BLAST ENERGY DISSIPATION USING VISCOELASTIC DAMPING PAD AND DESIGN OF A BLAST RESISTANT WALL

Abstract

This end term evaluation report gives an overview of the blast phenomenon and subsequent e ects on structures, behaviour of elastomer (viscoelastic materials) under cyclic loading, and an idea about blast energy dissipation using viscoelastic damping pads. It also gives idea of how a blast resistant wall can be designed despite being subjected to high impact loading. It has been seen that with suitable thickness of elastomer pad we can signi cantly reduce the blast pressure. Hence we can think about a proper blast resistant wall by dissipating blast pressure before it hits the wall. A linear spring { dashpot model has been built up and implemented in a common purpose nite element software ABAQUS. A parametric study of pressure reduction for di erent thickness of elastomer has been carried out for a particular type of viscoelastic material. Then using the transferred pressure for a speci c thickness of pad, a preliminary analysis and design has been carried out in SAP2000. However, the shear stress at base is much higher than the permissible value for the considered concrete grade and hence we have used a composite section of embedded I sections in concrete for the vulnerable ground support. Then again a rigorous modelling of the blast wall is done in ABAQUS with blast loading transferred through the pad. This includes constitutive modelling of concrete and steel. For steel elastic { perfectly plastic behaviour is chosen. Concrete Damaged Plasticity (CDP) model has been opted in ABAQUS to model brittle concrete material. A mesh convergence study has been performed to check the mesh sensitivity for the stress at a critical position on wall. Finally, full analysis is run and the damage contour is observed after one cycle of blast loading. To make the reinforced concrete structure safe, we have to make sure that there is no compression damage in the structure. Moreover, the valuable equipments inside the building have to be safeguarded against the surface blast induced ground vibration. For this purpose a trenching technique is adopted in between point of detonation and the face of the building. The trench is found to be very e ective even for a small constructable depth to reduce the shock ground acceleration by a great extent. This composite section with supporting shear walls along with a trench in between the detonation point and the face of the building make the whole structure stand safely after the explosion occurs