某桥移动模架荷载预压试验垮塌事故原因分析

Analysis of Causes of Collapse Accident in Preloading Test of Bridge Movable Framework

为研究移动模架荷载预压试验中垮塌原因,以某桥梁工程移动模架垮塌事故为例,通过查阅移动模架设计图纸及事故现场照片,初步推断了事故原因,并采用有限元软件建立该移动模架的整体结构分析计算模型,分析在各级预压荷载下结构整体变形、受力,在此基础上对受力最不利的横梁的强度、刚度和弹性稳定性进行了复核计算。结果表明:箱梁模板缺少沿桥纵向必要的刚性支撑,在预压荷载自重的纵向水平分力作用下,整个箱梁模板体系发生纵向平移;移动模架各片横梁之间间距较大,横梁面外刚度相对较弱;移动模架施工中真实的受载集度与预压试验的荷载均匀分摊方式的差异也会产生不安全因素。计算结果基本验证了推断结论的正确性,为防止类似事故发生提出了相关建议。

To analyze the causes of the collapse accident in the movable form work preloadingte s t,the movable form work collapse accident of a bridge project was cited as an example.By exam ining the draw ings of the m ovable form w ork and the accident site,the causes of the accidentw ere prelim inarily interfered.T he finite elem ent softw are was used to establish the global structuralanalysis and calculation model of the m ovable form w ork,to analyze the overall structural deformation and load bearing capacity in different preloading stages.Based on the calculation,thestren g th,stiffness and elastic stability of the cross beam s that carry the m ost unfavorable loadsw ere verified.T he results of the verification show that the form w ork of the box girder lacks stiffsupports along the bridge length,so that longitudinal translation w as observed on the overall boxgirder form w ork system under the action of the horizontal com ponents of the self w eight of thepreloading in the longitudinal direction.Because the spacings am ong cross beam s of the m ovableform w ork are big,the out-of-plane stiffness of the cross beam is relatively weak.U nsafe conditionswill also appear in the m ovable form w ork construction,relating to the real load carrying concentrationdegree and the uniform load allocation m ode in the preloading test.T he calculation basicallyverifies th at the interference is correct,and suggestions are given for the prevention of thesim ilar accidents.