A New Approach to Derive Normalized Pressure Impulse Curves for Elastic Members

Abstract

A pressure impulse (PI) diagram is a useful preliminary design tool for structural members against blasts. An extensive amount of investigation has been undertaken to generalize PI curves, using single degree of freedom (SDOF) theory, for elastic structural members. In this study, a new original approach also using SDOF theory, relying on the concept of effective pulse shape, is presented for determining a PI curve for any elastic member. The advantage of this approach is that it can be applied to any given type of blast load. The techniques and equations involved in this approach are outlined. Then, to assess the accuracy of this approach, elastic normalized PI curves generated using the new approach are compared against those obtained using the traditional methods. Finally, this approach is compared against other simplified techniques for determining elastic normalized PI curves. Keywords: Blast load; pressure impulse curve; single degree of freedom (SDOF) model. * Corresponding author. 1350016-1 J. Earthquake and Tsunami 2013.07. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 04/12/15. For personal use only. J. Dragos & C. Wu Lindberg, 1976;Li and Jones, 2005;Ma et al., 2007]. They are typically derived using the SDOF theory, thus, if the parameters used to define the SDOF parameters are accurate, the PI curve will also be accurate. A normalized PI curve represents a family of PI curves which, coupled with a set of expressions for minimum impulse and minimum peak reflected pressure, can be used to quickly determine the PI curve of any given structural member. Li and Meng [2002] and Krauthammer et al. [2007] undertook a dimensional analysis on PI curves for elastic members subjected to different pulse loads corresponding to external blasts. Three pulse load shapes were investigated; exponential, triangular, and rectangular. Li and Meng [2002] then used this to investigate, and thus attempted to generalize, the effects of pulse shape on the elastic normalized PI curve. In their approach, they introduced two new parameters which are functions of the shape of the pulse load. These two parameters are then used to determine a general function for an elastic normalized PI curve. Campidelli and Viola [2007] then attempted to extend the approach to be more applicable for a wider range of pulse shapes, instead of just exponential, rectangular, and triangular. They found that for some other pulse shapes, the errors involved using this method were quite significant. The main limitation of this approach is that within different regions of a PI curve, the shape of the pulse load experienced by the structural member changes. This is due to the relative relationship between the load function and the structural response [Krauthammer et al., 2007].In this study, the pulse load actually experienced by the structural member, which is related to the structural response, is defined as the effective pulse load. In this paper, the concept of effective pulse load, defined differently to that of ...

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