Summary and Conclusions

This article has presented a method of nonlinear analysis based on a compound-element that accounts for both member plasticity and semi-rigid connection behaviour. Depending on the properties of the compound element, connections can be categorized as being over-strength as for conventional fully – restrained or rigid connections, intermediate-strength as for partially-restrained or semi-rigid connections, and under-strength as for simple or pinned connections. Analysis results show that for an over-strength connection, both plasticity of the member and the semi-rigid nature of the connection affect nonlinear behaviour but the member strength dominates the failure state. An intermediate – strength connection has similar nonlinear behaviour but the connection strength dominates the failure state. For an under-strength connection, only the semi-rigid connection affects the nonlinear behaviour and the connection strength controls the failure state. Over-strength connections may be inappropriate for use in practice since their stiffness and strength are not fully utilized. A satisfactory design can be achieved if the connection and the connected member have about the same loading capacity.

A portal frame example demonstrated that the proposed method of nonlinear analysis can well predict the responses of structures with semirigid connections. Albeit, it was observed that the results are very dependent on properly modelling the behaviour of semi-rigid connections and that data from isolated connection tests may not be correct for assembled frameworks. The results show that the proposed method is effective and efficient for nonlinear analysis of steel frameworks taking into account flexural, shearing and axial stiffness degradation due to the combined action of member plasticity and semi-rigid connection behaviour.

Acknowled gements

This work forms part of the PhD research studies conducted by the first author under the supervision

of the other two authors, and was funded by research grants from the Natural Science and Engineering

Research Council of Canada.

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