Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

Kopp, Gregory A.

2nd Supervisor

Chen, Shuifu

Affiliation

Zhejiang University

Joint Supervisor

Abstract

Standing seam metal roof (SSMR) systems are widely used in low-rise buildings. This study aims to understand the behavior of SSMR systems, especially the failure mechanisms, under severe wind loads. Full-scale experiments conducted at Insurance Research Lab for Better Homes make it possible to examine the performance of SSMR systems with realistic dimensions and boundary conditions. The induced loads on the clips could be measured directly. The results show that there is a linear relationship between the wind pressure and clip reaction under low wind pressure (less than 500 Pa). It is found that load sharing among clips changes at higher pressures due to the large deformation of the roof panel. As a result, more loads transfer to the clips and fasteners at the roof edges. Finite element method considers all nonlinearities (e.g., geometric, contact, and material nonlinearities) in the wind-induced response of SSMR systems, which reveal the whole process of failure. The initial location of global buckling, the disengagement failure between panel and clip at seam were simulated, which is consistent with the observation from the experiment. Both the finite element method and experiment show that the roof panel undergoes overall buckling before the roof system reach the ultimate bearing capacity and the initial position of overall buckling is in the middle of the two clips near the seam. Moreover, the results show the boundary conditions have notable effects on load distribution while these were usually ignored by the current standards. An updated analytical model was proposed using the influence function concept. The performance of the standing seam can be considered as a continuous beam with modeling clips and fasteners as vertical springs. Using the Database-assisted design (DAD) method, the clip reactions under spatio-temporal varying pressure were studied, which is also compared with the results from standards. It is found that the estimated clip reactions using GB 50009 (2012) are much smaller than the peaks using the DAD method, which makes the clips more vulnerable under severe wind suction. In contrast, ASCE 7-16 gives a conservative estimation of clip reaction.

Summary for Lay Audience

The roof is one of the most vulnerable parts of low-rise buildings during severe wind storms, which have caused significant losses. Standing seam metal roof (SSMR) systems are widely used in low-rise buildings, while the load paths and failure mechanisms are still not fully understood. The traditional methods of estimating the uplift resistance of roof systems are generally through standardized tests, which do not consider the effects of boundary conditions.

In this thesis, full-scale test and finite element method have been used to improve the understanding of load paths and structural behavior of SSMR systems subjected to wind uplift load up to the limit state. The clip reaction influence functions have been obtained as well. The results indicate that this improved model provides better estimations for the clip reaction of SSMR systems. Theoretically, this model is applicable for roofs that subjected to spatial and time varying wind pressures.

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