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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 83
PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
Paper 113

Numerical Simulation of the Stressed Skin Diaphragms

Y. Liu and Q.L. Zhang

Department of Building Engineering, Tongji University, Shanghai, China

Full Bibliographic Reference for this paper
Y. Liu, Q.L. Zhang, "Numerical Simulation of the Stressed Skin Diaphragms", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 113, 2006. doi:10.4203/ccp.83.113
Keywords: skin diaphragm, shear behaviour, profiled sheets, finite element analysis, ANSYS.

Summary
The profiled sheeting acting as a diaphragm, commonly takes the form of cold-formed channels or zed purlins, screwed to corrugated sheeting. These purlin-sheeting systems have been the subject of numerous research projects conducted throughout the world [1,2,3]. Due to its complex assembly of light gauge steel sections and fasteners, there are mainly three kinds of methods to assess the stressed skin diaphragm at the present time, including the test, theoretical procedures and numerical simulation.

In mechanical engineering, numerical analysis has become a very powerful tool. A numerical investigation using finite element analysis (FEA) was performed and is presented in this paper. The objective of the numerical investigation presented in this paper is to develop an advanced non-linear finite element model (FEM) for the shear behavior of the stressed skin diaphragm. The finite element program ANSYS [4] was used to perform the numerical analysis. The finite element model was verified against the full scale diaphragm test recently conducted by Liu [5].

The measured cross-section dimensions and spring properties of the test specimens were included in the finite element model. Non-linear analysis was performed using the Newton-Raphson procedure. The total load was applied in a sequence of incremental load steps. Within each step, the nonlinear equilibrium equations were linearized through a tangent stiffness approach. Iterations at constant external load were performed to remove residual (unbalanced) forces arising from the use of linearized equilibrium equations. At the end of each step, total equilibrium conditions were satisfied within a small prescribed tolerance.

The profile sheeting was modelled using three dimensional thin shell elements with four nodes and six degrees of freedom per node, which are translations in the global directions and rotations about the and global directions. The thin shell elements have both membrane and bending capabilities. The purlin, which eventually supports the sheeting through fasteners, was modelled using beam elements, as well as longitudinal frame members. The frame elements had six degrees of freedom per node.

The fasteners were simulated in the finite model as a continuous spring system having two horizontal components that simulates the stiffness provided by the fastener in the in-plane transverse direction of the panel, and the vertical component that simulates the stiffness provided by the fastener in the in-plane axis direction of the panel. When the behaviour associated with a certain degree of freedom was assessed, the other two degrees of freedom were kept restrained. It is anticipated that in the advanced non-linear range of behaviour some degree of coupling exists between the three degrees of freedom. The force-displacement characteristics for the spring elements were determined, based on the result of joint tests recently conducted by Liu [5].

The results of the simulation show that the above proposed finite element model, using the non-linear finite element program ANSYS, provides a simulation which agrees well with the tests. Therefore, the model can be used for the prediction of the shear behaviour of the stressed skin diaphragm and can further be applied to relevant parametric studies.

References
1
Bryan, E.R. and El-Dakhakhni, W.M., "Shear flexibility and strength of corrugated decks", Journal of Structural Division, ASCE, 94(ST11), 2549-2579, 1968.
2
Davies, J.M., "Simplified diaphragm analysis", Journal of Structural Division, ASCE, 103(ST11), 2093-2109, 1977.
3
Nilson, A.H. and Ammar, A.R., "Finite element analysis of metal deck shear diaphragms", Journal of Structure Division, ASCE, 100(ST4), 711-725, 1974.
4
ANSYS Corporation. Structural Analysis Guide.2004.11.
5
Liu, Y., "Theoretical and experimental research on the stressed skin diaphragm of light-gauge steel structures", Ph.D Thesis, Tongji University, Shanghai, China, 2006.

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