Influence Of Environmental Temperature On The Static And Dynamic Characteristics Of Beam Type Bridge

The main principle of static and dynamic characteristics-based damage detection for bridge structure is damages cause changes in static and dynamic characteristics(displacement influence line,strain influence line and modal parameters,etc.).However,environmental temperature will also change the bridge static and dynamic characteristics,thus affecting the damage detection effect.There are few studies focus on the influence of environmental temperature on the static characteristics.On the other hand,the studies focus on the influence of environmental temperature on the dynamic characteristics are usually carried out for a specific bridge,which are not universal for other bridges.Considering the fact that concrete beam type bridges are the most widely used bridge type,this paper concentrates on the quantitative analysis of the influence of environmental temperature on the static and dynamic characteristics of beam type bridges.The iterative formulas for calculating the static and dynamic characteristics of concrete beam type bridges under environmental temperature are derived based on the analytical solution of the static and dynamic characteristics.Then,the effectiveness of the proposed iterative formulas is verified by numerical examples and laboratory tests.The main research contents of this paper are as follows:(1)The main factors affecting the static characteristics of the beam type bridges are identified from the perspective of the elastic modulus and geometric size of the material changed by temperature.The static finite element model of beam type bridges is established,and the bridge displacement and strain influence lines under different temperature are calculated.Based on the analytical formula of influence lines,the iterative calculation formula of the relation between influence lines and temperature is derived.The effectiveness and applicability of the iterative formula are verified by numerical examples of beam type bridges with uniform and variable cross sections.(2)The main factors affecting the dynamic characteristics of the beam type bridges are identified from the perspective of the elastic modulus and geometric dimension of the material changed by temperature.The dynamic finite element model of the beam type bridges is established to calculate the first three frequencies of the bridge under different temperature.Based on the analytical formula of frequencies,the iterative formula for calculating the relationship between frequencies and temperature is derived.The effectiveness and applicability of the iterative formula are verified by numerical examples of beam type bridges with uniform and variable cross sections.(3)Static tests of a simply supported beam and a continuous beam are carried out in the Environment Coupling Test Chamber.The displacement and strain responses of the beams are collected by sensors at different temperatures when the static load located at different positions,and then the displacement and strain influence lines are calculated to verify the effectiveness of the iterative calculation formula of static characteristics under temperature in laboratory environment.(4)Dynamic tests of a simply supported and a continuous beam are carried out in the Environment Coupling Test Chamber.The acceleration responses of the beams induced by hammer at different temperatures are collected by sensors,and the frequencies of the beams are identified.The effectiveness of the iterative calculation formula of dynamic characteristics under temperature is verified in the laboratory environment.