大型场馆异形钢结构屋面概念设计若干问题探讨

Discussion on concept design of long span special steel roof structures

本文提出了大型场馆异形钢结构屋面的概念设计问题。对于周边墙体封闭的“馆”类建筑,屋面风的体型系数一般为负,即受风吸作用。对于“场”类建筑,则应根据屋盖各部分形状与风向的相对关系来确定屋面受风吸还是风压。对于异形屋面排水问题,屋面形状应尽可能满足快捷排水的要求。排水路径要短,水流要向结构的支座处会聚,尽量避免聚向悬挑端。评定一个结构是否是空间结构,看其在结构效应中,是以弯曲为主还是以轴向拉压为主。如果是前者,则结构的厚度和跨度之比就要求较大;而对于以拉压效应为主的空间结构,则其厚度和跨度之比可以较小。铸钢节点用于杆件交汇数量多、交角小的节点,可以避免较大的应力集中。但对于少量几根钢管之间的连接,不太适合使用铸钢节点,采用相贯线焊接,也同样能满足受力要求。

This paper deals with the problem about the conceptual design of long span special steel roof structures. For those large-scale buildings with close walls around, the shape factor of the buildings under wind load are often negative, resulting uplift in the roof. For those large-scale buildings wihtout close walls around, the uplift or pressure wind on the roofs should be determined by the roof shape and tis relative position to the wind direction. Cautions should also be paid to the draining problem of special roof to avoid accumulation of water. Thus, the drainage path should be short enough, and water should be led to structual supports and should not be accumulated on the end of suspending elements, whether a roof structure is a space structure or a plain one is determined by the force in the roof. A roof structure with mainly bending effect can be considered as a plain roof, and its ratio of span and thickness is large. A spatial roof typically is formed by the effects of compression and tension, and the span to depth ratio is relatively small. Cast-steel nodes can be used where there are more members and the angles between neighboring members are small. Cast-steel nodes can have less stress concentration. For those nodes where only a few elements linked together, welding connection can meet the requirement of load-bearing instead of cast-steel node.