The Effects of Snow Loading on Lightweight Metal Buildings with Open-Web Steel Joists

Geis, Jamie Marie

Graduate Thesis Or Dissertation

The Effects of Snow Loading on Lightweight Metal Buildings with Open-Web Steel Joists Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/n583xv25x

Abstract

The implications and consequences of snow loading on buildings can be significant, with failures resulting in damage, casualties, and building downtime. This study seeks to probabilistically quantify the effects and consequences of snow-induced building failure and to examine the behavior and performance of lightweight metal buildings with open-web steel joists to snow overloading.One part of the study focused on the quantification of national and worldwide building failure trends. In terms of snow-induced incidents, 1,029 national and 91 international building failures revealed patterns of roof failure attributed to the amount of snow, rain-on-snow mixes, and building problems. Warehouses, factories, and commercial buildings were most commonly affected.The second part of the study centered on the analysis of open-web steel joist roof systems, which may be particularly vulnerable to snow-related failures. Seventy-one archetypical lightweight metal buildings were identified, each with different design characteristics that may have an influence on structural response. Nonlinear simulation models for seven archetypical buildings were developed and subjected to pushdown analyses under uniform snow loads. Each building was modeled independently and building responses were compared.Results from the nonlinear static pushover analyses show that the open-web steel joist roof systems yield when loaded with roof snow loads about double their design roof snow load capacities. This overload capacity implies that there is an adequate level of built-in safety when considering snow overload due to extreme or unanticipated snow events, such as rain-on-snow or drifted snow. All buildings exhibited the same type of response trend, with elastic linear responses up to the point of yielding, and inelastic strain hardening responses after the point of yielding. Through a deflection-controlled static pushover analysis, one building was analyzed with increasing incremental deflections at mid-span until the joist's maximum deflection was achieved, which resulted in major in-plane yielding of the top and bottom chords and movement of the neutral axis of the joist into the top chord. Advancement and development of the building models in this study will lead to a broad and representative set of models aimed with the intention of furthering our understanding of open-web steel joist roof systems.

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