Unified Evaluation of Failure Mechanism of Beam-Column Joint in Reinforced Concrete and Pre-stressed Concrete Frames

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Shear resisting mechanism and failure mechanism of plane and three-dimensional beam-column joint panels were studied through a series of static tests under reversed cyclic loading; twelve specimens with plane cruciform shape and two three-dimensional specimens made of pre-stressed reinforced concrete (called as PRC) and precast pre-stressed concrete (called as PCaPC).Conclusions drawn by the study are mentioned as follows.1) Joint panel covered by four transverse beams in PCaPC frames failed in shear similarly to R/C beam-column joints.2) The beam-column joint with unbonded tendons within a joint panel also failed in shear.3) Shear strength of cruciform PCaPC beam-column joint panel can be computed by the same manner as R/C beam-column joints, i.e., as a function of concrete compressive strength regardless of the bond condition along beam post-tensioning tendons and the arrangement of the tendons.4) Joint shear strength was enhanced to 25 percent or 13 percent by four or three transver … More se beams framing into the joint panel respectively comparing with that of a plane beam-column joint specimen.5) The capacity point of a set of maximum story shear forces in each direction under bi-lateral loading was located at the outside of rectangular bi-directional interaction surface of joint shear capacity. This means that safety to earthquake excitations can be sustained for a PCaPC beam-column joint by designing joints to shear forces in respective directions independently.6) For PRC plane beam-column joint specimens, three failure types were observed. A story drift angle at the peak shear capacity varied from 1.5 % to 2.9 %. For four specimens which were reinforced by deformed PC tendons and failed by beam flexural yielding, PC tendons ruptured after a story drift angle of 2 % and lateral story shear capacity descended remarkably.7) Residual flexural crack width at beam critical sections increased suddenly due to no tensile yielding but bond deterioration of beam longitudinal reinforcement or PC tendons. Less