A controlled rocking concentrically steel braced frame(CR-CSBF)is introduced as an alternative to conventional methods to prevent major structural damage during large earthquakes.It is equipped with elastic post-tensi...A controlled rocking concentrically steel braced frame(CR-CSBF)is introduced as an alternative to conventional methods to prevent major structural damage during large earthquakes.It is equipped with elastic post-tensioned(PT)cables and replaceable devices or fuses to provide overturning resistance and dissipate energy,respectively.Although CR-CSBFs are not officially legalized in globally valid codes for new buildings,it is expected to be presented in them in the near future.The main goal of this study is to determine the optimal design parameters consist of the yield strength and modulus of elasticity of the fuse,the initial force of the PT cable,and the gravity load on the rocking column,considering different heights of the frame,spanning ratios and ground motion types for dual-configuration CR-CSBF.Nonlinear time-history analyses are performed in OpenSees.This study aims to define the optimal input variables as effective design parameters of CR-CSBFs by comparing four seismic responses consisting of story drift,roof displacement,roof acceleration and base shear,and also using the Euclidean metric optimization method.Despite the previous research,this study is innovative and first of its kind.The results demonstrate that the optimal design parameters are variable for various conditions.展开更多
This paper presents a seismic topology optimization study of steel braced frames with shape memory alloy(SMA)braces.Optimal SMA-braced frames(SMA-BFs)with either Fe-based SMA or NiTi braces are determined in a perform...This paper presents a seismic topology optimization study of steel braced frames with shape memory alloy(SMA)braces.Optimal SMA-braced frames(SMA-BFs)with either Fe-based SMA or NiTi braces are determined in a performance-based seismic design context.The topology optimization is performed on 5-and 10-story SMA-BFs considering the placement,length,and cross-sectional area of SMA bracing members.Geometric,strength,and performance-based design constraints are considered in the optimization.The seismic response and collapse safety of topologically optimal SMA-BFs are assessed according to the FEMA P695 methodology.A comparative study on the optimal SMA-BFs is also presented in terms of total relative cost,collapse capacity,and peak and residual story drift.The results demonstrate that Fe-based SMA-BFs exhibit higher collapse capacity and more uniform distribution of lateral displacement over the frame height while being more cost-effective than NiTi braced frames.In addition to a lower unit price compared to NiTi,Fe-based SMAs reduce SMA material usage.In frames with Fe-based SMA braces,the SMA usage is reduced by up to 80%.The results highlight the need for using SMAs with larger recoverable strains.展开更多
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
Three full scale two-story steel concentrically braced frames(CBFs)were tested at the National Center for Research on Earthquake Engineering(NCREE)in Taipei.The specimen is a single bay with the braces arranged in a t...Three full scale two-story steel concentrically braced frames(CBFs)were tested at the National Center for Research on Earthquake Engineering(NCREE)in Taipei.The specimen is a single bay with the braces arranged in a two-story X-brace configuration.The main differences among the three tests are the brace types(hollow structural or wide-flange section)and the design criteria adopted for the gusset plate connections.Results of these three tests confirm that the two-story X-shape steel CBFs all have rather good energy dissipation characteristics up to a story drift of about 0.03 radians under the cyclically increasing lateral displacements.Severe brace local buckling and out-of-plane displacements were observed during each test.Tests confirm that both the 2tlinear and 8t-elliptical designs of the gusset plate connection provide satisfactory ductility for the steel CBF.Hollow structural section(HSS)braces fractured at a story drift smaller than that found using wide flange sections.The nonlinear fine element method(FEM)program ABAQUS was used to simulate the responses of the specimen.The base shear versus the story drift relationships obtained from the tests and the FEM analytical results are quite agreeable in various levels of lateral frame displacement.The analytical results confirm that the severe out-of-plane buckling of the braces can be accurately simulated.FEM analyses also illustrate that the steel moment resisting frame takes about 40%story shear when the inter-story drift is greater than 0.02 radians.展开更多
This study presents the investigation of the approach which was presented by Thaer M.Saeed Alrudaini to provide the alternate load path to redistribute residual loads and preventing from the potential progressive coll...This study presents the investigation of the approach which was presented by Thaer M.Saeed Alrudaini to provide the alternate load path to redistribute residual loads and preventing from the potential progressive collapse of RC buildings.It was proposed to transfer the residual loads upwards above the failed column of RC buildings by vertical cables hanged at the top to a hat steel braced frame seated on top of the building which in turn redistributes the residual loads to the adjacent columns.In this study a ten-storey regular structural building has been considered to investigate progressive collapse potential.Structural design is based on ACI 318-08 concrete building code for special RC frames and the nonlinear dynamic analysis is carried out using SAP2000 software,following UFC4-023-03 document.Nine independent failure scenarios are adopted in the investigation,including six external removal cases in different floors and three removal cases in the first floor.A new detail is proposed by using barrel and wedge to improve residual forces transfer to the cables after removal of the columns.Simulation results show that progressive collapse of building that resulted from potential failure of columns located in floors can be efficiently resisted by using this method.展开更多
文摘A controlled rocking concentrically steel braced frame(CR-CSBF)is introduced as an alternative to conventional methods to prevent major structural damage during large earthquakes.It is equipped with elastic post-tensioned(PT)cables and replaceable devices or fuses to provide overturning resistance and dissipate energy,respectively.Although CR-CSBFs are not officially legalized in globally valid codes for new buildings,it is expected to be presented in them in the near future.The main goal of this study is to determine the optimal design parameters consist of the yield strength and modulus of elasticity of the fuse,the initial force of the PT cable,and the gravity load on the rocking column,considering different heights of the frame,spanning ratios and ground motion types for dual-configuration CR-CSBF.Nonlinear time-history analyses are performed in OpenSees.This study aims to define the optimal input variables as effective design parameters of CR-CSBFs by comparing four seismic responses consisting of story drift,roof displacement,roof acceleration and base shear,and also using the Euclidean metric optimization method.Despite the previous research,this study is innovative and first of its kind.The results demonstrate that the optimal design parameters are variable for various conditions.
基金supported by the Ryerson University Faculty of Engineering and Architectural Science and the Natural Sciences and Engineering Research Council of Canada(NSERC)through Discovery Grant.
文摘This paper presents a seismic topology optimization study of steel braced frames with shape memory alloy(SMA)braces.Optimal SMA-braced frames(SMA-BFs)with either Fe-based SMA or NiTi braces are determined in a performance-based seismic design context.The topology optimization is performed on 5-and 10-story SMA-BFs considering the placement,length,and cross-sectional area of SMA bracing members.Geometric,strength,and performance-based design constraints are considered in the optimization.The seismic response and collapse safety of topologically optimal SMA-BFs are assessed according to the FEMA P695 methodology.A comparative study on the optimal SMA-BFs is also presented in terms of total relative cost,collapse capacity,and peak and residual story drift.The results demonstrate that Fe-based SMA-BFs exhibit higher collapse capacity and more uniform distribution of lateral displacement over the frame height while being more cost-effective than NiTi braced frames.In addition to a lower unit price compared to NiTi,Fe-based SMAs reduce SMA material usage.In frames with Fe-based SMA braces,the SMA usage is reduced by up to 80%.The results highlight the need for using SMAs with larger recoverable strains.
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funded by the National Center for Research on Earthquake Engineering(Taipei,China)and the US National Science Foundation through Grant CMS-0619161.
文摘Three full scale two-story steel concentrically braced frames(CBFs)were tested at the National Center for Research on Earthquake Engineering(NCREE)in Taipei.The specimen is a single bay with the braces arranged in a two-story X-brace configuration.The main differences among the three tests are the brace types(hollow structural or wide-flange section)and the design criteria adopted for the gusset plate connections.Results of these three tests confirm that the two-story X-shape steel CBFs all have rather good energy dissipation characteristics up to a story drift of about 0.03 radians under the cyclically increasing lateral displacements.Severe brace local buckling and out-of-plane displacements were observed during each test.Tests confirm that both the 2tlinear and 8t-elliptical designs of the gusset plate connection provide satisfactory ductility for the steel CBF.Hollow structural section(HSS)braces fractured at a story drift smaller than that found using wide flange sections.The nonlinear fine element method(FEM)program ABAQUS was used to simulate the responses of the specimen.The base shear versus the story drift relationships obtained from the tests and the FEM analytical results are quite agreeable in various levels of lateral frame displacement.The analytical results confirm that the severe out-of-plane buckling of the braces can be accurately simulated.FEM analyses also illustrate that the steel moment resisting frame takes about 40%story shear when the inter-story drift is greater than 0.02 radians.
文摘This study presents the investigation of the approach which was presented by Thaer M.Saeed Alrudaini to provide the alternate load path to redistribute residual loads and preventing from the potential progressive collapse of RC buildings.It was proposed to transfer the residual loads upwards above the failed column of RC buildings by vertical cables hanged at the top to a hat steel braced frame seated on top of the building which in turn redistributes the residual loads to the adjacent columns.In this study a ten-storey regular structural building has been considered to investigate progressive collapse potential.Structural design is based on ACI 318-08 concrete building code for special RC frames and the nonlinear dynamic analysis is carried out using SAP2000 software,following UFC4-023-03 document.Nine independent failure scenarios are adopted in the investigation,including six external removal cases in different floors and three removal cases in the first floor.A new detail is proposed by using barrel and wedge to improve residual forces transfer to the cables after removal of the columns.Simulation results show that progressive collapse of building that resulted from potential failure of columns located in floors can be efficiently resisted by using this method.
