Dynamic Characterization of a Real-Scale Prestressed Concrete Beam Tested Until Failure

Abstract

In this work, dynamic characterization of a simply supported beam is carried out during different steps in a failure load test. The main goal of this work is to evaluate the evolution of the structural dynamic parameters of the beam with different status of damage. Real-scale prestressed concrete beams are tested to investigate its shear behaviour as a part of a large research program at TU Delft. Four dynamic tests are performed at different damage status of the beam: firstly in the initial or undamaged condition; secondly after the first flexural cracks; then, after shear cracking; and finally in the full damaged condition. The dynamic excitation is performed with an impact load at fixed location on the top of the beam and the vibration data is recorded by three different systems. The first one is a cost-effective and open source monitoring equipment, consisting of seven low-cost accelerometers. The second system is based on five trusted high performance accelerometers. The last one is a commercial alternative consisting of four high accuracy piezoelectric accelerometers. Acceleration data is analysed afterwards using Operational Modal Analysis techniques to obtain modal frequencies, modal shapes and damping of the structure in the different states. The obtained dynamic behaviour of the structure and its results are discussed and compared. It is concluded that a change in the frequency of the first flexural mode is only observed when the damage in the beam is very significant, while no changes are observed with the occurrence of flexural and shear cracks.