整体式T梁桥温度荷载效应可靠性概率评价

Evaluation on Reliability Probability of Temperature Loading Effect of Integral T-girder Bridge

整体式桥梁上部结构(主梁)与下部结构(桥台)通过刚性或半刚性节点连接,具有减少支座及伸缩装置、改善行车舒适性、提高结构刚度与整体性等优点。整体式桥梁温度效应不仅要考虑上部结构的变形与应力,还要考虑其同下部结构的相互作用。为了预测温度荷载效应及进行温度荷载效应的可靠性评估,以某预应力混凝土整体式T梁桥为例,建立了考虑桩-土、桥台-土相互作用和材料非线性的数值计算模型,通过与实测温度效应(变形、内力)对比验证了其准确性与有效性。提出了简化的均匀温度与梯度温度荷载概率模型,分析了整体式桥梁在温度荷载概率模型作用下,结构响应(内力、应力)的概率分布类型与相关参数。基于荷载与抗力概率模型,运用蒙特卡洛模拟与Rackwitz-Fiessler方法进行了可靠性分析,确定了整体式混凝土T梁桥承载能力极限状态与正常使用极限状态下的可靠度指标β。结果表明:建立的数值模型在简化温度荷载作用下得到的桥台变形、主梁内力与实测结果相比误差小于8%,表明数值模型可准确有效模拟整体式桥梁温度效应;概率温度荷载作用下,主梁正弯矩服从标准正态分布,而负弯矩服从Weibull分布;由于整体式桥梁主梁受桥台部分约束,温度荷载对β的影响明显,因此可靠度分析必须考虑温度效应。

An integral bridge is constructed as rigid or semi-rigid connection between superstructure(main girder)and substructure(abutment),which has the advantages of reducing bearings and expansion joints,improving driving comfort and enhancing structural stiffness and integrity.The temperature effect on integral bridge should consider not only the deformation and stress of superstructure,but also its interaction with the substructure.To predict the temperature load effect and evaluate the reliability of temperature load effect,taking a PC integral T-beam bridge for example,a numerical calculation model considering the interactions of pile-soil and bridge abutment-soil as well as the material nonlinearity is established,and its accuracy and effectiveness are verified by comparing it with the measured temperature effects(deformation,internal force).A simplified probability model for uniform temperature and gradient temperature load is proposed,and the probability distribution types and related parameters of structural response(internal force,stress)of integral bridge under the action of temperature load probability model are analyzed.Based on the load and resistance probability model,the reliability analysis is conducted by using Monte Carlo simulation and Rackwitz-Fiessler method,and the reliability indicatorβof the integral concrete T-beam bridge in bearing capacity limit state and normal service limit state is determined.The result shows that(1)the errors between the bridge abutment deformation and the internal force of the main girder obtained by the established numerical model and those from measured result are less than 8%,indicating that the numerical model can accurately and effectively simulate the temperature effect of the integral bridge;(2)under the temperature probabilistic load,the positive bending moment of the main girder follows the standard normal distribution,while the negative bending moment follows the Weibull distribution;(3)the temperature load has significant influence onβdue to partially constrain provided by the main girder of the integral bridge,thus the temperature effect must be considered in reliability analysis.