In this paper,the seismic responses and resilience of a novel K-type superelastic shape memory alloy(SMA)self-centring(SC)eccentrically braced frame(EBF)are investigated.The simulation models of the SMA-based SC-EBF a...In this paper,the seismic responses and resilience of a novel K-type superelastic shape memory alloy(SMA)self-centring(SC)eccentrically braced frame(EBF)are investigated.The simulation models of the SMA-based SC-EBF and a corresponding equal-stiffness traditional EBF counterpart are first established based on some existing tests.Then twenty-four near-fault ground motions are used to examine the seismic responses of both EBFs under design basis earthquake(DBE)and maximum considered earthquake(MCE)levels.Structural fragility and loss analyses are subsequently conducted through incremental dynamic analyses(IDA),and the resilience of the two EBFs are eventually estimated.The resilience assessment basically follows the framework proposed by Federal Emergency and Management Agency(FEMA)with the additional consideration of the maximum residual inter-storey drift ratio(MRIDR).The novel SMA-based SC-EBF shows a much better resilience in the study and represents a promising attractive alternative for future applications.展开更多
The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated constructio...The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.展开更多
The self-centring brace is recognized as one of the practical solutions for mitigating catastrophic consequences caused by earthquakes and improving structural resilience.Compared to the current methods where self-cen...The self-centring brace is recognized as one of the practical solutions for mitigating catastrophic consequences caused by earthquakes and improving structural resilience.Compared to the current methods where self-centring capacity is typically provided by pre-stressed steel rods or disc springs,carbon fiber-reinforced polymer(CFRP)material of higher tensile strength and deformation capacity is emerging as a preferred alternative to traditional materials.Based on that,this study mainly aims to propose a novel self-centring buckling-restrained brace(SC-BRB)by using pre-stressed CFRP rods as self-centring components,named the CFRP-SC-BRB.First,component-level analysis was conducted by experimental and numerical methods,to verify the feasibility of the designed configuration.Cyclic and ultra-low-cycle fatigue tests on the specimen demonstrated the excellent performance of the CFRP-SC-BRB,with the peak force of the brace at the drift ratio of 1/120 over 2900 kN and a residual drift ratio controlled below 0.5%.Finite element models in refined and simplified methods were validated by the experimental results and theoretical prediction.Then,a series of system-level analyses are carried out on a prototype frame incorporating the proposed CFRP-SC-BRBs.Compared to the original design with conventional BRBs,seismic responses of the frame fully or partially replaced by the SC-BRBs show a competitive advantage in seismic performance.Especially for the SC-BRB frame with full replacement,the median residual inter-storey drift ratios are reduced by 29.3%and 50.5%under design basis and maximum considered earthquakes,respectively,compared to the conventional BRB frame.In conclusion,it is demonstrated that the proposed CFRP-SC-BRB is effective in improving seismic resilience both at component and system levels.Practical suggestions are also provided to address potential challenges in promoting the novel product in actual application.展开更多
For any prime p, all finite noncyclic p-groups which contain a self-centralizing cyclic normal subgroup are determined by using cohomological techniques. Some applications are given, including a character theoretic de...For any prime p, all finite noncyclic p-groups which contain a self-centralizing cyclic normal subgroup are determined by using cohomological techniques. Some applications are given, including a character theoretic description for such groups.展开更多
基金The authors are grateful for the financial supports from the Research Grants Council of Hong Kong through the GRF Project(No.PolyU 152246/18E)the National Key Research and Development Program of China(No.2019YFB1600700)the Hong Kong Polytechnic University(Nos.ZE2L,ZVX6,and P0035787).The findings and opinions expressed in this paper are solely those of the authors and do not represent the view of the sponsors.
文摘In this paper,the seismic responses and resilience of a novel K-type superelastic shape memory alloy(SMA)self-centring(SC)eccentrically braced frame(EBF)are investigated.The simulation models of the SMA-based SC-EBF and a corresponding equal-stiffness traditional EBF counterpart are first established based on some existing tests.Then twenty-four near-fault ground motions are used to examine the seismic responses of both EBFs under design basis earthquake(DBE)and maximum considered earthquake(MCE)levels.Structural fragility and loss analyses are subsequently conducted through incremental dynamic analyses(IDA),and the resilience of the two EBFs are eventually estimated.The resilience assessment basically follows the framework proposed by Federal Emergency and Management Agency(FEMA)with the additional consideration of the maximum residual inter-storey drift ratio(MRIDR).The novel SMA-based SC-EBF shows a much better resilience in the study and represents a promising attractive alternative for future applications.
基金Open Access funding enabled and organized by CAUL and its Member Institutions.
文摘The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.
基金Shanghai Science and Technology Plan Funding Project(No.20DZ2253000)the Shanghai Sailing Program(No.24YF2751000)the CSCEC Technology R&D Program(No.CSCEC-2022-Z-8).
文摘The self-centring brace is recognized as one of the practical solutions for mitigating catastrophic consequences caused by earthquakes and improving structural resilience.Compared to the current methods where self-centring capacity is typically provided by pre-stressed steel rods or disc springs,carbon fiber-reinforced polymer(CFRP)material of higher tensile strength and deformation capacity is emerging as a preferred alternative to traditional materials.Based on that,this study mainly aims to propose a novel self-centring buckling-restrained brace(SC-BRB)by using pre-stressed CFRP rods as self-centring components,named the CFRP-SC-BRB.First,component-level analysis was conducted by experimental and numerical methods,to verify the feasibility of the designed configuration.Cyclic and ultra-low-cycle fatigue tests on the specimen demonstrated the excellent performance of the CFRP-SC-BRB,with the peak force of the brace at the drift ratio of 1/120 over 2900 kN and a residual drift ratio controlled below 0.5%.Finite element models in refined and simplified methods were validated by the experimental results and theoretical prediction.Then,a series of system-level analyses are carried out on a prototype frame incorporating the proposed CFRP-SC-BRBs.Compared to the original design with conventional BRBs,seismic responses of the frame fully or partially replaced by the SC-BRBs show a competitive advantage in seismic performance.Especially for the SC-BRB frame with full replacement,the median residual inter-storey drift ratios are reduced by 29.3%and 50.5%under design basis and maximum considered earthquakes,respectively,compared to the conventional BRB frame.In conclusion,it is demonstrated that the proposed CFRP-SC-BRB is effective in improving seismic resilience both at component and system levels.Practical suggestions are also provided to address potential challenges in promoting the novel product in actual application.
基金Supported by the NSF of China(11171194)by the NSF of Shanxi Province(2012011001-1)
文摘For any prime p, all finite noncyclic p-groups which contain a self-centralizing cyclic normal subgroup are determined by using cohomological techniques. Some applications are given, including a character theoretic description for such groups.
