Seismic load tests on reinforced concrete columns strengthened by jacketing

Technical Abstract

Four reinforced concrete column units were tested subjected to stimulated seismic loading to investigate repair and strengthening techniques. The as-built columns were 350mm square and contained low quantities of transverse reinforcement as was typical of building columns designed and constructed in the pre-1970s.

The column units represented the column region between the midheights of successive storeys. A stub was present at the midheight of each unit to represent a portion of the two-way beams and alb at the beam-column joint. Two column units were tested, repaired and strengthened by jacketing and retested. The other two column units were strengthened by jacketing and retested.

The jacketing consisted of 100mm (3.94 in) thickness of added reinforced concrete. The new longitudinal reinforcement was placed through the floor slab. Two arrangements of transverse reinforcement in the jacket were investigated. The as-built columns displayed low available ductility and significant degradation of strength and much reduced strength degradation.

The retrofit of columns using reinforced concrete jackets was found to be successful but labour intensive.