Journal of Loss Prevention in the Process Industries 12 (1999) 199–205 Modelling the response of masonry structures to gas explosions C.W. Wong * , M. Karamanoglu School of Engineering Systems, Middlesex University, Bounds Green Road, London N11 2NQ,UK Abstract In practice no system is infallible no matter how stringent the safety standards and procedures are concerning the release and use of gas in the process industries. Structural damage arising from an internal explosion often has serious repercussions. It is, therefore, imperative for engineers to be able to predict the extent of the damage that may occur, and to develop means to mitigate such effects. An accurate prediction of the structural behaviour requires an accurate formulation of the material’s failure criteria. Experimental studies have shown that the response of masonry structures to gas explosions is non-linear. The cracking of masonry in tension and crushing of the material in compression are the major contributory sources of non-linearity. This paper presents a method of predicting the non-linear response based on the formulation of a numerical model to describe the material’s failure criteria. The model has been validated using full-scale explosion test data provided by the Building Research Establishment in the UK. Although some minor discrepancies have been observed, overall the simulated values correlated very favourably with the actual test data. The probable causes of discrepancies are also discussed at the end of this paper.  1999 Elsevier Science Ltd. All rights reserved. Keywords: Gas explosions; Structural safety; Masonry structures; Structural modelling 1. Introduction 1.1. General Accidental explosions within the process industries pose a major risk to the workforce and also to the integ- rity of the building. Experimental studies have shown that the response of masonry structures to gas explosions is non-linear (Ellis, Beak & Colwell, 1993). The major contributory sources of non-linearity are due to the pro- gressive cracking of the material in tension and the crushing of the material in compression during loading. The criteria determining failure depends on the magni- tude and combination of the multi-axial stresses that are present within the material. Currently, this cannot be handled easily by the Codes of Practice nor are there any empirical formulae available that can quantify the damage based on the combination of these stresses. This paper presents a step-by-step formulation of a * Corresponding author. Tel.: + 44-181-362-5241; fax: + 44-181- 362-5245; e-mail: c.wong@mdx.ac.uk 0950–4230/99/$ - see front matter  1999 Elsevier Science Ltd. All rights reserved. PII:S0950-4230(98)00058-8 numerical model to simulate the material’s failure cri- teria under loading. To implement the model, a computer program has been developed which complies with the specifications dictated by the numerical model. This pro- gram has been incorporated into the BERDYNE finite element software package to enable the response of masonry structures to gas explosions to be simulated. The formulation of this numerical model was carried out in parallel with full-scale explosion tests undertaken by the Building Research Establishment (BRE). The principal objective of the BRE experiment was to pro- vide experimental data for the validation of the numeri- cal model. Full-scale explosion tests were carried on both masonry and concrete panels. The comparative study presented in this paper refers to explosion tests no. 12 to 23, which were carried out on the masonry panel. 1.2. Failure criteria Brickwork exhibits distinct directional properties because of the mortar joints which act as planes of weak- ness. Ideally a failure criterion for brickwork should be expressed in a format which allows the influence of the