Snow Loading—Practicing Engineers and the Code: Fid-Bau Portal

Snow Loading—Practicing Engineers and the Code

Barnett, T. / Nuttall, B. / Wilcox, C.

There is widespread concern among practicing engineers that the clarity and usability of the building codes have radically diminished as the size and complexity of the codes have increased. One tool for assessing the ability of practicing engineers to consistently and reliably implement the code is the use of Trial Design Problems. The Trial Design Problem process consists of (a) developing a common engineering problem, (b) enlisting practicing engineers to complete the engineering problem using the code, (c) evaluating the engineering solutions submitted by practicing engineers, and (d) conveying the results of the problems to the engineering community and code development committees. The Design Practices Committee of the Structural Engineering Institute recently completed a Trial Design Problem related to snow loading per the ASCE 7-05 code and 2006 IBC. The quantitative analysis of the Trial Design Problem solutions indicated that while practicing engineers were able to consistently apply most of the basic ASCE 7 snow load provisions, some concerns with consistent application of the provisions were identified, including: (1) Using ASCE 7-05, approximately 10 percent of the practicing engineers incorrectly identified the roof exposure condition resulting in an under-estimation of the exposure coefficient and the snow load. (2) Using ASCE 7-05, over 20 percent of the solutions did not account for the projection drift load requirements at the parapet of the low roof. (3) Using ASCE 7-05, for those solutions which included a calculation of projection drift at the parapet, the value for the roof length upwind of the parapet in projection drift calculation was not uniformly selected. Based on the results of the quantitative analysis of the Trial Design Problem solutions, recommendations were made for clarifications to the Snow Load provisions of ASCE 7-05.