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按目前规范规定的分项系数进行结构设计时,不同荷载效应比下的可靠指标与目标可靠指标差别较大,并且规范没有建立分项系数与目标可靠指标的函数关系。针对这两个问题,提出了按设计值法确定分项系数的方法;优化分析了敏感性系数的取值,建立了分项系数与可变荷载效应标准值和永久荷载效应标准值比值的简化公式。研究表明,当敏感性系数表示为荷载效应比的关系式时,计算的可靠指标与目标可靠指标误差很小;每种可变荷载的组合系数可取为常数。
When the structural design is carried out according to the sub-factors of the current norms, the reliability index and the target reliability index under different load-effect ratios differ greatly, and the specification does not establish the functional relationship between the sub-factors and the target reliability index. In view of these two problems, the method of determining the partial coefficient by the design value method is proposed. The value of the sensitivity coefficient is optimized and the simplification of the ratio of the partial coefficient to the standard value of the variable load effect and the permanent load effect is established formula. The results show that when the sensitivity coefficient is expressed as the relation of load effect ratio, the error between the calculated reliability index and the target reliability index is small. The combination coefficient of each variable load can be taken as a constant.