Abstract: The relative simplicity of the single-degree-of-freedom (SDOF) method is one of the primary reasons why it is commonly used for design and analysis of blast resistant structures. The SDOF method describes the behaviour of a complex system by the response of a single ordinate. The solution to the resulting dynamic equation of motion may be easily obtained by graphical design aids, by applying an equivalent static force or by complete inelastic response time history analysis. The accuracy of the SDOF method is directly proportional to the level of refinement incorporated in estimating structural stiffness during elastic, cracked, and post yield regions of force-deformation relationship.
This paper describes an analysis technique to generate force-deformation characteristics of reinforced concrete members subjected to blast loading, for use in SDOF blast analysis. The following structural response mechanisms are incorporated in the analysis technique: i) the strain rate effect on material properties; ii) formation and progression of plastic hinging; iii) strength decay beyond peak load resistance; iv) strength and stiffness increase by externally bonded fibre reinforced polymer (FRP) sheets; v) prediction of FRP debonding behaviour; and vi) the computation of equivalent load-mass transformation factors. The resulting force-deformation characteristics are used to generate displacement time-histories of structural response using SDOF dynamic analysis. The validity of the analytical method is illustrated by comparing SDOF displacement time-histories with those obtained experimentally. Experimental displacement time-histories were generated through simulated blast testing of reinforced concrete slabs and walls using the University of Ottawa Shock Tube. The significance of generating detailed force-deformation relationship on predicted SDOF member behaviour is discussed and recommendations are made for research and practice.