DIRECT PREDICTION OF MAXIMUM DEFLECTION FOR PLASTICALLY DEFORMED STRUCTURES UNDER INTENSE DYNAMIC PULSE

After years of research, the membrane factor method (MFM) and saturation analysis (SA) method proposed and developed by Chinese scholars have been proven to be effective powerful tools in analyzing and predicting the large plastic deformation behavior of structural members such as beams and plates under intense dynamic loading such as impact and explosion. Based on recent results obtained by the combination of these two sets of theoretical tools, this paper proposes a direct prediction of deflection (DPD) method to predict the maximum (saturated) deflection of beams and plates subjected to intense loading pulses. This method does not rely on the governing equations of the structure; rather, it only needs to establish elementary equations based on the balance of internal and external work, whilst the former can be directly integrated from the expressions of relevant membrane factors. While the interaction between bending moment and membrane force (i.e., exact yield locus) is considered, the predictions on the maximum deflection can be simply obtained by solving the elementary equations, thus greatly simplifying the mathematical derivation. Compared with the complete solution, which considers both the exact yield criterion and the transient response phase, as well as the upper and lower bounds resulted from modal solution, the proposed DPD method can more simply yet still accurately account for the effect of membrane force on the load-carrying capacity of the structure in large deformation. Consequently, this DPD method can provide a series of calculation formulae on the maximum plastic deflection of beams and plates, which are more concise than complete solutions, more accurate than modal solutions, and easier for the use in engineering design. Combined with a refined pulse equivalency technique, this DPD method is expected to be further extended to other structures under general pulse loading and achieve a wide range of engineering applications.