运营荷载作用下钢混组合梁桥抗弯性能可靠度研究

Study on the Structural Reliability of Flexural Performance of Steel-concrete Composite Girder Bridges under Service Loads

为分析实际运营荷载作用下钢混组合梁桥的抗弯结构可靠度,建立了钢混组合梁结构可靠度评估方法。首先,确定了钢混组合梁抗弯失效的极限状态方程,并确定了采用i-HLRF算法计算结构可靠度指标;其次,建立了基于全截面塑性的钢混组合梁截面抗弯承载力计算模型,结合文献中105组钢混组合梁试验数据对该计算模型的不确定量度进行了分析;第三,建立了基于实测车辆数据计算桥梁构件荷载效应极值分布模型的方法;最后,结合某一钢混组合梁连续梁桥结构,计算了正弯矩和负弯矩区域的截面抗弯性能结构可靠度指标。结果表明:基于全截面塑性的抗弯承载力计算模型能够很好地表征钢混组合结构的试验极限承载能力,计算模型不确定性量度与各类结构设计参数没有显著相关性,并服从均值为1.02、变异系数为0.07的正态分布;案例桥梁正弯矩区域抗弯性能计算可靠度指标为4.55,而负弯矩区只有4.06,低于我国混凝土桥梁规范采用的目标可靠度指标(4.2)。

In order to study the structural reliability of flexural performance of steel-concrete composite girder bridge under service loads,a reliability calculation framework is established.First,the limit state equation of flexural failure is determined,and calculation procedures of structural reliability index using the i-HLRF algorithm are defined.Then,the calculation equation of flexural bearing capacity of steel-concrete composite beams based on the full plasticity theory is used,and the uncertainty of the calculation equation is analyzed by using 105 sets of experimental data from the literature.Next,the statistical approach of constructing the extreme value distribution of the traffic load effect based on measured traffic data is given.Finally,the reliability indexes of a continuous steel-concrete composite girder bridge under positive and negative bending moments are all evaluated.The results indicate that the calculation equation based on the full plasticity theory can well represent the flexural bearing capacity of the steel-concrete composite girders.The uncertainty measure of the calculation equation has a non-significant correlation with the structural design parameters and follows a normal distribution with a mean value of 1.02 and a variation of coefficient of 0.07.The reliability index of flexural performance under positive bending moment is 4.55,but the value becomes 4.06 under negative bending moment,which is lower than the target value of 4.20 that recommended for concrete bridges in the design specification of China.