Analytical method for simply supported Z-section purlins under wind uplift loading
Bai Fan 1,2 Yang Na1
1. School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
2. Beijing′s Key Laboratory of Structural Wind Engineering and Urban Wind Environment, Beijing Jiaotong University, Beijing 100044, China
Abstract：With the sheeting of the upper flange continuously restrained and the lower flange kept free, the stress distributions in the non-symmetric plane of the Z-section purlins appeared to be complicated, leading to the global or local instability problems at the web and lower flange. To address this problem, a semi-analytical model of predicting the longitudinal stresses of Z-section purlins considering both the lateral and rotational restraints imposed by sheeting under wind uplift. To calculate the longitudinal stresses of the roof purlins, formulas are derived based on the classical bending theory of the thin-walled beams. Test data collected from existing literatures are adopted to validate the model. It is shown that the results predicted by the proposed model agree well with the collected test data. Furthermore, the parameter analysis on the limit states of strength and stability considering the lateral bracing are conducted. The results show that the present model can be used to calculate the longitudinal stress distribution and the displacement; the stress distributions at the upper and lower flanges may vary with the change of the stiffness of restraint, so that the instability mode of purlins may switch from the local buckling to the distortion buckling.
