Effect of Heating and Cooling on Axially Restrained RC Columns with Special-Shaped Cross Section

This paper describes the performance of 12 axially restrained RC columns (four for each type of cross section, i.e., +-, T- and L-shaped cross section) under fire conditions that were recently finished in South China University of Technology. The main objective of the paper is to investigate the effect of axial restraint on RC columns during both expanding and contracting phases. The RC columns were all initially concentrically loaded and subjected to ISO834 standard fire on all sides. Axial restraints were imposed at the top of the columns to simulate the restraining effect of the rest of the whole frame. Different degrees of axial restraint were obtained by varying the length of the restraining beam. The boundary conditions of the columns were considered as fixed-fixed for all tests. It is found that restrained RC columns behave quite differently to isolated ones. No typical 'runaway' failure of isolated RC columns was observed in the fire test. Finally, the finite element software, SAFIR, is employed to conduct a numerical analysis of the tests.