PRECAST DOUBLE TEE ROOF COLLAPSE INVESTIGATION - A CASE STUDY

摘要

During heavy rains in 2009, a portion of a concrete double tee (DT) roof system of an industrial building collapsed. Subsequently, an investigation ensued in order to determine the cause, and if other DT members were damaged. Remaining DT members with deflections between one and three-and-a-half inches, under dead loads, were discovered and the authors were tasked with determining the cause of the deflection as others had opined the deflections were due to long-term creep. This paper outlines the investigative process including historical loading events/collapse, weather research, and methodology used to determine the cause of the large deflections. Through investigation, it was determined that the collapse was due to significant rainfall that occurred in a short time, coupled with an inadequate roof drainage system and poor maintenance of roof drains. Calculations showed that the excessive deflections were not due to long-term creep but to a one time loading event that caused the permanent strain set in the DT strands. Although prestress/precast concrete structures are resilient, this case study highlights the importance of proper design and maintenance. Architects, engineers, building owners, and maintenance personnel can all learn lessons through this case study.