Date of Award

8-2020

Degree Name

Doctor of Philosophy

Department

Engineering and Applied Sciences

First Advisor

Dr. Xiaoyun Shao

Second Advisor

Dr. Houssam Toutanji

Third Advisor

Dr. Daniel Kujawski

Fourth Advisor

Dr. Yufeng Hu

Keywords

Roof-to-wall connection, elastomeric adhesives, uplift capacity, fatigue analysis, wind lo ads, roof modeling

Abstract

Light-frame wood residential buildings are highly susceptible to damage caused by severe wind events such as hurricanes and tornados. Roof failures in residential buildings are commonly observed due to weaknesses of or missing connections. Roof-to-wall connections not only have significant influences on roof performance but also affect building resistance due to their critical role of transferring wind loads to the wall system and ultimately to the foundation. Roof fails when it has no sufficient wind uplift resistance due to improper selection or installation of construction materials (including fasteners) and strength degradation due to aging or long service. Toenailing is commonly used in roof connections, which was found to be inadequate in high-wind areas. One approach to improve roof performance is to use metal connectors in roof connections. However, it was found out that such an approach may result in a water leak due to fasteners' holes, weakening the substrate, and being susceptible to wind-induced fatigue damage. Elastomeric adhesives have been increasingly applied in civil engineering construction due to its ease of installation, long service life, environmental stability, cost-effectiveness, and better bonding performance over continuous interfaces and increase stiffness. The goal of this dissertation is, therefore, to enhance the performance of light-frame wood construction to resist the adverse effects of extreme wind events through developing an affordable, efficient, long-service, and nonintrusive roof connections using elastomeric adhesives (i.e., polyurethane and polyether). Specifically, their research tasks are carried out: (i) experimentally evaluate wind uplift resistance of the proposed adhesive connections using the monotonic uplift loading tests; (ii) experimentally evaluate the wind-induced fatigue performance of the connections under the fatigue cyclic loading tests; and (iii) numerically evaluate a three-dimensional roof structure with the adhesive connections under uniform and ASCE design wind pressures. The results from the monotonic tests show that the addition of adhesives significantly increases the uplift load capacity by (200%–460%) and energy dissipation by (200%–750%). The fatigue loading tests consist of both constant amplitude and realistic varying amplitude cyclic loadings. These tests' results show that adding adhesives to connections significantly increases the endurance limit by 250~330%. From the numerical analysis, it is observed that the three-dimensional gable roof structure using adhesive connections has reduced roof sheathing stresses (200~400%) and deformations by 200% under uniform uplift pressure. Moreover, the adhesive roof structure can resist a Category 4 wind speed (130-156 mph) per the ASCE 7-16 specification.

Access Setting

Dissertation-Open Access

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