Research On Temperature Effect And Static Combination Effect With Other Loads Of Long Span Railway Suspension Bridge In Mountainous Area

Limited by mountain canyon terrain and the requirement of sag-span ratio of main cables,large-span railway suspension bridge towers in mountainous areas are generally hollow thin-walled concrete high towers.The temperature difference between day and night in the gorge area is large and the temperature environment is more complicated than that in the plain area.Temperature is an important role in bridge design.The current specifications in China fail to reflect the particularity of the gorge environment.Large-span suspension bridges have remarkable flexibility characteristics,and when combined with other functions,temperature has a great influence on the static behavior of suspension bridges.In this paper,based on finite element analysis,the temperature field and temperature effect of bridge towers,suspension bridge temperature effect and combined effect of action in the gorge area are studied by combining test and theoretical analysis.The main research contents and conclusions are as follows:（1）The monitoring of sunshine temperature field in the test section of the bridge tower is carried out.The measured results show that the maximum diurnal temperature difference in the bridge site area can reach 24.8℃,and the maximum daily temperature can reach around 15 o’clock.Different weather and azimuth angles result in different solar radiation intensities and great differences in temperature field.On sunny days,the maximum temperature gradient along the wall thickness is 20℃Celsius.The non-uniform temperature distribution caused by sunlight mainly occurs within 80cm from the surface.（2）The finite element model is established and compared with the measured results,which proves the reliability of the finite element method.Afterwards,the finite element method is used to analyze various temperature field influencing factors and three typical temperature modes are formulated accordingly.The temperature action mode is put forward based on the distribution law of temperature field.The uniform temperature action range is taken as 38℃according to the daily average maximum and minimum temperature,and the maximum positive and negative temperature gradients are 22℃and-13.5℃respectively.（3）Two kinds of simplified models and calculation methods of solar radiation shielding effect are put forward,and their reliability is verified based on measured data.The influence of shielding effect on temperature field and temperature effect of bridge tower is analyzed by finite element method.The results show that the shielding effect of Canyon mountain increases the non-uniformity of temperature field along the direction of tower height,the maximum temperature difference of bridge tower surface along the direction of tower height is 13℃,and the shielding between towers increases South and south.The difference of temperature field of the North Tower is that the temperature difference between the towers on the south side of the two towers can reach up to 5.7℃.Both types of shielding effect increase the deformation of the bridge tower caused by temperature.（4）The daily variation law of temperature effect of suspension bridge is analyzed.The research results show that with the increase of daily temperature,the temperature of steel structure increases,the sag of main cable increases,the tensile stress of cable structure decreases,the main truss compressive stress of stiffening beam increases,the vertical displacement of stiffening beam,longitudinal displacement of end of beam and corner of end of beam increase,and the maximum daily variation is 0.75m,0.136m and0.95×10^-3rad;（5）The influence line rule of internal force and displacement of various components of suspension bridge and the change rule of static behavior with loading length are studied.Based on the actual length of trains,the loading length of trains is put forward as 550m.（6）The static behavior of suspension bridge under combined effects of various actions is analyzed.The combination of integral temperature rise and other actions is more disadvantageous to vertical and transverse displacement of stiffening beam and stress of cable and stiffening beam structure.The combination of integral temperature reduction and other actions is more disadvantageous to corner of beam end and force of bridge tower.It is proposed that the temperature effect caused by daily temperature variation as the main force can improve the safety of suspension bridge design.