Study Of Seismic Behavior For R.C Frame Post-cast Joint

In the past ten years, with the rapid development of the technology of appending layers and renovation, the remarkable economic and social benefits have been obtained. In the seismic areas, for reinforced concrete frame post-cast joints, it is very important to guarantee the dependability of beam-column joints and meet the need of earthquake-resistance. But up to now, there have been few research data about seismic behavior for R.C frame post-cast joints and very few attempts have been made to assess experimentally its dependability. So the experimental study and theoretical analysis of post-cast beam-column joints has become a subject which has important realistic significance at present.Before the joints are tested, experimental study of group bonded bars in concrete subjected to tension, the failure modes of adhesively bonded bars have been observed. According to the phenomenon investigation, the reduction coefficient of ultimate load carrying capacity is obtained. The influence of parameters such as steel diameter, bond depth, anchorage spacing has been discussed. Based on stress analysis of bonded bars under mixed bond-cone failure, the formula used in calculating the anchoring strength is presented in this paper.In this paper, tests of four representative R.C beam-column post-cast joints using chemistry adhesive to embed steel bars which are subjected to slow frequency cyclic horizontal action with constant axial force are carried out. In the tests, the whole crack and failure process and failure modes of the specimens have been observed under the repeated load, and load–deformation response curves, crack load, ultimate load and strain of steel bars have been recorded. Besides seismic behavior such as ductility, stiffness and energy dissipation capacity etc is analyzed. The analysis of results confirms that on the condition that it would meet the challenge of design code and the anchorage of embedded bars should be reliable, post-cast joints using chemistry adhesive to embed steel bars have satisfactory seismic behavior. It also shows that the way that the joint core is strengthened by outer-packed reinforced concrete should be effective in aseismic strengthening.Based on the analysis of concrete and transverse reinforcement, stress and force transfer mechanisms of beam-column joint is set forth. The shear strength's constituent and influencing factors of joints strengthened by outer-packed reinforced concrete are discussed, and its calculation formula for shear strength is primarily put forward. In addition, the analysis and derivation of crack strength of post-cast joints in theory are also given out, which interpret the ability to enhance break strength for outer-packed concrete.Finally, the design philosophy, material requirements and construction technology for R.C fame post–cast joints which steel bars are embedded in concrete by chemistry adhesive are presented in this paper, and a practical application for this kind of joint is introduced which can be referred by designers and researchers.