Research On The Static And Danymic Characteristics Of T-Frame And Tied Arch Composite Bridge

In the process of bridge construction,in order to meet the specific conditions for bridge construction,solve practical difficulties,and break through the bottleneck of structural application,bridge engineers constantly explore and innovate,and enrich the bridge structure systems through changing the basic system of bridge structure,combining or changing the mechanical condition.T-Frame and Arch Composite Bridge,a new type of composite system arch bridge,has been proposed to the flat terrain conditions that are not suitable for setting a large vice-span.In this paper,two Concrete T-Frame and Arch Composite Bridge are selected as the research background,Dalian Tiger Beach Bridge and Panjin Central Bridge.Focus on the static characteristics,parameters,ulitimate load-carrying capacity and seimic response characteristics of the T-Frame and Arch Composite Bridge,the main content as follows:(1)This paper studies the reasonable arch axis of the T-frame Arch Combined System Bridge,which is segmented catenary under the self-weight of arch ribs and concentrated forces of the suspenders.A program is developed to calculate the segmented catenary of variable cross-section arch under the self-weight of arch ribs and concentrated forces,and the iterative initial values of horizontal force and vertical force are suggested to improve the convergence speed of the program.The load cases for the determination of the segmental catenary are discussed.The comparative analysis on the internal forces of the arch ribs under the dead load and live load employed the different segmented catenaries,which are obtained by dead load and by the dead load plus half of live load respectively,is conducted.The calculation method of the reasonable arch axis for the arch with equal section under the self-weight of arch rib and uniformly distributed vertical load of the deck load is simplified,and the equation expression of the three-segmental catenary is given.(2)Combined with the project background of Dalian Tiger Beach Bridge and Panjin Central Bridge,a comparative analysis of T-Frame and Arch Composite Bridge,Continuous Beam-arch Combined System Bridge and Rigid-framed Tied Arch Bridge with equal span is conducted.The Structural system characteristics and design key points of the T-Frame and Arch Composite Bridge are summarized,and construction scheme is discussed preliminarily.Internal force formula for an arch with horizontal spring constraints and rotational constraints at both ends,whose arch axis employed the three-segmental catenary,under the self-weight of arch rib and uniformly distributed vertical load of the deck load is deduced.Based on the formula deduced in this paper,the static parameters of T-Frame and Arch Composite Bridge are analyzed.(3)In this paper,the full-bridge finite element models of Dalian Tiger Beach Bridge and Panjin Central Bridge are established.First,elastic stability and ulitimate load-carrying capacity considering geometrical and material nonlinearity of two Concrete T-frame Arch Composite System Bridges are analyzed,according to the loading mode of dead load and live load increasing simultaneously.Then,the influence of live load distribution on the ultimate bearing capacity of two T-Frame and Arch Composite Bridge are discussed,according to the loading mode of increasing live load only on the basis of dead load.Finally,the failure processes in two loading modes of the T-frame Arch Composite System Bridge under two kinds of live load distribution are summarized,obtain the control factors and give the measures to increase the ultimate bearing capacity of the T-frame Arch Composite System Bridge.(4)Taking Panjin Middle Bridge as the background,the seismic response of T-Frame and Arch Composite Bridge under longitudinal,transversal and vertical seismic are analyzed respectively,and the influences of geometric on seismic response are studied.The results show that geometric nonlinearity have great influence on the seismic response of the steel beam,while some influence on that of the arch ribs and little influence on that of the piers.The influence of geometric nonlinearity should be considered in the seismic response calculation.Bearing constraints at the bracket are the key problem should be solved in the shock absorption design of the T-Frame and Arch Composite Bridge.(5)According to the seismic response characteristics of the T-Frame and Arch Composite Bridge,this paper is focused on the longitudinal and transversal shock absorption schemes,the selection of damper parameters and the influence of geometric nonlinearity on the seismic response of the structure with damper.The results show that a large damping coefficient should not be matched with a small velocity index of the viscous dampers.Considering the influence of geometric nonlinearity,the structure with the shear keys and viscous dampers can not be well reset after the earthquake.In the parallel connection scheme of spring and viscous damper,the viscous dampers vibrate too frequently under the normal use state.In order to solve the two problems,this paper proposes a transverse combined shock absorption scheme by adding fuse support with shear key,spring and viscous damper connected in parallel.This paper compares and analyzes the damping effects of three lateral damping schemes:the combination of the fuse support with shear key and viscous damper,the parallel connection of spring and viscous damper,the fuse support with shear key and parallel connection of the spring and viscous damper.The results show that there are no significant differences among the three transverse shock absorption schemes.