桥上CRTS Ⅱ型底座板裂缝宽度时变可靠性研究

该文开展了不同环境温度下的桥上CRTS Ⅱ型底座板裂缝宽度时变可靠性研究。具体包括：比选确定了考虑钢筋锈蚀的底座板受拉钢筋有效截面积计算模型，建立了底座板纵向裂缝宽度极限状态函数，开展了列车荷载、桥梁变形和温度作用对底座板的作用效应分析；基于热力学传导公式，发展了基于气象信息的温度作用概率模型关键参数计算方法；考虑不同环境温度条件，开展了北京地区某桥上CRTS Ⅱ型底座板60年服役期内裂缝宽度时变可靠性分析。研究发现：底座板纵向裂缝宽度可靠性随服役时间的增长呈现下降趋势；正温度梯度较负温度梯度对底座板更为不利；裂缝截面处钢筋锈蚀会降低底座板裂缝宽度可靠性，且随着锈蚀程度的提高可靠指标下降速率明显加快；低温环境下底座板的裂缝宽度可靠性较低，应对低温环境下的底座板开裂失效模式加以重视。

Time-dependent reliability of crack width of CRTS Ⅱ foundation plate on bridge

In this work, the time-dependent reliability for crack width of China Railway Track System II (CRTS Ⅱ) foundation plate on bridge was investigated under different environmental temperature. This research mainly includes: the calculation model for effective cross-sectional area of tensile reinforcement in foundation plate considering corrosion of reinforcement shall be determined through comparison and selection, the limit state function of longitudinal crack width of foundation plate shall be established under the actions of train load, temperature and bridge deformation; based on the formula of thermal conductivity, the probabilistic models for axial temperature and temperature gradient actions are developed based on meteorological information, with the correlation coefficient of the two temperature actions being calculated; the time-dependent reliability analysis on crack width of CRTS Ⅱ foundation plate on a bridge in Beijing during its 60-year service life cycle was carried out under different temperature conditions. It is found that: with the increase of service time, the reliability of longitudinal crack width of the foundation plate tends to decrease; compared to the negative temperature gradient, the positive temperature gradient shall be more unfavorable to the structure; the reliability of the crack width of the foundation plate may be reduced due to reinforcement corrosion degradation, and the decline rate of the reliability index may obviously accelerate with the increase of corrosion degree; for low environmental temperature, the crack width reliability of the foundation plate is at a relatively low level, and more attention shall be paid to such cracks.