Experimental Investigation of the Behavior of Loaded Fiber Reinforced Concrete Beam Exposed to Fire

Abstract

The effect of direct fire on flexural behavior of small-scale fiber reinforced concrete beams under sustained loading has been studies through an experimental investigation. A mix of synthetic polypropylene structural macro and micro fibers has been used to obtain the effect of mixed fiber dosage on bearing capacity of simply supported beam under direct flame at its bottom face. The load-deflection, temperature gradient, spalling and durability time until collapse has been recorded and compared in different conditions. In order to know the effect of load level, the tests have been performed for 40% and 70% of the ultimate member capacity at normal temperature. Based on obtained test results, the use of macro synthetic fibers can increase the flexural ductility more than 50% and the durability time until failure up to 27%. The post fire behavior curves of all samples at the cooling phase have also been checked until the beam failure has been occurred including the weight losses due to spalling for both heating and cooling phases. A comparison with the results of conventional post fire loading tests on cooled samples showed that the results can be underestimated about 1.5 times compared to the direct fire test. It has also been shown that the level of sustained load directly affects the capacity, durability and ductility while the increase in the number of fibers do not necessarily improve the behavior in the same manner.