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Many reinforced concrete (RC) frame buildings in Nepal were significantly damaged by the 7.8 magnitude (Mw) earthquake in Nepal on April 25, 2015. To contribute to mitigate future earthquake disasters, the current study focuses on two specific characteristics of residential RC frame buildings in the capital city of Nepal, Kathmandu: the application of brick masonry infill to exterior and partition walls, and the conventional vertical extension of building stories different from the design. Although these factors are likely to significantly affect the seismic performance, their effects are frequently neglected in practical design and construction management in developing countries. Hence, the main objective of this research is to investigate and clarify the seismic performance of RC frame buildings considering the above factors through experimental and numerical investigations. The present paper (1) briefly introduces the characteristics of a typical residential RC frame building in Kathmandu, (2) illustrates the numerical modeling parametrically considering three different contributions of brick masonry infill walls and (3) investigates the seismic performance of the RC frame building considering the effects of the infill wall modeling and the vertical extension through numerical analyses. Consequently, it was found that the consideration of the in-plane stiffness and strength of the infill walls resulted in both positive and negative contributions to the seismic performance of low-rise (up to three stories) and medium-rise (more than three stories) buildings respectively, quantitatively clarifying significant effects of the presence of infill and the vertical extension. These findings contribute to provide realistic solutions to upgrade the seismic performance by utilizing or removing the brick masonry infill walls or by managing the building stories to mitigate future earthquake disasters on typical RC frame buildings not only in Nepal but also in other countries with similar backgrounds.

This paper deals with the effect of cover thickness in a reinforced concrete columns of 3-D (three dimensional) frame structures under progressive collapse assessment. The concrete cover protects the reinforcements of structural elements from corrosion and other environmental effects. Even under thermal effects, the concrete cover plays a vital role by preventing the temperature to reach the reinforcements which are present inside. An optimum amount of cover thickness must be provided to the structural elements to withstand sufficient loads and sustain environmental conditions. To study the influence of cover thickness in frame structures, a single-bay single-story 3-D reinforced concrete frame was analyzed under fire scenarios using ABAQUS (FEA). Two nominal cover thicknesses were adopted likely 40 mm and 45 mm for the columns in the frame structure as they are the main load-carrying element. The important structural aspects such as axial load-carrying capacity, thermal expansion, deformation, stiffness, bending moment, and shear force were studied under the considerations of frames with slab and masonry infill wall. It was observed that the nominal cover thickness of 45 mm increases the structural performance and thermal resistance, and can sustain other environmental conditions in a better way.

The existing seismic provisions across the world account the non-linear response of a structure in a linear elastic design implicitly using a constant behavior factor, or response reduction factor (R). However, this factor (R) does not address the effects of changes in structural configurations, which eventually alters the dynamic behavior of the structure. Hence, the adequacy of prescribing a constant factor to account for the variable dynamic characteristics of structural systems always appears contentious. Further, seismic analysis of RC buildings usually ignores the interaction of the infill wall with the structural frame leading to inappropriate evaluation of dynamic characteristics of the structure. Hence, in the present research, it is attempted to investigate the sufficiency of the code-based ‘R’ factor in assessment of seismic behavior using non-linear static analysis (NLS) and non-linear dynamic analysis (NLD) for the structural models considered. Moreover, the results obtained, clearly envisages the influence of structural configuration changes and interaction of the infill wall with the RC MRF on dynamic characteristics in terms of ductility and over strength values. It can be clearly observed that, the code specified constant ‘R’ for a particular structural type appears erroneous, emphasizing the need for its adequate estimation. This should involve consideration of the dynamic characteristics of the structure resulting in a realistic assessment of seismic demand, thereby contributing to a safe, functional and economical design configuration.

This study investigates the effect of infill walls on the risk of progressive collapse in reinforced concrete (RC) frames. Previous studies are suggestive of the effect of infill walls on improving the structural strength and rigidity against seismic failures. However, there are few studies on the effect of infill walls under vertical forces induced by progressive collapse. It is anticipated that infill walls would also contribute to the structural strength and rigidity during a progressive collapse. The results of this study can help better our understanding of the performance of concrete frames with infill walls during the progressive collapse. To this end, a three-dimensional model was developed for the nonlinear finite element analysis of an RC frame with infill walls under progressive collapse conditions. Experimental results have been used for calibrating the numerical model. The effect of the infill wall, infill wall arrangement, openings in the infill wall, and the opening size, location, and shape were investigated. According to the results, infill wall significantly increased structural strength and rigidity against progressive collapse. Moreover, studied alternatives may help better understanding of the performance of infilled RC frames during progressive collapse.

This paper presents a mechanical model developed for the simulation of the monotonic behaviour of Steel frames with Reinforced Concrete infill Walls (SRCW). In particular, it deals with a specific typology of SRCW, obtained from the classical one through the interposition of dissipative elements in the columns and by stiffening and shaping the steel frame’s corners in a way to prevent the brittle failure of the concrete in compression. This system has demonstrated in past researches to be able to overcome the typical problems of SRCWs and to assure, through a capacity design approach, a global ductile behavior. The selection of the main components to be included in the model is carried out on the base of the analysis of the available experimental tests and of the results of accurate 3D Finite Element model analyses. The behaviour of each component is represented though consolidated models present in the current state-of-the-art and, where necessary, calibrated using the results of the experimental and numerical analyses. The capacity of the proposed mechanical model in representing the global behaviour of the SRCWs is finally demonstrated comparing the results in terms of force–displacement curves with the ones obtained through the refined 3D Finite Element models.

A macro-modelling approach is proposed for representing the masonry infill walls in a non-linear analysis of infilled frame structures. The infill wall is modelled by equivalent struts. The paper presents a combination of an experimental testing method and analytical method to determine the constitutive law of the equivalent struts model. Thus, the model is based on the physical behaviour of the infill wall, rather than on empirical values that came from experimental or numerical tests of infilled frames. Upon requirement, the model can be developed to horizontal or vertical distortion of the infill wall. The strut model was incorporated in a detailed, micro non-linear two-dimensional finite element analysis and validated against reinforced concrete frames infilled by hollow concrete blocks and autoclaved aerated concrete blocks subjected to loss of supporting column scenario. The validation procedure showed that the model captures not only the stiffness and the resistance of a reinforced concrete infilled frame but also the failure mode and the pattern of cracking of the frame.

This paper investigated the interactive behaviors of infill walls and frames in steel plate shear wall (SPSW) systems reinforced by fiber-reinforced polymers (FRPs), using the finite element method. The effects of the system aspect ratio/height as well as the fiber type/orientation/content are also considered in the study. The results show that, in general, the use of FRPs improves the system strength/energy dissipation/secant stiffness, while it adversely affects the system ductility and it has no significant or clear effect on the system initial stiffness/damping ratio. The fiber modulus of elasticity and tensile strength properties have a dominant role in the composite system strength, while its ductility plays a major role in the failure time of FRPs. The use of FRPs slightly increases the level of stresses in the frame, while it affects the growth of stresses and thus the effectiveness of the infill wall in the initial stages of loading. In single-story SPSWs, the use of FRPs affects mainly the infill wall behavior, while in multi-story ones, due to a greater degree of wall–frame interaction, it affects both of the infill wall and frame behaviors.

During seismic events, high-rise buildings with soft ground storey are vulnerable to damage as there is a sudden change of stiffness along its height. In this study, different types of energy dissipation devices, which include lower toggle bracing, double-bracing fluid viscous damper, single-bracing fluid viscous damper and single-bracing friction damper, and traditional infill wall are implemented in a 12 storied soft-storey building to assess their influences on reduction of building’s responses during seismic events. These retrofitted buildings are analysed bi-directionally with various ground motion time history of Kolkata region, India. It is seen that energy dissipation devices proved to be better than traditional infill wall due to the fact that the devices enhance the damping capacity as well as stiffness strengthening to the building while traditional infill wall enhances only stiffness strengthening to the building.

Concrete block infill walls, due to their high strength and stiffness, can significantly influence the seismic behavior of the frames. The infill walls can increase the overall lateral frame strength and can also induce local failures in the surrounding frames. In general, if local failure can be avoided, the presence of the infill walls can provide additional reserved strength that can be beneficial to the frames. For this reason, a new RC frame with infill walls could be designed as a bare frame without considering the increase in strength, but measures must be taken to prevent local failures due to the infill wall-frame interaction. However, this infill wall-frame interaction is very complex, and clear design strategies to prevent local failures are not normally given in design codes. For this reason, two full-scale intermediate RC moment-resisting frame specimens with infill concrete block walls were tested under a horizontal cyclic load to study the infill wall-frame interaction. Finite element analysis was carried out to evaluate the response particularly on the infill-frame interactions. Based on the results, a design strategy to eliminate local failure in the surrounding frame is suggested. The proposed method is based on local plastic mechanism analysis of the column considering the variation in the column shear demand and column shear capacity at different states of the response as the frame deforms. The shear demand depends on the magnitude and direction of the bearing force from the infill wall. The column is considered as a captive or slender column depending on the restraint from the infill wall, thereby affecting the shear capacity of the column. The proposed approach can be readily applied without radically changing common design practices and design codes.

Several strengthening techniques such as steel plate bonding, external post-tensioning, steel bracing, or addition of new structural elements have been widely used to improve the seismic behaviour of structures, which suffer from earthquakes. Especially, adding infill walls and shear walls to the structures are preferred because of the added increase in lateral strength and stiffness. Nevertheless, applications of these techniques have some difficulties in terms of labour, cost, usage, and comfort for occupants. Due to these difficulties, the exterior shear wall, instead of an infill wall, is applied to strengthen structures, especially for public buildings like schools, hospitals, etc. In this study, the seismic behaviours of the exterior shear walls used to strengthen intact and damaged frames were investigated experimentally. For this purpose, reinforced concrete shear walls were positioned in parallel to the exterior sides of the damaged and the intact three-dimensional frames. Both frames were tested under cyclic loads. After the investigation, the hysteresis curve, strength envelope, stiffness degradation, and the energy dissipation capacity were obtained to reveal the seismic behaviour of the strengthening exterior shear walls. In addition to these, the differences in behaviours of the shear walls applied to damaged and intact frames were identified.

As a type of nonstructural component, infill walls play a significant role in the seismic behavior of high-rise buildings. However, the stiffness of the infill wall is generally either ignored or considered by simplified empirical criteria that lead to a period shortening. The difference can be greatly decreased by using a structural identification methodology. In this study, an ambient vibration test was performed on four on-site reinforced concrete high-rise buildings, and the design results were compared with the PKPM models using corresponding finite element (FE) models. A diagonal strut model was used to simulate the behavior of the infill wall, and the identified modal parameters measured from the on-site test were employed to calibrate the parameters of the diagonal strut in the FE models. The SAP2000 models with calibrated elastic modulus were used to evaluate the seismic response in the elastic state. Based on the load-displacement relationship of the infill wall, nonlinear dynamic analysis models were built in PERFORM-3D and calibrated using the measured modal periods. The analysis results revealed that the structural performance under small/large earthquake records were both strengthened by infill walls, and the contribution of infill walls should be considered for better accuracy in the design process.

The artificial bee colony (ABC) algorithm is a recently introduced swarm intelligence algorithm for optimization, which has already been successfully applied for the training of artificial neural network (ANN) models. This paper thoroughly explores the performance of the ABC algorithm for optimizing the connection weights of feed-forward (FF) neural network models, aiming to accurately determine one of the most critical parameters in reinforced concrete structures, namely the fundamental period of vibration. Specifically, this study focuses on the determination of the vibration period of reinforced concrete infilled framed structures, which is essential to earthquake design, using feed-forward ANNs. To this end, the number of storeys, the number of spans, the span length, the infill wall panel stiffness, and the percentage of openings within the infill panel are selected as input parameters, while the value of vibration period is the output parameter. The accuracy of the FF–ABC model is verified through comparison with available formulas in the literature. The results indicate that the artificial neural network, the weights of which had been optimized via the ABC algorithm, exhibits greater ability, flexibility and accuracy in comparison with statistical models.

The contribution of masonry infill frames to the lateral resistance of the structural frame is mostly neglected while designing the building structures. However, it is already shown in the literature that the masonry infill wall can have a positive or negative contribution by enhancing the stiffness of the infilled frame in most cases. The majority of research (either analytical or experimental) that already took a place in the literature focused on mechanical behavior of masonry-infilled single frames (one story and one bay). The lateral load carrying capacity of a single masonry infill wall in multistory structural frames that have multiple bays have not been deeply investigated. For such investigation, a three-story structural frame that has three bays is taken into the consideration in this study. The behavior of masonry infill walls at different locations are investigated for various neighboring conditions. It is observed that the resistance of a single masonry wall varies as the neighbor wall situation change and as the location of the wall in the frame changes. By using the numerical analyses results, an empirical correction factor is proposed for the equivalent compression strut stiffness of masonry infill wall that regards the location and neighboring conditions. It can be concluded that the proposed correction factor for equivalent compression strut models brings the estimation of the nonlinear behavior for whole structural frame to a safer level.

Engineered Cementitious Composite (ECC) is an advanced composite material with strain-hardening and multiple-cracking behaviors. In this study, two types of ECC materials were troweled on masonry infill walls strengthened with expansion bolt and interfacial agent. The seismic performance of the unreinforced and the ECC reinforced masonry structures was evaluated by the reversed cyclic loading test. The results showed that the application of the ECC on the masonry infill walls can improve the ultimate bearing capacity (in plane), ductility, stiffness and accumulative energy dissipation of the structure. Compared with the masonry structure with one side reinforced by the ECC, the structure with both sides reinforced by the ECC could better improve the ultimate bearing capacity, stiffness and cumulative energy dissipation with little difference on the ductility improvement. Moreover, the expansion bolt and the interfacial agent used to improve the connection between the ECC and the masonry structure have the ability to greatly increase the mechanical properties of the structure under cyclic loading.

This paper studies the influence of the shear studs distribution, in terms of local and global effects, on the behavior of dissipative hybrid Steel frames with Reinforced Concrete infill Walls (SRCWs). Dissipative SRCWs have been recently proposed as seismic resistant systems, capable of coupling the high stiffness of reinforced concrete walls with the advantages of dissipative systems, in which the energy dissipation takes place in localized and replaceable elements. However, experimental tests showed that the global behavior and the failure mechanism of such systems are strongly influenced by the shear studs distribution along the steel frame—reinforce concrete wall interface. In this paper, this issue is studied through suitable numerical models, calibrated on the base of the available experimental results. Several modeling options and strategies are considered and their influence on the final results has been assessed. The resulting numerical model is used to analyze the mechanical behavior of such system and to perform parametric analyses varying the shear studs distribution. The results obtained help the understanding of the mechanical behavior and of the resisting mechanisms activated on the studied system, supplying relevant information for the development of more accurate design rules.

Surveys on damaged and collapsed reinforced concrete (RC) buildings following recent earthquakes indicated that poor performance is associated with the influence of unreinforced masonry (URM) infill walls. In the event of an earthquake, a typical URM infill wall is subjected to a three-dimensional acceleration field and undergoes simultaneous in-plane (IP) and out-of-plane (OoP) loading. Depending on the direction of the seismic action, the observed damage mechanisms for URM infill walls may be classified as IP and OoP performance failures or a combination of both. Since the turn of the millennium, there have been a number of distinct experimental studies in the field of infilled frames, addressing the OoP response of URM infill walls. This has led to a number of numerical macro models able to represent the OoP behavior of the URM infill wall. The main limitation of the proposed models is the difficulty in using them as practical models, since all the proposed models were implemented in software tools without a graphical user interface (GUI), such as OpenSees. In this paper, one of the recently presented models is utilized and a methodology presented for a more practical and user-friendly implementation. The model previously validated using OpenSees is recalibrated and revalidated using the computer software SAP2000, which has a powerful GUI utilizing the material models and numerical elements available in the program library. The model considers the IP and OoP response as well as their interaction. For the determination of failure patterns, respective local damage grades for primary (frame) and secondary (infill wall) elements are defined. Finally, a four-story RC frame structure with URM infill walls, which was tested in the European Laboratory for Structural Assessment considering the IP response only, is used to assess the combined failure mechanism of URM infill walls through the concept of interaction curves.

The masonry infill walls influence substantially the response of reinforced concrete (RC) buildings under lateral loading due to their contribution to strength and stiffness. In the literature, there are several approaches for modelling the infill walls. However, they provide different results. In this study, the equivalent diagonal strut model was used. The basic parameter of this strut is its equivalent width. In the first stage of the study, various equations available in the literature for determining the width of the compressed diagonal strut were compared. Among them, Paulay and Priestley relation which gives approximately average value was selected for modelling the masonry infill walls. In the second stage of the study, a sensitivity analysis was performed by considering 2-, 4-, 6- and 8-storey RC bare frames and those with infill walls. Four different infill wall frame configurations, namely fully infilled frame, fully infilled-except first storey frame, interior bay infilled frame and interior bay infilled-except first storey frame, were adopted. Single-strut and three-strut models for simulating wall panels were used in all infilled frames. Thus, a total of 36 different RC frame models were evaluated through the nonlinear pushover analysis in order to appraise the infill wall effect on the overall response of the case study frame buildings. The analysis of the results indicated that the arrangement of the infill panels over the elevation of the frame remarkably influenced the performance of structures. Moreover, the serious capacity degradation was observed especially for the case of infills discontinued at the ground level.

The work presented in this study aimed to investigate the hysteretic behavior of composite partially restrained (PR) steel frame-reinforced concrete infill walls (PSRCW) with vertical slits, which consisted of a PR steel frame, a slit-reinforced concrete (RC) infill wall, and shear connectors. An experimental program at one-third scale of a one-bay by three-story PSRCW with vertical slits was tested under horizontal cyclic loading. The seismic behavior was examined in terms of the lateral load-carrying capacity, ductility, deformability, lateral stiffness, and energy dissipation. The results showed that this kind of structure exhibited superior ductility and deformability, as well as excellent energy-dissipation capacity. The slit RC infill walls exhibited flexure-dominated behavior and significantly increased the lateral load-carrying capacity. In contrast, the slit RC infill walls decreased the rotation demand on the PR connections from earthquake, which avoided the fracture failure of the beam-to-column connection. Additionally, the test results were verified, and relative parametric analyses of PSRCW with vertical slits were conducted by using a simplified macro fiber model to illustrate the factors that influence the structural hysteretic behavior.

In this paper, four large-scale one-story steel moment-resisting frame specimens have been tested. The first specimen is a onestory steel moment-resisting frame without masonry infill walls. The second is similar to the first but with infill wall having full physical contact to the frame. The other two are non-structural infill walls. The first non-structural infill wall has a complete decoupling from the frame, while the second has a full contact at the top of the wall and separated from the columns. The results of this paper have shown that life safety performance level for non-structural infill wall having a complete decoupling from the frame has satisfied the allowable story drift. This was not the case for infill wall having full physical contact to the frame or nonstructural infill walls sepatared from two sides.

This study focuses on the in-plane behaviour of unreinforced masonry (URM) infill walls installed in reinforced concrete (RC) frames. Five 1/4-scale model frames were designed based on a prototype RC building with URM infill walls in Turkey. The experimental parameters were the layout of the URM infill (its presence or absence), number of spans (single or double), number of stories (single or double), and stacking pattern of the URM infill (horizontal or vertical). Static cyclic loading tests were conducted to investigate the lateral force resisting mechanisms in the in-plane direction, which were evaluated based on the strain data measured on blocks forming the infill walls. The results indicated the following: (1) The vertically stacked infill did not form a typical diagonal compressive strut and showed lower seismic performance than the horizontally stacked infill. (2) For the specimens with horizontally stacked infill, the one-story, two-bay specimen formed a diagonal compressive strut in each infill wall similar to that formed in the one-story, one-bay specimen, whereas a steeper compressive strut through both stories appeared in the two-story, one-bay specimen. To verify the above strut mechanisms in the horizontally stacked infill, the compressive struts in the specimens were quantitatively identified based on strain data recorded on the infill. The identified compressive struts indicated that single strut models were applicable to multi-bay infilled frames; however, the stress transfer across floors should be considered in multi-story frames.

The method to determine the performance level thresholds of partially-restrained steel frame–reinforced concrete infill walls (PSRCW) with concealed vertical slits was presented within the framework of the performance based seismic design. Inter-story drift ratio is selected as a parameter to establish these thresholds based on the relationship between damage state and structural performance level. The damage analysis on the previous test results of PSRCW with concealed vertical slits is statistically investigated to quantify the performance level thresholds using the modified Park–Ang damage index model. The story damage state of a 5-story PSRCW with concealed vertical slits was also examined through nonlinear time history analysis. The maximum average inter-story drift ratio and damage index for this 5-story PSRCW with concealed vertical slits subjected to ten near-fault earthquake waves with velocity pulse were compared with the results from ten far-fault earthquake waves. For frequent and occasional earthquake hazard level, the velocity pulses of near-fault earthquake waves produce the similar damage upon PSRCW with concealed vertical slits in comparison with far-fault earthquake waves. However, for rare earthquake hazard level, the near-fault earthquake waves with velocity pulse cause more severe damage and larger inter-story drift ratio upon PSRCW with concealed vertical slits than the far-fault earthquake waves.

On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion stations were located in the areas with intensity V, VI, VII and IX, near the epicentre. The characteristics of the ground motion are discussed herein, including 1) ground motion was strong at a period of less than 1.4 s, which covered the natural vibration period of a large number of structures; and 2) the release energy was concentrated geographically. Based on materials collected during emergency building inspections, the damage patterns of adobe, masonry, timber frame and reinforced concrete (RC) frame structures in areas with different intensities are summarised. Earthquake damage matrices of local buildings are also given for fragility evaluation and earthquake damage prediction. It is found that the collapse ratios of RC frame and confined masonry structures based on the new design code are significantly lower than non-seismic buildings. However, the RC frame structures still failed to achieve the ‘strong column, weak beam’ design target. Traditional timber frame structures with a light infill wall showed good aseismic performance.

This study describes the effectiveness of the behavior resulting from strengthening infill walls in existing reinforced concrete frame systems with low resistance against earthquake effects using precast concrete panels. In this study, a strengthening method that can be applied without building occupants having to leave the building was investigated. For this purpose, six 1/2 scale, two-story and single span test specimens with brick infill walls and low earthquake resistance, which have common errors seen in existing reinforced concrete buildings, were generated. The first of test frames with equivalent properties was tested as the reference specimen under reversible repeatable lateral loads. Others were tested after high-strength concrete panels produced in different geometric shapes were strengthened by bonding them onto existing frame infill walls. Brick infill walls strengthened using concrete panels were modeled as shell elements by SAP2000 software package and the accuracy of experimental studies were compared with analytical results. Experimental and analytical studies demonstrated that the reinforcement method significantly improved properties, such as resistance to lateral loads, energy dissipation capacity, of brick infill reinforced concrete frames.

Development of sustainable concrete has now become a mandatory requirement today due to environmental problems posed by the production of conventional concrete. Many researchers focused their research toward finding alternate materials for cement, sand, steel, etc., and came out with good results. This paper focuses on feasibility of developing sustainable concrete using bamboo as infill, stiffener, and combination of infill and reinforcement in the wall panels. In addition, low-density polyethylene waste also tried as infill material with bamboo as diagonal member. The structural property of bamboo was studied for replacing the conventional steel by designing the wall panels with lower stiffness and weight to avoid the catastrophic effect. The strength and behavior of infill wall panels for different infill cases were studied under uniaxial in-plane loading. Parameters such as maximum load carrying capacity, load–deflection characteristics, and cost effectiveness of bamboo-based wall panel system were considered in the present study. From the experimental results, it was understood that bamboo-based wall panel behaved as a ductile member and failed after due to the formation of micro-cracks. Wall panel specimens were failed with an out-plan buckling and resisted the force such that the sudden collapse was avoided. It was concluded that an infill wall reduced lateral and vertical deflection, thereby decreasing the probability of collapse. Hence, an infill wall panel could be used as a substitute for conventional wall panel.

Masonry infill walls have many beneficial and disadvantageous effects on seismic performances of RC frames. Despite such remarkable effects, practicing engineers usually neglect the effects of infill walls on seismic behavior of structures. This study aims to demonstrate that neglecting the effects of infill walls during the nonlinear dynamic analysis of the RC frames may lead to the dramatic misunderstanding the seismic performance of the structure. To this end seismic response of 18 models of the same structure and different arrangements of the infill walls to four different ground motions were investigated using PERFORM 3D software. Results of this study revealed that changing the arrangement of infill walls may change the damage state of the building during an earthquake.

Steel frame and shear wall infill steel frame are two commonly lateral load resisting systems used in building structures. To realize the modulation of initial stiffness of steel structures, make it easily assembled and removed and prevent plastic hinges developing in the frame columns and collapse of all structure, a new anti-seismic infill wall system, composite steel plate deep beam (CDB), is introduced. The system uses steel plate deep beam with a precast reinforced concrete panel attached one side. This paper describes the experimental work related to the tests of CDB under cyclic loads. The experimental results of one pure steel frame (PF) and two composite steel plate deep beam infill steel frame (CDBF) with different span-height ratio are summarized and discussed, the hysteretic loops were obtained. Based on the test results, effects of the CDB on the load capacity, ductility, hysteretic property and energy-dissipation of the pure steel frame were analyzed. The results show that the CDB enhances the initial stiffness and load capacity by a large margin, and the hysteretic loops are replete and the skeleton curves have apparent stage of plastic flow, the ductility and energy dissipation capacity of the test specimens are enhanced. Lastly, regression analysis based on the tests data, and restoring force model can apply to elastoplastic response analysis of the CDBF systems. Therefore, the deep beam can be used as the first defense line of earthquake-resistance, and the steel frame can be used as the second.

In the seismic analysis of a framed building with masonry infill walls, it is necessary to model the effect of the walls on the lateral stiffness, strength and ductility of the building. The equivalent strut method is convenient for modelling the walls in a large building. However, an appropriate axial load versus deformation relationship for the strut is required in a nonlinear static method of seismic analysis, such as the pushover analysis. The present study proposes a nonlinear axial hinge property for the strut, with suitable performance levels. First, the equivalent strut method and the suitability of two approaches available in the literature for modelling the properties of the struts, are briefly discussed. Next, the nonlinear axial load versus deformation relationship is developed based on experimental data compiled from the literature. The parabolic–plastic relationship is idealized as a tri-linear axial hinge property, so that it can be incorporated in commercial software for undertaking pushover analysis. Next, the use of the hinge property is demonstrated in the pushover analyses of two framed reinforced concrete buildings. The pushover curves based on the proposed hinge property shows improved modelling of the inelastic drifts of the buildings. Although the modelling of a wall using a single strut has limitations, the proposed methodology is practical for a pushover analysis of a building.

The behaviors of infill wall in earthquakes show that infill masonry walls, which are used as nonstructural elements of concrete frames, are vulnerable when they are subjected to earthquake. In order to achieve an optimal anti-seismic behavior, or even stability, two methods of connection are investigated. The shaking table tests, with 1:3 scale walls of two-storey model subjected to horizontal earthquake loads, were carried out to investigate the out-of-plane behaviors with different connections between walls and beams. The test results show that the connection methods employed between walls and beams have a significant effect on the out-of-plane stability of infill walls. The walls bound by bars with the beams perform better than those with inclined bricks without gaps.

In the past researches, the influence of the weigh for the masonry infill walls on reinforced concrete frame was only considered in the calculation of the structure for the reinforced concrete frame buildings with masonry infill walls, the action of lateral resistant thrust of the masonry infill walls to reinforced concrete frame was usually neglected. A large of model experiments, theoretical analyses and investigations for the damage due to earthquake have been shown that reinforced concrete frame buildings with the masonry infill walls can not only raise the lateral resistant thrust of whole structure, but also put off the production of plastic hinge and raise the bearing capacity of whole structure. In this paper, a mixed element model was made up of the element for reinforced concrete frame bar and the plane element for masonry infill wall, This model, which was loaded by the statically admissible in groups horizontal load P and the identical vertical load was analyzed. The bending momentsMc on the column ends was obtained. The limited bending moments My was calculated under the given stiffness, reinforcement bar and ratio of axial pressure. From the calculation and comparison, the distinguish conditions of plastic failure under various the masonry infill walls and different stiffness were obtained, the mechanism of the plastic hinges on the frame was discussed.