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Seismic Behavior Modeling And Design Of Deep Wide Flange Steel Columns For Special Moment Frames
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Book Synopsis Seismic Behavior, Modeling and Design of Deep Wide-Flange Steel Columns for Special Moment Frames by : Gulen Ozkula
Download or read book Seismic Behavior, Modeling and Design of Deep Wide-Flange Steel Columns for Special Moment Frames written by Gulen Ozkula and published by . This book was released on 2017 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Steel Special Moment Frame (SMF) is a preferred seismic force-resisting system for its architectural flexibility and high ductility. To achieve economy in design and construction, there is a growing trend to use deeper columns (e.g., with a section depth larger than 14 in.) to limit the code-enforced story drift requirements in recent years. A deep column has larger slenderness ratios and is more vulnerable to both local and global buckling. Since AISC Seismic Provisions assume that plastic hinging will occur at not only beam ends but also column bases, little research was available on the deep column hinging behavior under axial compression and cyclic drift. A full-scale test program with thirty-seven deep columns subjected to both axial compression and cyclic drift was conducted. Test variables included sectional and member slenderness ratios for local and global buckling controls, axial force level, axial force type (constant versus variable), boundary condition (fixed-fixed versus fixed-flexible), transvers loading type (monotonic, cyclic, or near-faulty), axis of bending (strong-axis versus weak-axis) and bending type (uniaxial versus biaxial). From the database of this test program and a prior one with shallow (W14) stocky columns, three buckling modes were identified. Significant shortening was common to two buckling modes that were typical in deep columns, but not in shallow and stocky columns. While the observed buckling modes could be properly simulated by nonlinear finite element simulation, a practical procedure to predict the governing buckling mode was needed for both cyclic modeling and design purposes. One procedure which considered the interaction between flange and web local buckling was first proposed; the accuracy of the procedure was verified by results from both tested columns and a large number of numerically simulated columns. Second, the combined experimental and numerically simulated database was then used in a multi-variate regression analysis to establish expressions for the cyclic backbone curves; these curves are needed for ASCE 41-type performance-based nonlinear response analysis of SMF. Finally, the same database was used to establish the limiting width-thickness ratios for potential adoption by AISC Seismic Provisions. A novel approach which considered the axial shortening as the limit state was proposed to establish these limiting width-thickness ratios for column design.
Book Synopsis A Study on the Behavior of Deep, Slender Wide Flange Steel Beam-column Members in Seismic Applications by : Frida Pettersson
Download or read book A Study on the Behavior of Deep, Slender Wide Flange Steel Beam-column Members in Seismic Applications written by Frida Pettersson and published by . This book was released on 2016 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: To economically control the drift limits in special moment frames (SMFs), deeper columns than the traditional W14 sections have become more common. The drift of an SMF can be reduced by increasing the bending and shear stiffness of the columns in the frame, and this would also be accomplished by using deeper sections (Shen 2002). However, deeper columns need to be checked against instability since they are more sensitive to local buckling and weak-axis failure modes than stockier columns (NEHRP 2011). The SAC project investigated the behavior of steel moment resisting frame connections after the Northridge Earthquake and some results were extrapolated to column and beam members. However, the project only produced data that led to the prequalification of RBS connections for use with W12 and W14 columns. When testing was performed with deeper column sections, stability problems occurred (FEMA 2000). This study analytically investigates the behavior of deep columns with an exterior RBS connection in a special moment frame. The 40 assemblies studied were designed according to the AISC Provisions (AISC 341, AISC 358, and AISC 360) and modeled with finite element software. A floor slab was not included and monotonic loading displaced the beam tip by 6.0 in. Column sections investigated were W14x426, W24x192, W27x194, and W30x191. The columns were subjected to varying levels of axial load and had medium or weak panel zone strength. Geometric imperfections were included in all models, and some models also included residual stresses. From this study it was concluded that the column depth does not impact the behavior of the connection and deep columns can be used in SMFs. The results show that axial loads have no effect on the column behavior until very high axial loads are applied. It was also shown the twist of the column increases with increasing column depth. Columns with a doubler plate twist more than cases without a doubler plate and the column twist decreases with an increasing axial load.
Book Synopsis Seismic Behavior of Deep, Slender Wide-Flange Structural Steel Beam-columns by : Piyachai Chansuk
Download or read book Seismic Behavior of Deep, Slender Wide-Flange Structural Steel Beam-columns written by Piyachai Chansuk and published by . This book was released on 2018 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates nonlinear cyclic responses of deep wide-flange steel beam-columns, which are primarily used in Special Moment Frame (SMF) for their high in-plane, strong-axis moment of inertia to satisfy story drift limits specified in building codes. SMF design principles aim to achieve energy dissipation through plastic hinging of the beams, while flexural yielding of the columns at the base is also permitted. Although behavior of the beams has been extensively researched, that of the columns is lacking especially for deep columns (e.g., W18 to W36). Therefore, cyclic testing of deep columns was conducted to generate experimental database. Due to large width-to-thickness ratios of these sections, test results showed significant web and flange local buckling; some specimens also exhibited lateral-torsional buckling. These local and global instabilities resulted in significant axial shortening and flexural strength degradation. These behaviors differ significantly from those observed in prior testing of shallow W14 columns, featuring excellent ductility capacity at high axial loads. Additionally, the test matrix was designed to investigate the effects of section depths, varying axial loads, lateral-drift loading sequences, and boundary conditions on the column responses. Inevitably in this testing, the responses were also influenced by flexibility of column-end connections. To eliminate this undesired variable from the responses, a procedure was developed to correct the lateral drift response based on the second-order Timoshenko elastic theory. The effects of boundary conditions were further investigated using high-fidelity finite element software ABAQUS. Results show that fixed-fixed and fixed-rotating column responses can be converted to one another.
Book Synopsis Experimental Evaluation of Steel Wide-flange Columns in Moment-resisting Frames Under High Axial Load and Lateral Drift Demands by : Julien Cravero
Download or read book Experimental Evaluation of Steel Wide-flange Columns in Moment-resisting Frames Under High Axial Load and Lateral Drift Demands written by Julien Cravero and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Steel moment-resisting frames (MRFs) in seismic regions are designed to concentrate yielding in beams to dissipate the energy released by earthquakes. However, capacity design procedures in North American code provisions (CSA 2009; AISC 2010a) do not systematically prevent plastic deformations from occurring in columns. Under ground motions with a low probability of occurrence, steel columns as part of MRFs may develop plastic hinges which can lead to undesirable frame mechanisms. Due to a limited set of test data, the current modelling guidelines (PEER/ATC 2010; ASCE 2014) provide little guidance and often employ highly conservative component models for nonlinear modelling of steel columns. Thus, ASCE 41-13 (ASCE 2014) considers that a column possesses no plastic rotation capacity when the compressive axial load demands become larger than 50% of the critical load associated with the member. Hence, the seismic behaviour of steel columns needs to be characterized experimentally, in particular for high axial load and lateral drift demands. High axial load demands on columns are common in existing steel frame buildings due to gravity and can be increased by vertical accelerations and/or dynamic overturning effects in the case of end columns. This thesis intends to advance the state of knowledge on the hysteretic behaviour of steel columns with a large-scale testing program. Twelve column specimens utilizing W14 and W16 cross-sections that are typically used in steel MRFs are subjected to diverse axial and lateral loading sequences. Monotonic, symmetric and collapse-consistent loading histories are employed to push the columns far into the inelastic range and to assess their performance until collapse (i.e., point of loss of axial load carrying capacity). The transient effect on end columns within MRFs is also studied. Test results provide unique experimental data characterizing the cyclic behaviour of steel columns through the loss of their axial load carrying capacity. The effect of the local slenderness, the cross-section depth, the applied axial load ratio, the loading history and the steel material on the column performance is discussed. Moreover, test data are compared with pre-test simulation predictions carried out with a continuum finite element and a concentrated plasticity model.The thesis provides valuable insights on column performance under a wide range of seismic inputs, the interaction of axial load and lateral drift demands, strength and stiffness deterioration phenomena occurring at the component level and a failure mode associated with column axial shortening. In particular, experimental results show that all the tested column specimens exhibit an appreciable plastic rotation capacity even when subjected to high axial load demands. These results can serve to refine seismic design code provisions, revisit guidelines for the nonlinear analysis of steel columns and calibrate numerical models, on the basis of the proposed recommendations." --
Book Synopsis Collapse Risk Assessment of Steel Moment Resisting Frames Designed with Deep Wide-flange Columns in Seismic Regions by : Ahmed Elkady
Download or read book Collapse Risk Assessment of Steel Moment Resisting Frames Designed with Deep Wide-flange Columns in Seismic Regions written by Ahmed Elkady and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In the context of Performance-Based Earthquake Engineering, there is an increasing need to quantify the collapse resistance of frame buildings under severe ground-motion shaking. The primary objective of this thesis is to advance, through experimental and analytical research, knowledge on the collapse risk assessment of steel frame buildings with steel moment-resisting frames (MRFs) designed in highly seismic regions in North America. Emphasis is placed on the characterization of the steel column hysteretic behaviour as well as the composite floor action and the destabilizing effects of the gravity framing system of steel frame buildings with steel MRFs. The dynamic stability of beam-columns that utilize deep and slender wide-flange cross sections is investigated through full-scale experimental testing. Some of the unique features of the experimental program involve realistic boundary conditions, unidirectional and bidirectional lateral loading and the use of various types of lateral loading protocols. The experimental data provide insight on the damage progression and deteriorating mechanisms observed in wide-flange beam-columns. The hysteretic behaviour of a wide range of cross-sections is further evaluated through a corroborating finite element (FE) parametric study. The findings of the coordinated experimental and analytical research are used to proposed recommendations for the seismic design of steel beam-columns in steel MRFs. A comprehensive system-level analytical study is then conducted in order to evaluate the collapse risk of steel frame buildings with special moment-resisting frames (SMFs) as per ASCE (2010) and Type D Ductile steel MRFs per NBCC (2010). The contributions of the composite floor slab and the gravity framing system are included in the analytical model representations of the steel frame buildings. These contributions have been historically ignored in prior analytical studies. In that respect, a practical approach is developed for modeling (a) the non-symmetric hysteretic behaviour of composite steel beams and panel zones as part of fully-restrained beam-to-column connections; and (b) the hysteretic behaviour of steel beams as part of conventional single-plate shear-tab beam-to-column connections. The collapse risk of typical steel frame buildings with steel MRFs is evaluated based on advanced collapse metrics such as the mean annual frequency of collapse. Based on the findings of the comprehensive system-level analytical study, the strong-column/weak-beam ratio that is typically used in the seismic design of steel MRFs is re-assessed such that a uniform probability of collapse can be achieved over the life expectancy of the steel frame buildings. A new definition of system overstrength (i.e., dynamic overstrength factor) is also proposed." --
Book Synopsis Research Plan for the Study of Seismic Behavior and Design of Deep, Slender Wide Flange Structural Steel Beam-column Members by : NEHRP Consultants Joint Venture
Download or read book Research Plan for the Study of Seismic Behavior and Design of Deep, Slender Wide Flange Structural Steel Beam-column Members written by NEHRP Consultants Joint Venture and published by . This book was released on 2017 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this task was to develop a comprehensive long-range plan to research the seismic behavior of deep, slender wide flange structural steel beam-columns in steel frames. Development of the plan included the investigation of available information on beam-column member and connection behavior in the literature, and considered the differences and interrelationships between member, subassemblage, and system performance. The resulting plan includes a summary of tasks for conducting both experimental and analytical research, and is intended to be the first step in the development of national consensus guidelines for designing and assessing the seismic performance of deep, slender wide-flange beam-columns in steel frame systems.
Book Synopsis Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings (FEMA 350) by : Federal Emergency Agency
Download or read book Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings (FEMA 350) written by Federal Emergency Agency and published by FEMA. This book was released on 2013-03-16 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report, FEMA-350 - Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings has been developed by the SAC Joint Venture under contract to the Federal Emergency Management Agency (FEMA) to provide organizations engaged in the development of consensus design standards and building code provisions with recommended criteria for the design and construction of new buildings incorporating moment-resisting steel frame construction to resist the effects of earthquakes. It is one of a series of companion publications addressing the issue of the seismic performance of steel moment-frame buildings. The set of companion publications includes: FEMA-350 - Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings. This publication provides recommended criteria, supplemental to FEMA-302 - 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, for the design and construction of steel moment-frame buildings and provides alternative performance-based design criteria. FEMA-351 - Recommended Seismic Evaluation and Upgrade Criteria for Existing Welded Steel Moment-Frame Buildings. This publication provides recommended methods to evaluate the probable performance of existing steel moment-frame buildings in future earthquakes and to retrofit these buildings for improved performance. FEMA-352 - Recommended Postearthquake Evaluation and Repair Criteria for Welded Steel Moment-Frame Buildings. This publication provides recommendations for performing postearthquake inspections to detect damage in steel moment-frame buildings following an earthquake, evaluating the damaged buildings to determine their safety in the postearthquake environment, and repairing damaged buildings. FEMA-353 - Recommended Specifications and Quality Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications. This publication provides recommended specifications for the fabrication and erection of steel moment frames for seismic applications. The recommended design criteria contained in the other companion documents are based on the material and workmanship standards contained in this document, which also includes discussion of the basis for the quality control and quality assurance criteria contained in the recommended specifications. The information contained in these recommended design criteria, hereinafter referred to as Recommended Criteria, is presented in the form of specific design and performance evaluation procedures together with supporting commentary explaining part of the basis for these recommendations.
Book Synopsis Seismic Behavior and Design of Deep, Slender Wide-flange Structural Steel Beam-columns by : Piyachai Chansuk
Download or read book Seismic Behavior and Design of Deep, Slender Wide-flange Structural Steel Beam-columns written by Piyachai Chansuk and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Twenty-one W24 hot-rolled columns of ASTM A992 steel with five different sections were tested in Phase 1 of this research program to investigate the effects of slenderness parameters, constant axial load levels, lateral drift loading sequences, and weak-axis bending on the column base responses. It was observed that the webs of these sections with much larger h/ ratios were not as effective in restraining and delaying flange local buckling as those of shallow and stocky (e.g., W12 or W14) columns. Specimens with sections that satisfied the highly ductile requirement in the AISC Seismic Provisions still experienced significant damage and axial shortening due to the interactive flange and web local buckling. An unusual failure mode with local buckling coupled with lateral-torsional buckling was also observed for the first time. Based on these tests results, observed buckling modes were classified, and a simplified procedure to predict the governing buckling mode was proposed. Additional 23 columns including W14, W18, W24, and W30 sections were tested to further evaluate the effects of section depths, boundary conditions, and varying axial loads. Test results revealed that findings from Phase 1 testing could be extrapolated to deeper and shallower sections; the proposed procedure predicted very well the buckling mode of Phase 2 specimens. Allowing the column top end to rotate increased the story drift capacity but did not change the buckling mode. Results from varying axial load tests showed that first-story exterior columns behave very differently from the interior ones. W14 column test results showed that classifying a column as deep or shallow based on the nominal section depth may be inappropriate; the deep column phenomenon with significant interactive local buckling could develop in W14 columns with relatively slender web and flanges.
Book Synopsis Proceedings of the 11th International Conference on Behaviour of Steel Structures in Seismic Areas by : Federico M. Mazzolani
Download or read book Proceedings of the 11th International Conference on Behaviour of Steel Structures in Seismic Areas written by Federico M. Mazzolani and published by Springer Nature. This book was released on with total page 1192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Seismic Design of Reinforced Concrete Buildings by : Jack Moehle
Download or read book Seismic Design of Reinforced Concrete Buildings written by Jack Moehle and published by McGraw Hill Professional. This book was released on 2014-10-06 with total page 783 pages. Available in PDF, EPUB and Kindle. Book excerpt: Complete coverage of earthquake-resistant concrete building design Written by a renowned seismic engineering expert, this authoritative resource discusses the theory and practice for the design and evaluation of earthquakeresisting reinforced concrete buildings. The book addresses the behavior of reinforced concrete materials, components, and systems subjected to routine and extreme loads, with an emphasis on response to earthquake loading. Design methods, both at a basic level as required by current building codes and at an advanced level needed for special problems such as seismic performance assessment, are described. Data and models useful for analyzing reinforced concrete structures as well as numerous illustrations, tables, and equations are included in this detailed reference. Seismic Design of Reinforced Concrete Buildings covers: Seismic design and performance verification Steel reinforcement Concrete Confined concrete Axially loaded members Moment and axial force Shear in beams, columns, and walls Development and anchorage Beam-column connections Slab-column and slab-wall connections Seismic design overview Special moment frames Special structural walls Gravity framing Diaphragms and collectors Foundations
Book Synopsis STESSA 2003 - Behaviour of Steel Structures in Seismic Areas by : Federico Mazzolani
Download or read book STESSA 2003 - Behaviour of Steel Structures in Seismic Areas written by Federico Mazzolani and published by Routledge. This book was released on 2018-03-29 with total page 869 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting a comprehensive overview of recent developments in the field of seismic resistant steel structures, this volume reports upon the latest progress in theoretical and experimental research into the area, and groups findings in the following key sections: · performance-based design of structures · structural integrity under exceptional loading · material and member behaviour · connections · global behaviour · moment resisting frames · passive and active control · strengthening and repairing · codification · design and application
Book Synopsis Seismic Behavior of Concrete Filled Tube Column-wide Flange Beam Frames by : Ricardo Herrera
Download or read book Seismic Behavior of Concrete Filled Tube Column-wide Flange Beam Frames written by Ricardo Herrera and published by . This book was released on 2005 with total page 1484 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on the results from the analytical and experimental studies, CFT-MRFs can be successfully applied to seismic resistant design and their behavior can be studied using the analytical model developed in this study.
Book Synopsis Seismic Behavior of Moment-resisting Steel Column Bases by : Mohamed Fahmy
Download or read book Seismic Behavior of Moment-resisting Steel Column Bases written by Mohamed Fahmy and published by . This book was released on 2000 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Improved Seismic Design Recommendations for Wide-flange Columns in Ductile Steel Moment-resisting Frames Considering Three-dimensional Response by : Abrar Islam
Download or read book Improved Seismic Design Recommendations for Wide-flange Columns in Ductile Steel Moment-resisting Frames Considering Three-dimensional Response written by Abrar Islam and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental and Analytical Investigation of Panel Zone Behavior in Steel Moment Frames by : Sungyeob Shin
Download or read book Experimental and Analytical Investigation of Panel Zone Behavior in Steel Moment Frames written by Sungyeob Shin and published by . This book was released on 2017 with total page 844 pages. Available in PDF, EPUB and Kindle. Book excerpt: Steel moment resisting frames (MRFs) are one of the most commonly used lateral force resisting system for steel building construction located in regions of high seismic risk. Although steel moment frames were studied extensively following the 1994 Northridge Earthquake, one critical design issue is not yet completely understood: the role of the panel zone. Recent U.S. building codes have significantly increased the required shear strength of the panel zone for seismic applications. This leads to increased column sizes or the need for costly doubler plates. A number of past research studies showed that shear yielding of panel zones results in highly ductile behavior and provides a major contribution to frame deformation as an excellent source of energy dissipation. However, these same studies suggested that large panel zone shear deformation can cause high strain concentrations near the beam flange groove welds and can cause premature fracture at the joint. The overall goal of this research is to provide additional data to help answer the question: how much panel zone participation should be permitted in the inelastic seismic response of a steel moment frame? Despite a number of past studies on this issue, there are sharply conflicting views of how panel zones should be treated in design, both within the research community as well as within the building regulatory community. At the crux of the disagreements are concerns regarding fracture induced by panel zone yielding. There appears to be broad agreement that panel zone yielding is a highly ductile process. However, there is broad disagreement on the role that panel zone yielding plays in joint fracture. While there have been a number of past experimental studies on moment frame subassemblies with weak panel zones, the availability of data on large-scale specimens constructed using current US connection detailing and welding practices is very scarce. Further, the experimental database lacks critical data on panel zone behavior in deep columns and for columns subjected to significant axial forces. The primary focus of this dissertation is to provide much needed large-scale experimental data on the cyclic loading performance of steel moment frame joints with weak panel zones. The experimental study was supplemented by finite element analysis of the test specimens, intended to provide additional insights into the response of the test specimens. Cyclic loading tests were conducted on ten large-scale interior steel moment connections to study the seismic performance of the connections. The key variables for the tests were: panel zone strength; beam and column size; beam-to-column connection detail; and column axial stress. Nine of the ten test specimens performed well and met the acceptance criteria of 0.04 radian story drift angle for special moment frames in the current AISC Seismic Provisions. One specimen failed by fracture of the column flange just prior to achieving 0.04 radian story drift angle. In the experimental program, the weak panel zone specimens showed excellent performance, developing drift capacities as large as or larger than the strong panel zone specimens. The weak panel zone specimens exhibited less beam buckling and therefore less strength degradation than the strong panel zone specimens. Shear yielding of the panel zones in these specimens showed highly ductile behavior with stable hysteretic loops. The panel zone was an excellent energy dissipater. The results of this test program showed that acceptable performance of moment frame joints can be achieved over a range of panel zone strengths, varying from very weak to very strong. The experimental results also show that joints with weak panel zones can achieve very large inter-story drift angles prior to fracture. These experimental results suggest that current U.S. code requirements for panel zone strength merit reevaluation. Finite element models were developed of the test specimens, including a global model using shell elements and a local joint model using solid elements. The overall load deflection response of the test specimens predicted by the global models showed good agreement with the experimental results. Local joint models were developed to examine the potential for ductile fracture initiation using the Rupture Index. These studies suggested that the weak panel zone specimens should be far more prone to fracture than the strong panel zone specimens. This prediction, however, was inconsistent with the experimental observations. This suggest that using the Rupture Index as an indicator of the potential for ductile fracture initiation when comparing differing moment frame joint design options, as has been done by previous researchers, should be approached with caution.
Book Synopsis Proceedings of the 10th International Conference on Behaviour of Steel Structures in Seismic Areas by : Federico M. Mazzolani
Download or read book Proceedings of the 10th International Conference on Behaviour of Steel Structures in Seismic Areas written by Federico M. Mazzolani and published by Springer Nature. This book was released on 2022-05-07 with total page 1146 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume highlights the latest advances, innovations, and applications in the field of seismic design and performance of steel structures, as presented by leading international researchers and engineers at the 10th International Conference on the Behaviour of Steel Structures in Seismic Areas (STESSA), held in Timisoara, Romania, on 25-27 May 2022. It covers a diverse range of topics such as behaviour of structural members and connections, performance of structural systems, mixed and composite structures, energy dissipation systems, self-centring and low-damage systems, assessment and retrofitting, codes and standards, light-gauge systems. The contributions, which were selected by means of a rigorous international peer-review process, present a wealth of exciting ideas that will open novel research directions and foster multidisciplinary collaboration among different specialists.
Book Synopsis Cyclic Behavior and Design of Steel Columns Subjected to Large Drift by : James David Newell
Download or read book Cyclic Behavior and Design of Steel Columns Subjected to Large Drift written by James David Newell and published by . This book was released on 2008 with total page 411 pages. Available in PDF, EPUB and Kindle. Book excerpt: During an earthquake, steel braced frame columns are potentially subjected to high axial forces combined with inelastic rotation demand resulting from lateral story drift. Little design guidance is available concerning the reliability of steel columns under this level of combined loading. To evaluate the performance of wide-flange columns under high axial load and drift demand, specimens have been subjected to laboratory and analytical investigation. Nine W14 wide-flange columns were tested at different levels of axial force demand (35% to 75% of column yield strength) combined with lateral story drift demand of up to 10%. Since a specified loading sequence does not exist in building codes, one was developed based on the results of nonlinear earthquake time-history analysis of 3-story and 7-story buckling-restrained braced frame models. The first step in the loading sequence consisted of imposing simulated gravity load. Then in-phase, increasing amplitude cyclic axial load and story drift were applied. Experimental results showed that flange local buckling was the dominant buckling mode. Specimens achieved interstory drift capacities of 0.07 rad. to 0.09 rad., in part, due to the delay in flange local buckling resulting from the stabilizing effect provided by the stocky column web of the W14 specimens. The finite element analysis program Abaqus was used to model the column specimens and to perform a parametric study investigating the effect of flange and web local buckling, lateral-torsional buckling, and axial load. Analysis and experimental results were observed to be well correlated. The behavior of deep columns (W18 and W24) with higher web slenderness than the tested W14 sections was also investigated. Models of deep column sections showed significant strength degradation due to the interaction of flange and web local buckling. Testing and finite element analysis indicated that the plastic rotation capacities currently predicted by Seismic Rehabilitation of Existing Buildings (ASCE 41) are very conservative for axial load ratios above 0.5. At axial load ratios below 0.5 the plastic rotation capacity of some finite element models was less than that predicted by ASCE 41. Using the database of finite element analysis results and regression analysis, nonlinear models were developed to more accurately predict rotation capacity of steel wide-flange columns. These models consider the interaction of flange and web local buckling, lateral-torsional buckling, and axial load.
