【作者】 黄莉；

【导师】 邓华；

【作者基本信息】 浙江大学 ， 结构工程， 2013， 博士

【摘要】 当前的大跨度屋盖结构普遍采用轻型金属屋面系统,但结构设计时通常忽略屋面板对结构受力性能的影响。本文以常用的聚氨酯夹芯金属屋面板作为研究对象,对此类屋面板的刚度和阻尼性能、解析理论以及有限单元模型开展了研究,并进一步考察了屋面板刚度和阻尼性能对屋盖结构风致振动效应的影响。论文主要包括以下五个方面的工作：(1)对屋面板常用聚氨酯夹芯材料的基本力学性能进行了试验测定。发现聚氨酯夹芯的拉伸、压缩性能不同,且不同方向的力学性能也有明显的差异。指出聚氨酯夹芯可以假定为横观各向同性材料,并根据试验数据对其基本力学参数进行了拟合。进一步对聚氨酯夹芯的材料损耗因子进行了测定,给出了损耗因子随温度、频率的变化曲线。(2)对聚氨酯夹芯金属屋面板的整体阻尼特性进行了研究。分析了聚氨酯夹芯金属屋面板的模态损耗因子随檩距、夹心层厚度及面板厚度的影响,表明屋面板对于外部高频激励具有较高的阻尼耗能能力,聚氨酯夹芯层的阻尼特性对整个屋面板的阻尼特性起着决定性影响。考察了不同刚度、阻尼的屋面板在脉动风荷载作用下的动力反应,发现在风压传递过程中屋面板的有限刚度及夹芯层阻尼都会显著改变风压的脉动特性。(3)将面层压型金属板等代为正交各向异性的平板,进而将聚氨酯夹芯屋面板简化为上下面层厚度不同、且各层材料均为正交各向异性的夹层板。基于Hoff型夹层板理论,推导了屋面板的静力基本方程,并对该静力方程的解析方法进行了讨论。采用复模量法来表征聚氨酯夹芯的粘弹性特性,进一步推导了考虑夹芯层阻尼的屋面板横向振动的动力基本方程。(4)基于Hoff型夹层板理论,建立了一种定义在夹芯层中面上的八结点的矩形夹层板单元,每个结点具有5个自由度,3个线位移和2个转角。采用该单元模拟的屋面板在静荷载作用下的变形形式与更精细有限元分析结果相同,变形值基本接近。模态分析求得的基本振型与精细模型相同,自振频率也较接近。表明该夹层板单元能够有效模拟聚氨酯夹芯金属屋面板的静、动力特性。(5)通过两个算例考察了屋面板刚度和阻尼性能对屋盖结构风振效应的影响。分析结构表明是否考虑屋面板对结构的风振效应的计算结果存在明显的差异。屋面板刚度都是影响结构风致振动效应的主要因素。夹芯层阻尼会对刚度较大屋盖结构的风振效应产生的影响明显,影响程度还与屋面自身刚度相关。更多还原

【Abstract】 Currently, the light metal roofing system is widely used in large span roof structures, while the effect of roof panel is ignored in design. Actually, the wind pressure acts on the roof panel first, then passes through the roof panel to the purlins and arrived in the main structure finally. The article studies on the frequently-used polyurethane sandwich metal roof panel, focusing on its effect of finite stiffness and damping on the mechanical properties of roofing system, especially on the wind-induced vibration, the main parts as follow:(1) The article investigates the basic mechanical and damping properties of the polyurethane sandwich layer. Studies have found that the tensile and compression performance as well as the mechanical properties of different direction of polyurethane foam are different. So it can’t be considered as isotropy material. Parameters of transverse isotropic model are fitted according to the test data. The loss factor curve of polyurethane foam is measured by DMA, during witch, the factor loss-frequency and factor loss-temperature cure are obtained.(2) The damping properties of the polyurethane sandwich metal roof panel are investigated here. The model loss factor of the polyurethane sandwich metal roof panel is obtained, which is found to cause high damping energy dissipation on external high-frequency stimulation. Parameter analysis shows that the damping properties of the polyurethane sandwich metal roof panel are decisive to the damping properties of the whole roofing system. The finite stiffness of roof panel and the damping properties of sandwich layer will both change the characteristics of fluctuating wind pressure, by investigating the response of roof panel with different stiffness and damping properties under the action of pulsating wind load of dynamic response.(3) The pressed metal layer is equaled to orthogonal anisotropy plate, while polyurethane sandwich metal roof panel is also equaled to orthogonal anisotropy sandwich plate with different thickness of top and bottom layer. Based on the Hoff sandwich plate theory, the static equation of roof panel is obtained, and dicussed the analytic solutions. Complex modulus method is taken to represent the viscoelastic properties of polyurethane sandwich layer. Futher, the dynamic equation of the panel transverse vibration with the damping properties of sandwich layer is derived.(4) Based on the Hoff sandwich plate theory, a new kind of sandwich plate element is established, which is established on the middle surface of the sandwich layer as a rectangular element with eight nodes, each of which contains five freedoms:3linear displacements and2angular displacements.The roof panel simulated by this element has the same displacement as what is got in the accurate model, while the natural frequency of vibration is close to the accurate model. So, it is found to be effective enough to simulate the static and dynamic properties.(5) Effect of the stiffness and damping of roof panel on the wind vibration of the roof structures is investigated by two examples. The analysis result shows that whether to take the roof panel into account is definitely different on the calculation results of wind vibration.The stiffness of roof panel is the main factor to consider to the wind-induced vibration. The damping of sandwich layer has obvious effect on the roof structure with large stiffness, and how mcuh it causes depands on its stiffness.更多还原