1,067 research outputs found
Analytical investigation of the cyclic behavior and plastic hinge formation in deep wide-flange steel beam-columns
No full textThis paper investigates the cyclic behavior of deep wide-flange sections, used as columns in steel Special Moment Frames (SMFs), through detailed finite element (FE) analysis. A wide range of wide-flange sections is subjected to symmetric cyclic lateral loading combined with different levels of constant compressive axial load ratios representing the loading conditions of interior steel columns in SMFs. The FE simulations demonstrate that wide-flange beam-columns, with web and flange slenderness ratios near the current compactness limits of seismic design provisions (AISC 341-10), experience rapid cyclic deterioration in flexural strength under high axial load ratios. It is also found that deep wide-flange slender sections shorten axially to about 10 % of their length due to severe flange and web local buckling. Based on the FE simulations, for bottom story columns, where axial load ratios are in the range of 20–35 %, a reduction to about two thirds of the current compactness limit for highly ductile members would achieve a 4 % chord rotation while maintaining a flexural strength larger than 80 % of the expected plastic flexural strength of a steel column. The FE simulation results also suggest that the pre-capping rotation predicted by current modeling recommendations for steel components (PEER/ATC 72-1) is overestimated for sections with high web and flange slenderness ratios undergoing monotonic and/or cyclic lateral loading combined with high axial load levels. © 2014, Springer Science+Business Media Dordrecht.RESSLA
Effect of gravity framing on the overstrength and collapse capacity of steel frame buildings with perimeter special moment frames
No full textThis paper investigates the effect of the gravity framing system on the overstrength and collapse risk of steel frame buildings with perimeter special moment frames (SMFs) designed in North America. A nonlinear analytical model that simulates the pinched hysteretic response of typical shear tab connections is calibrated with past experimental data. The proposed modeling approach is implemented into nonlinear analytical models of archetype steel buildings with different heights. It is found that when the gravity framing is considered as part of the analytical model, the overall base shear strength of steel frame buildings with perimeter SMFs could be 50% larger than that of the bare SMFs. This is attributed to the gravity framing as well as the composite action provided by the concrete slab. The same analytical models (i) achieve a static overstrength factor, Ωs larger than 3.0 and (ii) pass the collapse risk evaluation criteria by FEMA P695 regardless of the assigned total system uncertainty. However, when more precise collapse metrics are considered for collapse risk assessment of steel frame buildings with perimeter SMFs, a tolerable probability of collapse is only achieved in a return period of 50years when the perimeter SMFs of mid-rise steel buildings are designed with a strong-column/weak-beam ratio larger than 1.5. The concept of the dynamic overstrength, Ωd is introduced that captures the inelastic force redistribution due to dynamic loading. Steel frame buildings with perimeter SMFs achieve a Ωd>3 regardless if the gravity framing is considered as part of the nonlinear analytical model representation. © 2014 John Wiley & Sons, Ltd.RESSLA
Full-Scale Testing of Deep Wide-Flange Steel Columns under Multiaxis Cyclic Loading: Loading Sequence, Boundary Effects, and Lateral Stability Bracing Force Demands
No full textThis paper discusses the findings from 10 full-scale steel column tests subjected to multiaxis cyclic loading. The columns use deep wide-flange cross sections typically seen in steel moment-resisting frames designed in seismic regions. The effects of boundary conditions, loading sequence, local web, and member slenderness ratios on the column hysteretic behavior are investigated. The test data underscore the influence of boundary conditions on the damage progression of steel columns. Local buckling followed by out-of-plane deformations near the plastified column base are the dominant failure modes in fixed base columns with a realistic flexible top end. Twisting may occur only at drifts larger than 3% even when the member slenderness is fairly large. The test data suggest that bidirectional loading amplifies the out-of-plane deformations but does not significantly affect the overall column performance. The loading sequence strongly affects the column’s plastic deformation capacity but only at story drifts larger than 2%. Above this drift amplitude, column axial shortening grows exponentially and becomes a controlling failure mode. Measurements of the lateral stability bracing force demands at the column top exceed the lateral brace design force specified in North American standards
Effect of composite action on the dynamic stability of special steel moment resisting frames designed in seismic regions
No full textSeismic assessment of steel frame structures is typically concerned with analytical modeling of the lateral load-resisting system only, ignoring the effect of composite action on its lateral stiffness and strength. Based on a recently developed database for deterioration modeling of steel beams with reduced beam sections (RBS), the effect of composite action on their bending strength and deterioration parameters (e.g. plastic rotation capacity, post capping rotation capacity, rate of cyclic deterioration) under cyclic loading can be quantified. These connections are widely used in United States in design of special steel moment resisting frames. A phenomenological model, which is able to simulate important deterioration modes when a steel component is subjected to cyclic loading, has been modified to incorporate slab effects on moment-rotation characteristics of composite steel beams. The effect of composite action on the collapse capacity of SMFs is demonstrated through a case study of an 8-story steel building.</p
sj-pdf-1-eqs-10.1177_87552930231172529 – Supplemental material for Backbone curve variations on steel building seismic response
No full textSupplemental material, sj-pdf-1-eqs-10.1177_87552930231172529 for Backbone curve variations on steel building seismic response by Bruce Maison, Matthew S. Speicher and Dimitrios Lignos in Earthquake Spectra</p
Modeling of the composite action in fully restrained beam-to-column connections: Implications in the seismic design and collapse capacity of steel special moment frames
No full textThis paper investigates the effect of the composite action on the seismic performance of steel special moment frames (SMFs) through collapse. A rational approach is first proposed to model the hysteretic behavior of fully restrained composite beam-to-column connections, with reduced beam sections. Using the proposed modeling recommendations, a system-level analytical study is performed on archetype steel buildings that utilize perimeter steel SMFs, with different heights, designed in the West-Coast of the USA. It is shown that in average, the composite action may enhance the seismic performance of steel SMFs. However, bottom story collapse mechanisms may be triggered leading to rapid deterioration of the global strength of steel SMFs. Because of composite action, excessive panel zone shear distortion is also observed in interior joints of steel SMFs designed with strong-column/weak-beam ratios larger than 1.0. It is demonstrated that when steel SMFs are designed with strong-column/weak-beam ratios larger than 1.5, (i) bottom story collapse mechanisms are typically avoided; (ii) a tolerable probability of collapse is achieved in a return period of 50 years; and (iii) controlled panel zone yielding is achieved while reducing the required number of welded doubler plates in interior beam-to-column joints
Dynamic stability of deep and slender wide-flange steel columns – full scale experiments
No full textIn North America, a common design practice for steel frame buildings with perimeter steel special moment frames (SMFs) is to employ deep and slender wide-flange steel columns (i.e., range of column depth, d > 16 inches). Till recently, very little was known regarding the hysteretic behavior of such members because of lack of available experimental data. This paper discusses selective findings from a full-scale testing program that was conducted at Ecole Polytechnique Montreal with the use of a 6-degree-of-freedom experimental setup. The testing program investigated the cyclic behavior of 10 full-scale beam-columns. The specimens had a depth of 24 inches (i.e., W24xl46 and W24x84 cross-sections) and were subjected under various lateral-loading protocols coupled with constant compressive axial load. The boundary conditions of the specimens simulated a fixed support at the column base and a flexible boundary at the column top end to mimic the flexibility of a beam-to-column connection at the floor level. The tested specimens represented typical interior first-story columns in mid-rise steel SMFs. This paper summarizes the main observations related to the effect of local and global slenderness ratios on the cyclic behavior of beam-columns. The effect of bidirectional lateral loading on the dynamic stability of beam-columns is also addressed. Observations related to the effect of the employed loading history as well as the lateral bracing force design requirements on steel wide- flange beam-columns are also provided based on the available experimental results.</p
Stability requirements of deep steel wide-flange columns under cyclic loading
No full textJust recently, valuable experimental data that characterized the hysteretic behavior of deep wideflange steel columns (i.e., column depth, d >16 inches) at full-scale became available. Such members are typically used in steel moment-resisting frames (MRFs) in North America. In order to expand the findings of the experimental program, an extensive parametric study is conducted using a validated continuum finite element (FE) modeling approach. The nonlinear behavior of more than 40 steel wide-flange cross-sections is investigated. Each steel column is subjected to a monotonic, a symmetric cyclic, and a collapse-consistent lateral loading protocol coupled with different levels of constant compressive axial load ratios. Based on the FE results, the cyclic deterioration in the column flexural strength and stiffness is evaluated. Accordingly, design recommendations are developed related to the seismic compactness criteria for highly ductile members such that column axial shortening can be reduced under design basis and lowprobability of occurrence earthquakes. The range of out-of-plane force demands is also evaluated for the lateral bracing design of columns in steel MRFs. In that respect, the current AISC provisions are evaluated. Empirical equations are developed for predicting the out-of-plane force demands and the plastic hinge length in steel wide flange columns.</p
EaRL—software for Earthquake Risk, Loss and Lifecycle Analysis
No full textPerformance-based earthquake engineering (PBEE) has become an increasingly popular framework to design, retrofit and manage structures. This probabilistic framework integrates data from the seismic hazard, structural response, damage fragility and damage consequences to compute structural performance metrics; thereby facilitating an effective communication to building owners and stakeholders besides the engineering community. In support of PBEE, a Matlab-based computational platform/software is developed that implements state-of-the-art loss estimation and seismic lifecycle analysis methodologies. The software aims to (1) facilitate the relatively challenging PBEE computations by providing an intuitive graphical user-interface, a wide range of data visualization options and collective features that adapt to different users’ preferences; and (2) provide an open-source platform for code and software development to support the continuously advancing aspects of the PBEE framework
Development of bidirectional cyclic lateral loading protocols for experimental testing of steel wide-flange columns
No full textSteel columns in frame buildings subjected to earthquake shaking undergo bidirectional lateral drift demands. Till now, the majority of past experimental and numerical studies were primarily concerned with the unidirectional column behavior. This paper proposes a procedure to develop representative bidirectional lateral drift histories for experimental testing of steel columns in moment-resisting frames (MRFs). To this end, a 3-dimensional numerical model of a prototype four-story building with perimeter MRFs is analyzed using a suite of ordinary ground-motion records. The first-story drift orbit is idealized in the form of elliptical drift cycles. Statistical data of parameters defining these elliptical drift cycles is collected. The data serves for the development of bidirectional symmetric loading protocols representative of design-basis earthquakes. The developed protocol is adopted in a testing program that assessed in full-scale the influence of bidirectional cyclic loading on steel columns
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