An updated analytical method for predicting the bracing behavior of Z-purlin supported standing seam diaphragm systems

Roof systems utilizing Z-purlins as a secondary member supporting a standing seam panel system are used extensively by the metal building industry. The Z-purlins rely on the diaphragm action in the standing seam panel system to provide lateral support and transfer forces to anchorages. The behavior of the standing seam system is highly nonlinear making prediction of the interaction between the Z-purlin and the standing seam system difficult. To better understand the behavior of the interaction between the purlins and the panel system, a series of non-linear shell finite element models were developed based on the test results of simple span systems. These models capture the non-linear flexibility of the connection between the purlin and the panel and show good correlation to the tests. Based on the results of the finite element models, an analytical method to predict the forces interacting between the purlin and the sheathing as well as the resulting diaphragm deformation was developed. This analytical method provides a foundation for additional analytical methodologies to predict the strength and stability of Z-purlin and standing seam panel systems

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