Experimental tests on retrofitted RC beam-column joints underdesigned to seismic loads. General approach

This paper presents an experimental program designed to determine the behaviour of steel jacketing used as a seismic strengthening system for reinforced concrete frame structures. Tests were carried out on a total of 20 full scale interior beam-column joints. Geometry and reinforcements were selected according to existing buildings, designed solely to gravity loads under strong beam-weak column concept. Column strengthening was performed in all specimens, and four different types of column-joint connection strengthening have been tested. Two types of beam reinforcement have been included in the experimental program. Tests were carried out by subjecting specimens to gravity and cyclic loads. The paper shows general results and conclusions, describing the failure modes of the specimens. Results show that the strengthening techniques and the axial loads applied on columns can have significant influence on the seismic behaviour of the joints.