Boundary Frame Members Research Articles

Lateral behavior of trapezoidally corrugated wall plates in steel plate shear walls, Part 1: Elastic buckling

This paper deals with the elastic shear buckling behavior of trapezoidally corrugated wall plates in vertically or horizontally Corrugated Steel Plate Shear Walls (CoSPSWs) considering constraints from neighboring subpanels and boundary frame members through eigenvalue buckling analyses and static analyses. Results showed that constraints from boundary frame members along the corrugated edges of wall plates had obvious influences on the shear buckling behavior, while constraints along the straight edges had negligible influence. When the waveform configuration remained the same, the global shear buckling stress of corrugated wall plates increased slightly with the plate thickness, reduced obviously with the straight edge length but barely changed with the corrugated edge length. When the external dimension and thickness remained the same, the global shear buckling stress of corrugated wall plates increased most significantly with the inclined subpanel width, corrugation angle, or corrugation depth. Formulas were proposed for the local shear buckling coefficient, global shear buckling coefficient and interactive shear buckling correlation coefficient of vertically and horizontally corrugated wall plates in CoSPSWs considering constraints from neighboring subpanels and the boundary members. A mode factor was defined to predict the dominant shear buckling mode, and a comprehensive formula was proposed to calculate the shear buckling stress of corrugated wall plates, with good accuracy within the given ranges of geometric parameters from practical engineering.

Simplified modelling and pushover analysis of infilled frame structures accounting for strut flexibility

AbstractSeismic assessment of structures is often performed using their force–displacement capacity or pushover curve computed via non‐linear static analysis. However, these analyses' reliability depends on the numerical model's detail and its ability to capture salient failure mechanisms. Simplified analysis methods offer effective means of identifying structural deficiencies and provide analysts with a sound understanding of key structural characteristics, such as the strength hierarchy, status of the structural damage in terms of limit state exceedance or the progression of the inelastic mechanism, in addition to providing a method with which to check numerical analysis results. This work builds upon the existing literature for simplified analysis of moment frame structures and describes a simplified pushover‐based analysis procedure for infilled frame structures. Individual storey responses are obtained by combining the flexural resistance of the frame and accounting for the axial resistance of the infill (modelled as an equivalent axial strut) and the boundary frame members, assuming both systems work in parallel. Then, the displaced shape of the structure is iteratively calculated for a given base shear, which can be repeated until a pushover curve is obtained with relative ease. The proposed procedure is tested and evaluated versus other available methods by analysing several infilled reinforced concrete frames. It is shown that the method can perform simplified pushover analysis with a high degree of fidelity while improving over the other similar methods currently available.

Seismic performance of reinforced concrete frame strengthened with an imperfect steel plate shear wall

In this research, the effects of imperfections in a steel plate shear wall (SPSW) used to strengthen a reinforced concrete (RC) frame were numerically examined using nonlinear finite element analysis. Three types of structures were analysed in this study: SPSW only, a one-story RC frame with an SPSW infill, and a multi-story RC frame with an SPSW. It was determined that the initial imperfections of a thin SPSW cause a dramatic reduction in the yield and ultimate capacity of the SPSW when analysed individually; however, the presence of RC boundary frame members addresses an important role in eliminating this reduction. In contrast, it was found that the SPSW prevents the shear cracking in the RC frame joints. Based on this point, a higher RC frame capacity together with high initial stiffness and ductility are registered when an SPSW is applied, and equations for estimating the system capacity were derived through this study.

Seismic performance of reinforced concrete frame strengthened with an imperfect steel plate shear wall

In this research, the effects of imperfections in a steel plate shear wall (SPSW) used to strengthen a reinforced concrete (RC) frame were numerically examined using nonlinear finite element analysis. Three types of structures were analysed in this study: SPSW only, a one-story RC frame with an SPSW infill, and a multi-story RC frame with an SPSW. It was determined that the initial imperfections of a thin SPSW cause a dramatic reduction in the yield and ultimate capacity of the SPSW when analysed individually; however, the presence of RC boundary frame members addresses an important role in eliminating this reduction. In contrast, it was found that the SPSW prevents the shear cracking in the RC frame joints. Based on this point, a higher RC frame capacity together with high initial stiffness and ductility are registered when an SPSW is applied, and equations for estimating the system capacity were derived through this study.

Experimental and Numerical Research on Steel Plate Shear Wall with Infill Plate Connected to Beam Only

Steel plate shear walls consist of thin infill steel plates attached to beams, called (horizontal boundary elements, HBEs), and columns (vertical boundary elements, VBEs) in structural steel frames. The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the ends of the HBEs. This design approach may result in very large demand on boundary frame members, especially VBEs in most cases. Several methods such as using LYP, perforating the infill plate and omitting connection of infill plate to columns have been proposed to reduce the moment and axial force demands on the VBEs. Study the behavior of steel plate shear walls omitting the connection of infill plate and columns is the main purpose of this research. A classic analysis base on PFI method along with quasi static cyclic experimental study has been performed in order to investigate the behavior of such a system. The results of the experimental study are used to verify numerical models. Behaviors of proposed system (overall capacity and initial stiffness) were compared with those of the conventional SPSWs. Results show that both parameters are reduced in comparison to the conventional SPSWs.

Behaviour of Steel Plate Shear Wall in Multi Span Moment Frame with Various Infill Plate Connection to Column

Steel plate shear walls consist of thin infill steel plates attached to beams, called (horizontal boundary elements, HBEs), and columns (vertical boundary elements, VBEs) in structural steel frames. The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the ends of the HBEs. This design approach may result in very large demand on boundary frame members, especially VBEs in most cases. Several methods such as using LYP, perforating the infill plate and omitting connection of infill plate to columns have been proposed to reduce the moment and axial force demands on the VBEs. The main purpose of this research is to study the behavior of steel plate shear walls with various connection of infill plate to columns in multi span moment frames. A numerical study has been performed in order to investigate the behavior of such a system. The results of proposed system were compared with those of the conventional SPSWs. Results show that reducing the infill plate connection to columns will reduce the axial forces in columns.

11.24: Impact of column flexural stiffness on behaviour of steel plate shear walls

ABSTRACTIn the past 40 years steel plate shear walls (SPSW) have seen increased application as vertical stabilization systems of structures. Steel plate shear walls (SPSW) may be considered as vertically installed cantilever composed of boundary frame elements (beams and columns) and very slender steel infill panel. In the past, the loss of stability of the infill plate was prevented by adding vertical and horizontal stiffeners, while the present application relies on post‐critical tension field action of the infill panel. For cost‐effective implementation of steel plate shear wall (SPSW) systems the infill steel panel needs to be completely utilized through ability of tension field formation over the entire steel plate. Due to such load bearing mechanism additional transverse forces are exerted on boundary frame members. Hence, in order to ensure expansion of the tension field throughout the entire infill panel the required minimal flexural stiffness of boundary frame element cross‐section shall be met. This requirement is based on assumptions valid for plate girders, where previous studies, indicate that for steel plate shear walls (SPSW) this requirement could be conservative or even completely unnecessary.This paper presents the results of experimental and numerical research. Laboratory testing included two different specimen groups. In order to determine the influence of the infill panel on the behaviour of moment resisting frame (MRF) three steel moment resisting frame (MRF) specimens were tested in the first group, while experiments of the second group included three steel plate shear wall (SPSW) specimens. In each specimen group flexural stiffness of the boundary columns was varied. Experimental results show that steel plate shear wall (SPSW) specimens whose boundary columns do not meet the required minimal flexural stiffness exhibited small “pull‐in” of their columns. Furthermore, the experimental data was used to calibrate numerical models that have been used for additional parametric numerical analyses. Specifically, the influences of three column flexural stiffness values as well as two steel grades of the infill panel were investigated for five different aspect ratio (L/H) values. Impact of the above parameters was assessed through comparison of residual relative horizontal displacement profiles.

Experimental and numerical investigation of novel partially connected steel plate shear walls

A steel plate shear wall system, consisting of a thin steel plate connected to the boundary frame members, is proposed as lateral load resisting system for use in the multi-storey building. To reduce the potential damage on the boundary elements caused by the tension field action in the steel plate after buckling, the steel plate is partially connected at the corner edges to the boundary frame members by bolts. Two scaled specimens were tested under cyclic loads to investigate the hysteretic behaviour of the partially connected steel plate shear wall (SPSW). Test results showed that the proposed SPSW exhibited good structural performance in terms of initial stiffness, shear resistance, ductility and energy absorption capability. An analytical method was developed to predict the shear resistance of the partially connected SPSW. The shear resistances obtained from the tests were compared with those predicted by the analytical method and a reasonable agreement was observed. In addition, a nonlinear finite element (FE) model was proposed to analyze the behaviour of the partially connected SPSW system. The accuracy of the FE models was verified by comparing the computed results with the cyclic load test results. Parametric analyses were then carried out to study the effects of plate slenderness ratio, plate aspect ratio (width/height), stiffness of the boundary frame members and initial plate imperfection on the lateral load resisting behaviour of the proposed steel plate shear wall system.

Structural performance of steel plate shear walls with trapezoidal corrugations and centrally-placed square perforations

Steel plate shear walls (SPSWs) are an efficient lateral force-resisting system, and can be designed with corrugated and/or perforated infill plates, depending on structural considerations, architectural requirements, and service design. This paper presents a study on the structural performance of SPSWs with horizontal trapezoidal corrugations and centrally-placed square perforations under monotonic loading. Finite element models were developed for assessment of the buckling stability, stiffness, strength, and ductility performances of the shear walls. To this end, parametric studies were performed by considering the web-plate corrugation angle, thickness, and size of opening as the varying parameters in the nonlinear pushover analyses. It was found that the design of the boundary frame members can be effective in minimizing the deformations imposed by infill plates, providing system ductility, and developing lateral load resistance through stable development of diagonal tension-field action in the web plate. The effects of introducing web-plate perforations, and increasing the size of the opening, on the structural performance were also investigated. Proper design and detailing of the SPSW, along with optimal selection of the web-plate geometrical and corrugation parameters, can ensure desirable structural behavior and seismic performance for such lateral force-resisting systems.

Analytical investigation of thin steel plate shear walls with screwed infill plate

A behavior model for screw connections is developed to provide a better representation of the nonlinear response of thin steel plate shear walls (TSPSWs) with infill plates attached to the boundary frame members via self-drilling screws. This analytical representation is based on the load-bearing deformation relationship between the infill plate and the screw threads. The model can be easily implemented in strip models of TSPSWs where the tension field action of the infill plates is represented by a series of parallel discrete tension-only strips. Previously reported experimental results from tests of two different TSPSWs are used to provide experimental validation of the modeling approach. The beam-to-column connection behavior was also included in the analyses using a four parameter rotational spring model that was calibrated to a test of an identical frame as used for the TSPSW specimens but without the infill plates. The complete TSPSW models consisting of strips representing the infill plates, zero length elements representing the load-bearing deformation response of the screw connection at each end of the strips and the four parameter spring model at each beam-to-column connection are shown to have good agreement with the experimental results. The resulting models should enable design and analysis of TSPSWs for both new construction and retrofit of existing buildings.

Hysteretic performance of SPSWs with trapezoidally horizontal corrugated web-plates

Previous research has shown that steel plate shear walls (SPSWs) are efficient lateral force-resisting systems against both wind and seismic loads. A properly designed SPSW can have high initial stiffness, strength, and energy absorption capacity as well as superior ductility. SPSWs have been commonly designed with unstiffened and stiffened infill plates based on economical and performance considerations. Recent introduction and application of corrugated plates with advantageous structural features has motivated the researchers to consider the employment of such elements in stiffened SPSWs with the aim of lowering the high construction cost of such high-performing systems. On this basis, this paper presents results from a numerical investigation of the hysteretic performance of SPSWs with trapezoidally corrugated infill plates. Finite element cyclic analyses are conducted on a series of flat- and corrugated-web SPSWs to examine the effects of web-plate thickness, corrugation angle, and number of corrugation half-waves on the hysteretic performance of such structural systems. Results of the parametric studies are indicative of effectiveness of increasing of the three aforementioned web-plate geometrical and corrugation parameters in improving the cyclic response and energy absorption capacity of SPSWs with trapezoidally corrugated infill plates. Increasing of the web-plate thickness and number of corrugation half-waves are found to be the most and the least effective in adjusting the hysteretic performance of such promising lateral force-resisting systems, respectively. Findings of this study also show that optimal selection of the web-plate thickness, corrugation angle, and number of corrugation half-waves along with proper design of the boundary frame members can result in high stiffness, strength, and cyclic performances of such corrugated-web SPSWs.

Effect of column stiffness on drift concentration in steel plate shear walls

Steel plate shear walls (SPSWs) are a lateral force resisting system consisting of thin infill steel plates surrounded by boundary frame members. Hysteretic energy dissipation and lateral force resistance of the system are primarily achieved through the yielding of the infill steel plates. However, during an earthquake event, the infill plates at different building stories may not yield simultaneously due to many factors such as overstrength of some infill plates and the actual lateral force distribution which is different from the one assumed in design, possibly resulting in inter-story drift concentrations in the system. This paper investigates the effect of column stiffness on mitigating drift concentration in SPSWs. Based on an example two-story SPSW, mathematical models are derived to characterize the system behavior and quantify the effect of column stiffness on the mitigation of drift concentration. Nonlinear static pushover analyses using finite element models are performed to further validate the developed models. Finally, based on the developed models, parametric analyses are conducted to investigate the effect of column stiffness over a practical range of the considered parameters, followed by a discussion of the minimum SPSW column stiffness specified in North American codes. The results from this investigation show that column stiffness should be a design parameter to ensure a reasonably uniform drift distribution and hence a more uniform infill plate yielding along the height of SPSW buildings.

Experimental investigation of thin steel plate shear walls with different infill-to-boundary frame connections

To make direct comparisons regarding the cyclic behavior of thin steel plate shear walls (TSPSWs) with different infill-to-boundary frame connections, two TSPSWs were tested under quasi-static conditions, one having the infill plate attached to the boundary frame members on all edges and the other having the infill plate connected only to the beams. Also, the bare frame that was used in the TSPSW specimens was tested to provide data for the calibration of numerical models. The connection of infill plates to surrounding frames was achieved through the use of self-drilling screws to fish plates that were welded to the frame members. The behavior of TSPSW specimens are compared and discussed with emphasis on the characteristics important in seismic response, including the initial stiffness, ultimate strength and deformation modes observed during the tests. It is shown that TSPSW specimens achieve significant ductility and energy dissipation while the ultimate failure mode resulted from infill plate fracture at the net section of the infill plate-to-boundary frame connection after substantial infill plate yielding. Experimental results are compared to monotonic pushover predictions from computer analysis using strip models and the models are found to be capable of approximating the monotonic behavior of the TSPSW specimens.

Analysis and design of FRP composites for seismic retrofit of infill walls in reinforced concrete frames

There is an urgent need to retrofit deficient mid-rise reinforced concrete (RC) frame buildings in Turkey. For this purpose, an efficient FRP retrofit scheme has been developed previously, in which hollow clay brick infill walls can be utilized as lateral load resisting elements after retrofitting. The main premise of this practical retrofit scheme was to limit inter-storey deformations by FRP strengthened infill walls that are integrated to the boundary frame members by means of FRP anchors. Based on the analytical model that was previously verified extensively by comparison with test results, a simplified model was proposed for use in displacement based design of FRPs for deficient RC frame buildings. FRP retrofit design and analysis of an actual deficient RC building located in Istanbul are presented herein both for the local design spectrum and Duzce ground motion. It was observed that the FRP retrofit reduced the damage induced to deficient columns by controlling story deformations. In this way, it was possible to satisfy the collapse prevention performance state in an efficient and economical manner.