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