公路钢筋混凝土桥梁正常工作年限计算方法及影响因素分析

A Method for Calculating Normal Working Life of Highway Reinforced Concrete Bridge and Analysis on Its Influencing Factors

针对目前公路桥梁设计规范中未提到的车辆反复荷载下的工作年限,本研究提出了正常工作年限的概念。为了判断工作年限是否满足设计年限要求,本研究以公路钢筋混凝土桥梁为研究对象,提出了一种快速计算桥梁工作年限的方法。该方法以基于Miner累积损伤准则的等效等幅应力幅法为基础,计算在车辆荷载作用下桥梁结构的累积损伤,并通过获取累积损伤与作用次数的关系,得到结构年均损伤度,由此得到桥梁工作年限。本研究将此方法应用于T梁桥的计算中,分析了跨径、横隔板、配筋率、车辆荷载、S-N曲线方程对工作年限的影响。计算结果表明:车辆荷载模型与S-N曲线方程这两个因素决定了工作年限的准确性,按照规范中的车辆荷载模型计算得到的年限远大于设计年限,而由于调查荷载的区域性差别很大,江苏和辽宁地区相比贵州地区,由于35 t以上重车车流量大,导致工作年限不满足规范要求;随着跨径的增大,T梁桥的工作年限相应增大,这与配筋率随着跨径增大而增大有关;横隔板的设置及受拉钢筋的配筋率对工作年限影响很大,不设横隔板比设置横隔板的工作年限降低了18%~63%;配筋率越低,工作年限降低速率越大。

Aiming at the working life of bridge under repeated vehicle loads which is not mentioned in the current bridge design specification, the concept of normal working life is put forward. In order to judge whether the working life can fit the requirement of design working life, taking reinforced concrete bridge as the research object, a method for fast calculating the working lives of this kind of bridges is proposed. On the basis of the equivalent constant amplitude stress amplitude method based on Miner cumulative damage criterion, the cumulative damages of the bridge structures under the vehicle loads are calculated, and the average annual damage degrees are obtained by obtaining the relationship between cumulative damage and loading times, thus the working lives of the bridges are obtained. Applying the proposed method to the calculations of T-beam bridges, the influences of span, transverse diaphragm, reinforcement ratio, vehicle load and S-N curve equation on the working life are analyzed. The calculation result shows that (1) Vehicle loading model and S-N curve equation determine the accuracy of working life. The working life calculated by the vehicle loading model in the specification is much longer than the design life. However, due to the regional differences of the investigation loads, compared with Guizhou Province, Jiangsu Province and Liaoning Province have the higher traffic flows of heavy-duty vehicles over 35 t, it results in the working life cannot meet the requirements in the specification.(2) With the increase of spans, the working live of the T-beam bridge increases correspondingly, which is related to the increase of reinforcement ratio with the increase of span.(3) The diaphragm and the reinforcement ratio have great influence on the working life. The working lives of the bridges without diaphragm are 18%-63% lower than those bridges with diaphragms;(4) The lower the reinforcement ratio, the greater the reduction rate of the working life.