海洋大气环境下钢筋混凝土梁可预期寿命设计方法

Design method of expected service life for reinforced concrete beams under marine atmospheric environment

基于时变可靠性分析,采用荷载与抗力分项系数,提出了海洋大气环境下钢筋混凝土梁可预期寿命设计方法。首先,基于混凝土中Cl^-传输模型确定了钢筋初始锈蚀时刻;其次,考虑钢筋锈蚀不均匀性对横截面积分布以及钢筋力学性能的影响,计算了锈蚀梁在预期服役寿命内的时变可靠指标;再次,对结构设计的初始目标可靠指标进行调整,从而保证结构在预期服役寿命内的最低可靠指标仍满足现行规范要求。在极限状态设计表达式基础上,通过可靠性分析计算了不同目标可靠指标调整值以及预期服役寿命要求下钢筋混凝土结构各构件梁荷载和抗力(受弯承载力)分项系数。最后通过钢筋混凝土梁的设计算例说明本文方法的有效性。

Based on time-dependent reliability analyses and the load and resistance factor design approach, a design method of expected service life was developed for reinforced concrete(RC) beams under marine atmospheric environment. First, the initial corrosion time of reinforcing bars was determined based on the Chloride ion transport model in concrete;and then, considering the influence of the variability of corrosion on both distribution of cross-sectional area and mechanical properties of rebars, time-dependent reliability indexes of corroded RC beams were calculated during their expected service lives. Besides, the initial target reliability indexes were redefined in order to ensure the reliabilities of RC beams during their entire expected service lives could meet the requirements of the relevant design specifications. Moreover, based on probability and limit states equations, the adjusted value of reliability index, and the load and resistance partial factors were determined for RC beams with different requirements for expected service live. Finally, the validity of the proposed approach was illustrated using several design cases.