剪力滞效应下箱型梁的可靠度分析

为了能够对箱型梁进行可靠度分析，通过结合基于附加挠度的一维离散有限元法和摄动随机有限元法建立了箱型梁新的随机分析方法。据此，建立了求解可靠指标的两种方法：基于验算点的迭代算法和其简化迭代算法。考虑第一种工况为弹性模量随机，第二种工况为弹性模量和荷载同时具有随机性，用两种方法对箱型梁进行了可靠度计算。结果表明：在对箱型梁进行可靠度分析时，随机参数选择不同变异系数情况下，两种方法存在误差相差不大；在变异系数不超过0.15时，与蒙特卡洛有限元法计算结果相比有较好的计算精度，第一种方法在两种工况下的误差分别小于4.66%和4.09%，第二种方法在两种工况下的误差分别小于6.28%和4.52%；随着随机参数变异性的增大，箱梁结构的计算可靠度相应降低；在弹性模量具有随机性的基础上，荷载具有随机性时，箱梁结构的可靠度也会相应降低。可见，在工程中需要考虑参数的随机性对箱梁可靠度的影响。

Reliability analysis of box girder under shear lag effect

In order to analyze the reliability of box girder, a new stochastic analysis method was established by combining one-dimensional discrete finite element method based on additional deflection and perturbation stochastic finite element method. Based on this, two methods for solving reliability index are established: the iterative algorithm of checking point and its simplified iterative algorithm. Considering that the elastic modulus is random in the first case and the elastic modulus and load are random in the second case, the reliability of box girder is calculated by the two methods. The results show that: when analysing the reliability of box girder, the errors of the two methods are not significantly different under different coefficients of variation of random parameters; when the coefficient of variation does not exceed 0.15, it has better calculation accuracy compared with the results of Monte Carlo finite element method, the error of the first method is less than 4.66 % and 4.09 % under two conditions, and the error of the second method is less than 6.28 % and 4.52 % ; the Calculated reliability of box girder decreases with the increase of random parameter variability; on the basis of the randomness of elastic modulus, the reliability of box girder will decrease correspondingly when the load has randomness. It is concluded that the influence of the randomness of parameters on the reliability of box girder should be considered in engineering.