Abstract
A review of the current state of the issue of describing the deformation of columns confined by CFRP jackets under of dynamic loading is carried out. The insufficiency of the study of elements under the influence of axial dynamic load is indicated. The dynamic increase factors (DIF) for concrete and CFRP, which are obtained by the results of existing experiments, are substantiated. Using the principle of the invariance of the potential energy of deformation of concrete at the time of its destruction under regime loading, a formula is obtained for determining DIF for ultimate relative strain of unconfined concrete. Based on the assumption of the same law of concrete deformation under static and dynamic loading, was obtained a diagram of concrete dynamic deformation confined by CFRP jackets. The diagram is valid in the range of strain rates 10−3-102 s−1. A comparison is made between a static diagram and a dynamic diagram derived from it. The characteristic of the main sections of the diagram is given. An increase in the strength and ductility of confined concrete at the initial stage of loading is obtained. At stresses equal to the tensile strength of limited concrete, its ductility is somewhat reduced. It was revealed that a significant increase in the bearing capacity of confined concrete begins at strain rates of 10 s−1 or more.
Highlights
Composite materials are most in demand when reinforcing reinforced concrete structures damaged as a result of accidents, which allows them to restore their original bearing capacity [1]
F d cc f cc Analyzing the dependence presented in figure 2, we note that a significant increase in the bearing capacity of limited concrete is observed at strain rates of more than 10 s-1
Following results were obtained: 1. Based on the assumption of the same law of deformation of concrete at static and dynamic loading, a deformation diagram of a concrete confined by CFRP jackets was obtained in the range of deformation rates of 10−3 -102 s-1
Summary
Composite materials are most in demand when reinforcing reinforced concrete structures damaged as a result of accidents, which allows them to restore their original bearing capacity [1]. There are many publications devoted to the study of the operation of elements strengthening by CFRP jackets at high strain rates Most of these works focus on emergency shock loads in the horizontal direction, for example, during explosions and collisions with vehicles [2, 3]. The technology of reinforcing columns with composite materials is quite relevant in seismically dangerous areas, due to the low weight of the strengthening elements This explains the ongoing work on the study of structures strengthening by CFRP jackets at seismic loading [4]. Suppose that the deformation of concrete strengthening by CFRP jackets at dynamic loading obeys the same laws as at static loading In this case, the parameters describing the deformation diagram fсo , ε сo , Eс , E f and ε f , are modified depending on the deformation rate by introducing the corresponding dynamic increase factors (DIF). To indicate the parameters of the diagram at dynamic loading, the superscript “d” is used
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