Cyclic loading test procedure, including gravity load, on RC beams for different failure modes

Experimental test setups and loading histories should reproduce the real conditions present in structures. However, most of cyclic tests procedures on beams do not include gravity loads in the loading history. This can lead to results differ from reality. An experimental campaign was carried out to access the failure mode of beam specimens subjected to reversed cyclic loading and simultaneous gravity load. Specimen CB1 reported in this paper is a continuation of the work previously reported by Gião et al. [1]. Specimens were tested in the Laboratory of Heavy Structures of Department of Civil Engineering, Faculty of Science and Technology of the Universidade NOVA de Lisboa. The loading history in both specimens was a combination of force and displacement control, respectively force control for maintaining a constant value of gravity load and displacement control for the cyclic displacement history. Since the objective of this study was the evaluation of the cyclic loading test procedure versus failure modes, the reinforcement ratio of specimen CB1 was different from specimen CB0, in order to modify the failure mode previously observed in specimen CB0. Specimen CB0 failed in flexure by concrete crushing and buckling of the compressed reinforcement bars, while specimen CB1 presented a flexural failure by rupture of the tensile reinforcement bars. Specimens CB0 and CB1 were simulated numerically in ATENA 3D Engineering software, which is a software designed especially for reinforced concrete structures. The concrete and reinforcing bars characteristics used in modelling were determined from laboratory tests, while interface bond-slip characteristics were based on Model Code 2010. Numerical models were tested under monotonic loading and experimental tests under cyclic loading. The results were comparable in terms of maximum load and ultimate deflection. Numerical non-linear analysis was able to predict the failure modes correctly and the obtained crack patterns were similar to the experimental ones.