 13 July 2016.

<https://www.youtube.com/watch?v=-IW4L-

UVO14&list=PL8q8YdTZlrVHNBKWEl_vIgLe7wEB_anu3>.

• Revert, Andres Belda.. “Estudio Experimental de la Influencia del Relleno de Mamposteria Sobre Porticos de

Hormigon Armado Frente a Acciones Horizontales.” Universitaria Politecnica de Valencia(July 2014).

• Freeman, Sigmund A. “Review of the Development of the Capacity Spectrum Methodd.” ISET Journal of

Earthquake Technology, Paper No. 438, Vol. 41, No. 1, March 2004, pp. 1-13

• Bharali, Ritukesh., Deka, Bhargob., & Pathak, Jayanta. “Retrofitting Open Ground Storey Building with

Masonry Walls in Guwahati City.” Indian Institute of Technology, Roorkee (2014).

• Leslie, Rahul. “The Pushover Analysis, Explained in its Simplicity.” Proceedings of 2nd National Conference –

RACE’13 at SAINTGITS College of Engineering, Kottayam (Unknown).

• Abdelkareem, K. H., Sayed, F. K. Abdel., Ahmed, M. H., & AL-Mekhlafy, N. “Equivalent Strut Width for Modeling

R.C. Infilled Frames.” Civil Engineering Department, Faculty of Engineering, Assiut University (2013).

• Unknown. “Non-linear Static Push-over Analysis.” n.p., n.d., https://www.architectjaved.com/nonlinear-

static-pushover-analysis/

• Unknown. “7. Masonry.” n.p, n.d., <http://www.ce.memphis.edu/7119/PDFs/FEMA356/ps-ch07.pdf>

Questions???

THANK YOU!