冲刷作用下钢管混凝土拱桥地震易损性分析

Seismic Vulnerability Analysis of CFST Arch Bridge Under Scour

地震和冲刷是导致桥梁发生损伤的两类主要自然灾害,为保证桥梁的抗震性能,有必要对冲刷作用下桥梁的地震易损性进行研究。分析了桥梁地震易损性理论与冲刷深度的计算方法,运用有限元软件建立了某一钢管混凝土拱桥的数值模型,根据地震易损性理论确定了各损伤状态下的损伤指标,建立了不同冲刷深度下的地震需求响应概率模型,进而得到了该拱桥拱肋和主梁的易损性曲线,并分析了冲刷深度与地面峰值加速度变化对拱肋和主梁地震易损性的影响。研究表明:桥梁拱肋和主梁在各损伤状态下的损伤概率均随着地面峰值加速度的增大而呈现非线性增加,其增速为先变快而后变缓;当地震峰值加速度较小时,冲刷深度的变化对于损伤概率几乎无影响,但当其大于某一临界值时,冲刷深度越大,拱肋和主梁发生损伤的概率显著提高;当冲刷深度和地震峰值加速度一定时,桥梁拱肋和主梁的损伤概率随着损伤程度的增加而减小。

Earthquake and scour are two major natural disasters that cause bridge damage.In order to ensure the seismic performance of bridges,it is necessary to study the seismic vulnerability of bridges under scour.In this paper,the seismic vulnerability theory of bridges and the calculation method of scour depth are analyzed,and a numerical model of a concrete-filled steel tube arch bridge is established by using finite element software.The seismic demand response probability model under the scour depth is used to obtain the fragility curves of the arch rib and main girder of the arch bridge,and the influence of the scour depth and the ground peak acceleration changes on the seismic vulnerability of the arch rib and main girder is analyzed.The research shows that the damage probability of bridge arch rib and main girder in each damage state increases nonlinearly with the increase of the ground peak acceleration,and the growth rate is firstly faster and then slower;when the earthquake peak acceleration is small,the change of the scour depth has almost no effect on the damage probability,but when it is greater than a certain critical value,the greater the scour depth,the higher the probability of damage to the arch rib and the main beam;when the scour depth and the seismic peak acceleration are constant,the bridge arch will be damaged.The damage probability of ribs and main beams decreases with the increase of damage degree.