A simplified algorithm was developed to construct the limit state line of multi random variables,aiming at overcoming the difficulty in the construction of limit state line by Rosenblatt transformation.By searching the expected values of variables which can satisfy the marginal distributions,joint cumulative distribution and reliability index simultaneously,the calculation of conditional distribution function and its inverse function was turned to find the inverse function of marginal distribution,and thus the construction of the limit state line was simplified.Taking some bridge tower-basement system as an engineering example and the wind-wave simultaneous observation data at the Weizhou marine station as statistic samples,the joint cumulative distribution function of wind and wave was estimated by an Copula function,the limit state line of wind and wave was constructed by the proposed algorithm,and the extreme load effects of the base shear force were estimated by the environmenlal contour (EC) method and compared with those estimated by a statistical extrapolation method.It is demonstrated that the extreme load effects estimated by the EC method together with the simplified algorithm is highly accurate.%针对基于Rosenblatt映射变换的极限状态曲线计算困难的现状,提出了多维随机变量极限状态曲线的简化算法.该算法通过寻找同时满足边缘分布、联合分布和可靠指标的变量估计值,将随机变量条件分布函数及其逆函数的求解转化为边缘分布函数的求逆,从而达到简化极限状态曲线计算的目的.以某跨海大桥桥塔-基础体系为工程实例,以涠洲岛海洋站风浪同步观测资料为环境变量统计资料,通过基于Copula函数的联合分布模型构造了风浪联合分布函数,根据简化算法计算了风浪极限状态曲线,利用EC法估计了桥塔-基础体系的基底剪力极限荷载效应,并与外推法的估计结果进行了比较.结果表明,基于简化算法和EC法的跨海大桥桥塔-基础体系基底剪力极限荷载效应具有较高的准确性.
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