Experimental study of concrete filled steel tube composite beam under hogging moment

Abstract

The main objective of this work is an experimental study of the concrete filled steel tube (CFST) composite beam under the influence of a hogging moment. The specimens are consisting of a steel tube filled with lightweight or normal concrete (CFST) and a reinforced concrete slab, perfobond connector is used to connect the steel tube and concrete slab. Seven specimens were cast and tested, five parameters are studied, specimen length, the strength of concrete which filling the steel tube, the influence of filling the steel tube, and existing of a concrete slab. To study the behavior of specimens the flexure test was done under hogging (negative) moment. The testing results including ultimate load, crack, load-deflection curve, and slip at the end and one-third span of the tested beam. The short specimen has a greater ultimate load than other specimens but a smaller bending moment. The local buckling appeared in the steel tube at a load ranged from 83.7% to 96.7% of the ultimate load, the ultimate load of the hollow steel tube composite beam is decreasing by 75.69% compared with the reference specimen, also the ultimate load was increased when the concrete compressive strength which filled steel tube increased. The slip was measured in two locations of the specimen, the slip at the end of the specimens is less than the slip in one-third of the specimens at the ultimate load.