Masonry Infill Panels Research Articles

Dynamic Tests of a Large-Scale Three-Story RC Structure with Masonry Infill Walls

ABSTRACT RC buildings with masonry infill walls are common throughout the world. There is uncertainty about the effect of the infill walls on the response of the building to earthquake demands. To shed light on this issue, a three-story, scaled reinforced concrete frame with masonry infill walls was subjected to two sequences of base motions in two series of tests. In Series 1, hollow masonry units were used. After completion of this series, the structure was repaired by replacing hollow masonry units with new solid units. Reinforced concrete confining elements were also added along the vertical edges of window and door openings in the first and second stories. The repaired structure was then tested with the same sequence of base motions in Series 2. On average, drift demands were 30% smaller in Series 2 and were nearly half what the drift demands were estimated to be for the bare RC frame alone. These results support the hypothesis that masonry infill panels can be used to control drift in low-rise structures, provided they do not cause column failures and provided they are restrained from out-of-plane collapse. Projections made based on the test results also support the idea that a Wall Index (ratio of masonry wall density to ten times the number of stories) exceeding 0.2% leads to acceptable earthquake response in low-rise buildings.

Influence Of Masonry Panels With Openings On The Seismic Response Of Reinforced Concrete Infilled Frames

Due to architectural considerations, openings are required in masonry infill panels. In this study, a pushover analysis is carried out to assess the behavior of RC infilled frames with emphasis on the effect of openings in the infills. The main parameters that will be considered concern the size, the location and the aspect ratio of the openings. Three reinforced concrete structures representative of rigid, semi-rigid and flexible structures are designed according to the Algerian seismic code. The numerical model of the structures consists of frame elements with concentrated plastic hinges at the ends and a nonlinear layered shell for the infills. The results obtained show that the presence of infills can drastically change the overall behavior of the structures by enhancing the strength capacities but with limited ductility and the presence of openings can modify the hinges locations and patterns according to their size, location and aspect ratio.

Nonlinear static analysis of Multistoried Building in Yemen

A large number of multi-story reinforced concrete (R/C) framed building structures in urban Yemen were constructed with masonry infills for economic, aesthetic or architectural reasons. We have investigated the effect of the layout of masonry infill panels over the elevation of masonry infilled R/C frames on the seismic performance and potential seismic damage of the frame under strong ground motions using nonlinear static push-over analysis based on realistic and efficient computational models. From output non-linear analysis, we compare Displacement and Base shear in the bare frame, infill wall frame, and ground, it is seen that at roof level, displacement at ground floor in the weak story is more than other two frames, and displacement in a bare frame is more than other two frames. Mostly hinges are formed in the beam than in the column.

Damage classification and derivation of damage probability matrices from L’Aquila (2009) post-earthquake survey data

Post-earthquake damage data represent an invaluable source of information for the seismic vulnerability assessment of the exposed building stock, as they are a direct evidence of the actual buildings’ performance under real seismic events. This paper exploits a robust and homogeneous database of damage data collected after the 2009 L’Aquila (Italy) earthquake, to derive damage probability matrices for several building typologies representative of the Italian building stock. To this aim, the first part of the work investigates several issues related to the definition of damage to be associated with each inspected building. Different approaches and damage conversion rules are applied, pointing out advantages and weaknesses of each one. Considering the widespread seismic damage observed on masonry infill panels and partitions of reinforced concrete constructions, the impact of this type of non-structural damage on empirical damage and functional loss distributions is explored. The second part of the study proposes different possible interpretations of the repartition of the observed damage in the different damage levels, showing in some cases a bimodal trend. Two novel hybrid procedures are outlined and compared with the classical binomial approach for predicting the subdivision of damage in the different levels. The application of the proposed methodologies to the different building typologies allows the selection, for each one, of the method providing the best fit to empirical results. The parameters required for the application of the optimal approach are reported in the paper, so that results can be used for forecasting the expected seismic damage in sites with similar seismic hazard and exposed buildings.

Seismic capacity of masonry infilled RC frame strengthening with expanded metal ferrocement

This research was to investigate the behavior of masonry infilled reinforced concrete frame strengthening with expanded metals under cyclic loading. In this study, a prototype frame was chosen from a three-story reinforced concrete building that was not designed for earthquake load. Three specimens were built to full scale of 1:1 ratio including, the reinforced concrete bare frame (BF), the brick masonry infilled frame (W) and the masonry infilled frame strengthening with an expanded metal sheet (W-SR). The specimens were tested under constant vertical load and cyclic lateral load. The infilled frame strengthening with expanded metal sheet (W-SR) provided the lateral strength, stiffness and energy dissipation capacity of 1.25, 1.26, 1.27 times those of the brick masonry infilled frame (W), respectively. An analytical model based on an equivalent strut was proposed for masonry infill panels. In this approach, the nonlinear behavior obtained from the masonry prism test results was employed to determine the lateral strength and stiffness of the masonry panel model. The hysteretic behavior of the infill panel and infilled frame was evaluated using a nonlinear structural analysis program, RUAUMOKO. The results of the hysteretic behavior were compared with the experimental results to validate the proposed model.

Nelinearna statička nasuprot inkrementalne dinamičke analize okvira sa ispunom sa otvorenom prvom etažom

Masonry infill, as a part of building structures, is characterised with significant in-plane strength and stiffness and it can greatly alter the response of structures exposed to seismic loads. Irregular distribution of infill in plane and along building height can lead to series of unfavourable effects (torsion effects, dangerous collapse mechanisms, soft or weak storey, variations in the vibration period, etc.). In order to investigate the influence of irregular distribution of masonry infill to the seismic performance of code designed reinforced concrete frames, an extensive nonlinear static and dynamic analysis was performed. Six reinforced concrete frames with different number of storeys, designed as bare frames were analysed. In the phase of assessment, all structures were upgraded with the masonry infill panels in all storeys except the first one. Masonry infill was defined with two different strength and stiffness characteristics. The obtained results show significant influence of masonry infill on the main structural characteristics: strength, stiffness and ductility, as well as on the seismic performance of analysed frames.

Seismic response of RC buildings during the Mw 6.0 August 24, 2016 Central Italy earthquake: the Amatrice case study

In the aftermath of the Mw 6.0 August 24, 2016 Central Italy earthquake, the authors carried out a reconnaissance survey in the municipality of Amatrice and gathered extensive photographic evidence of damage, with emphasis on 37 reinforced concrete buildings located outside the historical centre. Damage distribution is generally represented by widespread cracking and/or collapse of the masonry infill panels at the lower buildings’ stories. Moreover, damage was observed in the columns due to the interaction with masonry infill panels. Starting from the collected information, POST—a mechanics-based damage prediction model—was applied in order to compare predicted damage distribution and damage observed during the field reconnaissance. The comparison shows an overall good agreement between the results of the POST method and the observed damage with a slightly conservative tendency by POST.

Effects of shear rate on cyclic behavior of dry stack masonry joint

Dry stack masonry (DSM) constructed without mortar has been suggested for use in reinforced concrete (RC) frame structures. DSM can considerably improve the seismic performance of masonry infill panels and frames. For this type of structure, the characteristics of frictional forces between the bricks are crucial for energy dissipation, but few researchers have studied these forces. In this paper, a novel dynamic loading test concept is proposed. The dynamic friction characteristics of dry bricks were investigated using this concept. A numerical comparison between the novel test and a triplet test was conducted to validate the advantages and stability of the novel test concept. Nine different loading speed tests based on the novel test concept were conducted to study the effects of shear rate on the cyclic behavior of mortarless masonry joints. Investigating dynamic friction hysteretic curves yielded a dynamic friction characteristic model of dry brick joints, comprising five stages: presliding, softening transition, macroslip, hardening transition, and unloading stages. A formula regarding the Stribeck effect on the macroslip stage is proposed to calculate the dynamic friction coefficient, which is of noteworthy importance for use in day-to-day research on the dynamic friction characteristics of dry bricks.

Low‐seismic damage strategies for infilled RC frames: shake‐table tests

SummaryUnreinforced masonry (URM) infill panels are widely used as partitions in RC frames and typically considered as non‐structural elements in the design process. However, observations from recent major earthquakes have shown that under seismic excitation, the structural interaction between columns and infill walls can significantly alter the structural behaviour, thus causing catastrophic consequences. The purpose of this research was to propose and test an innovative low seismic damage detailing method, which isolates the infill panel from bounding columns with finite width vertical gaps during the infill panel construction phase and deploys steel wire connections in mortar layers anchored to columns. Taking into account the similitude requirements, a total of six one‐third scale, single‐storey single‐bay RC frames with different infill configurations and flexible connection details were carefully designed and tested on a shake‐table. Three real earthquake records were selected and scaled to ascending intensity levels and used as input signals. A series of thorough investigations including dynamic characteristics, hysteretic behaviour, failure mechanisms, out‐of‐plane vulnerabilities and the effect of different gap filling materials and load transfer mechanisms were rigorously studied. The experimental results indicate that the undesirable interaction between infill panels and bounding frame is significantly reduced using the proposed low seismic damage detailing concept. Direct shear failure of columns at an early stage is prevented, and structural redundancy at high levels of excitation can be provided. In general, the structural stability and integrity, and displacement ductility of infilled RC frames can remarkably be improved. Copyright © 2017 John Wiley & Sons, Ltd.

Modification Factor and Ultimate Strength of Infilled Frames, Rehabilitated by Concrete Covers

Most rehabilitation codes have a special part for regular masonry infill panels. However, they are completely silent for infills improved by concrete covers, probably for the lack of sufficient experimental test data. Shotcreting one side or both sides of the existing infills is one of the best methods to improve structural seismic behavior. Therefore, this paper focuses on the ultimate strengths and modification factors of this type of infill panels, based on the existing experimental data of the literature. The existing formula of the codes is improved to estimate ultimate strength of such infill panels. Furthermore, modification factors of primary and rehabilitated specimens are calculated and compared. In this regard, envelopes of the load–displacement behavior of the specimens are applied, as well. It is shown that envelops give more conservative values for the m-factor, compared with the standard backbone curves. It is shown that modification factor of masonry infill panels is decreased when rehabilitated by concrete covers; however, for clay tile infills, it remains almost unchanged.

Masonry Infill Panels with Openings, Modeling, Effect on Seismic Response of Concrete Frame and Example Study According the Provisions in Morocco «RPS 2011»

Masonry remains today an essential, even indispensable at buildings in Morocco, however, the lack of experimentation led to the neglect thereof in digital computing models especially the panels with openings. On the other hand, damage in seismic zones showed a significant participation of the latter on failure modes of a structure. It is noteworthy that the Moroccan earthquake regulations RPS 2000 Version 2011 advocates modeling masonry infill panels with two equivalent rods (cf. Art No. 7.3.3).

Review on Seismic Behavior of Infilled Frame Structures

Earthquakes prove that infill walls have a negative significant effect on concrete frame, e.g.: soft-storey, short column due to partial infills, torsional effects due to irregular and unsystematic placement infills and out-of-plane collapse. however, their influence still not taken in consideration, therefore, it is very important to define the behavior of the infill panels in the seismic response. Steel or reinforced concrete frames are currently used in buildings with infill panels which are generally ignored when analyzing the seismic effects, the fact that infill panels were not covered in the design stage and also in analyzes had led to a significant damage, e.g.: A l-Hoceima in Morocco - L’Asnam in Algeria and Pam in Iran. The interaction between frames and masonry infill panels in the seismic analysis becomes imperative to avoid such damage, indeed, these infill panels are not considered as structural elements in structural analysis, even if they have a significant contribution on the structures properties (stiffness, strength, ductility, energy dissipation capacity).

Assessment of the mainshock-aftershock collapse vulnerability of RC structures considering the infills in-plane and out-of-plane behaviour

One major challenge of earthquake risk mitigation is the assessment of existing buildings not designed with modern codes and the development of effective strengthening techniques. Particular attention should be given to reinforced concrete (RC) frame structures with infill masonry (IM) panels, as proved by their poor performance in recent earthquakes. From surveys on damaged and collapsed RC buildings, many buildings suffered severe damage or collapse due to the IM panels presence. It is observed that in-plane (IP) behaviour of IM can prevent the development of out-of-plane (OOP) strength mechanisms by arching effect. By contrast, in most cases the major damages were found in non-structural elements, particularly in clay IM, including diagonal cracking, OOP collapse or detachment of surrounding RC frames (the latter taking place in early earthquake instants) due to absence of or deficient connection to that frames. In a seismically active region, structures are subjected to multiple earthquakes, due to mainshock–aftershock phenomena or other sequences, leaving no time for rehabilitation of the buildings or rescue of the injured people between the events. This research pretends to assess the mainshock-aftershocks effects on an eight storey RC building. For this, different numerical models (considering different IM walls modelling strategies) were subjected to several non-linear dynamic analyses. The structure damage level was evaluated for different intensity levels of the aftershock-mainshock by the comparison between the maximum inter-storey drifts with drift limits suggested by international codes.

Numerical Study on the In-Plane and Out-of-Plane Resistance of Brick Masonry Infill Panels in Steel Frames

Masonry infill walls are one of the main forms of interior partitions and exterior walls in many parts of the world. Nevertheless, serious damage and loss of stability of many masonry infill walls had been reported during recent earthquakes. To improve their performance, the interaction between these infill walls and the bounding frames needs to be properly investigated. Such interaction can dramatically increase the stiffness of the frame in the in-plane direction. To avoid the negative aspects of inappropriate interactions between the frame and infill wall, some kind of isolation needs to be introduced. In this paper, three different configurations have been evaluated by using the general finite element software, ABAQUS. Nonlinear pushover and time history analyses have been conducted for each of the three configurations. Results showed that isolation of the infill from the frame has a significant effect on the in-plane response of infilled frames. Furthermore, adequate out-of-plane stability of the infill wall has been achieved. The results show that masonry infill walls that have full contact at the top of the wall but isolated from columns have shown acceptable performance.

Time-History Analysis of Reinforced Concrete Frame Buildings with Soft Storeys

This research study investigates the change in dynamic characteristics of reinforced concrete moment-resisting frame buildings without and with fully infill walls. In addition, building models with partially infill walls have also been investigated. A set of different building models have been developed to perform the analysis as (1) bare frame (without infill walls), (2) frame with fully infill walls, (3) frame models with infill panels and soft storey located at base level, 3rd storey level, 6th storey level, 9th storey level, and 12th storey level. The equivalent diagonal strut method has been utilized in order to account for the stiffness and structural action of the masonry infill panels. Dynamic time history, using two ground motion records from near and far-fault regions, has been used to perform the seismic analysis of the considered model configurations. The selected two ground motion records have been scaled to meet the expected peak ground acceleration in Cairo zone. The two ground excitations are applied separately in two orthogonal directions. The structural software package ETABS has been used in developing the building models and performing the simulation analysis. Some selected numerical simulation results in terms of storey shear forces, lateral deflections, interstory drift ratios and overturning moments at each storey level are obtained for all the considered configurations and presented in comparative way. Based on the obtained time-history results, it has been found that the dynamic storey responses for bare frame model significantly differ from the responses obtained for both fully infill and partially infill frame models.

Estimating Thrust Forces Resulting from Arching Action of Clay Brick Masonry Infill

AbstractASCE 41 requires that the thrust force effectuated by out-of-plane arching action of masonry infill panels against the bounding frame be considered in the assessment of masonry infill walls for which arching action is relied upon. Hence, a pre-existing but incomplete model for predicting the thrust force was amended with an empirical equation used to estimate the crushing strain of clay brick masonry based on experimental testing of masonry prisms and mortar cubes. The proposed empirical equation was used to estimate the out-of-plane wall rotation of masonry infill specimen panels, and the predicted values were compared with the experimental results from out-of-plane infill wall tests.

Seismic safety assessment of existing masonry infill structures in Nepal

Reinforced concrete (RC) buildings in Nepal are constructed with RC frames and masonry infill panels. These structures exhibit a highly non-linear inelastic behavior resulting from the interaction between the panels and frames. This paper presents an extensive case study of existing RC buildings in Nepal. Non-linear analyses were performed on structural models of the buildings considered as a bare frame and with masonry infill, in order to evaluate the influence of infill walls on the failure mechanisms. Five three-storey buildings with different structural configurations and detailing were selected. The effect of masonry infill panels on structural response was delineated by comparing the bare-framed response with the infill response. Seismic performance is evaluated with regard to global strength, stiffness, energy dissipation, inter-storey drift, and total deflection of the structure. A parametric analysis of structures with masonry infill is also performed. For this, the influence of different material properties is studied, namely diagonal compressive stress, modulus of elasticity and tensile stress of masonry infill panels. Study results show that masonry infill increases the global strength and stiffness of the structures; it decreases the inter-storey drift and hence the total displacement of the structure. The results quantify the influence of the infill panels on structural response and, in particular, the effect of the diagonal compressive strength of the masonry wall.

Procedures for calibration of linear models for damage limitation in design of masonry‐infilled RC frames

SummaryRecent earthquakes have confirmed the role played by infills in the seismic response of reinforced concrete buildings. The control and limitation of damage to such nonstructural elements is a key issue in performance‐based earthquake engineering. The present work is focused on modeling and analysis of damage to infill panels, and, in particular, it is aimed towards linear analysis procedures for assessing the damage limitation limit state of infilled reinforced concrete frames.First, code provisions on infill modeling and acceptance criteria at the damage limitation limit state are reviewed. Literature contributions on damage to unreinforced masonry infill panels and corresponding displacement capacity are reported and discussed.Two procedures are then proposed aiming at a twofold goal: (i) the determination of ‘equivalent’ interstory drift ratio limits for a bare frame model and (ii) the estimation of the stiffness of equivalent struts representing infill walls in a linear model. These two quantities are determined such that a linear model ensures a reliable estimation of seismic capacity at the damage limitation limit state, providing the same intensity level as that obtained from nonlinear analyses carried out on structural models with infills.Finally, the proposed procedures are applied to four‐story and eight‐story case study‐infilled frames, designed for seismic loads according to current technical codes. The results of these application examples are presented and discussed. Copyright © 2016 John Wiley & Sons, Ltd.

In-Plane Behaviour of a Reinforcement Concrete Frame with a Dry Stack Masonry Panel.

In order to improve the energy dissipation of the masonry infilled frame structure while decreasing the stiffening and strengthening effects of the infill panels, a new dry stacked panel (DSP) semi-interlocking masonry (SIM) infill panel has been developed. In this paper, the material properties of DSP and a traditional unreinforced masonry (URM) panel have been evaluated experimentally. A series of cyclic tests were performed to investigate the cyclic behaviour of the reinforcement concrete (RC) frame with different infill panels. The failure modes, damage evolution, hysteretic behaviour, stiffness degradation and energy dissipation were compared and analysed. We concluded that DSP is capable of significantly improving the seismic energy dissipation due to its hysteretic behaviour when the frame is in elastic stage without increasing the stiffness of the frame. Therefore, DSP or SIM panels can be considered as frictional dampers. Based on the experimental results, the influence of DSP was examined. Using the parallel model, the hysteretic loops of DSP subjected to different load cases were achieved. The typical full hysteretic loop for DSP could be divided into three distinct stages of behaviour: packing stage, constant friction stage and equivalent strut stage. The connection between the panel and the frame had a great effect on the transferring of different mechanical stages. The constant friction stage was verified to provide substantial energy dissipation and benefits to the ductility of the structure, which, therefore, is suggested to be prolonged in reality.

Analysis of the in‐plane response of earthen masonry infill panels partitioned by sliding joints

SummaryThe vulnerability of infilled frames represents a critical issue in many regions with high seismicity around the world where infills are typically made of heavy masonry as they are used for thermal control of the buildings because of their thermal inertia. In this context, the use of earthen masonry infills can give a superior performance because of their ability to regulate thermal‐hygrometric performance of the building and sustainability of its life‐cycle.This paper presents a numerical study on the seismic behaviour of infill walls made of earthen masonry and partitioned with horizontal wooden planks that allow the relative sliding of the partitions. The combination of the deformability of earthen masonry and the sliding mechanism occurring along the wooden planks gives a high ductility capacity to the in‐plane response of the infill and, at the same time, significantly reduces its stiffness and strength, as compared with traditional solid infills made of fired clay units. As a result, the detrimental interaction with the frame and the damage in the infill when subjected to in‐plane loading can be minimized.The numerical model is validated with results from an experimental study and is used to perform a parametric analysis to examine the influence of variations in the geometry and mechanical properties of the infill walls, as well as the configuration of the sliding joints. Based on the findings of this study, design guidelines for practical applications are provided, together with simple formulation for evaluating their performance. Copyright © 2016 John Wiley & Sons, Ltd.