Inelastic Analysis of Reinforced Concrete Columns with Short Lap Splices Subjected to Reversed Cyclic Loads

Abstract

A common deficiency in reinforced concrete columns built in the early 1970s or before is the detailing of lap splices. These splices are often short, poorly confined, and located immediately above the floor level where large inelastic demands can be expected during seismic actions. In this paper, an analytical model for estimating the seismic response of reinforced concrete columns with short lap splices is presented. The model is based on a local bond stress-slip relationship to estimate the bar stress and deformation at splice failure and includes degradation of stiffness and strength with increasing deformation amplitude and with the number of reversed cyclic lateral deformations. The proposed analysis procedure is validated against experimental data from cyclic loading tests on reinforced concrete columns with typical construction details of the early 1970s. The results show that. the strength of short lap splices can be predicted well using local bond-slip models derived from isolated anchored bars. Also, the calculated failure mode, lateral load resistance, and deformation corresponding to the splice failure were in good agreement with the measured values. A simple equation for calculating the bar stress at splice failure is presented as well. Use of the proposed equation resulted in excellent agreement between the measured and calculated strength at splice failure.