Bond strength of RC beams subjected to cyclic thermal loading

Bond strength of rebar lap splice in reinforced concrete beams has been investigated experimentally when they are subjected to cyclic thermal loading. One hundred and eleven RC beams of 100 x 150 x 1200 mm size were tested under flexure for the bond behavior of splices under four point loading. The beams were reinforced in tension zone only with a single Thermomechanically treated (TMT) steel bar of 8, 10 and 12 mm diameter. The beams were subjected to a number of thermal cycles varying from 7 to 28 with peak temperature taken as 100,200 and 300 degrees C. The effects of thermal cycles on the crack pattern, failure mechanism, first crack load and the bond strength have been discussed. The loss in bond strength is found to be more for 12 mm rebar diameter which is due to the splitting of concrete cover due to the lateral expansion of rebar. Beams reinforced with 8 and 10 mm diameter bar exhibited comparatively less damaging effects. The bond strength of the beams at lower temperature cycles of 100 and 200 degrees C is either at par with control or even more but it reduces by up to 44% at higher temperature (300 degrees C) depending on the severity of thermal loading. The results of study emphasize the need for developing appropriate guidelines for the design of RC structural elements used in comparatively high temperature environment with cyclic thermal loading conditions. (C) 2012 Elsevier Ltd. All rights reserved.