Unstiffened Steel Plate Shear Walls Research Articles

Research on steel plate shear walls stiffened with X-shaped restrainers: Hysteretic behavior and effect of height-to-thickness ratio of steel plate

This paper proposed a novel buckling restrained steel plate shear wall (simply referred to as XSPSW) composed of X-shaped restrainers, an infill steel plate, and boundary restrainers. The X-shaped restrainers are placed on both sides of the infill steel plate, and the infill steel plate is divided into a series of diagonally arranged square subplates with a small height-to-thickness ratio. The X-shaped restrainers can effectively restrain the shear bucking of the infill steel plate and improve the seismic energy dissipation capacity of the shear wall. A refined numerical analysis model of the unstiffened steel plate shear wall (USPSW) and XSPSW was established and the validity of the model was verified by experiment. Numerical analysis was conducted to investigate the force mechanism and hysteretic behavior of the XSPSW. The results demonstrate that the mechanical behavior of the XSPSW is controlled by the square subplate. Compared to the USPSW, the shear buckling capacity, peak load, and energy dissipation capacity of the XSPSW are higher by at least 17%, 5%, and 7%, respectively, and the constraint efficiency of the out-of-plane displacement is larger than 55%. With the decrease in the height-to-thickness ratio of the subplate, the improvements in the shear buckling capacity, peak load, and energy dissipation capacity are increased to 29%, 31%, and 20%, respectively. Moreover, the constraint efficiency of the out-of-plane displacement rises to 92%, and the hysteretic curve tends to be full. The influence of the height-to-thickness ratio of the infill steel plate on the bearing capacity and energy dissipation capacity of the XSPSW is less than 2.5% and 1.2%, respectively.

Comparative study of steel plate shear walls with different types of unbonded stiffeners

This paper presents a comparative study of the steel plate shear walls (SPSWs) with different types of unbonded stiffeners. Multiple ribs and precast concrete panels are installed for restraining the out-of-plane deformation of steel plates. The effect of spacing of unbonded ribs on the behaviour of SPSWs is first investigated through a finite element analysis. Subsequently, three 1/3-scale one-bay, two-storey SPSW specimens, namely unstiffened SPSW (US-SPSW), partially restrained SPSW (PR-SPSW) and completely restrained SPSW (CR-SPSW), are tested under cyclic loading. Test results indicate that specimens PR-SPSW and CR-SPSW exhibit similar load-carrying capacity, energy dissipation capacity, and stiffness degradation. Out-of-plane deformations of infilled steel plates, inward deformation of columns, and rotation of beam-column connections in both specimens PR-SPSW and CR-SPSW are effectively restrained, which alleviates the pinching phenomenon of hysteretic curves and stiffness degradation. As compared to the complete restraints for steel plates, partial restraints can increase the buckling area of the infilled steel plates and subsequently enhance the ductility of SPSW structure. They can also convert the deformation mode of infilled steel panels from the high-wave-low order to the low-wave-high order. In general, specimen PR-SPSW stiffened by unbonded multiple ribs with an appropriate spacing shows the excellent structural behaviour and constructability.

Shear‐displacement diagram of steel plate shear walls with precompression from adjacent frame columns

SummaryAn analytical model of the unstiffened steel plate shear wall (SPSW) considering precompression from the adjacent frame columns is proposed and experimentally verified. First, the distribution and transferring of the gravity loads between boundary columns and the infill steel plate was proposed. Second, the shear‐displacement diagram of the SPSW under compression–shear interaction was obtained, and to further consider the global bending deformation, the shear‐displacement diagram of the SPSW under compression–shear–bending interaction was obtained. Third, the load‐carrying capacities and deformations at the state of elastic buckling of the infill steel plate, the yield of Zones I and III, the yield of Zone II, and the yield of the boundary frame were presented. Finally, cyclic loading test on four scaled one story single bay unstiffened SPSWs under different axial forces at the top of the columns was carried out to verify the proposed analytical model. Shear‐displacement relationship, shear capacity, and envelope curves of the specimens were compared with the predicted values. Results indicate that the proposed analytical model can reasonably predict the decrease of the shear load capacity and stiffness of the SPSWs due to the existence of the axial load at the boundary columns.

Cyclic performance of cross restrained steel plate shear walls with transverse braces

This paper presents an investigation on the cyclic performance of cross restrained steel plate shear walls (SPSWs) with transverse braces. Transverse braces connecting to two columns are proposed to replace horizontal cross stiffeners on the infill steel plates. Effects of transverse braces on the performance of SPSWs are estimated through an experimental study and a finite element analysis. Two 1/3-scale two-story single-bay SPSW specimens, including one unstiffened SPSW and one cross restrained SPSW with transverse braces, are first tested under the quasi-static cyclic loading. Subsequently, finite element models for SPSWs are developed and verified by the test results. Cyclic performance of SPSW structures with different restrains for the infill steel plates are compared in terms of failure mode, loading capacity, energy dissipation capacity and stiffness degradation. Emphasis is given on the stress development and out-of-plane deformation of infill steel plates. The results show that use of transverse braces as the substitute of horizontal stiffeners enhances the loading capacity, energy dissipation capacity and ductility of SPSW structure. It is also effective to homogenize stress distribution and to restrain the out-of-plane deformation of infill steel plates, which finally decreases the additional bending moments applied to the columns. Compared with the unstiffened SPSWs, the maximum inward flexural deformation of columns in the cross restrained SPSWs with transverse braces is reduced by about 40.0%. It has demonstrated that the proposed cross restrainers combined with transverse braces are effective in improving the cyclic performance of SPSWs.

Effects of Aspect Ratio and Plate Thickness on the Behavior of Unstiffened Steel-Plate Shear Walls with Pinned and Rigid Connections

Unstiffened steel plate shear walls (SPSWs) have been in use mostly in recent years. In this numerical study, the buckling behavior of a single-storey single-bay unstiffened SPSW with two pinned and rigid beam-column connections under lateral loading is investigated. The SPSW had different wall aspect ratios (L/h=1, 1.5, 2, 2.5, and 3) and infill plate thicknesses (tw= 3, 5, and 7 mm). Their effect on the buckling behavior of SPSW was examined using buckling analysis in ABAQUS software. Results indicated that with the increase of infill plate thickness, the lateral resistance of unstiffened SPSW system increases, but by increasing wall aspect ratio, its resistance decreases. In both connection designs, the model with L/h=1 (square-shaped model) showed better ductility and higher stiffness and strength in all three thicknesses. Maximum shear stress responses of SPSW models showed that in pinned design with L/h=1, the most change in shear stress values was 8% when infill plate thickness reached from 5 to 7 mm; while for rigid connection, it was reported as 7% when it increased from 3 to 5 mm. This indicates that in rigid connection, increasing the infill plate thickness has less effect on the increase of lateral resistance. By examining the performance of rigid and pinned beam-to-column connections with different wall aspect ratio and infill plate thickness, it was found out that maximum shear stress in rigid connection increased by 11% compared to pin connection. It was concluded that an optimum unstiffened SPSW model had a wall aspect ratio of 1 and infill plate thickness of 7 mm.

Seismic Evaluation of Tall Unstiffened Steel Plate Shear Wall (SPSW) Systems with Emphasis on Reversal Phenomenon in the Higher Mode Pushover Curve

This paper attempts to study the seismic behavior of tall unstiffened steel plate shear wall (SPSW) systems with an emphasis on the higher-mode pushover analysis and to elaborate the relevant pushover curve. Improved pushover analyses (IPAs) including the modal pushover analysis (MPA) and the modified modal pushover analysis (MMPA) are used for the frames in which the higher-mode effects are substantially important. The conventional pushover analysis using the FEMA load distributions is also implemented. To achieve this goal, mid-rise (10 and 15-story) and high-rise (20 and 30-story) SPSW systems are investigated. To consider a detailed behavior of SPSWs in analyses, a three-dimensional (3D) finite element modeling is used. An interesting result is obtained that the higher-mode pushover analysis results in a reversal in the pushover curve for all of the unstiffened SPSW systems studied in this investigation that this phenomenon is rare in performance-based seismic engineering. The results provide evidence that among the above-mentioned pushover analyses, the MPA procedure is accurate enough for the seismic evaluation of tall SPSW systems. Furthermore, the MPA is computationally time efficient in comparison with the nonlinear response history analysis for this kind of structures with 3D finite element modeling in which there exist a large number of frame and shell elements.

Cyclic performance of stiffened steel plate shear walls with various configurations of stiffeners

In this study, experiments were conducted on five specimens of stiffened and unstiffened steel plate shear walls under cyclic loading. First, the specimens and frame design, material properties, and test setup were described. The behaviors of the unstiffened aluminum and steel infill plates were compared with three configurations of stiffened steel plate, i.e., cross-stiffened, circular-stiffened, and diagonally stiffened. The cross-sectional areas of the stiffeners were the same for all stiffened specimens. The results showed that the aluminum infill plate exhibited less ductility. By contrast, the unstiffened steel plate was very ductile, exhibiting a stable hysteresis curve and no tearing. The energy-absorption capacity of the steel plate shear walls increased for all stiffening configurations. Among all configurations, the cross-shaped stiffeners showed considerable increase in shear stiffness, ductility, and energy-dissipation capacity. The plate frame interaction method could predict the ultimate shear strengths of the unstiffened and cross-stiffened panels with good precision. The circular-stiffened steel shear wall seems to behave more desirably in high-amplitude displacements.

Strip Model Analysis for Steel Plate Shear Walls in Earthquake Resistant Structures

Unstiffened Steel Plate Shear Walls (SPSWs) are very effective structural systems designed to resist lateral forces. SPSW systems consist of thin web plates infilled within frames of steel horizontal and vertical boundary elements. The thin unstiffened web plates are expected to buckle in shear and to develop diagonal tension field after buckling under the action of horizontal loads. For unstiffened steel plates, buckling in shear occurs in the elastic range at low stress levels. This behaviour provides strength, stiffness and ductility and allows to have an appropriate level of energy dissipation through tension yielding of the web plates. This paper assesses the inelastic structural response and behaviour of Steel Plate Shear Wall systems using both a modified strip model approach and a new simplified strip model for only beam connected SPSWs. Both models are developed with plasticity concentrated elements and the performed analyses include the nonlinear behaviour of strips, also considering the compressive forces effects over the strip model elements. This research indicates fundamental aspects of the seismic performance of Steel Plate Shear Wall systems, such as energy dissipation capacity, panel ductility demand, seismic inter-story drift and design load demands in Vertical Boundary Elements (VBE) and Horizontal Boundary Elements (HBE) of the frame. The results obtained from the use of these models are compared with selected experimental and numerical results to enrich the research conclusions.

Stress state of steel plate shear walls under compression–shear combination load

SummaryThis paper investigates the stress state of the infill steel plate for the unstiffened steel plate shear walls (SPSWs) under compression–shear combination load. First, the infill steel plate is divided into three zones, the stress state of each zone under compression is derived, and the accuracy of the analytical model is verified by a series of numerical examples. Second, considering the combination effects of the gravity load and shear force from the adjacent boundary columns, the stress state of each zone is proposed and discussed. Then the shear capacity of the infill steel plate for the unstiffened SPSWs with gravity load acting on the top of the boundary columns is proposed. Finally, the shear capacity of 21 numerical SPSW specimens with various axial stresses of the boundary columns and different steel infill plate thicknesses is predicted.

Seismic upgrading of reinforced concrete frames with steel plate shear walls

The objective of this paper is to report on a study of the use of unstiffened thin steel plate shear walls (SPSWs) for the seismic performance improvement of reinforced concrete frames with deficient lateral rigidity. The behaviour of reinforced concrete frames during seismic activities was rehabilitated with an alternative and occupant-friendly retrofitting scheme. The study involved tests of eight 1/3 scale, one bay, two storey test specimens under cyclic quasi-static lateral loadings. The first specimen, tested in previous test program, was a reference specimen, and in seven other specimens, steel infill plates were used to replace the conventional infill brick or the concrete panels. The identification of the load-deformation characteristics, the determination of the level of improvement in the overall strength, and the elastic post-buckling stiffness were the main issues investigated during the quasi-static test program. With the introduction of the SPSWs, it was observed that the strength, stiffness and energy absorption capacities were significantly improved. It was also observed that the experimental hysteresis curves were stable, and the composite systems showed excellent energy dissipation capacities due to the formation of a diagonal tension field action along with a diagonal compression buckling of the infill plates.

Shear capacity prediction of steel plate shear walls with precompression from columns

SummaryThis paper investigates the shear capacity of the unstiffened steel plate shear walls with gravity loads from the adjacent boundary columns that is produced during the construction process. The distribution and transferring of gravity loads between boundary columns and the infill steel plate are proposed. Then, the infill steel plate is partitioned into 3 zones bounded on the effective length, the inclination angle, and shear capacity of each zone that is proposed and discussed, and the shear capacity of the infill steel plate is summed over the 3 zones. Finally, based on the three specimens tested by Park et al. (2007), shear capacity prediction of 18 more numerical steel plate shear wall specimens with the axial stresses of the boundary columns equal to 50 MPa, 100 MPa, 150 MPa, 200 MPa, 250 MPa, and 300 MPa are analyzed.

On the improvement of steel plate shear wall behavior, using energy absorbent element

Structural engineers have recognized unstiffened Steel Plate Shear Wall (SPSW) as an economical lateral resisting system, due to the post-buckling capacity, energy dissipation and deformability. This study investigates practical application of an added Energy Absorbent Element (EAE), subjoined to the SPSW in order to improve seismic behavior of the SPSW.The EAE is an aluminum shear panel with or without bracings and surrounding frame. Furthermore, a series of parametric studies are implemented to examine the effect of dimensions, position and formation of the EAE. It is assumed that the lateral loading is applied as quasi-static loading. Further, nonlinearity of the material and the geometry are included in the models. The results reveal that by adding the EAE adjacent to the surrounding frame of the SPSW, not only dissipated energy but also ultimate strength of the system can be efficiently increased.

Developing of steel plate shear walls braced with slidable multiple X-shaped restrainers: Hysteretic analyses and design recommendations

This paper proposed a light-weight buckling restrained steel plate shear wall (XSPSW) to improve the earthquake energy dissipation of unstiffened steel plate shear walls. It consisted of two slidable multiple X-shaped restrainers placed on the either side of a steel infill plate. The two restrainers could continue to provide out-of-plane restraint for infill plates to achieve stable energy dissipating capacity under cyclic reversal loads. Theoretical analyses and numerical simulating analyses have been conducted to investigate the hysteretic behaviors of XSPSWs and the stability of their sub-plates. Based on the analysis results, it could be concluded that the proposed XSPSWs were efficient lateral-load resisting members for the buildings in high seismic regions.

Influences of the gravity loads on the cyclic performance of unstiffened steel plate shear wall

Summary This paper is aimed at investigating the influences of gravity loads on the overall performance of the steel plate shear wall (SPSW) under the monotonic as well as cyclic loadings. A nonlinear finite-element model for SPSWs was developed and verified using monotonic tests carried out by Behbahanifard and Drivers et al. and the three large-scale three story cyclic test specimens (namely SC2T, SC4T and SC6T) carried out by Park et al.; very good predictions of the ultimate strengths, hysteresis properties and failure modes were obtained. Based on these three specimens tested by Park et al., nine more numerical SPSW specimens with the axial stresses of the boundary columns equal to 100 MPa, 200 MPa and 300 MPa were analyzed. The strength and tension strip angles under lateral monotonic loadings and the hysteresis properties and energy dissipation under lateral cyclic loadings were analyzed. Finally, the strength prediction method of the SPSWs with the flexure-dominate behavior originally proposed by Park et al. was modified to account for the tension-field action of the infill plates, and better prediction of the shear strength of the SPSW was obtained. Copyright © 2016 John Wiley & Sons, Ltd.

Seismic response estimation of steel plate shear walls using nonlinear static methods

One of the major components for performance based seismic design is accurate estimation of critical seismic demand parameters. While nonlinear seismic analysis is the most appropriate analysis method for estimation of seismic demand parameters, this method is very time consuming and complex. Single mode pushover analysis method, N2 method and multi-mode pushover analysis method, modal pushover analysis (MPA) are two nonlinear static methods that have recently been used for seismic performance evaluation of few lateral load-resisting systems. This paper further investigates the applicability of N2 and MPA methods for estimating the seismic demands of ductile unstiffened steel plate shear walls (SPSWs). Three different unstiffened SPSWs (4-, 8-, and 15-storey) designed according to capacity design approach were analysed under artificial and real ground motions for Vancouver. A comparison of seismic response quantities such as, height-wise distribution of floor displacements, storey drifts estimated using N2 and MPA methods with more accurate nonlinear seismic analysis indicates that both N2 and MPA procedures can reasonably estimates the peak top displacements for low-rise SPSW buildings. In addition, MPA procedure provides better predictions of inter-storey drifts for taller SPSW. The MPA procedure has been extended to provide better estimate of base shear of SPSW.

Behavior of stiffened and unstiffened steel plate shear walls considering joint properties

Steel plate shear wall (SPSW) systems have dual characteristics, the frame and infill wall action. The connection flexibility of frame joint not only changes the force and moment distribution, but also increases the lateral displacement and weakens the overall stability in SPSW structure. This paper presents the influence of hinged, rigid and semi-rigid connection joints on the behavior of SPSW structures. The bearing capacity, energy dissipation mechanism, failure mode, stress and deformation development process of the semi-rigid composite frame with steel plate shear walls under different stiffener forms were studied using experimental tests and finite element analysis. It was observed that with stiffeners the specimen yield load increased about 20% on the elastic stage, the ultimate bearing capacity of the diagonal stiffener was about 5% larger than the cross stiffener on the plastic stage, but the overall failure modes were basically the same. Additionally, the quantitative indications of the effect of joint stiffness on load carrying capacity were presented.

Experimental and numerical study of unstiffened steel plate shear wall structures

In order to investigate the seismic behaviors of unstiffened thin steel plate shear wall structure, tests of four three-story unstiffened steel plate shear wall specimens under cyclic loads were carried out. Parameters of the specimens included height-to-thickness ratio, span-to-height ratio and middle brace. The carrying capacity, hysteretic behavior, degraded characteristics, ductility, failure modes, energy dissipation capacity were analyzed and compared deeply. Besides, the nonlinear finite element method of shear wall structure was also established, which was verified by test results. Finally, the effect of column stiffness on load-carrying capacity was studied. The practical requirements of in-plane and out-of-plane stiffness of edge column were suggested. The experimental and numerical results showed that: this kind structure exhibits high strength, good energy dissipation capacity, and good ductility (the ductility coefficients are more than 3.0). When the inter-story drift angle reaches 1/50, the strength degradation is no more than 5%, indicating that the structure has good seismic behaviors. The span-to-height ratio has little effect on load-carrying capacity, while slightly affects the initial stiffness and ductility. The effect of height-to-thickness ratio (thickness) on load-carrying capacity is relatively larger than other factors. The middle braces do not improve the behaviors of structures. The stiffness of edge column has great effect on lateral load-carrying capacity of shear wall structures. The value of column stiffness index could be within 2.0–2.5 to achieve the sufficient constraints and economical benefit.

Behavior of unstiffened steel plate shear wall with simple beam-to-column connections and flexible boundary elements

This study investigates the effect of type of beam-to-column connections on the overall performance of steel plate shear wall (SPSW) systems under lateral loading condition. An analytical study using finite-element analysis has been conducted on a two-story SPSW system with rigid and pinned beam-to-column connections having constant panel aspect ratio and plate slenderness ratio. All boundary elements are designed as per the current code provisions. The influence of the type of connections between the web plates and the boundary elements on the overall performance of SPSW systems is also studied. In addition, the behavior of SPSW system with flexible boundary members along with pinned beam-to-column connections is also investigated under lateral loading condition. An experimental study has been carried out on a two-story SPSW specimen with flexible boundary elements to investigate its overall performance under the slow-cyclic loading. Based on the analytical and experimental results, various design issues of SPSW systems are discussed.

Experimental study of ring-shaped steel plate shear walls

A new type of steel plate shear wall (SPSW) has been developed which resists out-of-plane buckling. The ring-shaped steel plate shear wall (RS-SPSW) includes a steel web plate that is cut with a pattern of holes leaving ring-shaped portions of steel connected by diagonal links. The ring shape resists out-of-plane buckling through the mechanics of how a circular ring deforms into an ellipse. It is shown that the ring’s compression diagonal will shorten a similar amount as the tension diagonal elongates, essentially eliminating the slack in the direction perpendicular to the tension field. Because of the unique features of the ring’s mode of distortion, the load-deformation response of the resulting RS-SPSW system can exhibit full hysteretic behavior and possess greatly improved stiffness relative to thin unstiffened SPSW. The concept has been validated through testing on seven approximately 1 m × 1 m RS-SPSW panels and compared to the experimental response of a solid plate panel. General conclusions about the influence of different geometric parameters on plate behavior are made including limits on geometry that produce desirable hysteretic response.

Nonlinear seismic analysis of perforated steel plate shear walls

The behaviour of unstiffened steel plate shear walls with circular perforations in the infill plates is examined. A shear strength model of the infill plate with multiple circular openings is proposed based on a strip model. Eight perforation patterns in a single storey steel plate shear wall of two different aspect ratios were analyzed using a geometric and material non-linear finite element model to assess the proposed shear strength model. A comparison between the nonlinear pushover analysis and the proposed shear strength equation shows excellent agreement. The proposed model is used to design the boundary columns of three sample four-storey perforated shear walls. A comparison between the predicted design forces in the boundary columns for the selected shear walls with the forces obtained from nonlinear seismic analyses demonstrates the accuracy of the proposed simple model to predict the design forces in the columns.