To evaluate the importance of the canyon topography effects on large structures, based on a rigid frame bridge across a 137-m-deep and 600-m-wide canyon, the seismic response of the canyon site is analyzed using a two...To evaluate the importance of the canyon topography effects on large structures, based on a rigid frame bridge across a 137-m-deep and 600-m-wide canyon, the seismic response of the canyon site is analyzed using a two-dimensional finite element model under different seismic SV waves with the assumptions of vertical incidence and oblique incidence to obtain the ground motions, which are used as the excitation input on the pier foundations of the bridge with improved large mass method. The results indicate that canyon topography has significant influences on the ground motions in terms of inci- dent angle. The peak ground acceleration values vary greatly from the bottom of the canyon to the upper comers. Under ver- tical incident SV waves, at the upper comers of canyon the peak ground accelerations greatly increase; whereas the peak ground accelerations diminish at the bottom comers of canyon. Under oblique incident SV waves, the shaking of the canyon slope perpendicular to the incidence direction is much more severe than that of the opposite side of canyon. And the ground surface has been characterized by larger deformations in the case of oblique incident waves. It is also concluded that the low piers and frame of the continuous rigid frame bridge ape more sensitive to the multi-support seismic excitations than the flexible high piers. The canyon topography as well as the oblique incidence of the waves brings the continuous rigid frame bridge severe responses, which should be taken into account in bridge design.展开更多
The purpose of this paper is to use the conforma mapping method[1]to analyzeand evaluate the ground displacement and scattering of incident SH-waves, on thesurface of semi-canyon topography of arbitrary shape with li...The purpose of this paper is to use the conforma mapping method[1]to analyzeand evaluate the ground displacement and scattering of incident SH-waves, on thesurface of semi-canyon topography of arbitrary shape with lining in anisotropic media.The problem to be solved can be reduced to the solution of an infinite algebraicequation set by using the method of full-space expansion of Fourier progression Usingthe mapping function and scattering theory to solve problems due to semi-canyon topography with lining is just like mapping the semi-cylindrical canyon of arbitraryshape into a cylindrical canyon in full-space.Moreover,it is far practical inengineering practice.From the computational examples,it is obvious that the variation of displacement amplitudes on the surface near the canyon topography is rather sharp. especially when the freqencies of incident SH-waves increase.展开更多
he analytcal method is used for the problem of seattering of plane SH-waves bymultiple shallow circur-are cangons. The solution of multiple scattering of plane SH-wares is first expressed as the sum of series of solu...he analytcal method is used for the problem of seattering of plane SH-waves bymultiple shallow circur-are cangons. The solution of multiple scattering of plane SH-wares is first expressed as the sum of series of solutions im each of local coordinatesusing separation of variadles and is then converted into the form of dual infinite seriesof a local coordinate system by Graf’s addition formula suitable for the interior and exterior problems. The solution of the problem is finally reduced to solving a set of infinite algbraic dquations :Numerical results of scattering influence on the motion on the earth surace are presented for the two adjacent shallow circular- arc canyons with the same diameter and variable depth- to- width ratio ,and the effect of screening and interaction between canyons are discussed in the paper.展开更多
基金supported by National Natural Science Foundation of China (No. 50708100)National Science and Technology Support Project of China (No. 2006BAC13B02)partially by Basic Research Program of Institute of Mechanics Engineering, China Earthquake Administration (No. 2007B02)
文摘To evaluate the importance of the canyon topography effects on large structures, based on a rigid frame bridge across a 137-m-deep and 600-m-wide canyon, the seismic response of the canyon site is analyzed using a two-dimensional finite element model under different seismic SV waves with the assumptions of vertical incidence and oblique incidence to obtain the ground motions, which are used as the excitation input on the pier foundations of the bridge with improved large mass method. The results indicate that canyon topography has significant influences on the ground motions in terms of inci- dent angle. The peak ground acceleration values vary greatly from the bottom of the canyon to the upper comers. Under ver- tical incident SV waves, at the upper comers of canyon the peak ground accelerations greatly increase; whereas the peak ground accelerations diminish at the bottom comers of canyon. Under oblique incident SV waves, the shaking of the canyon slope perpendicular to the incidence direction is much more severe than that of the opposite side of canyon. And the ground surface has been characterized by larger deformations in the case of oblique incident waves. It is also concluded that the low piers and frame of the continuous rigid frame bridge ape more sensitive to the multi-support seismic excitations than the flexible high piers. The canyon topography as well as the oblique incidence of the waves brings the continuous rigid frame bridge severe responses, which should be taken into account in bridge design.
文摘The purpose of this paper is to use the conforma mapping method[1]to analyzeand evaluate the ground displacement and scattering of incident SH-waves, on thesurface of semi-canyon topography of arbitrary shape with lining in anisotropic media.The problem to be solved can be reduced to the solution of an infinite algebraicequation set by using the method of full-space expansion of Fourier progression Usingthe mapping function and scattering theory to solve problems due to semi-canyon topography with lining is just like mapping the semi-cylindrical canyon of arbitraryshape into a cylindrical canyon in full-space.Moreover,it is far practical inengineering practice.From the computational examples,it is obvious that the variation of displacement amplitudes on the surface near the canyon topography is rather sharp. especially when the freqencies of incident SH-waves increase.
文摘he analytcal method is used for the problem of seattering of plane SH-waves bymultiple shallow circur-are cangons. The solution of multiple scattering of plane SH-wares is first expressed as the sum of series of solutions im each of local coordinatesusing separation of variadles and is then converted into the form of dual infinite seriesof a local coordinate system by Graf’s addition formula suitable for the interior and exterior problems. The solution of the problem is finally reduced to solving a set of infinite algbraic dquations :Numerical results of scattering influence on the motion on the earth surace are presented for the two adjacent shallow circular- arc canyons with the same diameter and variable depth- to- width ratio ,and the effect of screening and interaction between canyons are discussed in the paper.
