火灾后钢-混凝土组合梁疲劳性能与疲劳寿命评估方法研究OA

To investigate the evolution law of fatigue performance of steel-concrete composite beams after fire exposure,stud shear tests and composite beam tests under sustained loading,heating,natural cooling,and subsequent fatigue loading were conducted to analyze the variation characteristics of the shear performance of stud bolts and the fatigue behavior of composite beams under different post-fire temperatures.The results indicate that the stud shear performance deteriorates with the increasing temperature.At 450 ℃,the shear capacity decreases to approximately 83％of its initial value,while the ultimate slip reduces to 60％.Fire exposure is also found to significantly alter the fatigue damage mechanism,as evidenced by increased mid-span deflections and enlarged slip at the steel-concrete interface in the shear span.Based on a validated finite element model,the post-fire mechanical response was further simulated,leading to the development of an empirical model for the stud stress concentration factor and a fatigue life prediction method applicable to stud root temperatures below 450 ℃.Further analysis results show that when the fire exposure temperature is 400 ℃,the logarithmic fatigue life of the composite beam increases by approximately 57％.However,fatigue life remains highly sensitive to load amplitude,with higher load amplitudes leading to a more rapid reduction in fatigue life.