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The objective of this paper is to provide details of the design and response of a full-scale cold-formed steel (CFS)-framed building that was tested under a series of dynamic excitations during different phases of construction. The seismic response of complete buildings framed from CFS is essentially unexplored, although significant work on the behavior of CFS members and subsystems, particularly shear walls has been conducted. The experiments described herein are the first tests of a CFS-framed building designed to North American seismic standards. Seismic testing was conducted using the twin shake tables at the University at Buffalo through the U.S. National Science Foundation Network for Earthquake Engineering Simulation program. The project was conducted in two phases. In the first phase, the building specimen was constructed and tested with only the structural components in place: CFS shear walls sheathed with oriented strand board (OSB), CFS gravity walls (unsheathed), and CFS-framed floor and roof diaphragms sheathed with OSB. Nondestructive testing and design basis earthquake-level testing were performed in this phase. In the second phase, a second building specimen was constructed, to identical specifications as in the first phase. However, the second building specimen was finished with nonstructural components including exterior sheathing of the perimeter gravity walls, gypsum-board sheathing of the interior of the perimeter gravity and shear walls, interior partition walls, ceilings, staircases, and exterior weatherproofing. Nondestructive testing was conducted at construction milestones, and the finished second-phase specimen was destructively tested at the maximum considered earthquake level. This paper presents the fundamental system-level response of these building specimens: period, percent damping, drift, and accelerations. The companion paper details component-level response. Overall, the work demonstrates the excellent performance of these structures under seismic excitation, while highlighting that this performance is related to the full system-level response and not just the designated elements in the lateral-force-resisting system. [ABSTRACT FROM AUTHOR]

This paper proposes a new kind of composite waffle slab that consists of orthogonal steel girders and flat RC slab. The steel beams help decrease the cracking that occurs with concrete, and using prefabricated RC slabs reduces the framework and speeds up the construction. An experimental investigation of steel-concrete composite waffle slabs is conducted, and the specimens are proved to have excellent ductility and load-bearing capacity. Then a mixed finite-element (FE) model combining the beam elements and shell elements is proposed to predict the behavior of composite waffle slab. Based on the numerical model, a series of parameter analyses are conducted, and the influences of different parameters on the mechanical behavior of the composite waffle slab are intensively investigated. Simplified formulas for the ultimate capacity of the composite waffle slab are derived based on the test observations and numerical analysis. Reasonable recommendations are proposed to help engineers design the composite waffle slab effectively. [ABSTRACT FROM AUTHOR]

Multitiered steel concentrically braced frames (CBFs) are commonly used to provide lateral resistance for tall single-story commercial, performing arts, sports, and industrial buildings. The seismic response of these frames is studied in this paper. A set of seven special concentrically braced frames (SCBFs), ranging from 9 to 30 m tall with two to six tiers, located in a high seismic area was designed according to the 2010 AISC Seismic Provisions. Fundamental behavior of the two- and four-tiered frames was investigated using three-dimensional (3D) finite element models with shell elements, with particular focus on the buckling response of the columns. The seismic frame response and column stability were then studied more broadly for all frames using more computationally efficient 3D finite element models with fiber-based beam-column elements, which were validated against the shell element models. Multitiered CBFs designed according to current multistory CBF procedures are shown to develop drift concentration in a single tier and high in-plane column bending demand, which in some cases leads to flexural yielding and column instability. As potential solutions to this problem, alternate design strategies were studied and their seismic performance is also presented. Designing for higher seismic forces did not appreciably improve column stability, but use of fixed column bases or buckling-restrained braces provided improved distribution of drift over multiple tiers and reduced the occurrence of column instability. Unlike multistory braced frame seismic design, column flexural demands are more important in multitiered braced frames and must be considered in seismic design. [ABSTRACT FROM AUTHOR]

Thin steel plate shear walls (SPSWs) are an effective lateral force resisting system and are increasingly being used in structures. Engineers require the ability to predict both elastic and inelastic structural responses of SPSWs accurately by a simplified model that is convenient to use. Based on the strip model, this paper proposes a new simplified model for SPSWs, called the three-strip model, in which the infill plates of SPSWs are replaced by three tension-only strips. Comparisons of experimentally obtained pushover responses of SPSWs and that predicted by the proposed model are given and reasonable agreement is observed. A parametric study examines the effect of aspect ratio and column flexibility on the accuracy of the predicted inelastic behavior from the three-strip model. In addition, the capacity of the proposed model in predicting frame forces is verified based on test and strip model results. It was found that the three-strip model can provide generally accurate results for SPSWs and meanwhile reduce modeling workload and computational expense. [ABSTRACT FROM AUTHOR]

This paper deals with the development of shear capacity equations for composite truss beams (CTBs). These equations are obtained from a purposely developed mechanics-based shear model. As opposed to commonly used approaches for the design of these structural elements, where the shear capacity is attained when the first pair of web steel bars yields, in this case the shear capacity is expressed as that causing n pairs of web steel bars to yield before concrete crushes. In this way, the performance of CTBs is maximized. Two different capacity equations are proposed: one, derived from an analytical method, explicitly takes into account the contribution of concrete to shear capacity, and the other, following most current codes, does not consider such contribution. The accuracy of the proposed capacity equations has been verified against the results of nonlinear analyses and experimental tests conceived and conducted to this aim. The comparison confirmed both the consistency of the proposed mechanical model with the experimental observations, and the capability of the capacity equations to predict the shear capacity of CTBs. [ABSTRACT FROM AUTHOR]

This paper describes a test program on a wide range of aluminum alloy square hollow section stub columns containing central circular openings. A total of 28 compression tests was conducted by applying uniform axial load to the specimens, which were fabricated by extrusion of square hollow sections using 6061-T6 heat-treated aluminum alloys. The column strengths; failure modes (including local buckling failure and material yielding failure); strain distribution along the quarter of square hollow sections at midheight of the columns; and load versus axial shortening curves of test specimens were obtained from the experimental investigation. The test results were compared with the design strengths calculated by using the current design rules given in the design specifications and design rules proposed by other researchers for perforated carbon steel structural members. It is shown that most of the current design rules for perforated carbon steel structural members are generally inappropriate, with comparatively high scatter of predictions for the design of perforated aluminum alloy stub columns. [ABSTRACT FROM AUTHOR]

A hysteretic model formulation is presented for simulation of the cyclic moment-rotation response of exposed column–base (ECB) connections, which are typically used to connect a steel column to a concrete footing in steel moment-resisting frames. The research is motivated by the potential for using these connections as dissipative elements within seismic design. The physical processes responsible for various forms of hysteretic response are outlined; these include: (1) seating and gapping between the base plate and footing leading to pinched hysteresis, and (2) a recentering effect of axial compressive load resulting in flag-shaped hysteresis. The proposed ECB model utilizes: (1) a trilinear backbone curve; (2) hysteretic rules for pinching, unloading, recentering, and reloading; and (3) modes of deterioration for four quantities, including strength and stiffness. The model has 16 parameters, of which 4 are classified as core parameters (meaning they can be determined through physics-based models), whereas 12 are classified as ancillary, such that they require empirical calibration. The model is fit to a series of experiments, and it is determined that it is able to simulate the key aspects of hysteretic response. Recommendations for calibration of model parameters are presented, and limitations of the model are outlined. [ABSTRACT FROM AUTHOR]