不均匀积雪致大跨网架结构局部损伤分析∗

Local Damages of Long‑span Grid Structure Caused by Uneven Snow Cover

摘要:

网架结构管球连接处局部损伤是此类结构的重要安全隐患。在风致雪漂移引起的不均匀积雪荷载作用下， 局部损伤会加剧，最终导致结构局部破坏。因此很有必要分析不均匀积雪荷载作用下带伤服役网架结构局部损伤劣化情况。采用 CFD 数值模拟技术，以一正放四角锥网架结构为研究背景，分析了在 90°风向角、12 m/s风速下，持续降雪 24 h中网架结构屋面不均匀积雪分布的变化情况，并建立可表征网架结构管球连接处存在裂纹损伤的多尺度模型，分析了网架结构节点存在不同裂纹尺寸局部损伤时，不均匀积雪致网架结构局部损伤劣化程度。结果表明：网架结构风致积雪不均匀程度非常显著，而且当网架结构管球连接处存在局部裂纹损伤时，在降雪中后期，有管球连接损伤的节点大多都出现了不同程度的裂纹扩展，节点为最不利分布的穿透型裂纹时，裂纹扩展最大为 15.64 mm。说明在持续特大降雪这种极端荷载作用下，带伤服役网架结构局部损伤将进一步加剧，危及结构使用安全。

Abstract:

Local damage of the pipe-ball joints in the grid structure poses a significant safety hazard. Such local damage will be aggravated under uneven snow cover caused by wind-induced snow drifting， eventually leading to partial structural failure. Therefore， it is necessary to analyze the degradation of the structure with local damage under the action of uneven snow load. The CFD numerical simulation technology is adopted to analyze the variation of uneven snow distribution on the roof of an orthogonal quadrangular grid structure under the continuous snowfall for 24 hours at the 90°wind direction and 12m/s wind speed. Then a multi-scale numerical model is established to characterize the crack damage at the pipe-ball joints of the grid structure， and the local damage deterioration degree of the grid structure caused by uneven snow cover is analyzed when there is local damage of different crack sizes at the joints of the grid structure. The results show that the uneven degree of the wind-induced snow cover on the grid structure is very significant， and when there are local crack damages at the pipe-ball joints of the grid structure， most of the joints with damage have different degrees of crack propagation in the middle and late stages of snowfall. The maximum crack propagation is 15.64 mm when the joint damage is the penetrating cracks with the most unfavorable distribution. It indicates that under the extreme load of continuous heavy snowfall， the local damages in the grid structure with existing cracks will be further aggravated， endangering the service safety of the structure.