Mechanical behaviour of A- Ⅲ steel rebars under monotonic loadings at seismic strain rates

摘要

As the reinforcing bars used in concrete structures located in earthquake-prone areas experience strain rates higher than normal quasi-static ones, it is necessary to have a comprehensive understanding of the behaviour of such materials under these rates of loading. In this work, in order to study the behaviour of grade A-III reinforcing-bar steel (based on the GOST standard, a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification), a number of monotonic tests on its tensile and compressive strength on (short and long) specimens at various strain rates, 0·002, 0·01, 0·02 and 0·04 s ~( −1 ) , experienced during earthquakes, were carried out. Similarly to the findings of others, the modulus of elasticity did not change with the rate of strain. However, while yield and ultimate stresses increased, ductility decreased as the strain rate increased. The parameters of the Cowper–Symonds and Johnson–Cook material models and the dynamic increase factor curves for this type of steel were obtained and compared with their counterparts for similar grades of reinforcing bar steels. Besides, the effects of strain rates on buckling behaviour of longer specimens were studied.