International Journal of Engineering and Technology Innovation, vol. 6, no. 4, 2016, pp. 284 - 293 Influence of Charge Shape and Orientation on the Response of Steel-Concrete Composite Panels Abraham Christian * , Lado Riannevo Chandra, Satadru Das Adhikary, Khim Chye Gary Ong National University of Singapore, 1 Engineering Drive 2, Singapore 117576, Singapore. Received 05 June 2016; received in revised form 15 August 2016; accepted 17 August 2016 Abstract Blast design codes usually generalize the shape of the charge as spherical or hemispherical. However, it was found that the blast overpressure of cylindrical charges differ greatly when compared with relevant analytical results generated with the charges assumed to be spherical. The objective is to use fully coupled 3D multi-material arbitrary Lagrangian Eulerian (MMALE) modelling technique in LS Dyna software to simulate the cylindrical charge blast loading. Comparison of spherical and cylindrical charge blast simulation was carried out to show the influence on peak overpressure and total impulse. Two steel-concrete composite specimens were subjected to blast testing under cylinder charges for benchmarking against numerical results. It was found that top detonated, vertical cylinder charge could give much higher blast loading compared to horizontal cylinder charge. The MMALE simulation could generate the pressure loading of various charge shape and orientation to be used for predicting the response of the composite panel. Keywords: blast, charge shape, MM-ALE, steel-concrete composite 1. Introduction Typical blast results, both experimental and numerical, as presented in many scientific papers usually provide details on the nature, mass and stand-off distance of the explosives used. However, the shape of the charge and the location of the detonator are rarely mentioned due to the assumption that eventually the blast wave shape transition into one typical of equivalent spherical or hemispherical charges. This approximation may be acceptable when the distance of interest is large (typically Z > 4 to 5 m/kg 1/3 [1] or greater than 3 m/kg 1/3 [2]). Nevertheless, it has been reported that the shape and orientation of the charge has considerable effect in close range blast scenarios, resulting in significant differences with regards to the predicted and measured pressures [3-5]. Current standards for blast-resistant design of buildings, e.g. UFC-3-340-02 [6] assume that the charge is spherical and ignore the effect of charge shape. Predictions performed using the UFC-3-340-02 underestimates the reflected overpressures when the charge is cylindrical and oriented vertically. However, the reflected overpressure is overestimated when the charge is either spherical or cylindrical, and in the latter oriented horizontally. For cylindrical charges, the ratio of charge length (L) to diameter (D) affects the pressure distribution and impulse in the immediate vicinity of the explosive; for large values of L/D, most of the energy is directed in the radial direction whereas for small values of L/D, and most of the energy is directed in the axial direction [5]. * Corresponding author. E-mail address: abraham.chr@nus.edu.sg