مقاله انگلیسی رایگان در مورد پاسخ های لرزه ای سازه های بتنی با توجه به میزان فشار – الزویر 2018

Reinforced concrete (RC) structures have been extensively used in multistory and high-rise buildings due to their advantages of excellent structural integrity, durability and high economic efficiency. During their service periods, RC structures may be subjected to strong earthquake ground motions. The strain rates of reinforcing steel and concrete materials at critical sections of RC structural members may reach as high as 1 s1 . Fu et al. [1] and Bischoff and Perry [2] systematically reviewed the compressive behavior of concrete at high strain rates, while the strain rate effect on the tensile strength of concrete was reviewed by Malvar and Rose [3] and Thomas and Sorensen [4]. It was reported that the compressive and tensile strength of concrete can be obviously increased at the strain rates induced by seismic loading. Moreover, the tensile strength of concrete is more susceptible to increase than the compressive strength. In addition, the mechanical properties of reinforcing steels under seismic strain rates were also examined by many researchers through dynamic loading tests [5–12]. The experimental findings indicated that the yield strength and ultimate tensile strength of reinforcing steels increase linearly with the logarithmical increase of strain rate, and the effect of strain rate on the lower strength reinforcing steels is more significant as compared with that on the higher strength reinforcing steels. In current literature, many investigations are focused on the effects of loading rates on the seismic behavior of RC members. The dynamic tests of simply supported and doubly reinforced beams were performed by Bertero et al. [13] to assess the influence of loading rate on the behavior of RC beams. It was found that the stiffness before the first yielding of reinforcing steel for the beams under the higher loading rate increases about 10% as compared with that for the beams under the lower loading rate. Significantly increases in the initial yield strength were also observed, but the effect of loading rate on the ultimate strength, flexural failure mode, measured strain, curvature and deflection ductility factors of the beams is not evident. The similar conclusions were obtained by Kulkarni and Shah [14], who carried out the experimental tests of seven pairs of RC beams subjected to static and high loading rates. It was also reported in the aforementioned studies that the failure mode of the RC beams may shift from brittle shear failure at the lower strain rate to the ductile flexural failure at higher strain rates. Otani et al. [15] performed a series of tests on four pairs of cantilever RC beams under static and dynamic loads to study the potential effects of strain rate. The specimens were tested in the vertical position and loaded horizontally using a dynamic actuator. The results showed that the seismic strain rate increased the flexural resistance of RC beams by 7%–20%. Li and Li [16] studied the dynamic behavior of simply supported RC beams with different shear spans through dynamic tests, in which the influence of loading rate on the bearing capacity, ductility, stiffness, failure mode and energy absorbing of beam specimens were systematically analyzed.