Seismic Vulnerability Analysis And Damage Control Of The Long-span Deck Type Steel Truss Arch Bridge In Transverse Direction

With more and more steel Bridges being built in China’s bridge engineering,the construction technology of steel Bridges in China has gradually reached the world leading level.Meanwhile,the seismic design theory of steel Bridges has also been greatly developed,but it still lags behind the construction of steel Bridges.Therefore,it is urgent to develop the seismic design theory of steel Bridges.This paper takes 1-490 m deck type steel-truss arch bridge as the engineering background,establishes the space model of the whole bridge,analyzes the stress characteristics of the main arch ring,and determines the seismic weakness of the background bridge.The vulnerability curves of each component and system were obtained by the capacity demand ratio model;And on this basis,based on the “one can three easy”(Controllable,easy to check,easy to repair,easy to change)of the seismic design principle,the vulnerability curves of each component and the system were obtained again by setting BRB components in the corresponding weak parts.The damage control of the background bridge after introducing BRB components was compared,and a reasonable damping system suitable for the background bridge was proposed.The research contents of this paper are as follows:(1)The development status and earthquake damage forms of steel truss arch Bridges at home and abroad are summarized,and the research status of seismic vulnerability of steel truss arch Bridges and the application status of BRB members in bridge structures are fully introduced,and expounds the research significance and content of this paper.(2)Midas Civil software was used to build the whole bridge element model,and the dynamic response and possible failure mechanism of the background bridge were studied,laying a foundation for seismic vulnerability analysis and damage control.(3)According to the basic principle of response spectrum method,the distribution characteristics of the internal forces and stresses in the main arch ring under different excitation modes are studied from the aspects of spatial coupling characteristics of the internal forces of the arch ring,the controlling component of the internal forces of the chord,the weak seismic position,and the comparison of the normal stresses of the chord.(4)By using PEER database,15 seismic waves were selected to determine the appropriate damage index,and the damage states were reasonably divided.The yield degree of each component of the background bridge under horizontal + vertical earthquake action was analyzed,and the nonlinear mixed element model of beam element and fiber element was established.Increment dynamic analysis method is used to calculate the regression mean and standard deviation,and the probability of damage transcendence of components is calculated and the vulnerability curve is drawn by using the relevant formulas of probability and statistics.Then,based on the series system,the first-order boundary method is used to draw the vulnerability curve of the system.(5)Study the reasonable placement of BRB components and the value of mechanical parameters,and set BRB components in the corresponding weak area.On this basis,the capacity demand ratio model is used to study the seismic vulnerability again,and the vulnerability curves of each component and system under different damage states are drawn.At the same time,compared with the vulnerability curves of each component and system without BRB members,the seismic performance of long-span steel truss arch bridge with vibration damping device is evaluated from the perspective of probability.