Reliability Of Long-span Concrete Box Arch Bridge Considering Arch Axis Deviation And Random Eccentricity

With the increase of span of concrete arch bridge,construction difficulty increases,and alignment deviation of main arch becomes more and more difficult to control.Previous studies have shown that the deviation of arch axis has a greater impact on the mechanical performance of arch bridge.The increase of span of arch bridge also leads to the increase of self-weight of arch bridge,which leads to a sharp increase in construction cost.Ultra-high performance concrete can better solve this problem.However,there are few studies on the reliability of concrete arch bridges under random eccentricity and the influence of arch axis deviation.Therefore,this paper has carried out corresponding research on ordinary concrete and RPC box arch bridges.The main work is as follows:(1)The main arch design of existing concrete arch bridges mostly checks the bearing capacity of equivalent eccentric components,and the influence of random variability of eccentricity is not fully considered.In view of this shortcoming,this paper analyses the random characteristics of eccentricity of key section of main arch under different load-effect ratios and its influence on the probability distribution of resistance.It is clear that the bearing capacity of key section of main arch under random eccentricity may change from concrete compression failure to concrete tension failure control.On this basis,Monte Carlo method is used to solve the reliability index of key section of concrete box arch bridge under different design eccentricity and different load effect ratio.The results show that within the range of parameter analysis,considering the random characteristics of eccentricity,in most cases,the reliability index decreases with the increase of the ratio of the bending moment produced by the temperature load and the self-weight load,and with the decrease of the absolute value of the axial pressure produced by the temperature load and the self-weight load,and the reliability index is much lower than the brittle failure of the first-order structure in the most unfavorable case.The reliability index of the design target is not safe,and the most unfavorable failure section may change when the deviation of arch axis is considered in concrete arch bridge.(2)Because there is no code for RPC arch bridge design,the checking calculation of material performance and bearing capacity of RPC box arch bridge designed in this paper refers to the existing technical specifications or existing research results,and the reliability index of RPC box arch bridge under different load-effect ratios of key sections is analyzed.The results show that the ratio of design eccentricity to section height of RPC box arch bridge is lower than that of ordinary concrete arch bridge,and it is less affected by the randomness of eccentricity;and the coefficient of variation of RPC strength is lower than that of ordinary concrete,which results in that the reliability index of RPC box arch bridge under different load effect ratios is higher than that of ordinary concrete arch bridge;under the influence of arch axis deviation,due to the deviation of key sections.The center distance is still small,the performance of RPC material is stable,and the reliability index decreases,but there is no significant change.