【作者】 王宁；

【导师】 孙建恒； 任小强；

【作者基本信息】 河北农业大学 ， 结构工程， 2015， 硕士

【摘要】 随着空间结构的跨度越来越大,厚度越来越薄,使得动力荷载在结构表面分布的敏感性也愈加明显,往往成为结构设计中的控制荷载,因此,网壳结构的稳定性问题成为空间结构研究的重点。目前,国内外学者对大跨度空间结构的动力稳定性和在地震作用下的倒塌分析进行了较多的研究,但对风荷载和雪荷载共同作用下结构的动力倒塌分析研究仍然十分有限。近年来,大范围雪灾不断发生,造成了巨额的经济损失和惨重的人员伤亡。从这些暴风雪引起结构破坏的事故分析中发现,强风带动积雪漂移或因日照等原因引起屋面雪压不均匀分布而导致雪荷载超过设计荷载是引起建筑物倒塌的主要原因。为此,本文以三向网格单层柱面网壳结构为研究对象,基于非线性有限元理论,在考虑材料非线性、几何非线性以及初始几何缺陷的情况下,比较系统的分析了该结构在不同风雪荷载组合作用下的动力失效破坏全过程,获得了结构荷载-位移曲线,并利用B-R准则确定结构的动力倒塌破坏临界风速。本文主要研究内容和成果如下:(1)利用非线性有限元法对三向网格单层柱面网壳进行了九种不同风雪荷载组合作用下的动力倒塌分析,通过对比分析各种组合作用下该结构的动力倒塌破坏临界风速,得出了迎风面作用半跨非均布雪荷载(较大雪压聚积在迎风面)与风荷载的组合为单层柱面网壳的最不利组合;并且无论是均布雪荷载作用还是非均布雪荷载作用,都是迎风面作用半跨雪荷载与风荷载组合时,单层柱面网壳的动力倒塌破坏临界风速最低;背风面作用半跨雪荷载和风荷载组合时,临界风速最高;而网壳结构全跨作用雪荷载与风荷载组合时,临界风速值介于前述两种组合之间。(2)研究了不同雪压对风雪荷载组合作用下的单层柱面网壳结构动力倒塌分析的影响,数值结果表明:全跨作用非均布雪荷载比全跨作用均布雪荷载的临界风速升高(降低)比率随着基本雪压的增加而减小(增大);迎风面作用半跨非均布雪荷载比迎风面作用半跨均布雪荷载的临界风速降低比率会随着基本雪压的增大而增大;背风面作用半跨非均布雪荷载比背风面作用半跨均布雪荷载时的临界风速升高(降低)比率随着基本雪压的增加而增大。更多还原

【Abstract】 As the span of space structure is increasing and the thickness is decreasing, the dynamic load distribution on the surface of the structure becomes more sensitive, which becomes a controlling factor in structural design. Therefore, the stability of reticulated shell structure is a focus in the study of space structure. Scholars at home and abroad have made a lot of researches on the dynamic stability of large span space structure and the seismic collapse analysis. However, the study of dynamic collapse under different wind and snow load is still very limited.In recent years, a wide range of snow disaster happens constantly which results in huge economic losses and serious casualties. Analysis of the accidents of structural damage resulting from snowstorm finds that the non-uniform distribution of snow pressure caused by strong winds blow and sunshine makes the snow load exceeds the design load, which is the main reason for structural collapse. Therefore, this paper, based on the nonlinear finite element theory, a finite element model was established for three way single-layer cylindrical Reticulated shells. Considering the material non-linearity, geometrical non-linearity and initial geometric imperfection, the paper systematically analyzes the whole process of dynamic failure and destruction of the structure under different wind and snow load combinations. By the load- displacement curve and using B-R criterion, the critical wind speeds of the dynamic collapse of the structure are determined. The main research contents and achievements of this paper are as follows:(1) Nonlinear finite element method is used to analyze the dynamic collapse of the three-way grid single-layer cylindrical reticulated shell in nine situations of wind and snow load combinations. Through comparing the critical wind speeds of the dynamic collapse of the structure in different situations, it is found that the combination of non-uniformly distributed snow load(a heavy snow accumulated on the windward side) on the windward side and wind load combination is the most disadvantageous combination for single-layer cylindrical reticulated shell; in addition, no matter uniform distribution or non-uniform distribution of snow load, when snow load on the windward side is combined with wind load, the critical wind speed of the dynamic collapse is minimum; when snow load on the leeward side is combined with wind load, the critical wind speed reaches maximum; when snow load on the full span of the reticulated shell structure is combined with wind load, the critical wind speed value is between those of the former two combinations.(2) The influence of different snow pressures on the dynamic collapse analysis of single-layer cylindrical reticulated shell structure under different wind and snow load combinations is analyzed, and the numerical results indicate: the increase(decrease) ratio of the critical wind speed under the action of a full span of non-uniformly distributed snow load, compared with that under the action of a full span of uniformly distributed snow load, decreases(increases) with the increase of the basic snow pressure; the decrease ratio of the critical wind speed under the action of non-uniformly distributed snow load on the windward side, compared with that under the action of uniformly distributed snow load on the windward side, increases with the increase of the basic snow pressure; the increase(decrease) ratio of the critical wind speed under the action of non-uniformly distributed snow load on the leeward side compared with that under the action of uniformly distributed snow load on the leeward side, increases with the increase of the basic snow pressure.更多还原