3-D Modeling of Pyramid Cover Systems to Retrofit Hexagonal Core Sandwich Structures

Document Type : Original Article

Authors

1 Ph. D. Egyptian Engineering Military Department.

2 Professor, Structural Engineering Department, Faculty of Engineering, Ain Shams University, Cairo.

3 President of Technical Research Department, Cairo, Egypt.

4 Associate Professor, Civil Engineering Department, Military Technical College, Cairo, Egypt.

Abstract

Abstract
Fortified structures are considered very important structures in military enginee ring
fields due to a continuous development of conventional weapon. The f ortified
structures are constructed above or underground. Blast wave causes structure damages
based on explosive weight and distance between charge and target. Armoured doors are
used in fortified structures in order to protect people, weapons, and ammunition from
blast waves. Sandwich armoured steel door may be damaged as it is hit by blast waves.
In the present study, the prediction of the sandwich armoure d steel doors performance
under the impact of blast wave effect is highlighted. A 3-D numerical model is
proposed to study pyramid cover system (PCS) layer to retrofit sandwich armoured steel
doors using a 3-D nonlinear finite element analysis (FEA). Hexagonal core sandwich
(XCS) doors are used so as to study blast mitigation using the PCS layer. Blast field
test is implemented to understand performance of armoured XCS doors with and
without the PCS. The study presents a comparison between the field blast test and the
finite element analysis results to assess the accuracy of the proposed 3-D finite element
model (FEM). The constitutive model for this analy sis contains elasto-plastic materials.
An elasto-plastic model is employed to represent the armoured doors, the concrete wall
of the fortified structure, and the PCS layer. The proposed model is programmed and
linked to an available computer program Auto dyn3D (2005).
The 3-D nonlinear FEM takes into account the effects of the blast load, the connection
between the armoured doors and the frame fixed to the concrete wall, and the PCS
layer. The effects are expressed in terms of displacement -time history of the sandwich
armoured doors and pressure-time history on armoured XCS doors as the explosive
wave propagates. The behavior of the sandwich armoured XCS doors sheltered by the
PCS is investigated and presented under blast waves obt ained from detonating 1-kg, 2-
kg, and 3-kg TNT explosive charge at a scaled distance of 1 m.

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