Characteristic of UHPFRC and New Applications

Public awareness of the seismic performance of civil engineering structures has increased against earthquakes. The authors are developing a seismic retrofit method for RC piers that utilizes ultra high performance fiber reinforced concrete (hereafter, UHPFRC). The placement of UHPFRC in the cover part imparts resistance against the large bending and compressive stresses that occur during earthquakes and prevents crushing of the cover, and we have devised a method to retrofit existing RC piers by using two types of UHPFRC that can be applied in situ. it is possible to plaster UHPFRC onto vertical surfaces by adjusting the mix proportion. The ductility of the pier was evaluated by cyclic loading test on mock-up specimens of a pier base retrofitted by this method. It was confirmed that reinforcing the pier base with UHPFRC that can be applied in situ increased the ductility by approximately 1.4 times and improved the seismic performance. A sprayable UHPFRC was developed and required to allow its application to vertical surfaces by spraying. UHPFRC can be applied in situ to existing piers by plastering or spraying for retrofitting purposes, and it was found that the seismic performance of the pier can be easily improved.