Performance Assessment of RC Columns Subjected to Non-Uniform Fire Exposure

Fire in buildings is one of the most destructive accidental loads that may occur during its design lifetime which can significant loss of life and property. Past building fire incidents indicated the necessity of incorporation of its effect in structural design approaches. Currently, the fire design of RC columns is based on the prescriptive method suggested in National Building Code (NBC) 2016 and IS 456: 2000 which only provides minimum dimensions and cover values for various fire durations with an assumption that all column faces will be subjected to fire exposure simultaneously. However, in realistic scenarios the columns may be subjected to non-uniform/uniform fire scenarios viz. 1-, 2-, 3-face fire exposures are non-uniform and all 4 face fire exposures is uniform, depending on their location in building and location of fire. As the modern design approaches are moving towards the performance based design, the assumption of uniform fire case does not holds good. This paper presents a comparative study of column capacities subjected to non-uniform fire exposures computed using Tan and Yao method and compares with column capacities computed by zoning method of Eurocode-2. In this study a set of columns of an existing educational building with different fire exposure conditions are considered. The collapse load for those columns is determined by both Eurocode-2 method which considers uniform fire case and Tan and Yao method which considers non-uniform case. The variation in their collapse loads from both methods is shown. The study also provides the actual fire rating of columns subjected to non-uniform fires which is an aspect of public fire safety in buildings.