numerical modelling of masonry infill walls participation in the seismic behaviour of rc buildings

Numerical Modeling of masonry infill walls participation inthe seismic behavior of RC buildings

André Furtado | Hugo Rodrigues | António Arê[email protected]

Numerical Modeling of masonry infill walls participation in the seismic behavior of RC buildings

Hugo Rodrigues | Workshop on Multi-Hazard Analysis of Structures using OpenSees – OpenSeesDays Portugal | Porto, July 03-04, 2014

Influence of masonry panels in buildings response

• Infill masonry panels are usually considered in the design of new structureshas non-structural elements, and its influence in the structural response isdisregarded

• Infill masonry panels may change drastically:• the global lateral stiffness and strength of the building structures• the natural frequencies and vibration modes• the energy dissipation capacity• a brittle behavior and failure mechanism

• Common infill masonry panels can modify drastically the global structuralbehavior attracting forces to parts of the structure that were not designed tosupport them, leading to unexpected behavior/response and collapsemechanisms



Influence of masonry panels in buildings response

(Crisafulli, 2010)



Types of failure of infills masonry walls

P

P

P

P

P

P

P

P

P

P

Shear-friction failure Diagonal tension failure Crushing of the corners

Detachment frame-infillMonolitic behaviour

The seismic response of an infilled frame building structure is very complex, andusually 3 different damage or failure patterns/mechanisms can be distinguish:



Observed damages in recent earthquakes - Field evidence

Possible causes: Balcony excessive deformation (cantilevers);dimensions of the masonry leafs; improper support conditions;poor connection conditions of the external leaf; no ties oranchoring systems either between inner and external leafs and/orbetween infill walls and the structural frame




Damage to masonry enclosure walls – in-plane response (interfaceseparation between infills and resistant structure, diagonalcracking, corner crushing)

P

P

P

P




Damage to masonry enclosure walls – in-plane response (diagonal cracking)




Out-of-plane failure of masonry enclosure walls




Damage to infill masonry walls:

- in-plane response (interface separation between infills andresistant structure, diagonal cracking, corner crushing)

- out-of-plane collapse




Short column mechanism

Possible cause: wall openings in masonry enclosures



Modeling of infill masonry walls

Macro-models:

• More simplified than the micro-models

• Allow for a representation of the global

behavior of the infill masonry panels and

of their influence in the buildings

response

• Equivalent strut model is the most used

Infilled frames are complex structural systems and exhibit a highly nonlinear behavior.This fact complicates the analysis and explains why infill panels has been considered as"non-structural elements", despite their strong influence on the global response ofbuildings.

Micro-models:

• Detailed modeling

• Allow interpretation of the behavior at

local level

• Allow to obtain the cracking pattern, the

ultimate load, and the collapse

mechanisms

• High computational effort

• Need for a large number of parameter

• Useful for the calibration of global

models




The equivalent strut model was suggested by Poliakov andimplemented by Holmes and Stafford Smith in the 1960s.

Later, many researchers improved this basic model. Today, the strutmodel is accepted as a simple and rational way to represent the effectof the masonry infill panel in the global response of buildings.

The main advantage of themulti-strut models, in spiteof the increase ofcomplexity, is the ability torepresent the actions in theframe more accurately.




The typical strut models are not able of represent the response of theinfilled frame when horizontal shear sliding occurs in the masonrypanel. For this case, Leuchars & Scrivener proposed the modelillustrated.

A recent NZSEE Bulletin article, “Analytical modeling of infilled framestructures” [Crisafulli et al., 2000], provides a review of macro andmicro models, and reports on some comparative studies betweenequivalent strut models and FEM (‘solid’ element) models.



Previous Research• Simplified global macro-model

• Represents the infill panel behaviour and its influence in the building response to seismic loadings

• An upgrading of the bi-diagonal strut model

• Considers the strength and stiffness degradation interaction in both directions of loading

• 4 strut elements with rigid linear behaviour that support a central element where the non-linear behaviour is concentrated

• Non-linear behaviour characterized by a monotonic curve with 5 branches for eachloading direction, and corresponding hysteretic rules

elemento

Não-Linear

Bielas

F

K0

K1

+

K2

+

K3

+

K4

+

u

F2

+

F1

+

F3

+

u1+

u2+ u3

+ u4+

1

2

3

4

5

Rodrigues, H.; Varum, H.; Costa, A. (2010) - Simplified macro-model for infill masonry panels -Journal of Earthquake Engineering, World Scientific Publishing, doi 10.1080/13632460903086044, Vol. 14, Issue 3, March 2010, pp. 390-416.



Proposed approach

elasticBeamColumnStrut behavior in planeResidual stiffness in the OP direction

non-linearBeamColumnOnly with axial Non-linear behaviorPinching4



Proposed approach

The uniaxial material Pinching 04 wasadopted to represent the hystereticrule

i) Cracking (cracking force Fc, crackingdisplacement dc)

ii) Yielding (yielding force Fy, yieldingdisplacement dy)

iii) Maximum strength correspondingto the beginning of crushing (Fcr andcorresponding displacement dcr)

iv) Residual strength (Residualstrength Fu and residual displacementdu)

The envelope can be obtained based on recommendations from past researchers (Zarnicand Gornic,1997 and Dolsek and Fajfar,2008) and observations from experimental tests(Mazounry,1995 and Shing et al, 2009) and from recommendation codes (FEMA)



Numerical model calibration – One-storey one-bay infilled RC frame

• Reduced scale - 2/3

• Simplified masonry model

• Tests on sample materials of concrete and masonry used to calibrate the numerical model

0.15 0.420.150.42

0.35

0.20

0.165

1.625

4.20[ m ]







Without infill

0.15 0.420.150.42

0.35

0.20

0.165

1.625

4.20[ m ]







0.15 0.420.150.42

0.35

0.20

0.165

1.625

4.20[ m ]




• Good agreement betweennumerical and experimentalresults

• Model able to well representthe masonry strength andstiffness degradation,energy dissipation




Manzouri (1995) and Shing et al (2009) found that the maximum strength (Fmax) occurs at

approximately 0.25% drift

The maximum strength can be calculated through the equation proposed by Zarnic and

Gornic (1997) and later modified by Dolsek and Fajfar (2008).

)11(818.02

1

1

max

CC

ftLF tpin

Lin h'

t

'1 925.1h

LC in

ftp is the masonry cracking stress obtained based

on experimental test

Post-peak strength degradation or residual strength is based on Dolsek and Fajfar (2008)

that estimate that the displacement at residual strength is five times of the displacement

of maximum strength




Two different approaches were tested:

• Calibrated with experimental results

• Recommended parameters




• Good agreement betweennumerical and experimentalresults

• Model able to well representthe masonry strength andstiffness degradation,energy dissipation



• 3D Models• Regular buildings

Under going work

PT4 PT8

4 Storeys3 bays x 5 bays




Under going work

PT4 PT8



• Dynamic time-history Analysis

• The building was submitted toseismic motions in order to berepresentative of a moderate-high European seismic hazardscenario



Under going workPT4

PT8

Bare frama Full infilled soft-storey



Under going workPT4



Under going workPT8



Final comment and future work• Masonry infill walls have a complex behavior due to the properties of their

materials and to the interaction mechanisms with the surrounding frame

• The response prediction of masonry infilled frame structures can be achievedby computational modeling. The application of simplified nonlinear numericalmodels, associated with the increasing computational power, allow for theinclusion of infill masonry models in the structural assessment of existingbuilding structures and in the design of new buildings

• The proposed infill masonry model was calibrated with the results of oneexperimental test. The numerical results shows that generally the modelproposed was able to represent the response of the structures in terms ofdisplacements evolution, and cumulative dissipated energy

• The proposed macro-model can be a useful tool in the development andcalibration of simplified rules for the analysis of infilled frame structuresunder horizontal loadings, accounting for important mechanical features ashysteretic behavior, strength and stiffness degradation, pinching and damageevolution, function of the deformation demands

• The main challenge is the possibility of considering the out-of-plane collapseof the infill masonry panel …. Under going work …



Final comment and future work



Obrigado!!!Thank you!!!

This research was developed under financial support provided by “FCT -Fundação para a Ciência e Tecnologia”, Portugal, namely through the research project PTDC/ECM/122347/2010 - RetroInf – Developing Innovative Solutions for Seismic Retrofitting of Masonry Infill Walls.

Numerical Modeling of masonry infill walls participation inthe seismic behavior of RC buildings

André Furtado | Hugo Rodrigues | António Arê[email protected]

numerical modelling of masonry infill walls participation in the seismic behaviour of rc buildings

Engineering

infill panels

brittle behavior

nonlinear behavior

detailed modeling

building structures

global response ofbuildings

failure patternsmechanisms

complex structural systems