Assessment of the Bending Behaviour of RC Beams Under Impact Loads with DIC

Abstract

Current times have shown that expenditure in defence assets is still necessary, including protective structures against impacts and blasts. Reinforced concrete (RC) structures are widely used for the construction of protective structures, but their real behaviour under dynamic loads is not completely understood yet. It is well known that RC structures are very sensible to brittle failure in the dynamic range, without taking advantage of the full bending capacity. However, if designed carefully, RC structures might still avoid brittle failures, developing an energy-absorbing bending failure. To evaluate the energy dissipation capacity of RC structures it is essential to include the influence of the dynamic effects, such as strain-rate sensitivity of materials and the progressive development of inertia forces.

The present paper studies experimentally the behaviour of three bending-critical RC beams, tested under low-velocity impact loads with different span-to-depth ratios. This type of test is very destructive and produces time-varying effects along the beam length. Hence, non-contact full field measurement techniques are an ideal alternative to traditional sensors. A state-of-the-art method, using digital image correlation (DIC) with a high-speed camera, has been employed to analyse the dynamic behaviour of the beams. The study has focused on the obtention of the sectional forces from the experimental data. The results have been employed to verify a numerical methodology to estimate internal forces distribution.