摘要:
相较于混凝土楼梯,钢结构旋转楼梯具有其质量轻、跨度大、承载力高、整体刚度好等特点,因此钢结构楼梯安装便捷、成本较低,在各种商业和办公类建筑中得到广泛运用。但国内现有规范图集中并没有对一些跨度较大且形状不规则的楼梯的设计方法进行规定。针对济南某商务中心下沉广场处的钢结构旋转楼梯设计中因楼梯形状不规则、跨度大所产生的复杂计算问题,提出箱梁式、梁式、图集板式和箱式踏步4种不同的结构设计方案,采用有限元分析软件SAP 2000建立钢旋转楼梯的整体模型,分别对4种方案进行了静力分析、模态分析,并对旋转楼梯构件进行了截面设计,同时采用3种不同的人行激励荷载工况进行了舒适度分析。从结构刚度、构件强度、楼梯整体舒适度等方面对4种方案进行比较,研究同一形状下不同结构形式的楼梯的受力特性,得出各个结构设计方案的优缺点,并确定最终设计方案。分析结果表明:4种方案在变形、强度和舒适度方面均能满足设计要求;4种方案的最大位移均发生在旋转楼梯中部,其中方案2的挠度最大,说明对楼梯底部进行封板,使楼梯踏步板形成箱型闭口截面,可以有效地增加楼梯的刚度;在楼梯休息平台与梯段相连的转折点出存在较大的应力集中,通过考虑材料非线性,对楼梯进行非线性分析,可知此处的应力集中现象对楼梯强度影响较小;对于应力集中的区域,可以对此处钢箱梁进行加厚处理由16 mm厚增加至20 mm厚。舒适度研究的重点在于控制动荷载下结构加速度,由于在自振频率满足要求的情况下依然会出现加速度响应过大的情况,因此对于复杂结构舒适度问题应采用时程分析,结合它们在稳定状态时的加速度进行综合评定。对4种方案的设计结果进行比较,在受力方式、整体美观程度、施工方便程度、楼梯造价等方面进行综合考虑,确定箱式踏步楼梯作为最终设计方案。
Abstract:
Compared with concrete stairs, steel stairs with light deadweight, large span, high bearing capacity, good overall stiffness and other characteristics are easy to install and low cost, and are widely used in various commercial and office buildings. However, the design methods of some structures with large span and irregular shape are not specified in the existing domestic standard drawings. Aiming at the complicated calculation problems caused by the irregular shape and large span of the steel structure spiral staircase at the sunken square of a business center in Jinan, this paper proposes four different structural design schemes of box girder, beam, atlas plate and box step. The finite element analysis software SAP 2000 is used to establish the overall model of the steel spiral staircase, and the static analysis and modal analysis are carried out for the four schemes. The cross-section design of the spiral staircase component is compeleted, and the comfort degree of each scheme is analyzed by using three different pedestrian excitation load cases. The four schemes are compared from the aspects of structural stiffness, component strength and overall comfort of stairs. The mechanical properties of stairs with different structural forms and the same shape are studied. The advantages and disadvantages of each structural design scheme are obtained, and the final design scheme is determined. The analysis results show that the four schemes can meet the design requirements in terms of deformation, strength and comfort. The maximum displacement of the four schemes occurs in the middle of the spiral staircase, and the deflection of scheme 2 is the largest, which indicates that sealing the bottom of the staircase to form a box shaped closed section of the stair treads can effectively increase the stiffness of the stairs. There is a large stress concentration at the turning point where the rest platform is connected to the ladder. By considering the nonlinearity of the material, the nonlinear analysis of the staircase shows that the stress concentration has little influence on the strength of the staircase. For the area of stress concentration, the steel box girder can be thickened from 16 mm to 20 mm thick.The focus of comfort research is to control the structural acceleration under dynamic load. When the natural frequency meets the requirements, the acceleration response will still be too large. Therefore, for comfort problems of complex structure, time history analysis should be adopted, combined with their accelerations in stable state for comprehensive evaluation. The design results of the four schemes are compared, and the box step stair is determined as the final design scheme after comprehensive consideration of the mechanical characteristics, overall aesthetic degree, construction convenience, stair cost, etc.
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