Experimental Research And Analysis Under Low Frequency Cyclic Loading Of Frame's Joints Poured With Beams' Concrete

In the reinforced concrete high-rise frame structures, it is not proper if the sectional area of the columns is too big, and the axial force ratio of columns should not surpass the limitation. So the columns are often using the high-strength concrete. But the high-strength concrete is not proper and require to the beams and slabs which are mainly used as bending resistance component. So the strength of the concrete in the columns is usually higher than that of the beams. In construction, the column-beam joints is usually poured with the same strength concrete as columns, it requires high construction technology and some problems are difficult to solve such as formwork planning, construction joint and quality of construction. So it is screaming for the column-beam joints poured with the same strength concrete as beams and slabs in construction. But because of the absence of the research about this construction method, it is seldom used in construction in China.In the test research of the most radical plane column-beam joint specimens are done, so the feasibility and the problem for this construction method could be discussed. Seven column-beam joint specimens which is subjected to cyclic loading are tested. These column-beam joints are poured with the same strength concrete as beams. The axial force ratio, the shear compression ration and the strength gradation of concrete between column and beam for specimens are controlled strictly in the test. Based on measurement of strains of both horizontal stirrups in the joint core and longitudinal reinforcement passing through the joint, and the research of the specimens' ductility, energy-dissipation capacity and bond deterioration of reinforcement passing through the joint, the influence of the column-beam joints poured with the same strength concrete as beams on the integrated seismic performance of the specimens is investigated. As following conclusions have been got:â‘  It is feasible that the column-beam joints poured with the same strength concrete as beams.â‘¡ The strength gradation of concrete between column and beam is not the principal factor which influences stiffness degradation and energy-dissipation capacity of specimen. But when the strength gradation ratio and the axial force ratio is lower at the same time, bond deterioration of reinforcement passing through the joint will appear early, leading to the stiffness degradation of specimen subjected to iterative load.