Infill Steel Plate Research Articles

Cyclic tests of steel plate shear walls using box‐shape vertical boundary elements with or without infill concrete

SummaryThe steel plate shear wall (SPSW) is an effective lateral force resisting system in which unstiffened steel infill plates are connected to the horizontal and vertical boundary elements (VBEs) on all sides of the plates. The boundary elements must be designed to resist the tension field force of the infill panels. When the VBEs are made from a steel box section, the flange of each box VBE connected with the infill panels can be pulled out‐of‐plane by significant panel forces, called pull‐out action. This study investigates capacity design methods for box VBEs in SPSWs. Simplified fixed beam and portal frame models aim to estimate the pull‐out responses of the flange of the box sections with and without infill concrete, respectively. In this study, cyclic tests of three full‐scale two‐story SPSWs using box VBEs with or without the infill concrete are conducted. Inelastic pushover analyses of the finite element models are conducted. The tests and analytical results confirm that the proposed design methods, which aimed to prevent the full yield of the flange under the pull‐out action, are applicable. Furthermore, the test and analytical results suggest that the initial yielding of the flange of box VBEs under the collective effects of the pull‐out action on the flange, the gravity load, and the sway action on the SPSW represents a local yielding. A strict prohibition of the initial yielding on the flange under the aforementioned collective effects is not recommended for pursuing a cost‐effective design. Copyright © 2017 John Wiley & Sons, Ltd.

Experimental study of cross stiffened steel plate shear wall with semi-rigid connected frame

There is complex interaction between the infill steel plate and frame edges in the steel plate shear wall structure. The bearing capacity and stiffness of SPSW structure not only depends on the section sizes of frame and wall, but also relates to the stiffness of joint connection. The beam-to-column connection is easy to construct using semi-rigid joints which enhances the deformation and energy dissipation capacities of SPSW structure and effectively avoids the brittle failure of traditional welded joint. Based on the pseudo static test of cross stiffened SPSW structure with semi-rigid connected frame, this paper analyzes the failure mode and energy dissipation mechanism of the structure, discusses the influence of joint connecting forms and arrangement of stiffeners on the seismic performance of the structure. According to the results, the effect of the beam-to-column connection stiffness on the bearing capacity of SPSW structure is small and the differences among the ultimate bearing capacities are less than 5%. When the inter-story displacement angle is 1/50, the ductility factor is between 3.69 and 4.4, which indicates that SPSW structure is good in plastic deformation capacity. The cross stiffeners divide the thin steel plate into small cell plates. By setting the cross stiffeners, the thin steel plate is divide into small cell plates, and mainly pattern of local buckling.

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.

Seismic behavior of Self-Buckling-Restrained Steel Plate Shear Wall made by two incline-slotted infill plates

This paper presented seismic behavior of a novel Self-Buckling-Restrained (SBR) Steel Plate Shear Wall (SPSW) that was made by two Incline-Slotted Infill Plates (ISIPs) which were tied together by one rubber plate. The directions of the incline slots on the two ISIPs were opposite. Stable cycling responses of the SBR-SPSW could be achieved since at least incline strips on one plate were in tension under the cycle load. At the same time, the strips in tension could provide lateral support to those in compression on the other plate. Behaviors of the SPSW with two ISIPs and with one Solid Infill Plate (SIP) were compared to show advantages of the proposed SBR-SPSW. The stress state changed from the tension-compression bi-direction stress state in a SIP to uniaxial tension or compression in an ISIP. The cracks that usually encountered in a solid steel infill plate under repeated shear buckling could be avoided. And the incline steel strips yielded sequentially that could provide energy dissipation capacity at small drift ratio. At the same time, the ISIP could always ensure the plate yield prior to the frame yield. Parameters of ISIP, including the infill plate thickness, the strips width and the slot width, were investigated through finite element analyses. Shear strengths of the SPSW with two ISIPs decreased with the increase in slot width and increased with the increase in strip width. Design recommendation for the SBR-SPSW was provided as results of theoretical and numerical analysis. The shear strength of the SBR-SPSW made by two ISIPs could be calculated by simplified theoretical equations on the safe side.

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.

Experimental testing on CFRP strengthened thin steel plates under shear loading

This paper presents an experimental study on thin steel plates strengthened by CFRP layers under shear loading. A series of laboratory tests were conducted on scaled one-story steel shear panel models with hinge type connections under cyclic quasi-static loading. One of the specimens is un-stiffened and selected as a reference sample of three others specimens. Steel infill plates are strengthened by CFRP layers with different numbers of layers and orientations. The results indicate that the strengthening of thin steel plate by CFRP layers increases ultimate strength, secant stiffness and energy absorption. Comparisons are made between the performance of CFRP and GFRP strengthened steel plates under cyclic shear loads. It was shown that both materials were effective at increasing stiffness and strength of the system. The increased ratio is similar for both FRPs when two layers are applied. However, adding additional two layers of CFRP does not provide extra benefit in terms of stiffness and energy absorption although there is still benefit for ultimate strength.

Experimental and numerical study on steel-concrete composite shear wall using light-weight concrete

In the present study, the behaviour of concrete stiffened steel plate shear wall (CSPSW) using precast light weight-concrete panels is experimentally and numerically investigated. Three one-bay one-story CSPSW specimens were designed, fabricated, and tested. The steel materials and dimensions of all specimens were the same; however, their precast concrete panels were different. One of the specimens had a precast normal-weight concrete panel on one side of the infill steel plate; on the other hand, another specimen had a light-weight one. The third specimen had two light-weight concrete panels on both sides of the steel plate. The quasi-static cyclic test results indicate that CSPSW with a light-weight concrete panel is a reliable lateral load-resisting system for steel structures. In addition, the shear capacity of specimen with light-weight concrete was approximately similar to specimen with normal-weight one. Therefore, it can be inferred the new system is able to reduce the seismic mass and improve the behaviour of steel structures. In this study, the light-weight concrete panel was 36% lighter than normal-weight panel. Based on the test data, specimens could tolerate high inter-story drift between 5.04% and 6.24% until the shear capacity decline in 80% of the maximum shear load recoded in the test. It should be mentioned that the infill steel plate of CSPSW undergoes entirely inelastic deformation and dissipates significant seismic energy through large lateral displacement.

Study on seismic retrofit of structures using SPSW systems and LYP steel material

Steel plate shear walls (SPSWs) have been shown to be efficient lateral force-resisting systems, which are increasingly used in new and retrofit construction. These structural systems are designed with either stiffened and stocky or unstiffened and slender web plates based on disparate structural and economical considerations. Based on some limited reported studies, on the other hand, employment of low yield point (LYP) steel infill plates with extremely low yield strength, and high ductility as well as elongation properties is found to facilitate the design and improve the structural behavior and seismic performance of the SPSW systems. On this basis, this paper reports system-level investigations on the seismic response assessment of multi-story SPSW frames under the action of earthquake ground motions. The effectiveness of the strip model in representing the behaviors of SPSWs with different buckling and yielding properties is primarily verified. Subsequently, the structural and seismic performances of several code-designed and retrofitted SPSW frames with conventional and LYP steel infill plates are investigated through detailed modal and nonlinear time-history analyses. Evaluation of various seismic response parameters including drift, acceleration, base shear and moment, column axial load, and web-plate ductility demands, demonstrates the capabilities of SPSW systems in improving the seismic performance of structures and reveals various advantages of use of LYP steel material in seismic design and retrofit of SPSW systems, in particular, application of LYP steel infill plates of double thickness in seismic retrofit of conventional steel and code-designed SPSW frames.

Case Study on Retrofit of Steel Plate Shear Walls Using Low Yield Point Steel Infill Plates

Steel plate shear walls (SPSWs) have been frequently used in seismic design and retrofit of buildings over the past three decades or so. Employment of infill plates made of low yield point (LYP) steel with considerably low yield stress and high elongation capacity is believed to provide the possibility in order to improve the structural and seismic characteristics of such lateral force-resisting systems. Among the various benefits is the early yielding of LYP steel infill plates, which can result in greater energy absorption capacity and limitation of the plastic deformation demand to the surrounding frame structure. On this basis, a case study is performed using numerical simulations and reported in this paper on the seismic retrofit of SPSWs using LYP steel infill plates of double thickness. It is shown that the retrofit of a steel shear wall using a LYP steel infill plate of double thickness can result in desirable plate-frame yielding sequence and interaction. Moreover, this retrofit strategy can improve the initial stiffness, buckling stability, and energy dissipation capacity of the existing SPSW system.

The effect of concrete panel thickness upon composite steel plate shear walls

In this study, the analytical study of concrete stiffened steel plate shear wall (CSPSW) with a reinforced concrete panel on one side and with gap between the concrete panel and steel frame is conducted. CSPSWs have a variety of infill steel plate and reinforced concrete panel thicknesses. The results show that the behavior of CSPSWs and corresponding steel plate shear walls (SPSWs) is utterly disparate. The infill steel plate of SPSW resists lateral load by development of tension fields, as the infill steel plate initiates elastic buckling. However, in CSPSW, the elastic buckling of the infill steel plate is prevented by the introduction of the reinforced concrete panel; hence, the infill steel plate carries out lateral load by pure shear yield. Moreover, during the lateral load, CSPSW undergoes four stages: initial elastic stiffness, shear yield stiffness, post-shear yielding stiffness, and pre-failure stiffness.The reinforced concrete panel thickness has a remarkable and direct influence upon the shear capacity and the ultimate strength of the CSPSW; furthermore, it is dependent upon the thickness of infill steel plate. Increasing the concrete panel thickness up to a specific value, the shear capacity and the ultimate strength enhance; however, while increasing it beyond that, the shear capacity and the ultimate shear strength of CSPSW remain constant. CSPSW provides a higher initial elastic stiffness, greater shear capacity, and higher ultimate strength as compared to its corresponding SPSW. The ductility ratio and energy absorption of CSPSW is improved owing to introduction of reinforced concrete panel as well.

Seismic behaviour of slab-on-girder steel bridges equipped with ductile steel infill plate end diaphragms

Damage suffered by slab-on-girder steel bridges during low-to-moderate seismic excitations reveal the deficiency of standards and codes and indicate the necessity of obtaining insight to the lateral load path and the capacity of individual component and assembled systems. In this paper, to improve the seismic performance of this type of bridges, the lateral load path was initially studied. Subsequently, thin steel infill plates were placed on the seismic load path to dissipate the imposed energy. The results indicate that the use of stocky infill plates with common yielding stress as end diaphragms leads to elastic behaviour of the end diaphragm, at least up to displacement corresponded to the ultimate strength of the substructures, whereas thinner infill plates with low yield stress exhibit an appropriate energy dissipation capacity, and a significant amount of transmitted lateral load will be decreased through their plastic deformation.

Structural performance of unstiffened low yield point steel plate shear walls

Employment of low-yield stress steel plates in shear wall systems has been demonstrated in a number of studies to be a promising alternative for improving the buckling stability, energy absorption capacity, and serviceability of these lateral force-resisting systems, in which material yielding of infill plates may occur either before or after or even at the same time as geometrical buckling. Accordingly, based on their slenderness parameter as well as buckling and yielding behavior, infill plates in steel shear wall systems may be divided into slender, moderate, and stocky categories with respective early buckling, concurrent buckling and yielding, and early yielding characteristics. Such a classification enables the accurate evaluation of buckling and yielding behavior of low yield point steel plate shear walls, which can consequently result in efficient structural and economical design of these lateral force-resisting as well as energy dissipating systems. On this basis, this paper assesses the structural behavior as well as plate–frame interaction characteristics of unstiffened low yield point steel plate shear wall systems via finite element and analytical approaches. Following the experimental validation of the numerical modeling, advantages of use of low yield point steel as compared to the conventional steel are demonstrated. Subsequently, the structural performances of code-designed shear walls with slender, moderate, and stocky low yield point steel infill plates are evaluated comparatively. Finally, the effectiveness of a modified plate–frame interaction (PFI) model in predicting the response of steel shear wall systems with moderate and stocky infill plates is demonstrated.

Seismic design and behavior of low yield point steel plate shear walls

Steel plate shear walls (SPSWs) with low yield point (LYP) steel infill plates have been demonstrated in a number of studies to be efficient and promising lateral force-resisting and energy dissipating systems. In fact, use of LYP steel with extremely low yield stress and high elongation capacity compared to the conventional steel enables the employment of infill plates with improved buckling stability, serviceability, and damping characteristics. In contrast to the commonly-used slender and conventional steel plates with relatively low buckling and high yielding capacities, LYP steel plates can have low yielding and high buckling capacities due to the early yielding of the steel material. On this basis, this paper aims at evaluating the structural behavior and performance of SPSWs with unstiffened LYP steel infill plates designed per AISC 341 seismic provisions which typically address SPSWs with slender infill plates. Effects of plate aspect ratio, and combined compressive and shear forces acting on the web plate are also considered in this study. Numerical analysis of the code-designed LYP steel shear wall models demonstrates the efficient strength, stiffness, and cyclic performances of such systems. In addition, the effectiveness of some design requirements specified in AISC 341 code is evaluated based on the behavior of the SPSW components, and design recommendations are provided accordingly. Finally, a modified plate-frame interaction (PFI) method is used to predict and characterize the behavior of SPSW systems with low yielding and relatively high buckling capacities, the effectiveness of which is verified by comparing the predicted response with experimental and numerical results.

Probabilistic assessment of structures with SPSW systems and LYP steel infill plates using fragility function method

Steel plate shear walls (SPSWs) have been used as primary lateral force-resisting systems in seismic design of new and retrofit of existing buildings. Employment of low yield point (LYP) steel infill plates with considerably low yield strength and high ductility, on the other hand, has been shown in a number of studies to improve the structural performance of SPSW systems. By considering the various sources of randomness and uncertainties involved in the design and retrofit process, adoption of a probabilistic methodology can result in a robust seismic performance assessment of such structural systems. This paper presents the results of a study on the seismic performance and vulnerability of retrofitted structures employing SPSW systems and LYP steel material through probabilistic seismic demand analysis (PSDA). Three 9-story code-designed and retrofitted structural models including a moment-resisting and two SPSW frames are considered. Appropriate seismic response and ground motion intensity parameters, and damage as well as repair states are selected. Structural and nonstructural drift and acceleration fragility functions are subsequently developed based on nonlinear time-history analysis results. The effectiveness of SPSW systems in improving the seismic performance and reducing the vulnerability of buildings is demonstrated through seismic response assessment and fragility analysis. Also, it is shown that employment of relatively thicker LYP steel infill plates in seismic design and retrofit of SPSWs results in smaller damage potential and better seismic performance of such systems.

Buckling and yielding behavior of unstiffened slender, moderate, and stocky low yield point steel plates

Steel plates may be classified as slender, moderate, and stocky based on their distinctive behavior characterized by geometrical buckling and material yielding. Slender plates undergo elastic buckling first and then yield in the post-buckling stage, while stocky plates yield first and then undergo inelastic buckling. Moderate plates, on the other hand, buckle and yield simultaneously. The development of low yield point (LYP) steel enables the application of steel plates with improved buckling and energy absorption capacities as lateral force-resisting and energy dissipating elements in structures. On this basis, buckling and yielding behavior of LYP steel plates with various support and loading conditions is studied in this paper from the point of view of their application in steel plate shear wall (SPSW) systems. The limiting thicknesses of standalone plates corresponding to concurrent geometrical buckling and material yielding are determined theoretically and verified through detailed numerical simulations. Effects of using LYP steel and plate aspect ratio parameter on the required limiting plate thickness as an effective parameter in seismic design of SPSW systems are investigated as well. In addition to the studies on the performance of plates with two and four restrained edges and also applicability of some extrapolation techniques for predicting the critical buckling load of moderate plates, detailed studies are performed on determination of the limiting plate thickness in code-designed SPSW systems. Based on the findings of this study, some practical recommendations are provided for efficient seismic design of SPSW systems with LYP steel infill plates.

SEISMIC EVALUATION OF CODE DESIGNED STEEL PLATE SHEAR WALLS UNDER MAINSHOCK-AFTERSHOCK EARTHQUAKE SEQUENCES

Structures are often subjected to sequences of mainshock and aftershocks during their service life. Strong aftershocks have been known to cause extensive structural damage and losses of human lives in addition to the damage and losses of the mainshock. Steel plate shear walls (SPSWs) have recently attracted considerable interest as a promising lateral-resisting system in seismic-prone regions. The SPSWs consist of steel beams and columns with a thin infill steel plate. The unstiffened thin plates are expected to buckle at low seismic loads and develop tension field action that enables favorable ductility and energy dissipation. The American Institute of Steel Construction's Seismic Provisions prescribe a capacity-based design methodology that uses SPSWs as primary seismic force resisting systems, and require the design of SPSWs to be consistent with the design requirements for other ductile steel seismic force resisting systems. This paper presents numerical analysis of a code-designed eight-story SPSW building that was subjected to consecutive mainshock-aftershock earthquake events. Ground motions developed for the SAC project were selected and scaled to simulate the main shock events at maximum considered earthquake (MCE) level, and large aftershocks events at design base earthquake (DBE) level. Nonlinear response history analysis using the finite element program OpenSees were conducted to investigate the performance of the code designed SPSWs. It was demonstrated that the designed SPSW has good performance under mainshock-aftershock sequences.

Progressive collapse-resisting capacity of framed structures with infill steel panels

In this study the effect of infill steel panels on enhancing the progressive collapse resisting capacity of moment frames is evaluated, and a simple design procedure for infill steel plates is proposed to enhance the progressive collapse resisting capacity of steel moment frames. The progressive collapse potentials of model structures are evaluated by arbitrarily removing a center column and carrying out nonlinear static pushdown analyses using the nonlinear finite element analysis code ABAQUS. The performances of structures with partial or perforated infill panels are also studied. Then a preliminary design procedure for infill steel panels is proposed based on the equivalent single brace simplification of steel panels. The analysis results show that the infill steel panels, even the partial infill panels or panels with perforation, are effective in reducing the progressive collapse potential of moment frames. It is also shown that the proposed design procedure may be effective in preliminary design of infill steel panels to prevent progressive collapse of steel moment frames.

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 study of steel plate shear walls with infill plates strengthened by GFRP laminates

In this paper, the nonlinear behavior of the composite steel plate shear walls, in which steel infill plates was strengthened by the fiber reinforced polymers (FRP), is experimentally investigated. Tests are designed to evaluate the effect of Glass-FRP layers, the number of GFRP layers and the orientation of GFRP layers on the stiffness, shear strength, cumulative dissipated energy and other major seismic parameters in the composite steel plate shear walls. Experimental models are scaled as one-story steel shear panel models with hinge type connections as boundaries at four corners. In the first test, unstiffened steel infill plate is used for the testing as a reference test. However, in the next four tests, strengthened steel infill plates were used with different numbers and orientation of GFRP layers. Each test was performed under fully reversed cyclic quasi-static loading in the elastic and inelastic response zones of the specimens, in compliance with the ATC-24 (1992) test protocol. The experimental results indicated that by strengthening the infill steel plates yield by laminates strength, ultimate shear strength and cumulative dissipated energy can be significantly increased. The paper therefore presents the background, procedure and set-up used as well as the test results.

Probabilistic evaluation of effect of column stiffness on seismic performance of steel plate shear walls

The lateral force resistance and hysteretic energy dissipation capacity of steel plate shear walls (SPSWs) are primarily provided through yielding of the infill steel plates attached to the boundary frame of the system. As such, it is desirable to achieve uniform distribution of infill plate yielding at every story of an SPSW system during an earthquake event. This paper investigates the effect of column stiffness on infill plate yielding distributions in representative two-story and six-story SPSWs. Specially considered in the investigation are the uncertainties existing in infill plate strength and lateral force distributions along the vertical direction. Three probabilistic evaluation methods including the Monte Carlo method, the Latin Hypercube Sampling method, and the Rosenblueth’s 2K+1 Point Estimate method, are considered. It is shown that all methods are stable and effective for this investigation; however, the Rosenblueth’s 2K+1 Point Estimate method requires the least computational cost. The results from the probabilistic evaluation show that increasing column stiffness and story ductility capacity can be effective to achieve infill plate yielding at each story of an SPSW. However, the minimum column stiffness required in the codes in North America does not necessarily lead to infill plate yielding at every story of a multi-story SPSW.