极限状态法和容许应力法用于重载铁路钢筋混凝土梁受力性能评价的对比

Comparison Between Limit State Method and Allowable Stress Method for Evaluating Mechanical Properties of Reinforced Concrete Girders for Heavy Haul Railway

为了探究一座足尺重载铁路钢筋混凝土T梁的抗弯承载力,并与Q/CR 9300—2018《铁路桥涵设计规范(极限状态法)》和TBJ 2—1985《铁路桥涵设计规范》规定的设计承载能力进行对比,进而对极限状态法和容许应力法设计理论进行对比分析,选取一片采用容许应力法设计的12 m跨度钢筋混凝土足尺T梁(专桥(88)1024)作为研究对象,首先基于两种设计方法进行正截面抗弯承载力计算,继而根据静力加载破坏试验中钢筋应力、T梁的变形和裂缝发展状况以及最终破坏状态,得到T梁实际承载能力并与理论分析结果进行对比。结果表明:破坏试验得到的实际承载能力是极限状态法计算的1.59倍,说明按容许应力法设计的钢筋混凝土T梁抗弯承载力有较大的安全储备;极限状态法的钢筋应力容许值略低于容许应力法的容许值,实际钢筋应力比理论计算值低9%,约为极限状态法容许值的95.8%,能满足极限状态法的要求;挠度的试验值比两种理论计算的挠度低约8%,满足挠度的容许值要求;裂缝宽度的试验值均比理论计算值大21%,但仍满足裂缝宽度的容许值要求。该梁经过多年运营,其抗弯承载力、应力、挠度和裂缝宽度仍可满足铁路桥涵设计规范极限状态法的要求。

In order to explore the bending bearing capacity of a full-size heavy haul railway reinforced concrete T-girder,and compare it with the design bearing capacity specified in Q/CR 9300—2018 Code for Design on Railway Bridge and Culvert(Limit State Method)and TBJ 2—1985 Code for Design on Railway Bridge and Culvert,and then compare and analyze the design theory of limit state method and allowable stress method. A 12 m span reinforced concrete full-size T-girder(special bridge(88)1024)designed by the allowable stress method was selected as the research object. First,the flexural bearing capacity of the normal section was calculated based on the two design methods. According to the reinforcement stress,deformation,crack development and final failure state of the T-girder in the static loading failure test,the actual bearing capacity of the T-girder was obtained and compared with the theoretical analysis results. The results show that the actual bearing capacity obtained from the failure test is 1.59 times of that calculated by the limit state method,which indicates that the flexural bearing capacity of reinforced concrete T-girders designed by the allowable stress method still has a large safety margin. The allowable value of the reinforcement stress of the limit state method is slightly lower than the allowable value of the allowable stress method,and the actual reinforcement stress is 9% lower than the theoretical calculation value,about 95.8% of the allowable value of the limit state method,which can meet the requirements of the limit state method. The test value of deflection is about 8% lower than the deflection calculated by the two theories,meeting the allowable value requirements of deflection. The test value of crack width is 21% larger than the theoretical calculation value,but it still meets the allowable value requirements of crack width. After years of operation,the bending capacity,stress,deflection and crack width of the girder can still meet the requirements of the limit state method in the code for design in railway bridge and culvert.