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.

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.

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.

Experimental study on shear performance of partially precast Castellated Steel Reinforced Concrete (CPSRC) beams

Yong Yang,Yunlong Yu,Yuxiang Guo,Charles W. Roeder,Yicong Xue,Yongjian Shao 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.2

A new kind of partially precast or prefabricated castellated steel reinforced concrete beam, which is abbreviated here as CPSRC beam, was presented and introduced in this paper. This kind of CPSRC beam is composed of a precast outer-part and a cast-in-place inner-part. The precast outer-part is composed of an encased castellated steel shape, reinforcement bars and high performance concrete. The cast-in-place inner-part is made of common strength concrete, and is casted with the floor slabs simultaneously. In order to investigate the shear performance of the CPSRC beam, experiments of six CPSRC T-beam specimens, together with experiments of one cast-in-place SRC control T-beam specimen were conducted. All the specimens were subjected to sagging bending moment (or positive moment). In the tests, the influence of casting different strength of concrete in the cross section on the shear performance of the PPSRC beam was firstly emphasized, and the effect of the shear span-to-depth ratio on that were also especially taken into account too. During the tests, the shear force-deflection curves were recorded, while the strains of concrete, the steel shapes as well as the reinforcement stirrups at the shear zone of the specimens were also measured, and the crack propagation pattern together with the failure pattern was as well observed in detail. Based on the test results, the shear failure mechanism was clearly revealed, and the effect of the concrete strength and shear span-to-depth ratios were investigated. The shear capacity of such kind of CPSRC was furthermore discussed, and the influences of the holes on the steel shape on the shear performance were particularly analyzed.

Study on mechanical performance of composite beam with innovative composite slabs

Yunlong Yu,Yong Yang,Xianwei Zhou,Charles W. Roeder,Xudong Huo 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.3

A new type of composite beam which consists of a wide flange steel shape beam and an innovative type of composite slab was introduced. The composite slab is composed of concrete slab and normal flat steel plates, which are connected by perfobond shear connectors (PBL shear connectors). This paper describes experiments of two large-scale specimens of that composite beam. Both specimens were loaded at two symmetric points for 4-point loading status, and mechanical behaviors under hogging and sagging bending moments were investigated respectively. During the experiments, the crack patterns, failure modes, failure mechanism and ultimate bending capacity of composite beam specimens were investigated, and the strains of concrete and flat steel plate as well as steel shapes were measured and recorded. As shown from the experimental results, composite actions were fully developed between the steel shape and the composite slab, this new type of composite beams was found to have good mechanical performance both under hogging and sagging bending moment with high bending capacity, substantial flexure rigidity and good ductility. It was further shown that the plane-section assumption was verified. Moreover, a design procedure including calculation methods of bending capacity of this new type of composite beam was studied and proposed based on the experimental results, and the calculation methods based on the plane-section assumption and plastic theories were also verified by comparisons of the calculated results and experimental results, which were agreed with each other.

Evaluation on Structural Performance of PC Composite Beam According to Types of Connection Plate

Yong-Sung Choi,유정한,Hyeon-Gu Kim,Charles W. Roeder 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.6

Recently, construction methods have been developed in the construction industry to solve problems such reducing construction period and cost. One of them is the precast concrete (PC) composite beam, which has advantages such as economic feasibility and quality assurance by utilizing the advantages of steel and reinforced concrete structures using Gerber beams. PC composite beams are made of PC beams in the form of embedded connection plates at the factory, and are connected together with slab concrete after pin connection using high-strength bolts at the site to form one body. As the PC composite beam uses the connection plate, it is possible to apply the Gerber beam, so it is possible to optimize the fl exural moment distribution. However, the current structural design standard does not provide specifi c information on the height or embedded length of the connection plate, making it diffi cult to design. Therefore, the scope of the study was limited to PC composite beams, the form was divided into continuous and discontinuous, and the infl uence variables were set to plate height and embedded length to conduct fi nite element analysis. As a result of the analysis, the embedded length is the factor that has the greatest infl uence on the structural performance of PC composite beams. The composite beam with a height of 300 mm and a length of 1200 mm was found to be the most effi cient with a fl exural strength of 505 kN m and a defl ection of 8.9 mm. The results of this study can be used as the basis for the details and structural design methods of PC composite beams.

Static Experiment on Mechanical Behavior of Innovative Flat Steel Plate-Concrete Composite Slabs

Yong Yang,Ru-yue Liu,Xudong Huo,Xianwei Zhou,Charles W. Roeder 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.2

A new type of composite slab is introduced in this paper, which is composed of normal fl at steel plates and concrete slabs, connected and interacted by perfobond shear connectors (PBL shear connectors). Experiments on six specimens of this type of composite slab, loaded at two symmetric two-points, were described in this paper to get mechanical behaviors under bending moments. During the experiments, the crack patterns, failure modes, failure mechanism and ultimate bending capacity of specimens with composite slab were investigated, and the strains of concrete and fl at steel plates were also measured and recorded in order to obtain the moment action. From the experimental results, it was found that composite interaction between the steel plate and the concrete fully developed, and such composite slab was verifi ed to have good mechanical performance with high bending capacity, substantial fl exural rigidity and good ductility. Plane section assumption was also verifi ed and moreover, a design approach including calculation methods of bending capacity and fl exural rigidity was established and proposed based on the experimental results, and the calculation methods were also verifi ed and revised on the basis of comparisons of the calculated results and experimental results. Results from this paper provide references for the application of this new type composite slab.