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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 81
Edited by: B.H.V. Topping
Paper 158

Second Order Analysis of Scaffolds with Semi-Rigid Connections

U. Prabhakaran+, R.G. Beale* and M.H.R. Godley+

+Department of Real Estate and Construction,
*Department of Mechanical Engineering,
Oxford Brookes University, Oxford, United Kingdom

Full Bibliographic Reference for this paper
U. Prabhakaran, R.G. Beale, M.H.R. Godley, "Second Order Analysis of Scaffolds with Semi-Rigid Connections", in B.H.V. Topping, (Editor), "Proceedings of the Tenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 158, 2005. doi:10.4203/ccp.81.158
Keywords: scaffold, connection, semi-rigid, moment rotation, non-linear, stability function, second order analysis.

Steel scaffolds are extensively used to provide access and support to permanent works during different stages of their construction. These structures are generally slender and prone to fail by elastic instability. The elastic buckling load of a scaffold is strongly influenced by the stiffness of the connections, which exhibits semi-rigid deformation behaviour that can contribute substantially to the stability of the structure as well as to the distribution of member force. The moment rotation curve of these joints is found to be highly non-linear.

In the proprietary scaffolds and pallet rack structures the joints often exhibit different behaviour under clockwise and anti-clockwise rotations and frequently have very low stiffnesses including the possibility of looseness at the connection. The looseness contributes to the overall deflection of the structure under loads [1]. These joints often deform plastically at low loads and hence elastic unloading curves are not parallel to the initial moment-rotation curves. Reloading occurs along the same line as the unloading line. In addition, due to the slender nature of scaffold structure, the geometric non-linear interactions between the axial load and lateral deformations increase the complexity of the analysis.

For the purpose of design and analysis, the moment rotation curve is often assumed to be bilinear or multilinear and the same curve is used for both sagging and hogging moments. In this case, the predicted behaviour of the structure may be quite unrealistic compared to that of the actual structure.

In the past there has been several experimental and analytical research to improve the analysis of scaffold structures [2,3,4,5,6,7]. However little work has been reported on the effects of non-linear behaviour of the moment curvature relationship of these joints. Similar curves have been published in relation to pallet rack structures [8,9]. These results are primarily concerned with experimental testing of joints and obtaining empirical formulae. Abdel-Jaber [10] proposed a computer program to handle the non-linear behaviour of the moment curvature relationship of these joints. However the work was done using a MathCAD spread sheet and cannot be generalised.

This paper proposes a generalised computer procedure for the second order analysis of two dimensional scaffold model using stability functions [11]. Further the program incorporates the non-linear moment curvature behaviour of semi-rigid connections. The load displacement relationship predicted by the proposed program compares well with experimental results.

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