PSI - Issue 81

Olena Romashko-Maistruk et al. / Procedia Structural Integrity 81 (2026) 269–275

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these correction coefficients has been found. And it should be, since such a relationship exists between the characteristics themselves and can be described by the elastic-plastic coefficient of concrete k .

Nomenclature  stress  strain f

strength

elastic modulus

E

strain rate coefficient

έ k

dynamic increase factor

DIF

2. Literature review Usually, the change in compressive strength of concrete under dynamic loads is estimated by the known dynamic increase factor c ck d ck f f DIF / ,  . The vast majority of researchers (Rasch (1962); Mainstone (1975); Dilger et al. (1984); Malvern et al. (1985); Bischoff and Perry (1991); CEB-FIP (1991); Williams (1994); Fujikake et al. (1998); Tedesco and Ross (1998); Grote et al. (2001); Fib (2012); Long et al. (2016); Lee et al. (2017); Sun et al. (2022)) associate it with the strain rate of concrete and only according to Cowell (1966), Dilger et al. (1984), Kono et al. (2001), Othman and Marzouk (2016) c DIF it also depends on the class of concrete, which is confirmed by the results of numerous experimental studies. The strength of concrete under long-term loads is estimated as a fraction of its standard strength under static loads ck l ck lc f f / ,   (relative level). This level is only in some cases associated with the class of concrete and is in no way related to its strain rate (Graf and Brenner (1937); Shank (1949); Rüsch (1956); Sell (1959); Awad and Hilsdorf (1971); Stöckl (1972); Smadi et al. (1985); Iravani and MacGregor (1998); Tasevski et al. (2018)). The available results of studies of the relative deformability of compressed concrete under dynamic loads 1, 1 / d c с   are extremely few today. Moreover, by their nature they are also very contradictory. Thus, according Hjorth (1976), Hughes and Watson (1984), Dilger et al. (1984), the deformability of compressed concrete decreases with increasing strain rate, and according Watstein, (1953), Rostasy et al. (1984), Bischoff and Perry (1991) on the contrary, it increases without any logical justification. The vast majority of dependencies for predicting the deformability of compressed concrete are associated exclusively with its strain rate. More unambiguous are the results of studies of the relative deformability of compressed concrete under the action of long-term loads 1, 1 / l c с   in conditions of its "creep". Almost all researchers (Graf and Brenner (1937); Shank (1949); Rüsch (1956); Sell (1959); Awad and Hilsdorf (1971); Stöckl (1972); Smadi et al. (1985); Iravani and MacGregor (1998); Tasevski et al. (2018)) indicate an increase in the relative deformability of compressed concrete under conditions of "creep". All dependencies for predicting the deformability (creep) of compressed concrete are quite complex, related to the level of stresses, but not to the strain rate of concrete. In general, the change in the modulus of concrete elasticity under the action of dynamic loads d c с E E / , has been studied by many scientists. All the proposed dependences on its relative growth are mostly associated only with the strain rate of concrete (Fujikake et al. (1998); Dejian and Lu (2008); Shi et al. (2020)). The relative decrease in the modulus of concrete elasticity under "creep" conditions is quite obvious, but no dependences for its prediction have been proposed to date. Thus, the above analysis shows that the interdependence of the main physical and mechanical characteristics of concrete with a change in the strain rate remains unexplored to date. 3. Problem statement and solution method In general, these studies are aimed at establishing the relationship between the strength and deformation characteristics of compressed concrete when changing its strain rate. A complex integral parameter that connects the specified characteristics is the elastic-plastic coefficient of compressed concrete. Therefore, establishing the analytical dependence of this coefficient on the strain rate of concrete will allow predicting its deformability under any type of loads. The basis of these studies is a generalized deformation-force model of concrete resistance to force influences of any type and intensity (Romashko and Romashko (2019b); Romashko (2021)), as well as the well-known law of conservation of the specific potential energy of materials deformation even at the moment of their destruction (Romashko and Romashko (2019a); Romashko and Romashko-Maistruk (2022)).