Strain rate is a vital factor for the design of a RC (Reinforced Concrete) member under blast loading. At present,it is not scientific and cut down the believability to assume the strain rate is a constant or to take the loading rate insteadof the strain rate. In this paper, an analytical model of RC beams with flexible supports is presented, in which theelasticity, damping, and lumped mass of flexible support are taken into account. Theoretical method of strain rate for RCbeam with flexible supports under blast loading is developed based on Euler-Bernoulli beams. It is indicated that themaximal values of strain rate are increased as the blast impulses and the overpressures increased, but the loading rateshave not obvious influences on the strain rates. The maximal values and the vibration frequencies of strain rate are increasedas support stiffness increased. The maximal values of strain rate are decreased as support damping increased, andthe attenuation values of strain rate are accelerated. Calculations show that it will result in an overestimation of DIF (DynamicIncrease Factor) to take the loading rate instead of the strain rate.
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