我国现行建筑结构设计规范可靠度的校核与分析

根据可靠度校核的非迭代方法推导了检验设计值点是否为设计验算点(理想设计值点)的公式,并建立了可接受设计值点的判断准则。采用非迭代方法对我国现行建筑结构设计规范中的15类典型构件的实际可靠指标进行校核,并对比分析了《建筑结构可靠性设计统一标准》(GB 50068-2018)对荷载分项系数调整带来的构件可靠指标变化。结果表明:荷载分项系数调整后,各类构件的实际可靠指标平均值比目标可靠指标大0.8,比调整前的可靠指标平均提高了0.28;混凝土、砌体和木构件的综合安全系数提高为原来的1.05倍,钢构件的综合安全系数提高为原来的1.07倍。各类构件以及同类构件在不同荷载比例和组合下的实际可靠指标差异很大,"恒荷载+风荷载"组合下构件的可靠指标明显低于"恒荷载+楼面活荷载"组合。不同类型荷载设计值的保证率差异过大是导致可靠指标离散性偏大的主要原因。永久荷载效应比例较大时,多数构件的设计值点不是可接受设计值点,既有建筑结构鉴定时的荷载标准值及荷载分项系数存在优化的空间。

Verification and Analysis of Reliability of Current Design Codes for Building Structures in Our Country

Based on a non-iterative method of reliability verification,a formula to check whether the designvalue point is the ideal design one was derived,and a criterion to judge the acceptable design value point was established.The actual reliability index of fifteen types of typical members in current design codes for building structures in our country was checked using the non-iterative method,and change of the reliability index of structural members caused by adjustment of the load component coefficient in GB 50068—2018"Unified standard for reliability design of building structures"was compared and analyzed.The results showed that the average value of the actual reliability index of various members was 0.8 larger than the target one after adjustment of the load component coefficient,and the average value of the reliability index was 0.28 larger than the one without the adjustment.The comprehensive safety factor of concrete,masonry and wood members was increased by 1.05 times,and that of steel components by 1.07 times.The actual reliability index of variousmembers and similar members varied greatly under different load ratios and combinations.The reliability index of components under the combination of"constant load+wind load"was significantly lower than that under the combination of"constant load+floor live load".The large difference of guarantee rate between design values of different load types was the main reason for the large dispersion of reliability index.When the proportion of permanent load effect was large,the design value point of most members was not the acceptable design value point,and the standard value and component coefficient of load in the existing building structure appraisal can be further optimized.