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SE3-002
15:20
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15:40
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Seismic Capacity of Deep Steel Columns and Their Influence on the Collapse Response of Steel Special Moment Frames
Deep, wide-flange steel columns have been widely used in U.S. seismic zones since the late 1990s. However, their susceptibility to local and global instabilities under seismic loading is not yet fully understood. This paper presents recent studies that computationally investigate the seismic behavior of deep steel columns and their influence on overall system response. The employed finite element models are capable of capturing the full range of instabilities and frame collapse behavior. A parametric study at member-level is performed to identify key variables affecting axial capacity of deep steel columns. The subsequent system-level simulations confirm that the identified variables also can be influential in collapse capacity of frames. Based on the simulation results, highly ductile limits that consider all key variables are proposed to ensure adequate ductility of special moment frames with deep columns under severe seismic loading.
Sherif El-Tawil, Tung-Yu Wu, Jason McCormick
collapse analysis, deep steel columns, finite element simulation, seismic loading
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SE3-015
15:40
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15:55
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MECHANICAL RESPONSE OF CONCRETE-FILLED FRP-WRAPPED STEEL CORRUGATED TUBE COLUMNS
FRP-Wrapped Steel Corrugated Tube (FWSCT) is a novel shell system consisting of a spiral corrugated steel tube and Fiber Reinforced Polymer (FRP) shell. The spiral corrugated steel tube serves as a mold for wrapping fiber and woven prepreg, which resolves the challenge of demolding the FRP shell with ribbed inner surface from a mandrel after cure. This paper presents the experimental work of the concrete-filled FWSCT column. A total of 36 cylindrical specimens were tested under uniaxial compression. The test parameters included three different types of confinement tube: (1) spiral corrugated tube, (2) spiral corrugated tube with prepreg fiber strands, and (3) GFRP wrapped enhanced spiral corrugated tube. To study the influences of concrete cross section, the cylinders with solid section, hollow section and hollow section with interior spiral corrugated tube were prepared. In addition, to verify the performance under seismic load, three large size concrete columns jacketed by FWSCT with zero, five layers and eight layers of GFRP respectively were tested. The column specimens jacketed only by spiral corrugated tube failed in shear at a low drift level. Jacketed by FWSCT with 5-layer and 8-layer GFRP, the column specimens illustrated a ductile response up to 8% drift.
Chung-Sheng Lee, Hao-Hsiang Tan, Chung-Che Chou, Kai-Yi Wu, V-Liam Chin
axial compression, Confined Concrete, Glass Fiber Reinforced Polymer (GFRP), Seismic Load, Steel Corrugated Tube
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SE3-016
15:55
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16:10
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PERFORMANCE EVALUATION OF A NOVEL BOX SECTION COLUMN BASE WITH SELF-CENTERING ABILITY
A column is a critical component that should sustain a vertical load; it is difficult to repair a column when it is damaged. To reduce the repairing cost and time to recover the structural performance or functionalities of the buildings from the earthquake, a new type of self-centering column base is proposed in the study. The column base consists of a short H section inner column and the outer box section column. The inner column which is designed with a base plate is placed on the foundational beam, and the pre-tension members are adopted to provide compression force on the column-foundation interface to develop the restoring moment. The box section column is placed from the top of the inner column and bolted to the base plate of the inner column. So that the box column sustain the axial load but would not afford the extra axial force from the pre-tension members. A section reduced steel rod assembled with a steel tube is developed as a buckling restrained damper to dissipate energy at the connection. A series of full-scale, static cyclic tests were conducted with the constant axial load applied on the column. The results indicate that the column base exhibits a stable self-centering behavior and energy dissipation ability up to a plastic rotation of 3%. The maximum strength reached 71% of the full plastic moment of the column.
Yu-Lin Chung, Kuan-Ting Kuo
Box section column, column base, self-centering, steel rod damper
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SE3-018
16:10
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16:25
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SEISMIC TEST AND ANALYSIS OF WIND-TURBINE HOLLOW STEEL ROUND COLUMNS WITH A LARGE DIAMETER-TO-THICKNESS RATIO
A round-hollow steel section (round-HSS) is widely used in wind-turbine column construction. Experimental studies on the flexural and cyclic behaviors of large diameter-to-thickness (D/t) round-HSS columns are limited. Three steel round-HSS column specimens with a D/t ratio of 240 were planned for the test. The specimens, made from ASTM A36 steel, had a clear height of 4745 mm, diameter of 1440 mm, and thickness of 6 mm. In addition, one specimen was wrapped by the Glass-Fiber-Reinforced Polymer (GFRP) material. Specimen 1 was tested under an increasing monotonic loading, and Specimens 2 and 3 were tested under increasing cyclic loading. Specimens 1 and 2 exhibited inward-local buckling at a drift angle of 0.0025 rad. Specimen 3 with GFRP wrapping at the bottom end exhibited inward-local buckling at a drift angle of 0.005 rad. Test results indicated that the ductility of Specimen 1 under a monotonic loading is larger than those of Specimens 2 and 3 under a cyclic loading. The round-HSS columns had a ductility of 1.02~1.65 before the lateral load decreased 10%. The lateral flexural strength of the GFRP-wrapped column increased around 5~11% compared to other specimens without GFRP wrapping. When the column section with a D/t ratio greater than 240, the AISC (2016) and JRA (2002) standards overestimate the flexural strength, but the flexural strength predictions based on the ASME (2006), ASCE (2011) and EN1993-1 (2007) standards are reasonable. Nonlinear time history analyses were conducted on a 10-MW wind-turbine tower to obtain seismic demands.
Min-Chen Kuo, Chung-Che Chou
GFRP, Round-HSS section, Wind-turbine column
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SE3-017
16:25
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16:40
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SEISMIC PERFORMANCE OF CONCRETE FILLED STEEL TUBULAR (CFST) COLUMNS WITH VARIED AXIAL LOADS
A concrete filled steel tubular (CFST) column is designed and constructed as a beam-column member in buildings. However, there is less information on the seismic behavior of CFST columns under high axial compressive load from past studies to be revealed. This paper mainly investigates the seismic performance of square CFST columns subjected to different axial compressions. A total of four full-scale specimens was tested by combined loads of axial compressive and lateral cyclic forces. For the axial compressive loads, three specimens were subjected to constant axial compressions with ratios of P/P0 = 0.15, 0.35 and 0.55, respectively, and one was applied varied axial compression with ratio of P/P0 varying from 0.15 to 0.55 that is an assumption for designing exterior columns in a typical moment resistance frame (MRF) system. An identical loading protocol according to the AISC 341-16 code was adopted as the basis of cyclic lateral displacement loading for all four specimens. Test results show that there were differences in yielding and buckling process of the steel tubes’ ends, lateral strength, deformation capacity and lateral stiffness degradation of the column with various cases of axial compressive loads. For the three CFST specimens with constant axial compression, the specimen with higher axial compression reduced its lateral strength and deformation capacity. Another important thing was detected in Specimen CFST42-15/55C with varied axial compression. That is a difference in lateral strength and deformation capacity between two cases of lateral loading in positive and negative directions. Therefore, it was found that Specimen CFST42-55C possesses the lowest lateral strength and deformation capacity compared with three other specimens and its deformation performance was 1.29% of average interstory drift ratio. The study results demonstrate that these square filled composite columns satisfy a highly seismic requirement in the case of axial compression less than or equal to 0.35 P0 with their average ultimate interstory drift ratio more than 3.00%. To improve the seismic performance of this type CFST column, limiting axial compression of the column (upper value: 0.35 P0) is one of the most effective ways.
HAO DINH PHAN, KER-CHUN LIN
axial compression, CFST columns, interstory drift ratio, ratio of B/t, seismic performance
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