Date of Award

Spring 1-1-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Abbie Liel

Second Advisor

Ross Corotis

Third Advisor

George Hearn

Abstract

Snow loads account for a majority of roof damage and associated losses in the United States. The significant impact that snow related failures can have on the safety of people and the economic losses associated with business closures and repair costs make the design and mitigation of snow related failures very important. The purpose of this thesis is to develop models to predict roof snow loads, for use in performance-based engineering. Performance-based snow engineering can provide decision makers with a better, quantitative understanding of snow related risks.

Two probabilistic models were developed to have an understanding of the factors that affect the magnitude and distribution of roof snow load. The models developed are different from building codes and standards, where the model predicts the roof snow load for a single snow event instead of a 50-year maximum roof snow load used in design standards. The first model predicts uniform roof snow loads, given a ground snow load and roof characteristics; the second model predicts non-uniform drifting snow loads for multilevel roofs, given ground snow load, ground snow density and roof characteristics.

Ground snow load hazard curves, or predictions of the probability that a specified ground snow load level will be exceeded in a particular year, are available from weather data. The probabilistic load models can be used in a performance-based engineering framework to predict the likelihood that certain critical deflections or stresses will be exceeded. In this study, the models are used to predict deflections and stresses in an open walkway roof structure. Hazard curves were developed to show the probability of exceedance of a critical deflection for different ground snow loads. Hazard curves of this type can be used in analysis of other light-weight steel structures to develop metrics of structural failure and collapse that can help building owners decide whether to invest in retrofitting roofs.

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