Research On Static And Dynamic Characteristics Of Medium And Small Span Steel Truss Girder Bridges

Steel truss girder bridges are mainly used in railway bridges,and are rarely used in urban and highways.However,there are many special advantages in the field of highway and urban roads:Fast erection speed and the shortest time to interrupt traffic;Adapt to the needs of fast and heavy traffic;Add landscape to cities and roads,etc.Because of the light weight of the steel structure,it is easily affected by the dynamic load,so the study of mechanical properties of steel truss girder bridge is an important issue we need to study.At present,the research results on the dynamic characteristics of medium and small span steel truss girder bridge are relatively rare.The formula for estimating the fundamental frequency of steel truss girder bridge structure in the current code of China is still lacking,so it is necessary to study the static and dynamic characteristics of steel truss girder bridge.Taking the steel truss bridge as the engineering background,through the static and dynamic load test,and the finite element model of steel truss bridge structure is established by using finite element software sap 2000,the static and dynamic characteristics of steel truss bridge are studied and analyzed in this paper.The main research contents are as follows:1.The static load test was carried out on the steel truss bridge.The measured values and theoretical calculation values are compared and analyzed.The analysis results show that the strength and stiffness of the structure meet the design requirements,and the steel truss bridge is in elastic working state.2.The dynamic load test of the steel truss girder bridge was carried out,and the structural dynamic characteristics of the steel truss bridge are studied and analyzed.The structural base frequency,mode shape and impact coefficient of the steel truss girder bridge were mainly studied.The experimental results show that the measured values of natural frequency,damping ratio,mode shape and impact coefficient are in good agreement with the analytical values.3.The influence of the fundamental frequency of the steel truss bridge on the basic frequency of the bridge structure is studied and analyzed.The regularity of the change of the basic frequency of the structure of the steel truss bridge with the influence factors is summarized,and the basic frequency estimation formula of steel truss girder bridge structure is established by using the principle of multiple linear regression.The results show that the estimated value of the fundamental frequency of the test bridge structure is close to the measured value and finite element analysis value,which shows that the formula of the fundamental frequency of the steel truss girder bridge proposed in this paper is reliable,and provides a basis for estimating the impact force of vehicle loads on highway bridges.4.The finite element model of the whole bridge is established,and the seismic behavior of each member of the steel truss bridge under earthquake action is studied and analyzed.The analysis results show that in the response spectrum analysis and time history analysis,the members of the weak seismic part of the structure are obtained.At the same time,the stress of each member is less than the allowable stress of the steel,and the structure has good seismic performance.