A pushover procedure with a load pattern based on the height-wise distribution of the combined modal story shear and torsional moment is proposed to estimate the seismic response of 3D asymmetric-plan building frames....A pushover procedure with a load pattern based on the height-wise distribution of the combined modal story shear and torsional moment is proposed to estimate the seismic response of 3D asymmetric-plan building frames. Contribution of the higher modes and torsional response of asymmetric-plan buildings are incorporated into the proposed load pattern. The proposed pushover method is a single-run procedure, which enables tracing the nonlinear response of the structure during the analysis and averts the elusiveness of conducting multiple pushover analyses. The proposed method has been used to estimate the response of two moment-resisting building frames with 9 and 20 stories. The obtained results indicate the appropriate accuracy and efficiency of the proposed procedure in estimating the trend of the drift profiles of the structures resulted from nonlinear time history analyses.展开更多
Currently, for the analysis of complex bridge based on beam element, the calculation of cross-section torsional inertia moment is still an unresolved technical problem. Most current calculation of section torsional in...Currently, for the analysis of complex bridge based on beam element, the calculation of cross-section torsional inertia moment is still an unresolved technical problem. Most current calculation of section torsional inertia moment is an approximate analytic method for two-dimensional cross-section, which is not fully consistent with the actual situation, and do not consider the effects of diaphragm in bridge. In order to analyze accurately cable-stayed bridge, suspension bridge and other complex bridge structures based on beam element, the calculation method of section torsional inertia moment based on finite element method (FEM) is invented in this paper. Firstly, setting up local cantilever fine model with solid element or shell element and applying torsion on the end of cantilever. Secondly, calculating the torsion angle of cantilever by FEM method and then the torsional moment through equivalent beam method. Finally, the examples of the section torsional moment calculation of concrete model with solid element with diaphragm and steel girder box model with shell element with diaphragm are used to verify the calculation method, which is applied to the suspension bridge design and construction control special software SBNA developed by Research Institute of Highway Ministry of Transport. Taizhou Bridge under construction is one of the examples.展开更多
The aim of this study was to quantify the effect of torsion deformity on the lower limb kinetics during the loading response phase of gait. A total of 24 subjects: 6 end-staged medial knee OA with torsion deformity (T...The aim of this study was to quantify the effect of torsion deformity on the lower limb kinetics during the loading response phase of gait. A total of 24 subjects: 6 end-staged medial knee OA with torsion deformity (TKO), 8 without torsion deformity (KOA), and 10 controls (CON) were imaged using computed tomography (CT). Internal moment of support and sagittal hip, knee and ankle joint moments were assessed using gait analysis. TKO showed greater external rotations of the proximal tibia and the distal femur compared to subjects with medial knee OA without torsion deformity and controls. TKO showed greater moment of support and a greater knee extensor moment when compared to controls when supporting the weight of the body during gait. The TKO intorsion deformity occurred as a result of a proximal malrotation of the tibia. In the presence of torsion deformity, the kinetic synergy of the lower limb showed increased total moment of support for subjects with medial knee OA. The greater extensor output from TKO may be the result of an increased muscular response to overcome an interrupted inter-segmental exchange of accelerations during the loading response phase of gait.展开更多
Numerical solutions could not perform rapid system-level simulation of the behavior of micro-electro-mechanical systems（MEMS） and analytic solutions for the describing partial differential equations are only availab...Numerical solutions could not perform rapid system-level simulation of the behavior of micro-electro-mechanical systems（MEMS） and analytic solutions for the describing partial differential equations are only available for simple geometries.Model order reduction（MOR） can extract approximate low-order model from the original large scale system.Conventional model order reduction algorithm is based on first-order system model,however,most structure mechanical MEMS systems are naturally second-order in time.For the purpose of solving the above problem,a direct second-order system model order reduction approach based on Krylov subspace projection for the coupled dynamic study of electrostatic torsional micromirrors is presented.The block Arnoldi process is applied to create the orthonormal vectors to construct the projection matrix,which enables the extraction of the low order model from the discretized system assembled through finite element analysis.The transfer functions of the reduced order model and the original model are expanded to demonstrate the moment-matching property of the second-order model reduction algorithm.The torsion and bending effect are included in the finite element model,and the squeeze film damping effect is considered as well.An empirical method considering relative error convergence is adopted to obtain the optimal choice of the order for the reduced model.A comparison research between the full model and the reduced model is carried out.The modeling accuracy and computation efficiency of the presented second-order model reduction method are confirmed by the comparison research results.The research provides references for MOR of MEMS.展开更多
文摘A pushover procedure with a load pattern based on the height-wise distribution of the combined modal story shear and torsional moment is proposed to estimate the seismic response of 3D asymmetric-plan building frames. Contribution of the higher modes and torsional response of asymmetric-plan buildings are incorporated into the proposed load pattern. The proposed pushover method is a single-run procedure, which enables tracing the nonlinear response of the structure during the analysis and averts the elusiveness of conducting multiple pushover analyses. The proposed method has been used to estimate the response of two moment-resisting building frames with 9 and 20 stories. The obtained results indicate the appropriate accuracy and efficiency of the proposed procedure in estimating the trend of the drift profiles of the structures resulted from nonlinear time history analyses.
基金National Science and Technology Support Program of China(No.2009BAG15B01)Key Programs for Science and Technology Development of Chinese Transportation Industry(No.2008-353-332-190)+1 种基金National Natural Science Foundation of China(No.50908211)Scientific Research Item from Ministry of Transport(No.200831822343)
文摘Currently, for the analysis of complex bridge based on beam element, the calculation of cross-section torsional inertia moment is still an unresolved technical problem. Most current calculation of section torsional inertia moment is an approximate analytic method for two-dimensional cross-section, which is not fully consistent with the actual situation, and do not consider the effects of diaphragm in bridge. In order to analyze accurately cable-stayed bridge, suspension bridge and other complex bridge structures based on beam element, the calculation method of section torsional inertia moment based on finite element method (FEM) is invented in this paper. Firstly, setting up local cantilever fine model with solid element or shell element and applying torsion on the end of cantilever. Secondly, calculating the torsion angle of cantilever by FEM method and then the torsional moment through equivalent beam method. Finally, the examples of the section torsional moment calculation of concrete model with solid element with diaphragm and steel girder box model with shell element with diaphragm are used to verify the calculation method, which is applied to the suspension bridge design and construction control special software SBNA developed by Research Institute of Highway Ministry of Transport. Taizhou Bridge under construction is one of the examples.
文摘The aim of this study was to quantify the effect of torsion deformity on the lower limb kinetics during the loading response phase of gait. A total of 24 subjects: 6 end-staged medial knee OA with torsion deformity (TKO), 8 without torsion deformity (KOA), and 10 controls (CON) were imaged using computed tomography (CT). Internal moment of support and sagittal hip, knee and ankle joint moments were assessed using gait analysis. TKO showed greater external rotations of the proximal tibia and the distal femur compared to subjects with medial knee OA without torsion deformity and controls. TKO showed greater moment of support and a greater knee extensor moment when compared to controls when supporting the weight of the body during gait. The TKO intorsion deformity occurred as a result of a proximal malrotation of the tibia. In the presence of torsion deformity, the kinetic synergy of the lower limb showed increased total moment of support for subjects with medial knee OA. The greater extensor output from TKO may be the result of an increased muscular response to overcome an interrupted inter-segmental exchange of accelerations during the loading response phase of gait.
基金supported by National Natural Science Foundation of China (Grant No. 50775201)National Science & Technology Major Project of China (Grant No. 2009ZX04014-031)PhD Programs Foundation of Ministry of Education of China (Grant No. 200803350031)
文摘Numerical solutions could not perform rapid system-level simulation of the behavior of micro-electro-mechanical systems（MEMS） and analytic solutions for the describing partial differential equations are only available for simple geometries.Model order reduction（MOR） can extract approximate low-order model from the original large scale system.Conventional model order reduction algorithm is based on first-order system model,however,most structure mechanical MEMS systems are naturally second-order in time.For the purpose of solving the above problem,a direct second-order system model order reduction approach based on Krylov subspace projection for the coupled dynamic study of electrostatic torsional micromirrors is presented.The block Arnoldi process is applied to create the orthonormal vectors to construct the projection matrix,which enables the extraction of the low order model from the discretized system assembled through finite element analysis.The transfer functions of the reduced order model and the original model are expanded to demonstrate the moment-matching property of the second-order model reduction algorithm.The torsion and bending effect are included in the finite element model,and the squeeze film damping effect is considered as well.An empirical method considering relative error convergence is adopted to obtain the optimal choice of the order for the reduced model.A comparison research between the full model and the reduced model is carried out.The modeling accuracy and computation efficiency of the presented second-order model reduction method are confirmed by the comparison research results.The research provides references for MOR of MEMS.
