钢筋名义极限应变控制下的混凝土梁桥抗弯承载力计算原理与试验研究

Principles of Calculation and Experimental Study of Flexural Capacity of Concrete Girder Bridges under Nominal Ultimate Strain Control of Steel Reinforcement

为研究由钢筋名义极限应变控制下的预应力混凝土桥梁抗弯承载能力,根据平截面假定推导了相关计算公式,并与现行规范公式计算结果进行比较。依托云南省国省干线公路桥梁加固改造工程,对更换下来的2片20 m预应力混凝土T形梁桥进行单梁静载试验,分析其破坏过程、破坏形态以及不同加载阶段力学性能的变化规律,将试验结果与理论计算进行比较。同时,针对现浇层和预制T梁的叠合构件,提出了考虑层间剪力的抗弯承载能力计算方法,并以标准跨径为20 m和30 m的简支T梁通用图为基准,得出不同翼板宽度及预应力配束下的承载能力提高系数。研究结果表明:由钢筋名义极限应变控制的预应力混凝土桥梁抗弯承载能力与规范计算结果相差不大,但钢筋达到名义极限应变时,受压区混凝土远未达到极限应变;预应力混凝土T梁开裂之后,其抗裂性能退化明显,但抗弯承载能力试验值仍大于理论计算值;现浇层对于预应力混凝土T梁桥抗弯承载能力具有一定的贡献,虽然提升程度较小,但现浇层与预制梁的层间剪力由现浇层压应力提供,因此在结构设计中应保证现浇层具有较高的强度和黏接性能。

In order to study the flexural load capacity of prestressed concrete bridges under the control of nominal ultimate strain of steel reinforcement,relevant formulas were derived according to the assumption of flat cross-section,and the calculation results were compared with those of the current specification calculations.Relying on the reinforcement and reconstruction project of national and provincial trunk highway bridges in Yunnan Province,a single girder static load test was carried out on 2 pieces of 20 m prestressed concrete T-girder bridges replaced,to analyze the damage process,damage morphology,and the change rule of mechanical properties at different loading stages,and to compare the test results with the theoretical calculations.At the same time,for the stacked members of the cast-in-place layer and precast T-beam,the calculation method of flexural capacity considering interlayer shear was proposed,and the generalized diagram of simply supported T-beam with standard span of 20 m and 30 m was taken as a benchmark,so as to derive the coefficient of capacity improvement under different wing plate widths and prestressing bundles.The results show that the bending capacity of prestressed concrete bridge controlled by the nominal ultimate strain of reinforcement is not much different from the standard calculation results,but when the reinforcement reaches the nominal ultimate strain,the concrete in the compression zone is far from reaching the ultimate strain.After the cracking of the prestressed concrete T-beam,its cracking performance degradation is obvious,but the test value of the bending capacity is still greater than the theoretical calculation value.The cast-in layer has a certain degree of improvement on the bending capacity of prestressed concrete T-beam bridge.The cast-in layer has a certain degree of improvement on the bending capacity of the prestressed concrete T-beam bridge.The cast-in layer has a certain contribution to the flexural load capacity,although the degree of enhancement is small,the interlayer shear force between the cast-in layer and the precast girder is provided by the compressive stress of the cast-in layer,so the cast-in layer should be guaranteed to have high strength and adhesive properties in the structural design.