Understanding Damage Mechanism of Concrete Slabs Exposed to Contact Explosion with Innovation of Efficient Retrofitting Solution

Abstract

Concrete structures exposed to contact explosions, can behave brittlely accompanying highly damage in a certain portion like concrete cratering, spalling or fragmentation, and steel bar rupturing. Fragmentation of high speed resulting from concrete spall may cause severe human accidents. So it is important to reduce concrete fragments and improve collapse resistance of the structural element. A new retrofitting strategy is introduced in current investigation which prevents fragmentation with complete efficiency . To mitigate contact explosion effects on civil structures & infrastructures, a new type of concrete named UltraHigh-Performance-Concrete (UHPC) is now widely studied, examined and applied practically in many projects worldwide. UHPC has a superior mechanical properties like high strength (compressive and tensile), large energy absorption capacity beside good workability and anti-abrasion ability compared to normal strength concrete(NRC). Most of the recently published experiential work concentrated on the behavior of UHPC slabs under the effects of far or near blasts. on the other hand, the contact explosion tests are relatively limited experimentally Because of the risky procedure and security restrictions and expensive in terms of test preparation and measurements of results. So, the real and accurate finite element models are needed to address this gap and understanding the real contact-explosion behavior of both NRC and UHPC slabs. The numerical analysis based on nonlinear dynamic finite elements allows gaining insight into the complex damage mechanisms occurring in the concrete plates and not directly noticeable & recorded by difficult experimental tests. In this study, coupled smoothed particle hydrodynamics (SPH) method and finite element method is utilized to simulate the contact blast tests. Numerical results are compared with the experimental observations, and the feasibility and accuracy of the numerical model are validated. The validated numerical model introduced a useful and efficient tool for designing potential blast-retrofitting solutions which can completely prevent the local material damage and fragmentations in both NRC & UHPC slabs subjected to contact blast loading.