中低速磁浮标准箱梁弯曲抗裂试验及性能评价

Bending Test and Performance Evaluation of Medium and Low Speed Maglev Standard Box Girder

研究目的:磁浮列车对箱梁的刚度和强度要求极高,但目前尚无针对磁浮箱梁进行抗裂性能的相关试验。为了评估中低速磁浮箱梁的受力性能,本文对长沙25 m磁浮标准箱梁开展弯曲抗裂静载试验,通过测试标准箱梁在荷载作用下的位移、应力和裂缝开展情况,评估预制梁在实际工作状态中的强度、刚度及抗裂性,为磁浮列车的正常运营提供试验依据,并为类似工程提供数据支撑。研究结论:(1)磁浮标准箱梁开裂前处于弹性工作状态,刚度能够满足设计要求;(2)实测箱梁开裂荷载为258.9 kN,较理论值有较大提高,可评定为全预应力梁抗裂合格;(3)梁体开裂前截面应变分布基本符合平截面假定,实测中性轴位置与理论值相差极小;(4)箱梁开裂后截面应变有明显重分布,随荷载增大,梁体跨中裂缝宽度逐渐增大,加载至372.2 kN时箱梁跨中最大裂缝宽度达0.053 mm;(5)本文研究表明25 m磁浮标准箱梁的受力性能满足规范要求,其构造和设计可在中低速磁浮工程中推广应用。

Research purposes:Maglev trains have extremely high requirements on the rigidity and strength of the box girder,but there is no relevant test on the crack resistance of the maglev box girder.In order to evaluate the mechanical performance of the medium and low speed maglev box girder,this paper carried out a bending crack resistance static load test on the Changsha 25 m maglev standard box girder.By testing the displacement,stress and crack development of the standard box girder under load,the strength,stiffness and crack resistance of precast beams were evaluated in actual working conditions,to provide test basis for the normal operation of maglev trains,and provide data support for similar projects.Research conclusions:(1)The girder is in the elastic state before the cracking,and the stiffness can meet the design requirements.(2)The measured cracking load is 258.9 kN,which is higher than the theoretical value.It can be evaluated as the crack resistance of the full prestressed girder.(3)The strain distribution of the cross section of the girder before the crack is basically conformed to the assumption of the flat section,and the difference between the measured neutral axis and the theoretical value is very small.(4)The cross-section strain of box girder is obviously redistributed after cracking.With the increasing of the load,the width of cracks in the mid span increases.When loading up to 372.2 kN,the maximum crack width of the box girder is 0.053 mm.(5)The research in this paper shows that the mechanical performance of the 25 m maglev standard box girder meets the requirements of the specification,and its structure and design can be popularized and applied in medium and low speed maglev projects.