A simplified multisupport response spectrum method is presented.The structural response is a sum of two components of a structure with a first natural period less than 2 s.The first component is the pseudostatic respo...A simplified multisupport response spectrum method is presented.The structural response is a sum of two components of a structure with a first natural period less than 2 s.The first component is the pseudostatic response caused by the inconsistent motions of the structural supports,and the second is the structural dynamic response to ground motion accelerations.This method is formally consistent with the classical response spectrum method,and the effects of multisupport excitation are considered for any modal response spectrum or modal superposition.If the seismic inputs at each support are the same,the support displacements caused by the pseudostatic response become rigid body displacements.The response spectrum in the case of multisupport excitations then reduces to that for uniform excitations.In other words,this multisupport response spectrum method is a modification and extension of the existing response spectrum method under uniform excitation.Moreover,most of the coherency coefficients in this formulation are simplified by approximating the ground motion excitation as white noise.The results indicate that this simplification can reduce the calculation time while maintaining accuracy.Furthermore,the internal forces obtained by the multisupport response spectrum method are compared with those produced by the traditional response spectrum method in two case studies of existing long-span structures.Because the effects of inconsistent support displacements are not considered in the traditional response spectrum method,the values of internal forces near the supports are underestimated.These regions are important potential failure points and deserve special attention in the seismic design of reticulated structures.展开更多
In this study, a number of nonlinear time-history dynamic analyses are conducted on a part of Tehran water distribution network to investigate its functionality during transient large ground motions. The network is of...In this study, a number of nonlinear time-history dynamic analyses are conducted on a part of Tehran water distribution network to investigate its functionality during transient large ground motions. The network is of 950-meter length, consisting of ductile iron pipes segments of 6-meter length. Pipes are modeled using beam elements and springs characterize the connections. Considering the time lag between support inputs, and the nonlinear soil-pipe interaction, by scaling the amplitude of the Tab as earthquake record, incremental dynamic analysis is carried out on the network in two orthogonal directions and the sensitivity of the network response is examined. Furthermore, the effects of variations in soil damping and soil spring stiffness are also studied in the network analysis. Finally the effect of changes in angle between incoming wave and pipeline is considered on a simplified network. Results show that the points other than critical ones at network intersections remain almost intact and when the angle of incidence is 30 degrees the stress and rotation peak.展开更多
基金Major Program of National Science Foundation of China Under Grant No.90715005Program for New Century Excellent Talents in University Under Grant No. NCET-07-0186Doctoral Fund of Ministry of Education of China Under Grant No.200802860007
文摘A simplified multisupport response spectrum method is presented.The structural response is a sum of two components of a structure with a first natural period less than 2 s.The first component is the pseudostatic response caused by the inconsistent motions of the structural supports,and the second is the structural dynamic response to ground motion accelerations.This method is formally consistent with the classical response spectrum method,and the effects of multisupport excitation are considered for any modal response spectrum or modal superposition.If the seismic inputs at each support are the same,the support displacements caused by the pseudostatic response become rigid body displacements.The response spectrum in the case of multisupport excitations then reduces to that for uniform excitations.In other words,this multisupport response spectrum method is a modification and extension of the existing response spectrum method under uniform excitation.Moreover,most of the coherency coefficients in this formulation are simplified by approximating the ground motion excitation as white noise.The results indicate that this simplification can reduce the calculation time while maintaining accuracy.Furthermore,the internal forces obtained by the multisupport response spectrum method are compared with those produced by the traditional response spectrum method in two case studies of existing long-span structures.Because the effects of inconsistent support displacements are not considered in the traditional response spectrum method,the values of internal forces near the supports are underestimated.These regions are important potential failure points and deserve special attention in the seismic design of reticulated structures.
文摘In this study, a number of nonlinear time-history dynamic analyses are conducted on a part of Tehran water distribution network to investigate its functionality during transient large ground motions. The network is of 950-meter length, consisting of ductile iron pipes segments of 6-meter length. Pipes are modeled using beam elements and springs characterize the connections. Considering the time lag between support inputs, and the nonlinear soil-pipe interaction, by scaling the amplitude of the Tab as earthquake record, incremental dynamic analysis is carried out on the network in two orthogonal directions and the sensitivity of the network response is examined. Furthermore, the effects of variations in soil damping and soil spring stiffness are also studied in the network analysis. Finally the effect of changes in angle between incoming wave and pipeline is considered on a simplified network. Results show that the points other than critical ones at network intersections remain almost intact and when the angle of incidence is 30 degrees the stress and rotation peak.
