Blast Resistant Design
Full Session with Abstracts
338132-13 - A BLAST TESTING AND NUMERICAL STUDY FOR OPEN WEB STEEL JOISTS
Saturday, April 21
10:00 AM - 11:30 AM
This paper provides important findings that can be used for more accurate blast assessments of open web steel joists. The findings can also lead to more comprehensive future studies on the subject, and result in significant improvements in addressing the blast-resistance of buildings with OWSJs.
Open web steel joists (OWSJ) are widely used in various building structures in the US and around the world. These joists have proven to be a good option for light-weight framing to carry gravity and environmental loads on roofs and floors.
However, due to limited data on OWSJ performance under blast loads, it can be a challenge for structural engineers to determine the ultimate blast capacity of the OWSJs they encounter. The current blast design criteria for OWSJ appear to be conservative by permitting rather small deformation, considering some explosion accident photos show large deflection of certain OWSJ without collapsing. Adding to the seemingly conservative blast design criteria, the commonly used simplified analysis techniques, such as single degree of freedom analysis, tend to over-predict the deformation of OWSJ under blast loads.
Many existing buildings with OWSJs that are subjected to blast loads include those located in chemical processing plants or sensitive government buildings. When assessing the blast response of the OWSJs, their deformation is often calculated by simplified analysis tools and compared to current response criteria. If the calculated deformation exceeds the response criteria, the OWSJ is considered failed and structural retrofit may be in order.
Structural blast retrofit for roof structures consisting of OWSJs are often difficult and rather costly. Therefore, a more accurate assessment of OWSJs’ blast resistance can be very beneficial.
A blast testing and numerical study for OWSJs was carried out to investigate the blast response and failure modes of two specific OWSJs. The results showed that 1) these joists performed much better than predicted by the simplified analyses using the current response criteria, and 2) the joists did not fail in the more brittle shear mode as determined by some of the commonly accepted response criteria.
This paper discusses the approaches and results of the study. This study can lead to more comprehensive future studies of the blast resistance of OWSJs, which should result in significant improvements and potential cost savings in addressing the blast-resistance of buildings with OWSJs.