Effect Of Infill Walls Research Articles

Beneficial Effects of Infill Walls on the Structure and Foundation Lateral Performance Under the Effect of Seismic Loads

Beneficial Effects of Infill Walls on the Structure and Foundation Lateral Performance Under the Effect of Seismic Loads

Effect of infill walls on seismic performance of multi-story buildings with shear walls

Effect of infill walls on seismic performance of multi-story buildings with shear walls

The Seismic Performance of Infill and Retrofitted Structural Walls under Earthquakes

To account for the effects of infill walls, the Iranian Code reduces the period of the structure. As a result, filler walls in the plane of structural frames result in significant changes in the properties they possess; therefore, the resistance, stiffness, ductility, distribution of internal forces, and other characteristics of such a frame with an empty frame differ greatly. In this research using 7 far-field earthquakes, a nonlinear time history analysis was performed on reinforced concrete frames with and without masonry infill walls. The maximum relative displacements between the stories were determined. Also, to evaluate the seismic performance of structural masonry walls, the fragility curve of unreinforced masonry walls retrofitted with FRP sheet based on different scenario under the effect of earthquake loads has been investigated by the finite element method. According to the results, the presence of infill walls reduces the number of plastic hinges as well as the maximum relative displacement between the stories. Furthermore, by increasing the number of FRP sheet layers and the reinforced area of the FRP sheet to the entire wall of an unreinforced structural wall, the seismic behaviour of the wall is more effective than other reinforcement patterns and damages the wall less.

Effect of infill walls on progressive collapse behavior of self-centering precast concrete frame

To study the effect of infill walls on the progressive collapse resisting-performance of self-centering precast concrete (PC) frame structures, three 1/2 scaled, two-span and two-story self-centering PC frame specimens with and without infill walls were tested under quasi-static pushdown loading regime. The test results showed that the failure modes of self-centering PC frames were governed by concrete cracking and local spalling at the beam ends under progressive collapse scenario. Compared with self-centering bare frame, the presence of infill walls provided additional load path, thereby reducing the concrete damage at the beam ends to some extent. The full infill walls with lower strength could still increase the initial stiffness and peak resistance of self-centering bare frame to 2.47 times and 1.33 times, while the infill walls with 20% opening ratio could increase to 2.21 times and 1.19 times, respectively. Nevertheless, the infill walls also reduced the self-centering capacity of the structures. Numerical analyses further indicated that the magnitude of prestress force of steel strands between beams and columns, the strength of bed joints as well as the width of infill walls had a great effect on the progressive collapse of self-centering infilled frames. Finally, based on numerical results, a reduction factor formula was proposed to quickly estimate the structural resistance of self-centering infilled frames with different opening ratios.

Collapse performance of post-tensioned steel frames considering influence of infill walls

The aim of this paper is to study the effect of infill walls on load resisting behaviors of post-tensioned (PT) steel frames against collapse. Three planar PT steel frames are simulated using finite element (FE) method, one of which has no infill wall while the other two are installed with infill walls. The applied loads, lateral displacements, failure patterns, stress developments in infill walls, resisting mechanisms, as well as re-centering capabilities of three PT steel frames are studied and the role that infill walls play is discussed. Parametric analyses are conducted to investigate influences of magnitude of PT forces and critical material properties. Results indicate that infill walls work as compressive struts, significantly increasing initial stiffness, resistance and story drifts of PT steel frames, and play as energy dissipation devices during the collapse process. The existence of opening makes the stiffness distributed discontinuously throughout infill walls, greatly changing the failure pattern and increasing story drifts of PT frames. The resistances of infilled PT steel frames increase with increasing PT forces, bed joints strength and masonry unit strength in the initial stage. A design scheme is also developed to precisely predict the collapse resistance of infilled PT steel frame structures.

Seismic behavior of hinged steel frames with masonry infill walls

Historic buildings are important parts of our cultural heritage and contribute to the social and economic of communities. Hinged steel frames with masonry infill walls were extensively used in conserved historical buildings built in the early 20th century in Shanghai, China. Those historical buildings are characterized by low strength in materials and the seismic actions were not properly considered in designs. Therefore, a better insight into their seismic performance assessment is necessary for both structural rehabilitation and maintenance of historic architectural features. This paper describes an experimental and numerical investigation on seismic behavior of hinged steel frames, with a special focus on the effect of masonry infill walls. Shaking table tests were conducted on two 1:4 scaled three-story, two-bay hinged steel frame model structures, i.e., a bare steel frame (Model M1) and a steel frame with masonry infill walls (Model M2). Three seismic records, i.e., Shanghai artificial signal (SHW-II, which was specified for the type IV soft base conditions in Shanghai), El Centro signal (obtained from the Imperial Valley earthquake in 1940) and Pasadena signal (obtained from the Kern County earthquake in 1952) were selected. The failure modes, dynamic characteristics, acceleration, inter-story shear forces as well as inter-story drifts of the two model structures were measured and compared. Three-dimensional finite element (FE) models of hinged steel frames with and without masonry infill walls were established. Effects of the stiffness of beam-column joints and the distribution of infill walls were also investigated. Results indicated that masonry infill walls altered the distribution of lateral force and increased the stiffness of the frame, leading to a noticeable reduction of structural deformation. The effect of infill walls was related to the ratio of stiffness of the walls to that of surrounding frames. In addition, a soft-story mechanism could occur in the case of partially infilled frames.

Assessment of the effects of infill walls’ layout in plan and/or elevation on the seismic performance of 3D reinforced concrete structures

Assessment of the effects of infill walls’ layout in plan and/or elevation on the seismic performance of 3D reinforced concrete structures

The effect of precast concrete infill wall on the seismic performance of PCCSW

Lateral stiffness provided by infill walls to the building structures is generally neglected in designs. However, the infill walls, served as the main nonstructural component, have significant influence on the seismic behavior of the main structures during seismic events. To investigate the effects of the infill walls on the seismic behavior of the precast concrete (PC) coupled shear walls (PCCSW) with infill walls, lateral cyclic loading tests were conducted on three PC coupled shear walls, including two specimens with rigid and flexible connections between the PC coupled shear walls and infill walls, and a specimen without infill walls for comparison. The test results showed that the infill walls can improve the strength and stiffness of the PC coupled shear walls but at the cost of the ductility and energy dissipation, especially for the specimen PCCSW with rigid connection. In addition, the finite element analysis (FEA) models of the PC coupled shear walls were proposed, and the reliability and accuracy of the FEA models were validated based on the test results. Subsequently, a parameter study was conducted to assess the influence of the critical parameters on the mechanical behaviour of the shear wall. Finally, the simplified calculation methods for the peak strength of the shear wall were also proposed, and the theoretical results matched well with the test and simulation results.

Seismic performance of RC frames with self-centering precast post-tensioned connections considering the effect of infill walls

This paper presents the seismic performance evaluation of self-centering precast post-tensioned concrete (SCPPTC) frames with infill walls. The SCPPTC connection system consists of all-steel bamboo-shaped energy dissipaters (SBED) and prestressed tendons, which provide energy dissipation capacity and self-centering capability, respectively. Using modeling parameters calibrated with experimental tests, nonlinear numerical models of SBED, SCPPTC connection, infill walls, and 2D SCPPTC frames were developed in OpenSees, to compare the performance of the structures with different types of infill wall layouts. Nonlinear static pushover and incremental dynamic analysis (IDA) were performed to study the effect of infill walls on the overall response of SCPPTC frames, in terms of stiffness, strength, maximum interstory drift ratio,θmax, the maximum residual interstory drift ratio, θr,max, and the normalized post-tensioned force. Using the IDA results, the study also developed fragility curves and estimated the collapse margin ratios. The results demonstrated that the shear strength of the SCPPTC frame was improved from 4.19% to 12.2%, and the initial secant stiffness of the SCPPTC frame was augmented from 22.9% to 88.3% with increasing filling rate. The totally infilled SCPPTC frame (SCPPTC-ToI) exhibits a 19.86% lower θmax than that of pilotis-infilled SCPPTC frame (SCPPTC-PiI) under rare earthquakes, and the maximum prestress of SCPPTC-ToI was also 7.14% lower than that of SCPPTC-PiI. With the increase in filling rate, θr,max increased by a maximum of 120.45%. The pronounced soft layer led to the highest failure and collapse probabilities of SCPPTC-PiI among all SCPPTC frames at the same performance level.

Collapse capacity assessment of non-ductile open ground story reinforced concrete frame

It is a well-known fact that the absence of infill walls at the ground story, which is termed as “open ground story” may lead to a soft-story deficiency, especially in the case of non-ductile buildings. The previous severe earthquakes have shown that catastrophic destruction may occur in such a condition. Therefore, the seismic assessment of open ground story reinforced frames, where the effects of infill walls are incorporated, is of vital importance. However, the effects of infill walls are generally disregarded or considered indirectly in the seismic assessment procedures of the codes. This may mislead the actual condition of the open ground story buildings at different performance levels. This study aims to assess a non-ductile reinforced concrete frame with an open ground story regarding the collapse prevention performance level. The pushover and incremental dynamic analyses results are evaluated following the code limitations for collapse prevention. The results demonstrate the measure of misleading caused by the ignorance of infills at the upper stories while applying these code limitations.

Evaluating the effect of infill walls on seismic responses of post-tensioned self-centering concrete frames based on a new analytical model

This paper proposes a numerical model with the lump plasticity rotational springs for the simulation of post-tensioned self-centering (PTSC) concrete frames. The analytical connection model that is able to properly capture the joint responses and connection damage is incorporated in the rotational springs. The static and dynamic numerical results are validated against those obtained using the fiber-based structural model. Furthermore, the proposed numerical model is adopted in the seismic response prediction of PTSC frames with infill walls (IWs) and various energy dissipation components. Incremental dynamic analysis is performed through the scaling schemes based on Sa(T1) and PGA, and the effects of IWs and energy dissipators on the structural responses under different ground motion inputs are compared. The numerical results indicate a remarkable reduction in the inter-story drifts of the PTSC frames with IWs as compared to the bare frames under the same Sa(T1). Nevertheless, when subjected to ground motions with large PGAs, the damage of IWs would induce rapidly increased inter-story drifts in the lower floors, which may exceed the drifts of bare frames under the same earthquake intensity. This study highlights the accuracy of the proposed numerical model and the importance of considering IWs in the seismic response predictions of PTSC concrete frames.

Seismic resilience assessment of buildings considering the effects of mainshock and multiple aftershocks

Seismic resilience assessment is a hot topic for highlighting the functional recovery of structures in post-earthquake environments. The current resilience assessment method generally ignores the effects of aftershocks, even though more than 85% of mainshocks are followed by multiple aftershocks that further increase functionality loss and recovery time. This study proposes a method to quantify the resilience of structures under mainshocks and multiple aftershocks. The concept of aftershock affecting time window is proposed to assess the effects of aftershocks on the recovery time of structures. Additionally, the effects of infill walls on the state-dependent fragility results and resilience of the structure are considered in this method. The proposed method is applied to two reinforced concrete (RC) frame structures, and the effects of multiple aftershocks and infill walls on the resilience are quantitatively studied. The results indicate that multiple aftershocks increase the economic loss by 20%–30% on average, and the aftershock affecting time can account for more than 20% of the total recovery time. The exclusion of infill walls in the finite element model of the structure induces a significant bias in the resilience assessment results at a minimum level of 25%.

The influence of ground motion duration on the energy based assessment of buildings with infill walls

Infill walls are often used in buildings to divide the residential area in order to meet the architectural requirements and are considered as non-bearing structural elements. In some buildings, infill walls are not used in the frames of the ground floors for commercial or other architectural purposes. Thus, vertical infill wall discontinuity is formed and it appears as an irregularity by earthquake regulations. At the same time, this situation has caused damage to the structures in some earthquakes. Nowadays, traditional seismic design based on strength and resistance is considered not an adequate way to design structures under earthquake effects. Besides, the role of ground motion duration on the seismic performance of building structures has been subject of research recently. One of the methods of defining damage in earthquake resistant design is the energy approach. For this purpose, in this study, the effect of infill walls on the seismic assessment of structures exposed to short and long duration ground motions was performed on dissipated seismic energy approach. Nonlinear time history analyses were performed in two cases, fully infilled and infilled except for the ground floor. Classification of ground motion durations is based on a threshold of 25 s of significant duration (D5-95), and ground motions were evaluated as two different recording pairs of short and long duration. Using spectrally matched short and long duration earthquake records, nonlinear time history analyses were performed for building models and the results were evaluated over hysteretic energy. The analyses showed that the hysteretic energy demands depend on both the ground motion duration and the infill wall placement in the building.

Effect of masonry infill walls on the nonlinear response of reinforced concrete structure: October 30, 2020 İzmir earthquake case

On October 30th, 2020, at 14:51, İzmir was hit by an Mw = 6.6 magnitude earthquake. The earthquake caused significant damage in Bayraklı, Karşıyaka, and Bornova districts. Structural damage and life losses were observed to be concentrated in Bayraklı region of İzmir. Twelve reinforced concrete buildings were collapsed in Bayraklı.Previous devastating earthquakes have shown that the damaged buildings are not very high-rise buildings, generally the lower storeys of which are car parks, and commercial enterprises, and there are no infill walls on the ground storeys. The same happened in the buildings destroyed in the October 30, 2020, İzmir earthquake.In this study, the effects of infill walls in reinforced concrete buildings under earthquake effects were investigated. For this purpose, a building damaged in the 2020 İzmir earthquake was examined. The building discussed in the study was modeled in the SAP2000 V22 finite element program in two different ways, with and without infill walls, using the real parameters of the building. As a result of the study, the results of the analysis were compared, and it was observed that the infill walls positively affected the features of the building, such as period, ground storey shear force, column bearing capacity, inter-story drift ratio, and base shear forces on the ground storeys, and increased the base shear force.

Investigation of Seismic Performance for Low-Rise RC Buildings with Different Patterns of Infill Walls

Evaluating the structural performance of low-rise RC buildings with infill walls is an essential issue in Thailand, as most infill walls were not designed for lateral load resistance. The purpose of this study was to predict the structural behavior and illustrate the effects of infill walls. Residential, commercial, and educational buildings were selected as representative buildings with different patterns of infill walls. Based on the results, infill walls contributed to considerable strength and stiffness. Most of the infill walls that affected the low-rise buildings were at the ground floor level. The behavior of the buildings that had a contribution of infill walls was found to be brittle until the infill walls collapsed, and then the buildings became ductile. Some patterns in which infill walls were placed improperly led to a torsional effect, resulting in columns in the affected areas reaching failure criteria more than those without this effect. Considering the NLRHA procedure, only infill walls on the ground floor contributed to the building being subjected to a ground motion. The fully infilled frame tended to reach the infill crack before the other patterns. For the UMRHA procedure, only the first vibration mode was adequate to predict seismic responses, such as roof displacement and top-story drift.

Seismic collapse assessment of reinforced concrete frames infilled with hollow concrete bricks

Lessons from past earthquakes indicate that infill walls affect the seismic collapse resistance of the frame. However, research on quantifying the effect of infill walls on the frames’ seismic safety is limited. Therefore, this paper focuses on this issue. Firstly, the finite element models of reinforced concrete frame infilled with hollow concrete bricks (HCB) are developed and validated by a laboratory test of a one-span one-story infilled frame. Then, the earthquake-induced collapses of infilled frames are simulated and discussed. The influence of the HCB infill wall arrangement on the seismic collapse resistance of frames with different heights is quantitatively studied. The results indicate that the HCB infill wall reduces the collapse resistance capacity by 24.5% for frames with an open ground floor. In contrast, the improvement in the collapse resistance by infill walls gradually decreases with the increase in structural height for frames with continuous HCB infill walls. The collapse resistance can even be reduced when the frame exceeds eight stories.

The Over-Strength Coefficient of Masonry-Infilled RC Frame Structures under Bidirectional Ground Motions

The over-strength coefficient is one of the key factors for the seismic safety of a structure. For RC frames, the infill wall may improve the lateral bearing capacity, while the seismic demand increases as well, which leads to the unexpected seismic performance of an infilled RC frame in past earthquakes. Therefore, it is necessary to systematically study the over-strength effect of the infilled RC frames from the point of seismic capacity and demand. In this paper, 36 RC frame structures with/without infill walls are designed, and the corresponding finite element modelings, considering the in-plane and out-of-plane performance coupling effect of infill walls, are established to conduct incremental dynamic analyses (IDA). The seismic capacity values of over-strength coefficients are calculated, utilizing the IDA results under bidirectional ground motions. The effects of seismic precautionary intensity and number of stories on the over-strength coefficient of the RC frame with/without infill walls are discussed. The over-strength coefficient capacity value of the infilled frame is apparently higher than that of the bare frame, due to the contribution of infill walls. However, the seismic demand analysis of the over-strength coefficient shows that the capacity–demand ratio of masonry-infilled RC frame structures is greatly reduced, especially for the bottom soft-story infilled frame.

Farklı Dolgu Duvar Malzemelerinin ve Planda Yerleşimlerinin Betonarme Bir Yapının Davranışına Etkisi

It is known that infill walls affect the strength and rigidity of the structure, although the effect of infill walls is neglected in the calculation and design of reinforced concrete structures. In this study, the effects of two different infill wall materials, namely vertically perforated brick and gas concrete block, and different wall locations on a ten-storey symmetrical structure with six spans in the x-direction and three spans in the y-direction with a reinforced concrete framed load-carrying system were investigated. According to Turkey Building Earthquake Code-2018, 16 models were examined in the SAP2000 program, which is based on the finite element method. Infill walls with different materials are defined in the program as a single equivalent pressure bar according to their properties. The effects of different infill wall types and different infill wall placements on the horizontal displacement of a reinforced concrete framed structure, relative storey drifts, strength, and the performance target of the building under horizontal and vertical loads were examined on the models made. As a result of the research, it was observed that infill wall material types and infill wall location significantly reduced the horizontal displacement of the structure in both directions, while increasing the rigidity of the structure and decreasing its period.

Evaluation on the progressive collapse resistance of infilled reinforced concrete frames based on numerical and semi-analytical methods

The effect of infill walls on the progressive collapse behaviour of reinforced concrete (RC) frames should be fully considered due to the formation of alternative load paths. To explore the configuration that could affect the progressive collapse resistance of infilled RC frames, parametric analyses are performed based on the validated simulation method. In the study, the impact introduced by the extra tie and integrity rebars in walls is emphasised. It is indicated that the variation in the reinforcement ratio of tie rebars leads to a limited change in structural progressive collapse resistance. In contrast, with the arrangement of the integrity reinforcement, the progressive collapse resistance of the infilled frames is enhanced and the propagation of the diagonal cracks in partial infill walls is suppressed. The notable re-ascending trend in the resistance curve for models with integrity rebars reveals the significant development of the catenary action in the integrity reinforcement. Then, with the help of linear regression and gene expression programming (GEP) techniques, a semi-analytical model is proposed for the prediction of the load-bearing capacity of infilled frames after column loss. In the prediction model, the linear effect of geometrical parameters and the non-linear effect of openings on the progressive collapse resistance are included by introducing three modification coefficients. Based on the statistical assessment, the capability of this explainable model is verified, and the appropriate amount of integrity reinforcement to mitigate the progressive collapse is discussed.

Effect of Material Used for Infill Wall and Its Shape on the Seismic Performance of RC Frame

Abstract: RC frame structure is one of common used building structures. Previous studies show that infill wall significantly contribute to the seismic performance imposed on RC frame structure, increasing structural stiffness and hence leading to decrease structure's natural period. However under strong earthquake, infill wall not only holds up large lateral seismic force but also limits the deformation of beams and columns. In most of the previous studies on the behaviour of reinforce concrete building considering the effect of infill wall, rectangular shape of brick is taken into account. In this study, an attempt has been made to look over the effect of infill wall material type and its shape on the seismic performance of RC frame. This study will be restricted with single bay frame with two types of bricks a) Clay brick, b) Fly ash brick. The different shapes under consideration are rectangle and square. This study also contains the effect of size of infill wall units. The stress in concrete, lateral force resisting capacity and displacement results have been obtained by finite element analysis and compared for all the cases. Keywords: RC frame, Infill, Micro modelling, FEA, ABAQUS