Steel Bar Joist Performance: Design Deficiencies and Defectsby John F. Duntemann, Elstner Assoc, Inc, Northbrook, United States,
Donald F. Meinheit, Elstner Assoc, Inc, Northbrook, United States,
Abstract: Several failures of steel bar joist roofs have been investigated by the authors in the past decade. Many of these failures or performance problems have corresponded to bar joists manufactured in the 1960's and early 1970's. The in-situ performance, failure modes, disparities between the prescribed allowable load and actual capacity, deficiencies from manufacturing, and metallurgical defects are discussed. Case studies are reviewed and include discussions on open web (J and H-Series) and longspan (LH-Series) steel joists. Loadings from snow drift and ponding are generally the roof loadings that have caused the problems, however, relatively uniform loads have also caused problems on bar joists with metallurgical defects. Failure investigations have shown that performance can be a function of the manufacturing process, material chemistry, welding and/or design details.
Subject Headings: Bars (structure) | Joists | Material failures | Failure analysis | Snow loads | Failure modes | Structural failures
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