Behavior of Exterior Beam Column Joints with Diagonal Cross Bar and Headed Bars

Abstract

Beam column joints are one of the most critical components of a reinforced concrete structure, especially if the structure is likely to be subjected to lateral loads. Failure of beam column joint during earthquake is governed by bond and shear failure mechanism, which is brittle in nature. Unsafe design and detailing within the joint region jeopardizes the entire structure, even if other structural members conform to the design requirements. Use of standard 900 and 1800 hooked bars up to required development length often results in steel congestion, difficult fabrication and construction, as well as poor concrete placement. Use of the headed bar can offer a potential solution for these problems and may also ease fabrication, construction, and concrete placement. This paper presents the experimental work carried out on four different arrangements of reinforcement of beam column joints. The aim of the research is to investigate the pull-out behaviors such as strength, failure mode, and crack patterns of different arrangements of reinforcement in exterior beam column junctions. All joints were tested by using reversed cyclic loading. In the first arrangement, the beam bars are extended in the column for distance Ld+(10xDia) from the inner face of column. In the second arrangement the beam bars are crossed diagonally in the beam column junction. In the third arrangement headed bars are provided with all heads in two parallel planes, whereas in the fourth arrangement, the heads are provided in two orthogonal planes.