The Earthquake Engineering Online Archive

An approach for improving seismic behavior of reinforced concrete interior joints

Galunic, Branko; Bertero, Vitelmo V.; Popov, Egor P.

UCB/EERC-77/30, Earthquake Engineering Research Center, University of California, Berkeley, 1977-12, 116 pages (530/G23/1977)

The interior joints of reinforced concrete moment-resisting frames are vulnerable to severe bond deterioration of the beam main bars passing through the column during severe cyclic loadings such as might occur in a major earthquake. In conventionally designed interior joints, cracks form on the beams at both faces of a column and, if their main reinforcing bars are sufficiently strained, the bars can be simultaneously pulled from one side and pushed from the other. The bars could then slip through the columns, greatly reducing the stiffness in the beam-column assemblies. An approach is suggested for obviating this problem by avoiding the high straining of the bars at the face of the column by forming the plastic hinges with the resulting significant cracking away from the column faces. Two schemes for achieving this by proper detailing of the main beam reinforcement are reported. One such scheme involves bending some of the main beam bars at a properly computed distance from the column. In the alternative scheme, some of the bars are cut off at a properly determined distance from column faces. Experimental results show that the approach of forcing the development of the plastic hinges away from the column is very promising for solving the problem of severe bond deterioration of the main bars passing through the column, and that, for the subassemblage tested, either of the schemes used gives excellent results.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-77-30.pdf (8 MB)