Collapse of Two Steel Buildings after Snow Accumulated on Their Roofs

In early February 2017, near Yakima, Washington, snow accumulation on the roof triggered the collapse of a 125 foot by 85 foot single-story, steel building (Building 1) originally constructed in 2011. Two days later, about 100 feet away, a separate, similarly constructed building (Building 2), originally constructed in 2012, collapsed due to similar circumstances. The authors were hired to investigate the cause of the collapses for potential subrogation. Security video recorded the entire sequence of the Building 1 collapse. From the video, the snow depth on the roof was estimated to be 15 to 22 inches. Field investigation found that flange bracing for the steel column frames was not installed as specified. Each column frame was observed to have buckled at the same location as the missing bracing. The collapse was determined to be caused by the omitted bracing that reduced the column's capacity to resist the imposed load.