New Details for Reinforced Concrete Beam-Column Joints To Improve Their Seismic Behavior Near Failure

Abstract eng:
Even when results of tests of beam-column joints of reinforced concrete buildings subjected to earthquake-type load are widely available in literature, information about their behavior for large cycles of rapidly variable displacements, representative of the situation near collapse of the building, is difficult to find. Is also difficult to find information about seismic performance of arrangements of transverse reinforcement different from conventional 90° hoops. In this work, about fifty close to real size ( 1/3 scale) RC corbel beams representing external beam-column joints of seismic frames or, better said, the part of the beam close to the joint, were tested subjected to an alternating rapidly variable cyclic load acting on the free end, simulating seismic solicitation. Large displacements were applied, most time destroying test specimen. Tests were performed at the Civil Engineering Department laboratory of the UTFSM. Different ways of detailing beam, and joint were studied. Recent new tests, performed on elements with 45 deg. (and 135 deg.) inclined beam stirrups, confirm the ability of this type of shear reinforcement for keeping the integrity of building elements, retarding crushing and spalling of concrete, resulting in a gradual and ductile failure. Improved 45 deg – 135 deg, easy to build shear reinforcement designs are proposed and some conceptual errors in placing bars of this type of reinforcement, and its consequences, are showed.

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