EFFECTS OF VARIOUS BEAM-BAR ANCHORAGES ON THE STRENGTH AND DEFORMATION OF PRECAST REINFORCED CONCRETE BEAM-COLUMN JOINTS

摘要

This experimental investigation was carried out to study the influence of the anchorage method of precast concrete beam main bars on the strength and deformation of interior beam-column joints. Bars passing straightly through the joint, bars mechanically connected at the joint panel, bars bent 90 degrees inside the joint and bars lapped at the column face were the main parameters for this experiment. Seven specimens, four of them designed to have beam yielding failure, and the rest to fail in shear at the joint panel, were tested. The following information was obtained. Among the beam yielding type specimens, the specimen with bottom bars bent 90 degrees has almost same strength that the obtained for the monolithic specimen. On the other hand, the specimens with main bars lapped at the column face or mechanically jointed inside the joint panel, showed a gradual increase of their maximum strength because of a local increase of the strain in the beam bars. For the beam column joint shear failure type specimens, the ratio joint shear stress (_Jτ_(max)) to compressive concrete strength (_Jσ_B) was about 0.27, regardless of the main bar anchoring method. The deformation of precast beam due to the pull out of main reinforcing bars at the column face for specimen with mechanical joint was smaller compare to the monolithic specimen, On the other hand the specimen with lapped bars showed most of the deformation concentrated at the column face due to pull out of the beam main bars.