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A platform for research: civil engineering, architecture and urbanism
Seismic resistance of a hybrid shearwall system
Earthquake design of buildings involves the creation of a structural system capable of resisting the seismic forces in a ductile manner. Postearthquake observations have shown that the failure of many reinforced concrete buildings has been due to the inability of the lower-story columns to resist the earthquake imposed loads. Failure of these members are often related to an inappropriate layout of the reinforcement in the upper and lower regions of these columns (insufficient column-tie sizing and spacing, leading to tie failure as well as buckling of the longitudinal reinforcement). Considering these observations, a new hybrid structural system for both moment resistant frame and shearwall buildings, which was proposed by Bouwkamp 1990, has since been studied at the Darmstadt University of Technol-ogy. The system involves the use of prefabricated composite columns consisting of steel tubular thin-walled sections filled with concrete and typical reinforced concrete beam-slab floors. In case of shear walls, the composite columns are used as edge members of the concrete shear walls. In principle, the steel tubular column section replaces effectively the longitudinal column reinforcement and provides the confinement for the (core) concrete. Realizing that the connection between the composite columns and concrete beam-slab floor as well as between the shear-wall edge members and concrete wall are critical, the connection design at the interface of the different elements has been a major subject of study. Earlier research on the design and seismic response of hybrid moment resistant frames have shown that this system can be used effectively for the aseismic design of ductile moment resistant frames. The present study has focussed on the use of this system for shear wall type buildings. Ten alternative interface designs, reflecting a one-third scale model of the edge region of the first story shear wall of an 8-story building, have been developed and tested. The model shear wall was designed with a double-layered 10 x 10 cm mesh having f 8 mm bars vertically and f 6mm bars horizontally. Horizontal anchor bars between composite column and concrete wall extended through holes in the steel column section, were spaced at 10 cm o.c. and directly connected to the wall reinforcement. Also, an interface arrangement with inclined (45-degree) anchor bars as well as headed shear studs welded to the steel tube section were investigated. All specimen were tested under cyclic alternating displacement-controlled loads. Main results in terms of force-displacement, shear force- shear distortion and force-slip re-lation are presented and discussed. A non-linear FE computer program, ANSYS 5.7 has been used to study the inelastic cyclic response under shear of the different interface connections (IFC) tested. Two models have been developed to capture the interface behavior between edge column and RC wall panel. Firstly, a model with non-linear springs, interconnecting the common interface nodal points of the wall panel and steel tube have been introduced. The non-linear spring-characteristics were taken from the empirically derived mechanical model idealising the force-slip relationship at the interface. Secondly, a simple truss-like model capable of capturing the interface behavior has been derived. A comparison between experimental and numerical results show an excellent agreement and clearly support the validity of the both models developed in this study for predicting the non-linear response of the hybrid shear wall system under earthquake load conditions.
Seismic resistance of a hybrid shearwall system
Earthquake design of buildings involves the creation of a structural system capable of resisting the seismic forces in a ductile manner. Postearthquake observations have shown that the failure of many reinforced concrete buildings has been due to the inability of the lower-story columns to resist the earthquake imposed loads. Failure of these members are often related to an inappropriate layout of the reinforcement in the upper and lower regions of these columns (insufficient column-tie sizing and spacing, leading to tie failure as well as buckling of the longitudinal reinforcement). Considering these observations, a new hybrid structural system for both moment resistant frame and shearwall buildings, which was proposed by Bouwkamp 1990, has since been studied at the Darmstadt University of Technol-ogy. The system involves the use of prefabricated composite columns consisting of steel tubular thin-walled sections filled with concrete and typical reinforced concrete beam-slab floors. In case of shear walls, the composite columns are used as edge members of the concrete shear walls. In principle, the steel tubular column section replaces effectively the longitudinal column reinforcement and provides the confinement for the (core) concrete. Realizing that the connection between the composite columns and concrete beam-slab floor as well as between the shear-wall edge members and concrete wall are critical, the connection design at the interface of the different elements has been a major subject of study. Earlier research on the design and seismic response of hybrid moment resistant frames have shown that this system can be used effectively for the aseismic design of ductile moment resistant frames. The present study has focussed on the use of this system for shear wall type buildings. Ten alternative interface designs, reflecting a one-third scale model of the edge region of the first story shear wall of an 8-story building, have been developed and tested. The model shear wall was designed with a double-layered 10 x 10 cm mesh having f 8 mm bars vertically and f 6mm bars horizontally. Horizontal anchor bars between composite column and concrete wall extended through holes in the steel column section, were spaced at 10 cm o.c. and directly connected to the wall reinforcement. Also, an interface arrangement with inclined (45-degree) anchor bars as well as headed shear studs welded to the steel tube section were investigated. All specimen were tested under cyclic alternating displacement-controlled loads. Main results in terms of force-displacement, shear force- shear distortion and force-slip re-lation are presented and discussed. A non-linear FE computer program, ANSYS 5.7 has been used to study the inelastic cyclic response under shear of the different interface connections (IFC) tested. Two models have been developed to capture the interface behavior between edge column and RC wall panel. Firstly, a model with non-linear springs, interconnecting the common interface nodal points of the wall panel and steel tube have been introduced. The non-linear spring-characteristics were taken from the empirically derived mechanical model idealising the force-slip relationship at the interface. Secondly, a simple truss-like model capable of capturing the interface behavior has been derived. A comparison between experimental and numerical results show an excellent agreement and clearly support the validity of the both models developed in this study for predicting the non-linear response of the hybrid shear wall system under earthquake load conditions.
Seismic resistance of a hybrid shearwall system
Shirali, Noor Mohammad (author)
2003-05-26
Theses
Electronic Resource
English
DDC:
690
Cyclic behavior of hybrid shearwall systems
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