Anchorage of Web-Bonded CFRP Retrofitting on RC Joints with Variable Column & Beam Widths and with Cross-Beams Present

Abstract

One increasingly accepted solution for retrofitting a structurally deficient reinforced concrete (RC) joint so as to avoid brittle joint core failure following an earthquake is the shifting of potential plastic hinge location away from the joint. This can be achieved by retrofitting the joint with beam-flange- or beam-web-bonded fibre reinforced plastics (FRPs). Two difficulties with web-bonded FRP-retrofitting concerning their anchorages were investigated experimentally. The first arises when the column is wider than the beam hence hindering the proper bonding of the FRP sheet(s) to the concrete at the location of the abrupt change in width. Beam-column joints were built with this change in width, patched with grout transition slopes and retrofitted with web-bonded Carbon FRP (CFRP). Testing shows that the CFRP sheets were still prone to delamination. The second difficulty is the common occurrence of cross-beams branching out from the joint thereby negating the possibility of simple anchoring of the FRP at the column as mentioned above and requiring the anchorage of the FRP sheets by other means such as anchorage at the cross-beams. Two types of anchorages, one with CFRP wraps and the other with metal clamps, were investigated on specimens from previous tests after they have been repaired and CFRP-retrofitted. Anchorage by clamps was found to be superior to anchorage by wraps.