Repeated The Ductility Of Reinforced Concrete T-beams Under Cyclic Loading

As a kind of growing-up aseismatic structure, steel reinforced concrete(SRC) has shown the world the extraordinary seismic performance in all previous earthquakes. Associated with domestic and overseas research development, this thesis selects T-section SRC framed beams as experimental samples, in which the I-shaped steel is asymmetric, to do some research about their ductility.Through the test under repeated and reversed loading, it analyses the ductility development of bi-directional by means of carrying capacity, ductility coefficients and framework curves etc. It is set that the ductility at reverse loading begins with the yield of I-shaped steel's bottom flange. It is also obvious that the adhisive failure is incident at the interface of I-shaped steel upper flange and concrete. So it is suggestive that the practical situation should be taken account into to set essential and enough shear-keys. In addition, compact and close-circuit stir-ups can strengthen the adhesive performance between the I-shaped steel and concrete, and also the ductility.Aiming at characteristics of yield point of T-section SRC beams at reverse loading, it presents four kinds of yield points ,which are the tension reinforcement's yield point,I-shaped steel's yield point,equivalent yield point and the yield point at the 85% of maximum load. Using moment-curvature method, it is obvious that the third kind of yield point lies between the first and the second yield point all the time, so it is feasible to have it as the calculational yield point in the calculation of sectional curvature ductility, thus unifying the criterion of curvature ductility with reinforced concrete and prestressed concrete structures and others. Besides, by changing the parameters such as the location of I-shaped steel and width of the beam flange etc,it is concluded that it is rational to regard the yield of I-shaped steel's bottom flange as the yield point of the section. At the same time, it is also concluded that the location of I-shaped steelbar has a deeper effect on the curvature ductility than the width of the beam flange.