Structural modelling of support scaffold systems

In this paper, accurate three-dimensional advanced analysis models are developed to capture the behaviour of support scaffold systems, as observed in full-scale subassembly tests consisting of three-by-three bay scaffold systems with various combinations of lift height, number of lifts and jack extension. The paper proposes methods for modelling spigot joints, semi-rigid upright-to-beam connections and base plate eccentricities. Material nonlinearity is taken into account in the models based on the Ramberg-Osgood expression fitted to available experimental data. Actual initial geometric imperfections including member out-of-straightness and storey out-of-plumb are also incorporated in the models. The ultimate loads from the nonlinear analyses were calibrated against failure loads and load-deflection responses obtained from full-scale subassembly tests. The numerical results show very good agreement with tests, indicating that it is possible to accurately predict the behaviour and strength of complex support scaffold systems using material and geometric nonlinear analysis. The paper highlights the main difficulties in the numerical modelling of support scaffold systems, and describes mechanical models for implementing base plate, U-head and spigot joints in the analysis.     

脚手架系统几何缺陷及节点刚度研究

介绍了脚手架系统几何缺陷的现场测量结果,包括柱子、框架的几何缺陷及荷载偏心。在浇筑混凝土前,测量现场脚手架系统的实际初始几何缺陷和荷载偏心。对随机抽取的构件进行试验,研究节点刚度,获得绕水平轴及竖轴的转角。对节点构造(双向、三向及四向节点)、弯曲轴、荷载方向进行试验。对数据进行统计分析,使其能应用于脚手架系统模拟和概率评估中。     

Investigation of geometric imperfections and joint stiffness of support scaffold systems

This paper describes the findings from various site measurements of geometric imperfections of support scaffold systems, also known as falsework in industry. The measurements consist of out-of-straightness of the standards (uprights), out-of-plumb of the frame and loading eccentricity between the timber bearer and the U-head screw jack. The measurements were taken from different support scaffold construction sites before the pouring of concrete, representing actual initial geometric imperfections and loading eccentricity encountered in practice. The paper also reports the results of support scaffold joint tests. The tests were performed on randomly chosen used components to investigate the joint stiffness for rotations about vertical and horizontal axes. Tests were performed for various joint configurations (two-way, three-way, and four-way connections), bending axes, and loading directions. The statistical analysis of the data is presented in the paper for practical application in modelling and probabilistic assessment of support scaffold systems.