双重因素影响下CFRP加固混凝土梁的时变抗剪可靠度分析

Time-dependent Shear Reliability Analysis of Concrete Beams Strengthened with CFRP under the Influence of Dual Factors

为了计算在环境与疲劳荷载双重作用下CFRP加固混凝土梁的时变抗剪可靠度,以侧面内嵌CFRP加固混凝土梁为研究对象。首先,建立加固梁的抗力模型;其次,构建双重作用下加固梁斜截面承载力极限状态功能时变函数;最后,基于JC法计算不同荷载频率下混凝土梁加固前后的时变抗剪可靠度。结果表明,双重作用下,在服役基准期的50%以内时,混凝土梁抗剪可靠度随服役时间呈现缓和线性下降,而后降低速率快速增大;混凝土梁抗剪可靠度随年交变荷载频率的增加而逐渐降低,年交变荷载频率对混凝土梁的可靠度变化的影响非常明显。另外,在服役基准期的58%之后,采用侧面内嵌CFRP对混凝土抗剪梁进行加固,可以继续服役基准期的12%左右。总地来看,采用侧面内嵌CFRP加固后,混凝土梁的服役寿命在一定程度上有所提高。但是,建议宜在服役前期对混凝土梁进行抗剪加固。

In order to calculate the time-dependent shear reliability of concrete beams strengthened CFRP under the dual effects of environment and fatigue loads,the concrete strengthened beams with side near surface mounted(SNSM)are taken as the research object.First,the resistance model of the strengthened beam is established;secondly,the time-varying function of the ultimate state function of the load-bearing capacity of the oblique section of the reinforced beam is constructed under the dual action;finally,based on the JC method,the time-varying shear reliability of the concrete beam before and after strengthening are calculated under different load frequencies.The results show that under the influence of dual effects,the shear reliability of concrete beams decreases linearly with the service time within 50% of the service reference period,and then the rate of decrease increases rapidly.The shear reliability of concrete beams gradually decreases with the increase of the annual alternating load frequency.The influence of the annual alternating load frequency on the reliability of concrete beams is very obvious.In addition,when the concrete beam has been in service after 58% of its reference period,it can be strengthened with SNSM CFRP,which can increase the service basic life by around 12%.In general,the service life of concrete beams strengthened with SNSM CFRP can be improved to a certain extent,however,it is recommended that the concrete beam should be strengthened in the early stage of service.