The Seismic Research On Long-span Steel Arch Bridge Based On Pseudo Excitation

Arch bridge is characterized by its beautiful appearance, easily constructed and relative lower cost, so it can be considered as a most competitive style among the long-span bridge. With the development of China's bridge-building, there have been some new shapes, the complex structure of long-span steel arch bridge. And China is a quake-prone country, to ensure that the bridge under the load of security operations is of great significance. This article research the long-span steel arch bridge seismic performance analysis. The study will include:(1) Introduced the concept of pseudo excitation method to study the basic theory of random vibration, an analysis of the structure of the stationary random earthquake with the smooth and non-random effect under the law of the virtual encouragement. At the same time, use Fortran program with iterative solutions and change the earthquake response spectrum into a power spectrum, random vibration method in order to carry out the structural analysis of the response to the earthquake. In the current lack of ground acceleration measured power spectral data is a certain practical value.(2) Using Fenghua bridge for the project background, the establishment of Fenghua bridge finite element model to study the steel arch bridge with the same characteristics of the earthquake response. Respectively on the vibration characteristics of steel arch bridge, spectral response characteristics, research the effects of different geometric stiffness matrix. Modal analysis of the previous 40-and-order vibration frequency, low-vibration mode of comparison, and lists 14 changes in the mode of order; not included in the initial stress of the stiffness matrix (geometric stiffness matrix) [ K_σ]and included [ K_σ]the impact of the two The circumstances under which the vibration characteristics of spectrum under the reaction and response characteristics were analyzed, and got very meaningful conclusion.(3) Response time for analysis, respectively, the displacement and the internal forces were researched, and considered the traveling wave effect. Adopted a revised calculation of Tianjin seismic wave, proceed Three-dimensional line incentives analysis of the internal force, internal force under the effect of traveling wave analysis, three-dimensional traveling waves in line with the incentive effects of the largest internal force of comparison, the displacement of comparison ,and so on. Know that long-span Steel arch bridge of the sensitivity of the top is much smaller than the foot of the arch , or even negligible; and the foot of the arch is the most damaged part under the ground motion (plastic hinge appears). The wave effect made the internal forces of the foot of the arch comparatively increased. So the wave effect can not be ignored in long-span arch bridge seismic design , such as the conclusion.(4) Researched the cross-up stiffness. Set up three models, using seismic records as part of the Wenchuan incentives were on the longitudinal, horizontal + longitudinal and horizontal + longitudinal + vertical and analyzed the internal force and moment plane of the main arch. We got that the steel arch bridge with the smaller cross-up stiffness in the earthquake the internal force is larger than the steel arch bridge with the larger cross-up stiffness. But the distributions of internal forces are closer, the foot arch cross-section is control section, a larger cross-up stiffness will help reduce the main arch-axis force; the horizontal plane earthquake incentives made larger moment of the arch and it is an important factor in security. Larger cross-up stiffness is adverse; by the three-dimensional structure respond to the effects it can be seen that the cross-cutting incentives, full-bridge horizontal vibration significantly increases the main internal force of the arch, and so on.