Numerical Modeling of Masonry Infill Walls in RC Buildings

Numerical Modeling of masonry infill walls participation in
the seismic behavior of RC buildings
André Furtado | Hugo Rodrigues | António Arêde
hugo.f.rodrigues@ipleiria.pt

Numerical Modeling of masonry infill walls participation in the seismic behavior of RC buildings
Influence of masonry panels in buildings response
• Infill masonry panels are usually considered in the design of new structures
has non-structural elements, and its influence in the structural response is
disregarded
• 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 structural
behavior attracting forces to parts of the structure that were not designed to
support them, leading to unexpected behavior/response and collapse
mechanisms
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
(Crisafulli, 2010)

Types of failure of infills masonry walls
The seismic response of an infilled frame building structure is very complex, and
usually 3 different damage or failure patterns/mechanisms can be distinguish:
P
P
P
P
Monolitic behaviour Detachment frame-infill
P
P
P
P
P
P
Shear-friction failure Diagonal tension failure Crushing of the corners

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 or
anchoring systems either between inner and external leafs and/or
between infill walls and the structural frame

Damage to masonry enclosure walls – in-plane response (interface
separation between infills and resistant structure, diagonal
cracking, 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 and
resistant structure, diagonal cracking, corner crushing)
- out-of-plane collapse

Short column mechanism
Possible cause: wall openings in masonry enclosures

Modeling of infill masonry walls
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 of
buildings.
Micro-models:
Macro-models:
• Detailed modeling
• More simplified than the micro-models
• Allow interpretation of the behavior at
• Allow for a representation of the global
local level
behavior of the infill masonry panels and
• Allow to obtain the cracking pattern, the
of their influence in the buildings
ultimate load, and the collapse
response
mechanisms
• Equivalent strut model is the most used
• 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 and
implemented by Holmes and Stafford Smith in the 1960s.
Later, many researchers improved this basic model. Today, the strut
model is accepted as a simple and rational way to represent the effect
of the masonry infill panel in the global response of buildings.
The main advantage of the
multi-strut models, in spite
of the increase of
complexity, is the ability to
represent the actions in the
frame more accurately.

The typical strut models are not able of represent the response of the
infilled frame when horizontal shear sliding occurs in the masonry
panel. For this case, Leuchars & Scrivener proposed the model
illustrated.
A recent NZSEE Bulletin article, “Analytical modeling of infilled frame
structures” [Crisafulli et al., 2000], provides a review of macro and
micro models, and reports on some comparative studies between
equivalent 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 each
loading direction, and corresponding hysteretic rules
elemento
Não-Linear
Bielas
F
2
K0
+
K1
3
+
K2
+
K3
+
K4
u
+
F2
+
F1
+
F3
+ u2
u1
+ u3
4
+ u4
+
1
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
elasticBeamColumn
Strut behavior in plane
Residual stiffness in the OP direction
non-linearBeamColumn
Only with axial Non-linear behavior
Pinching4

Proposed approach
The uniaxial material Pinching 04 was
adopted to represent the hysteretic
rule
i) Cracking (cracking force Fc, cracking
displacement dc)
ii) Yielding (yielding force Fy, yielding
displacement dy)
iii) Maximum strength corresponding
to the beginning of crushing (Fcr and
corresponding displacement dcr)
iv) Residual strength (Residual
strength Fu and residual displacement
du)
The envelope can be obtained based on recommendations from past researchers (Zarnic
and 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
4.20
0.42 0.15 0.15 0.42
0.165
0.20
1.625
0.35
[ m ]

• Reduced scale - 2/3
• Simplified masonry model
• Tests on sample materials of
concrete and masonry used to
calibrate the numerical model
Without infill
4.20
0.42 0.15 0.15 0.42
0.165
0.20
1.625
0.35
[ m ]

• Good agreement between
numerical and experimental
results
• Model able to well represent
the masonry strength and
stiffness 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).
L  t 
f
0.818 (1 2 1)
F in tp
  C
 
max 1
C
1
Lin h'
t
C  Lin
1 ' 1.925
h
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

PT4 PT8
4 Storeys
3 bays x 5 bays
• 3D Models
• Regular buildings
Under going work
8 Storeys
3 bays x 5 bays

Under going work
PT4 PT8
4 Storeys
3 bays x 5 bays
8 Storeys
3 bays x 5 bays
• Dynamic time-history Analysis
• The building was submitted to
seismic motions in order to be
representative of a moderate-high
European seismic hazard
scenario

Under going work
PT4
PT8
Bare frama Full infilled soft-storey

Under going work PT4

Under going work PT8

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 achieved
by computational modeling. The application of simplified nonlinear numerical
models, associated with the increasing computational power, allow for the
inclusion of infill masonry models in the structural assessment of existing
building structures and in the design of new buildings
• The proposed infill masonry model was calibrated with the results of one
experimental test. The numerical results shows that generally the model
proposed was able to represent the response of the structures in terms of
displacements evolution, and cumulative dissipated energy
• The proposed macro-model can be a useful tool in the development and
calibration of simplified rules for the analysis of infilled frame structures
under horizontal loadings, accounting for important mechanical features as
hysteretic behavior, strength and stiffness degradation, pinching and damage
evolution, function of the deformation demands
• The main challenge is the possibility of considering the out-of-plane collapse
of the infill masonry panel …. Under going work …

Final comment and future work

Obrigado!!!
Thank you!!!
Numerical Modeling of masonry infill walls participation in
the seismic behavior of RC buildings
André Furtado | Hugo Rodrigues | António Arêde
hugo.f.rodrigues@ipleiria.pt
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 in RC Buildings

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