Stress transmission of retrofitted concrete columns to jackets

Abstract

Concrete jacketing is one of the most common retrofitting techniques for concrete columns. However, the stress transmission mechanisms of this system are still not fully understood and appropriate design procedures are still not established. In this experimental study eight jacketed columns with different stirrup arrangements and various bonding conditions were tested in order to analyse the failure mechanisms of these members. It was observed that in rectangular columns 60% of the load is transmitted across the corners and the remaining 40% across the sides. The stress transmission from the column to the jacket depends on shear capacity at the interface. The applicability of the ACI 318-05 shear-friction model is also evaluated. According to this model, reinforcement must be provided across the contact surface to resist the relative displacement across it. Despite this limitation, it is shown that the Mattock formulation can be applied with minor modifications for the design of concrete jackets, and that the experimental results show reasonable agreement with calculated values.