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RISS 인기검색어
- 검색키워드
- 저자 : Dawn E. Lehman (검색결과 3 건)
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Improved Seismic Design of Steel Frame Connections
Charles W. Roeder,유정한,Dawn E. Lehman 한국강구조학회 2005 International Journal of Steel Structures Vol.5 No.2
drifts. Response of steel framing systems depends to a large part on the inelastic deformation capacity of the framing elements.Recent research into the seismic performance of moment resisting frames has shown that improved response, includingincreased ductility, is posible if limited yielding is also permitted in the conection in addition to the beams, and the resistancesof these yield mechanisms are balanced. Adverse effects of premature failure are controled by balancing the failure modeframe guset plate connections. In this paper, the design methodology to balance the yield mechanisms and failure modes ispresented with the objective of improving the seismic response of stel framing systems. Initially, the strategy is demonstratedfor special steel moment resisting frames with welded-flange-welded-web connections. Next, the design procedure istheoreticaly applied to special concentrically braced frames. Past experimental results are used to develop improved designAdditional research that is required to finalize the design procedure for braced frame systems is discussed.
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Concrete Filled Steel Tubes for Bridge Pier and Foundation Construction
Charles W. Roeder,Max T. Stephens,Dawn E. Lehman 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.1
Concrete filled steel tubes (CFSTs) are composite members that are commonly used in many countries today. CFST components are used in the United States, but they are more common in Asia, in part because the connections used in Asia are quite labor intensive and there are not standard connections in the U.S. In addition, US design specifications are prepared by separate groups for structural steel and reinforced concrete structures and so composite systems that use CFST components are not overseen by a single group and as such there are several conflicting design standards. In the US, steel tubes used for CFST are more slender (i.e., the diameter-to-thickness, D/t, ratio is larger) than some other countries, and labor practices (structural steel labor is different than reinforcing steel labor) also cause potential conflicts in construction. As a result, CFST has had some use in tall building construction in the US, but very limited use in bridge construction. A research program at the University of Washington has been in progress to address many of these issues with an eye towards universal design expressions, simpler, standardized connections and promotion of accelerated bridge construction (ABC). The research has resulted in recent changes to the American Association of State Highway Officials (AASHTO) bridge design specification as well as state departments of transportation (DOTs), which supports the increased use of CFST in bridge piers and pile and drilled-shaft foundations. An experimental research study which included 19 CFST pier-to-footing (or pile-cap) connection tests and 8 CFST pier column-to-precast pier cap tests was performed. These connections provide good performance under both seismic and gravity loads and address the concerns of US construction. These connections, their design rules and requirements, and their impact on composite behavior and system performance are discussed. These results permit rapid and economical construction of CFST bridge piers, piles and drilled shaft foundations. They encourage the use of more slender and economical tubes, while achieving the benefits of composite construction.
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Concentric X-Braced Frames with HSS Bracing
Keith D. Palmer,Charles W. Roeder,Dawn E. Lehman,Taichiro Okazaki,Carol K. Shield,Jacob Powell 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.3
Concentrically braced frames are stiff, strong systems frequently used to resist wind and seismic loading; in regions of high seismicity in the US special concentrically braced frames (SCBFs) are used. CBF configurations vary, but in low rise or other structures with modest levels of demands single-story, X-configured braced frames (X-braced) are commonly used. The brace sections used also vary but hollow structural sections (HSS) are the most common in the U.S. Although important, in part because low-rise structures sustain large demands, few research programs have focused on the single-story X-brace configuration. A large research program was undertaken to understand and improve the response of SCBFs with selected testing on single-story X braced SCBFs. The test matrix consisted of two, full-scale planar X-braced frame experiments and one nearlyfull-scale three-dimensional X-braced frame. The tests were designed using a new design and detailing philosophy, called the Balanced Design Method. In this paper, application of this design method to the frame is investigated, with a focus on the center-splice connection. The results show that the ultimate inelastic deformation capacity of the system is less dependent on the specific design detail at this splice. Additionally, the bi-directional load testing indicated that the out-of-plane demands did not impact the system performance.
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