宁波保国寺大殿风振性能研究

Research on wind-induced response of the main hall of Baoguo Temple

为了更科学地保护我国传统木构建筑,需要研究我国江南地区传统木构建筑的风振性能,为此,以江南地区最古老、保存最完整的佛教木构建筑——保国寺大殿的主殿为例进行风振性能研究。首先基于三维激光扫描获得的真实可靠的保国寺大殿的几何信息,采用SAP2000有限元软件建立主殿的有限元模型,并进行动力特性分析。再利用MATLAB软件编写脉动风速时程,并将风压作用于有限元模型上分析,得到主殿的风振响应。得到结构模态、位移时程曲线、位移谱曲线、加速度响应,并对时程位移风振系数和规范风振系数进行对比。结构的振动响应主要由前三阶振型控制,在强风荷载作用下,最容易出现的变形就是南北向振动、东西向振动和扭转振动;各个典型节点的最大位移均在侧向位移容许值内;迎风面阑额中心位移最大、屋面上半部次之、屋面下半部及檐柱柱头最小;主殿相连的两个部分的加速度相差较多,屋面和屋身的连接节点应成为日后保国寺大殿的保护重点;时程风振系数变化与规范风振系数的变化规律不同是因为结构横向刚度分布不均匀;时程风振系数是规范风振系数的1.2~1.4倍,这是由于按照规范计算风振系数的过程中只考虑了第一阶振型的影响而忽略其他所有振型的结果;规范风振系数的计算只适用于形状、质量沿高度不变的高耸结构,不适用于类似本研究中的低矮木构传统房屋结构。

In order to study the wind-resistance characteristics of traditional timber structures in the south Yangtze River regions,the main hall of Baoguo Temple,which is the best-preserved and the oldest Buddhist timber building in this region,was studied in terms of its wind-resistance characteristics. First,a model of the main hall was built based on precise geometric information acquired by 3 D laser scanning and the finite element SAP2000 software,and its dynamic characteristics were analyzed. Then MATLAB software was used,based on AR model,to generate the time history curves of fluctuating wind speed and fluctuating wind pressure. The generated wind pressure was applied to the SAP2000 hall model for analysis. The results obtained were as follows： the structural modes,displacement response curves,displacement response spectrum curves,acceleration response,and comparison between the wind vibration coefficients obtained by the time history analysis of wind pressure and the wind vibration coefficients were calculated according to the code. Some conclusions could be drawn： 1） the displacement response of this structure is controlled mainly by the top three natural modes; under the strong wind pressure,the deformation most likely to occur is the north-south horizontal vibration,the west-east horizontal vibration and the torsional vibration;2） all the displacements of typical joints are in the allowable range of values of lateral displacement; 3） the displacement of the center of the architrave in the windward side is the largest,with that of the top roof the second and those of the lower roof and the pillar top the smallest; 4） the accelerations of roof and columns of the main hall differ a lot and the roof-column connection joints should be of great importance in the future protection plans; 5） the wind vibration coefficients obtained by the time history analysis of wind pressure with the wind vibration coefficients calculated according to the code are obviously different,which is mainly due to the non-uniform transverse stiffness distribution of the structure; 6） the wind vibration coefficients obtained by the time history analysis of wind pressure are 1. 2 ~ 1. 4 times as big as those calculated according to the code because the code method only considers the effect of the first mode; 7） the wind vibration coefficients calculated according to the code are only suitable for the structure the mass and shape of which are invariant with the change of height,and are unsuitable for low-rise structures such as the Main Hall of Baoguo temple.