Post on 10-May-2018
Proceedings of the 6th International Conference on Mechanics and Materials in Design,
Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, 26-30 July 2015
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PAPER REF: 5730
MONOTONIC AND CYCLIC CHARACTERIZATION OF THE OUT-
OF-PLANE BEHAVIOUR OF INFILL MASONRY WALLS
André Furtado 1, Hugo Rodrigues
2 (*), António Arêde
1
1Faculty of Engineering, University of Porto, Porto, Portugal 2Department of Civil Engineering, Polytechnic Institute of Leiria, Leiria, Portugal (*)Email: hugo.f.rodrigues@ipleiria.pt
ABSTRACT
During the last years, it has been observed that the contribution of the masonry infill walls
should be considered in the structural response of the existing buildings Typically infill
masonry walls are considered non-structural elements; however when subjected to
earthquakes, they tend to interact with the surrounding RC frames which can result in
different failure modes, with in-plane failure and the out-of-plan collapse.
An experimental campaign of full scale masonry infill walls was performed in order to better
understand and characterize the out-of-plane behaviour of infilled masonry panels, in
particular with and without in-plane damage. Three experimental tests were made, two out-of-
plane tests (monotonic and cyclic) in original infill masonry panels and another out-of-plane
test in a third infill panel damaged during a previous in-plane test. In the paper, the results of
the experimental tests are presented and discussed in terms of hysteretic force-displacement
curves, damage evolution, stiffness degradation, infill panels’ capacity and energy dissipation.
Keywords: masonry infill walls, static cyclic test, out-of-plane behaviour, experimental
response
INTRODUCTION
The contribution of the infill walls to the building’s seismic performance can be favourable or
not, depending on a large series of uncertain phenomena, detailing aspects, mechanical
properties, and others. Technical surveys on damaged and collapsed reinforced concrete (RC)
buildings in recent earthquakes in Europe have identified that a large number of buildings that
suffered severe damage or collapse had their poor performance associated with the influence
of masonry infill panels, particularly in the southern region of the Europe, such as L’Aquila
(Italy, 2009) [1], Lorca (Spain, 2010) [2, 3] and Emilia (Italy, 2012) [4]. Typically the infill
masonry walls are considered non-structural elements; however when subjected to
earthquakes, they tend to interact with the surrounding RC frames which can result in
different failure modes, among which are the in-plane failure and the out-of-plane (OP)
collapse.
The infills OP behaviour has been observed as one of the most important critical failures of
such type of non-structural elements (Figure 1) [5-7]. One of the major factors that cause the
OOP instability and poor performance is the deficient/insufficient support-width on the
reinforced concrete (RC) beams and/or slabs, normally adopted to minimize the thermal
bridges effect, no connection between the interior and the exterior panel and finally no
connection to the surrounding RC frames [1].
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Seismic Behaviour Characterization and Strengthening of Constructions
Fig. 1 - Masonry infill walls earthquake out
It is required a deeper knowledge of the
subjected to OP loadings proceeded
appear as a useful tool allowing
cyclic experimental tests. Thus, a
was performed at the Laboratory of Earthquake an
better understand and characterize the monotonic and cyclic infill masonry panels’ OP
behaviour of. For this, two experimental tests were made (monotonic and cyclic) in original
infill masonry panels. The geometr
statistical study about geometric characterization of the Portuguese reinforced concrete
buildings with masonry infill walls, representative of the construction in the 1950
decades [8]. Along the paper the experimental results
of hysteretic force-displacement curves, damage evolution, stiffness degradation, infill panels’
capacity and energy dissipation.
OVERVIEW OF THE EXPERIMENTAL CAMPAIGN
Test programme and specimen’s description
Within the scope of the present experimental campaign, two out
infilled RC frames were performed
be 4.80x3.30 m, with the RC columns and beams cross section of 0.30x0.30m and0
receptively. In Figure 2, is illustrated the infilled RC frame geometry and the corresponding
columns and beams dimensions and reinforcement detailing. The dimensions of the specimen
is representative of the Portuguese building stock, and particul
infill panels that were observed to collect a complete geometric characterization.
collected data was utilized to derive probabilistic distributions, whose goodness
partially verified with a statistical test.
modelling development of nonlinear models for masonry infill panels, or computation of
Seismic Behaviour Characterization and Strengthening of Constructions
-1454-
Masonry infill walls earthquake out-of-plane collapses examples
deeper knowledge of the behavior of these non-structural elements
proceeded or not of in-plane damage. Thus the
allowing characterizing their behavior such through
experimental tests. Thus, an experimental campaign of full scale masonry infill walls
was performed at the Laboratory of Earthquake and Structural Engineering (LESE) in order to
better understand and characterize the monotonic and cyclic infill masonry panels’ OP
behaviour of. For this, two experimental tests were made (monotonic and cyclic) in original
infill masonry panels. The geometry of the infill panels were defined taking into account a
statistical study about geometric characterization of the Portuguese reinforced concrete
buildings with masonry infill walls, representative of the construction in the 1950
the experimental results will be presented and
displacement curves, damage evolution, stiffness degradation, infill panels’
capacity and energy dissipation.
OVERVIEW OF THE EXPERIMENTAL CAMPAIGN
Test programme and specimen’s description
the scope of the present experimental campaign, two out-of-plane tests of full
infilled RC frames were performed. The general dimensions of the specimens were selected to
be 4.80x3.30 m, with the RC columns and beams cross section of 0.30x0.30m and0
, is illustrated the infilled RC frame geometry and the corresponding
columns and beams dimensions and reinforcement detailing. The dimensions of the specimen
is representative of the Portuguese building stock, and particularly of a data of 1500 masonry
infill panels that were observed to collect a complete geometric characterization.
collected data was utilized to derive probabilistic distributions, whose goodness
partially verified with a statistical test. The results from the study can be used in structural
modelling development of nonlinear models for masonry infill panels, or computation of
plane collapses examples.
structural elements when
e experimental tests
their behavior such through static or dynamic
n experimental campaign of full scale masonry infill walls
d Structural Engineering (LESE) in order to
better understand and characterize the monotonic and cyclic infill masonry panels’ OP
behaviour of. For this, two experimental tests were made (monotonic and cyclic) in original
y of the infill panels were defined taking into account a
statistical study about geometric characterization of the Portuguese reinforced concrete
buildings with masonry infill walls, representative of the construction in the 1950-1990
ll be presented and discussed in terms
displacement curves, damage evolution, stiffness degradation, infill panels’
plane tests of full-scale
. The general dimensions of the specimens were selected to
be 4.80x3.30 m, with the RC columns and beams cross section of 0.30x0.30m and0.30x0.50
, is illustrated the infilled RC frame geometry and the corresponding
columns and beams dimensions and reinforcement detailing. The dimensions of the specimen
arly of a data of 1500 masonry
infill panels that were observed to collect a complete geometric characterization. The
collected data was utilized to derive probabilistic distributions, whose goodness-of-fit were
The results from the study can be used in structural
modelling development of nonlinear models for masonry infill panels, or computation of
Proceedings of the 6th International Conference on Mechanics and Materials in Design,
Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, 26
fragility models. In addition, the statistical parameters such as mean values, standard
deviations, probability density functions and their goodness
for all the entire parameters [8]
Fig. 2 - Infilled RC frame specimen dimensions
The two infill panels had equal geometry with the overall dimensions of 2.30x4.20x0.15m,
and a hollow horizontal clay brick type was used, such this is one of the most common
masonry type in Portugal. No reinforcement was used to connect the infill
surrounding RC frame. The infill panel was constructed as an external leaf and placed in the
external side of the RC beam.
Experimental test setup
The out-of-plane test consisted on the application of
through a system composed by seven nylon airbags
steel structure, as illustrated in Figure 3 and 4.
composed by five vertical and four horizontal alignments of steel bars that
connected. Twelve reinforcement bars cross the RC elements were used to transmit the
reaction from the pressure applied by the airbags in the infill panel. The reinforcement bars
were placed strategically to capture the load distribution throu
frame. In order to avoid the load concentration on the RC elements crossed by the
reinforcement bars, it was used distribute plates
Additionally, it was addicted to the experimental setup twelv
transmission by the reinforcement bars for the reaction steel structure. A wood platform were
placed in the front of the steel structure to support the airbags.
After the realization of the experimental tests it was conclud
equilibrated test setup allows to perform out
any structure to restraint the RC bare frame such it wasn’t verified any out
displacement in the top and bottom beams or e
applied through a hydraulic jack that was placed between a head steel profile in the top of
each column and was connected to the steel profile foundation through two dywidag bars. The
connection between dywidag
Thus this axial load application allows to perform also in
Proceedings of the 6th International Conference on Mechanics and Materials in Design,
Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, 26-30 July 2015
-1455-
fragility models. In addition, the statistical parameters such as mean values, standard
ity functions and their goodness-of-fit have also been investigated
[8].
(a)
(b)
(c)
Infilled RC frame specimen dimensions (a) General dimensions (b) columns and
and reinforcement detailling.
The two infill panels had equal geometry with the overall dimensions of 2.30x4.20x0.15m,
and a hollow horizontal clay brick type was used, such this is one of the most common
masonry type in Portugal. No reinforcement was used to connect the infill
surrounding RC frame. The infill panel was constructed as an external leaf and placed in the
plane test consisted on the application of a uniformly distributed surface load
ough a system composed by seven nylon airbags, which reacts against a
steel structure, as illustrated in Figure 3 and 4. This self-equilibrated steel structure is
composed by five vertical and four horizontal alignments of steel bars that
welve reinforcement bars cross the RC elements were used to transmit the
reaction from the pressure applied by the airbags in the infill panel. The reinforcement bars
were placed strategically to capture the load distribution throughout the entire infilled RC
In order to avoid the load concentration on the RC elements crossed by the
reinforcement bars, it was used distribute plates transmitting the loads uniformly.
Additionally, it was addicted to the experimental setup twelve load cells to control the load
transmission by the reinforcement bars for the reaction steel structure. A wood platform were
placed in the front of the steel structure to support the airbags.
After the realization of the experimental tests it was concluded that this experimental self
equilibrated test setup allows to perform out-of-plane experimental tests without the need of
any structure to restraint the RC bare frame such it wasn’t verified any out
displacement in the top and bottom beams or even in both of the columns The axial load was
applied through a hydraulic jack that was placed between a head steel profile in the top of
each column and was connected to the steel profile foundation through two dywidag bars. The
bars and the head and foundation steel profile are articulated.
Thus this axial load application allows to perform also in-plane experimental tests.
fragility models. In addition, the statistical parameters such as mean values, standard
fit have also been investigated
b)
c)
b) columns and (c) beams dimensions
The two infill panels had equal geometry with the overall dimensions of 2.30x4.20x0.15m,
and a hollow horizontal clay brick type was used, such this is one of the most common
masonry type in Portugal. No reinforcement was used to connect the infill panel and the
surrounding RC frame. The infill panel was constructed as an external leaf and placed in the
a uniformly distributed surface load
which reacts against a self-equilibrated
equilibrated steel structure is
composed by five vertical and four horizontal alignments of steel bars that are rigidly
welve reinforcement bars cross the RC elements were used to transmit the
reaction from the pressure applied by the airbags in the infill panel. The reinforcement bars
ghout the entire infilled RC
In order to avoid the load concentration on the RC elements crossed by the
uniformly.
e load cells to control the load
transmission by the reinforcement bars for the reaction steel structure. A wood platform were
ed that this experimental self-
plane experimental tests without the need of
any structure to restraint the RC bare frame such it wasn’t verified any out-of-plane
ven in both of the columns The axial load was
applied through a hydraulic jack that was placed between a head steel profile in the top of
each column and was connected to the steel profile foundation through two dywidag bars. The
bars and the head and foundation steel profile are articulated.
plane experimental tests.
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Seismic Behaviour Characterization and Strengthening of Constructions
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(a)
(b)
(c)
Fig. 3 - Layout of the out-of-plane experimental test setup (a) Front view (b) Lateral View (c) Plan view.
Where, 1- Foundation Steel profile; 2- Dywidag steel bar (ø30mm) used to connect the
foundation steel profile and reaction slab; 3- steel bar (ø20mm) that connect the RC frame to
the foundation steel profile; 4 – Dywidag steel bar (ø30mm) used to apply the axial load; 5 –
head steel profile; 6 - steel bar (ø20mm) that connect the RC frame and the reaction structure
7 – distributed load plate; 8 – Reaction self-equilibrated steel structure; 9 – counterweight; 10
– wood platform 11 - hydraulic jack; 12 – Wooden pallet; 13- wood platform; 14 – infill
panel; 15- RC column; 16- Distributed load plate used in the RC column
(a)
(b)
Fig. 4 - General view of the experimental test setup a) Front view b) Lateral view
Proceedings of the 6th International Conference on Mechanics and Materials in Design,
Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, 26-30 July 2015
-1457-
The level of pressure inside the airbags was controlled by two pressure valves that were
commanded in function of the out-of-plane displacement of the central point of the infill panel
that was used as a control node and was continuously acquired through a data acquisition
system during the tests (Figure 5a). Previously to the experimental campaign it was performed
a calibration methodology between the load cells (Figure 5b) and the airbags in order to
obtain the relationship in terms of load distribution with the increase of the distance between
the steel structure and the maximum extent of the airbags.The axial load was controlled by
two load cells with the maximum capacity of 350kN, placed in the top of each column (Figure
5c).
(a) (b) (c) Fig. 5 - General view of a) Pressure valvs b) Load cells and c) axial load cells.
Instrumentation
The instrumentation of the experimental tests was composed by a total of twenty three
variable displacement transducers (LVDTs), as illustrated in Figure 6, and were divided in 3
different groups according to the corresponding measurement objective: i) measurement of
the infill panel out-of-plane displacements (13 LVDTs) ii) measurements of the out-of-plane
rotation between the infill panel and the surrounding RC frame (8 LVDTs) and iii)
measurement of the RC frame out-of-plane displacements (4 LVDTS).
Fig. 6 - Layout of the out-of-plane experimental tests instrumentation.
Loading condition
As previously stated, the aim of the present experimental campaign is to better understand the
out-of-plane behaviour of the infills behaviour, in particularly when submitted to monotonic
and cyclic loading. Additionally, it was varied the axial load condition between the two
experimental infill panels such as the monotonic test was subjected to an axial load value of
Legend:
OOP masonry infill
wall displacement
OOP rotation
infill - RC frame
OOP RC frame
displacement
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Seismic Behaviour Characterization and Strengthening of Constructions
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300kN (Inf_01) and the other one wasn’t subjected to any axial load (Inf_02). This loading
condition was defined to better understand the axial load effect in the out-of-plane response of
the masonry infill wall.
Cyclic out-of-plane displacements were imposed at the infill panel with steadily increasing
displacement levels. The adopted load paths are summarized in Figure 7 and for each lateral
deformation demand level, three cycles were repeated. The following nominal peak
displacement levels (in mm) were considered: 2.5; 5; 7.5; 10; 15; 20; 25; 30; 35; 40; 45; 50;
50; 55; 60; 65;70 60 and 65. The control node adopted in both of the experimental tests was
defined to be the central point of the masonry infill panel where is expected to occur the
concentration of the deformation
Fig. 7 - Loading history: out-of-plane input displacement at the control node.
EXPERIMENTAL RESULTS
Aiming at characterize the monotonic and cyclic out-of-plane behaviour of the infill masonry
walls, with and without axial loading in the RC columns, the force-displacement hysteresis
are presented in Figure 8a and b respectively. The out-of-plane drift is calculated in function
of the infill panel central point.
The analysis of the force-displacement hysteretic behaviour focused on the following main
issues: i) the comparison and identification of the main differences in the shapes of the
envelopes of the monotonic and cyclic response test results; ii) evaluation of the initial
stiffness, cracking force and corresponding drift iii) characterisation of the correlation found
between the maximum strength and the cracking force iv) characterization of the strength
degradation.
The results’ analysis can be summarised as described in the following:
The initial column stiffness was slightly affected by the axial loading in the RC columns. It
was verified in the infill panel Inf_01 about 5% more initial stiffness when comparing with
the other one;
Proceedings of the 6th International Conference on Mechanics and Materials in Design,
Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, 26-30 July 2015
-1459-
The initial cracking was verified for lower out-of-plane drift values for the Inf_02, about 10%.
The cracking force in both experimental tests was about 50kN.
The maximum out-of-plane force was 10% higher for Inf_01 and occurred for higher out-of-
plane drift demand (about 15%). It was verified that the relationship between the maximum
out-of –plane force and the cracking force higher for the Inf_01.
Finally, it can be observed a higher strength degradation for the Inf_01 when compared with
the Inf_02.
(a) (b)
Fig. 8 - Out-of-plane force-displacement hysteresis: a) Inf_01 b) Inf_02.
Aiming at a detailed observation of the damage evolution during the experimental tests within
the present work testing campaign, each test was stopped at the end of the last cycle of each
displacement level in order to highlight and register new cracks in the last cycle and/or the
evolution of existing ones. Visual observation of the damage evolution during the tests
yielded the information described in the following paragraphs. The final damage shape of
both of the infill panels are presented in Figure 9 and 10.
It was observed for both of the experimental tests that the initial crack was in the top joint
between the RC beam and the first line of bricks, and initiated between 0.0075 and 0.01m;
At the displacement when occurs the maximum force, it was observed in the Inf_01 test a
vertical cracking in the middle of the infill panel, and in the Inf_02 it was observed a trilinear
cracking similar to the slabs with similar constrains conditions;
The final cracking shape of the Inf_01 was vertical, with detachment between the infill panel
and the surrounding RC frame in the top and bottom joints, as can be observed in Figure 9. In
the In_02 it was observed a trilinear cracking with the deformation concentrated in the middle
point of the wall, with slight cracking in the top joint, and are illustrated in Figure 10. In the
back of both of the experimental tests it was observed similar cracking, with only cracking of
the top joints and crushing of some bricks.
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Seismic Behaviour Characterization and Strengthening of Constructions
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Fig. 9 - Final cracking shape of Inf_01: a) Front view b) Back view.
(a) (b)
Fig. 10 - Final cracking shape of Inf_02: a) Front view b) Back view.
CONCLUSION
This paper reports an experimental campaign carried out at the Laboratory of Earthquake
Engineering at the Faculty of Engineering of University of Porto in order to study the out-of-
plane behaviour of masonry infill walls. For this, two full-scale infill panels were constructed
and were subjected to out-of-plane monotonic and cyclic loading, with and without axial
loading at the RC columns. The out-of-plane loading was applied by an airbags system that
reacts in a self-equilibrated structure. The experimental test setup was presented, including all
the instrumentation and loading condition
Proceedings of the 6th International Conference on Mechanics and Materials in Design,
Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, 26-30 July 2015
-1461-
It was observed that the infill panel subjected to monotonic loading and with axial load in the
RC columns had about 5% more initial stiffness when comparing with the other one. The
maximum out-of-plane force was 10% higher for the infill panel subjected to monotonic
loading and occurred for higher out-of-plane drift demand (about 15%). Finally, it can be
observed a higher strength degradation for the Inf_01 when compared with the Inf_02.
For both of the experimental tests was observed that the initial crack was in the top joint
between the RC beam and the first line of bricks, and initiated between 0.0075 and 0.01m.
The final cracking shape of the infill subjected to monotonic out-of-plane loading was
vertical, with detachment between the infill panel and the surrounding RC frame in the top
and bottom joints. In the other was observed a trilinear cracking with the deformation
concentrated in the middle point of the wall, with slight cracking in the top joint. In the back
of both of the experimental tests it was observed similar cracking, with only cracking of the
top joints and crushing of some bricks.
Further experimental studies will be realized in the future regarding to the characterization of
simples or double leafs infill masonry walls out-of-plane behaviour with and without
previously out-of-plane damage.
ACKNOWLEDGMENTS
The authors would like to acknowledge the technicians of the Laboratory of Earthquake and
Structural Engineering (LESE), Mr. Valdemar Luis and Mr. Nuno Pinto for their support in
the experimental activity reported in this paper, and Preceram for the provision of all the
bricks used in the experimental tests. This experimental 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.
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Seismic Behaviour Characterization and Strengthening of Constructions
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[5]-G. Calvi and D. Bolognini, "Seismic response of reinforced concrete frames infilled with
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Panels " Journal of Earthquake Engineering, Volume vol. 14, pp. 390 - 416 2010.
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Portuguese RC building stock with Infill Masonry walls," presented at the 9th International
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