Robert G. Driver

Analysis of Steel Plate Shear Walls Using the Modified Strip Model

Unstiffened steel plate shear walls are an effective and economical method of resisting lateral forces on structures due to wind and earthquakes. Structural engineers require the ability to assess the inelastic structural response of steel plate shear walls using conventional analysis software that is commonly available and is relatively simple and expeditious to use. The strip model, a widely accepted analytical tool for steel plate shear wall analysis, is refined based on phenomena observed during loading of steel plate shear walls in the laboratory. Since the original strip model was proposed as an elastic analysis tool, these refinements are made primarily to achieve an accurate representation of yielding and eventual deterioration of the wall, although moderate improvements in initial stiffness predictions are also made. In assessing each of the proposed refinements, modeling efficiency is evaluated against the accuracy of the solution. A parametric study using the modified strip model examines the effect of varying the angle of inclination of the tension strips on the predicted inelastic behavior of the model. Notably, it was found that the ultimate capacities of steel plate shear wall models with a wide variety of configurations vary little with the variation of the inclination of the strips.

Performance of Steel Shear Connections under Combined Moment, Shear, and Tension

Beam-to-column connections play a critical role in a structural systems ability to resist widespread collapse by redistributing loads should localized damage occur due to an unanticipated extreme loading event such as a vehicular collision or an accidental explosion. Following the damage of a column in a steel frame designed to carry gravity loads, the strength and ductility demands on adjacent shear connections change substantially from those considered in conventional design. In addition to shear forces, large deflections can lead to the development of significant axial tension through what is known as catenary action. The behavior of steel shear connections under the combined effects of moment, shear, and tension has not been studied extensively and is not generally well-understood. However, this information is essential to assessing and improving the collapse resistance of structures. This paper presents the results of full-scale physical tests designed to investigate the behavior of common steel shear connections under load histories emulating the anticipated effects of the loss of an adjacent column, including large rotations and the development of axial tension. A variety of relative proportions of moment, shear, and tension were used for each type of connection, which included shear tab, single angle and double angle specimens, in order to permit a broad assessment of connection robustness applicable to different building geometries. This study examines the relative performance of these connection types, as well as the effects of connection geometry and combined loading. Observed connection capacities, ductility limits, and failure modes are presented and discussed.

Experimental Investigation of External Confinement of Reinforced Concrete Columns by Hollow Structural Section Collars

Methods are available for strengthening circular reinforced concrete columns that confine the concrete using primarily membrane action. Since these methods are not as effective for square and rectangular columns, a relatively simple noninvasive scheme is proposed that confines the concrete with a combination of significant flexural and axial stiffness. An experimental investigation of the behavior of square concrete columns strengthened by steel hollow structural section (HSS) collars has been carried out. This initial phase of the research considered only axial loading and consisted of a total of 11 full-scale column tests. Two control columns with conventional internal tie reinforcement and nine columns with external confinement by HSS collars were tested. The effects of collar stiffness, spacing, type of corner connection (bolted or welded), and active confining pressure on the confined material curve have been studied. The results indicate that the provision of HSS collars results in considerable enhancement in strength as well as ductility.

Behavior of Steel Shear Connections under Column-Removal Demands

AbstractAn understanding of the behavior of shear connections in steel gravity frames under the unique combinations of moment, shear, and axial force relevant to extreme loading conditions is necessary to assess the vulnerability of a structure to disproportionate collapse. However, such an understanding is currently limited by a deficiency of physical test data. To investigate the inherent robustness of commonly used steel shear connections, an experimental program consisting of 35 full-scale physical tests was completed. Specimens included shear-tab, welded-bolted single-angle, bolted-bolted single-angle, and bolted-bolted double-angle connections. A testing procedure was developed that imposed on a connection the force and deformation demands that would be expected in the bays immediately adjacent to a compromised column in a symmetrical multibay frame. Various geometric arrangements of each connection type were tested, and each arrangement was subjected to a range of loading histories representing dif...

Full-scale Tests on Shear Connections of Composite Beams Under a Column Removal Scenario

In this research, the progressive collapse behaviour of a shear connection of a composite beam has been investigated experimentally. Steel shear/simple connections are widely used in composite gravity framing systems and their behaviour under conventional loading is well understood. However, their response and robustness under the column removal scenario is still largely unknown. While the slab itself can participate in maintaining the integrity of the overall floor system, its presence also amplifies the demand on the steel connections after experiencing initial flexural action. As the column pulls down progressively, which results in a large vertical deflection, the shear connection reaches its capacity under tension-dominant action. The contribution of the concrete slab to the steel connection demands plays an important role in determining the failure mode, load carrying capacity, and ductility of the connections. The main objective of the experimental program is to study the behaviour of steel shear connections in the presence of a concrete slab under a column removal scenario. The test results show the performance of the connection in terms of rotational ductility and ultimate load capacity.

Beam Design Force Demands in Steel Plate Shear Walls with Simple Boundary Frame Connections

AbstractWhere simple beam-to-column connections are used in the boundary frame of a steel plate shear wall and the tension fields in the infill plates are assumed to be uniform and at the yield stress for capacity design, the moment and shear force distributions in each beam are statically determinate, while the axial force distribution is highly indeterminate and depends on several contributing factors. In this paper, in addition to quantifying appropriate moment and shear force distributions for use in design, a simple but powerful analysis method is presented for evaluating the beam’s axial force demand. The method is based on the principle of capacity design and nonlinear finite element simulations of wall systems with different numbers of stories, infill plate aspect ratios and thicknesses, and lateral load distributions. The axial force demands are highly dependent on the mechanism of load transfer to the system from the floor and roof diaphragms and the shear force distribution in the compression c...

Economical Steel Plate Shear Walls for Low-Seismic Regions

AbstractPrevious research on steel plate shear walls (SPSWs) and current design codes have focused principally on achieving highly ductile behavior through stringent detailing requirements. As such, the system is generally considered to be economical only in high-seismic regions. However, lower demands in other regions may permit the use of more economical options. This paper describes a proposed concept for SPSWs that meets the intent of capacity design, while greatly improving competitiveness in seismic regions where maximum ductility is not required. A large-scale, 2-story SPSW specimen was tested to evaluate the associated performance. The wall had standard double-angle beam-to-column shear connections and was tested under vertical gravity load concurrent with reversing lateral loads at each floor level. The specimen survived 25 lateral load cycles, 18 of which were in the inelastic range. The test results indicated that excellent performance can be expected in low-seismic regions, despite significant...

Performance of Type D and Type LD steel plate walls

A finite element model is developed to study the behaviour of unstiffened steel plate walls. The model includes both material and geometric nonlinearities and strain rate effects. The model is first validated using the results from quasistatic and dynamic experimental programs. The validated finite element model is then used to study the performance of four storey and eight storey steel plate walls with moment-resisting beam-to-column connections under spectrum compatible seismic records for Vancouver and Montreal. Two different steel plate wall types defined in the current Canadian standard CAN/CSA-S16–01 are considered, namely, Type D (ductile) and Type LD (limited-ductility) plate walls. All the Type D walls, designed according to the capacity design provisions, exhibit better inelastic seismic responses than the Type LD plate walls. The analyses of eight storey steel plate walls show that in high seismic regions, such as Vancouver, medium- to high-rise Type LD plate walls may exhibit yielding in colum...

Generalized Component-Based Model for Shear Tab Connections

AbstractThe behavior of a conventional steel single-plate (shear tab) connection is highly dependent on the type of loading to which it is subjected. Although these connections have been studied primarily under shear loading, reflecting their common usage in gravity framing, their behavior under combined loading scenarios is more complex. The objective of this study is to develop and validate a component-based mechanical shear tab connection model that accounts for the interactions of shear, axial load, and moment. The component-based methodology allows for the division of the connection into its constituent parts and for modeling of the force-deformation relationship of each part separately. Thus, the connection response to a broad array of load combinations can be obtained on the basis of the geometric and material properties of the connection. The model is validated against experimental results from a variety of loading regimes, and the sensitivity of the model performance to the connection and model p...

Behavior of Shear Tab Connections under Column Removal Scenario

Shear connections in beams are conventionally designed to transfer shear forces only. It is assumed that there is no substantial moment transfer due to the fact that beam end rotation is allowable. The shear tab, or fin plate, connection is one of the simplest and most cost-effective shear connection types and, although its behavior under gravity and cyclic loading has been established, its response to the column removal scenario that is commonly considered for progressive collapse analysis is still relatively unknown. In this paper, challenges involved in numerical studies for simulating the performance of shear tab connections when a column has been compromised are discussed. Modeling definitions for performing highly nonlinear analysis are discussed and recommendations are made regarding obtaining verification by available experimental data. Shear, axial force, and moment versus chord rotation diagrams are presented for both numerical and experimental results and conclusion are made.