铁路箱梁静载试验开裂原因分析及控制措施

Cause Analysis and Control Measures to Cracking of Railway Box Girder

通过预制后张法预应力混凝土铁路桥箱形简支梁静载试验出现的1.0级荷载开裂问题,对开裂原因进行全面分析。重点剖析由于蒸养拆模、混凝土水化热高峰期拆模,造成混凝土芯部与表面、表面与环境温差超过15℃的标准要求,致使混凝土内部温差应力超过其抗拉极限强度而早期开裂的原因。论证静载试验在1.0级时,当混凝土抗拉极限强度fct=0,则抗裂安全系数Kf=λ,梁体在静载试验时出现1.0级开裂的必然性,进一步阐明混凝土温差应力超限是箱梁静载试验开裂的主要原因,提出预防出现早期裂缝的控制措施。

With regard to the cracking identified under the static test for prefabricated post-tensionedprestressed concrete railway bridge simply supported box girder, this paper analyzes the causes ofcracking with focus on early cracking due to the fact that the concrete inner temperature difference stressexceeds the tensile ultimate strength, which is caused by the temperature difference between the core andsurface of the concrete, and the temperature difference between the surface and the environment in excessof the restricted 15 益on account of the form removal during steam curing and in peak period of concretehydration heating. The author demonstrates the inevitability of cracking during beam static load level1-0 test with concrete tensile limit strength fct =0, and anti-crack safety factor Kf =0, further elucidatesthat it is the concrete transfinite temperature stress that gives rise to box girder cracking, and puts forwardcontrol measures to prevent early cracks.