钢筋混凝土结构整体承载能力、可靠度和整体抗力系数校准--以简支梁为例

Calibration of global load⁃carrying capacity reliability and global resistance factor of reinforced concrete structures-taking a simply supported beam as an example

目前,基于构件承载能力极限状态的荷载抗力系数设计法或分项系数法是世界各国土木工程结构设计规范所主要采用的概率极限状态设计方法,目前这两种方法存在两个基本矛盾,需要发展基于结构整体可靠度的整体安全系数设计方法。总结钢筋混凝土结构整体承载力设计值和整体抗力系数的确定方法,将FIB混凝土结构整体抗力系数设计法与结构整体可靠度理论相结合,提出钢筋混凝土结构整体承载能力可靠度和整体抗力系数的校准原理。以双面配筋钢筋混凝土结构简支梁为例,通过非线性有限元分析和蒙特卡洛模拟,校准得到钢筋混凝土简支梁的整体承载能力可靠度和整体抗力系数,研究发现钢筋混凝土简支梁的整体承载力可靠指标总体大于构件承载力可靠指标,且整体可靠度指标和构件可靠度指标均远大于目标可靠度指标,表明《建筑结构可靠性设计统一标准》(GB 50058—2018)的目标可靠度指标有较大提升空间。

At present,load resistance factor design(LRFD)method or patrial factor design(PFD)method based on ultimate limit state of structural members is the main probability-based limit state design method adopted by structural design codes in the field of civil engineering around the world.There exits two fundamental contradicts in the current LRFD and PFD method,it needs to develop the global safety factor design method based on structural global reliability theory.The approaches to determine the global load-carrying capacity design value and the global resistance factor were reviewed,and then,through the combination of the global resistance factor method for reinforced concrete structures by FIB with the structural global reliability theory,the calibration principle of global load-carrying capacity reliability and global resistance factor of reinforced concrete structures was proposed.The simply-supported beam with doubly reinforced rectangular section was taken as an example,through Monte Carlo simulation and nonlinear finite element analysis,the global load-carrying capacity reliability and global resistance factor of the simply-supported reinforced concrete beam was calibrated.It is found that the global load-carrying capacity reliability of the simply-supported reinforced concrete beam is overall larger than the member load-carrying capacity reliability of the beam,and both global reliability and member reliability indices are much larger than the target reliability index respectively.It shows that there is much space for improving the values of the target reliability in the reliability design of building structures(GB 50058—2018).