直立锁边金属屋面风揭破坏全过程分析

Analysis of the Whole Process of Wind Uplift Failures of Metal Roofing with Standing Seams

直立锁边金属屋面长期服役过程中,由于各种因素的影响,风揭破坏时有发生。国内外学者对其破坏过程及破坏形式进行一定探索,而风揭破坏阶段的划分及各阶段的标志仍缺乏清晰界定。使用自主设计的试验装置,以区域面力代替均布风吸力对直立锁边金属屋面进行静态承载力试验,结合表观现象与3D点云模型研究其破坏过程。研究发现:金属屋面的破坏过程可分为弹性、塑性、强化、失效、后承载力5个阶段,分别对应卸载变形可恢复、咬边处竖向板顶部与支座底部接触、竖向板顶部沿支座底部水平滑移,竖向板与水平夹角迅速扩展、竖向板顶部滑移至支座底部尽头,卷边间缝隙迅速增大、单边脱扣。对于服役状态下的金属屋面,在进入“塑性阶段”后,就已产生不可恢复的永久变形,应及时补强加固。设计时可依据抗风承载力及安全极限荷载给出2种承载限值。

During the long service life of metal roofing with standing seams,wind uplift failures often occur due to various factors.Scholars both domestically and internationally have explored the failure process and form.Despite these efforts,a precise delineation of the stages of wind uplift failure and distinctive markers for each stage is still lacking.The static load-bearing capacity of metal roofing with standing seams was tested with a test apparatus designed independently,where the uniform wind uplift was replaced with the regional surface force.The failure process was analyzed based on visible phenomena and a 3D point cloud model.The study revealed that the failure process of metal roofing can be divided into 5 stages:elastic stage,plastic stage,strengthening stage,failure stage,and post-load-bearing stage,corresponding to the recovery of deformation after unloading,contact between the top of the vertical plate at the undercut and the bottom of the support,horizontal sliding of the top of the vertical plate along the bottom of the support,rapid expansion of the angle between the vertical plate and the horizontal plane,and sliding of the top of the vertical plate to the end of the bottom of the support,with a rapid increase in the gap between the rolled edges and unilateral release.After entering the“plastic stage”,metal roofing in service undergoes irrecoverable permanent deformation and therefore requires timely reinforcement.In the design,two load-bearing limits can be set according to the wind resistance capacity and ultimate safety load.