[Univ of Cambridge] [Dept of Engineering]
The nonlinear analysis of shear-weak gridshells

Marcus Aberle


The low shear stiffness of certain gridshells can result in a different behaviour than that generally observed for shell structures.

This thesis investigates the nonlinear behaviour of such shear-weak gridshells. The current methods of analysis of these structures are reviewed and the importance of various parameters on their pre- and post-buckling behaviour is studied.

To model the individual gridshell members, new stability functions and bowing expressions that allow for the effect of axial loads on the bending stiffness and the change in effective axial stiffness due to bending moments, are derived and verified by numerical and experimental studies. These new formulations, based on power series, are applicable for any degree of shear stiffness and any axial load.

This is followed by the presentation of a solution procedure, which combines the Dynamic Relaxation method with different iteration control procedures.

The new element formulations, together with the proposed solution procedures are implemented into an essentially new computer program. This program is verified against examples found in the literature, and by comparison with the results obtained from buckling experiments conducted on a 1.2m span gridshell model made of thermoplastic polyester. The program is then employed to assess the post-buckling behaviour of a 12m span shear-weak gridshell model built in Japan, and the results are compared to the available experimental values of this structure.

The study indicates that the limit load along with the imperfection sensitivity, and the sensitivity to asymmetric loading of gridshells are directly dependent on their in-plane and out-of-plane shear stiffnesses, and also on the size of the loaded area.

[Cambridge University | CUED | Structures Group | Geotechnical Group]

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