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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 86
Edited by: B.H.V. Topping
Paper 225

A Complete Nonlinear Finite Element Analysis for the Effects of Surface Explosions on Buried Structures

N. Nagy, M. Mohamed and J.C. Boot

School of Engineering, Design and Technology, University of Bradford, United Kingdom

Full Bibliographic Reference for this paper
N. Nagy, M. Mohamed, J.C. Boot, "A Complete Nonlinear Finite Element Analysis for the Effects of Surface Explosions on Buried Structures", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 225, 2007. doi:10.4203/ccp.86.225
Keywords: buried structure, soil-structure interaction, FEM, blast loads, crater, damage.

This paper presents a new complete model simulating the whole system of a buried concrete structure under the effects of blast loads with a particular focus on the response of the buried structure. A two dimensional axisymmetric nonlinear finite element modelling was developed, using a numerical code ABAQUS/Explicit [1]. The Arbitrary Lagrange Euler Coupling formulation is used to model the soil region near the explosion to eliminate the distortion of the mesh under high deformation while the conventional finite element method is used to model the rest of the system. The elasto-plastic Drucker-Prager Cap model is used to model the soil behaviour. The explosion process was simulated using the Jones-Wilkens-Lee (JWL) equation of state and the concrete damage plasticity model to simulate the concrete behaviour. The contact interface between soil and structure is simulated using the general Mohr-Coulomb friction concept, which allows for sliding, separation and rebound between the buried structure surface and the surrounding soil. The behaviour of the whole system is evaluated using a numerical example in which the structure is modelled as cylindrical reinforced concrete structure with constant thickness of 0.5 m through all its elements and internal height of 3.0 m. The structure is buried in the soil at depth of 4.0 m below the ground surface. The structure was centred under the surface explosive charge.

The results obtained for the example problem indicate that there is a good agreement between crater diameter and that obtained by previous investigations obtained by [2]. The results also highlight the significance of the first peak of the structural response to the explosion load, and the overriding significance of different parameters. In addition the importance of the interface effects between soil and structure including the slip action has been demonstrated.

The model proposed herein is able to capture the realistic behaviour of the buried structure under the blast loads taking into account the effect of interface characteristics and all the physical processes with smooth numerical execution.

Moreover the proposed model makes use of a variety of highly nonlinear material models to enhance the reliability of the simulation results. The new model provides researchers and designers with a computational tool for designing of buried concrete structures. Through the model, the damage failure mode, the damage failure locations, the extent of strength and serviceability improvement due to the chosen dimensions and locations can be obtained.

ABAQUS Theory Manual, Version 6.5 published by Hibbitt, Karlsson and Sorensen Inc. USA. 2003.
D. Ambrosini, B. Luccioni and R. Danesi, "Influence of the Soil Properties on Craters Produced By Explosions on the Soil Surface", Mecánica Computacional, XXIII, 2004.

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