GFRP CONTROL REBARS FOR RELOCATION OF PLASTIC HINGE REGIONS IN STEEL REINFORCED CONCRETE BRIDGE COLUMNS

摘要

During a seismic event, bridge columns constructed in seismic zones experience formation of potential plastic hinges at their ends. The formation of a plastic hinge at the column's bottom end causes damage to the supporting foundation. Post-earthquake retrofit of bridge foundation is very difficult and expensive. In order to eliminate foundation damage and move the plastic hinge region away from the spliced bar region, in recent years, the location of potential plastic hinge region has been moved away from the column-foundation joint. This has been done by the use of addition steel control rebars extended over a certain length at the bottom of the column. When used as control rebars, Glass fiber reinforced polymer (GFRP) rebars are superior to steel rebars in relocating plastic hinge regions. In a steel reinforced concrete column, GFRP rebars could be used as control rebars, only. The primary advantage of the use of GFRP rebars is low bond stresses at the interface between the control rebars and the surrounding concrete, as a result, they cause significantly less damage to the column's concrete core during a seismic event. This paper will present guidelines for the use of GFRP rebars for controlling the location of plastic hinge regions in steel reinforced concrete bridge columns. The recommendations are based on extensive study of the properties of concrete columns reinforced with hybrid reinforcements. These reinforcements consist of primary steel bars and auxiliary GFRP control bars. The results of this investigation suggest that GFRP bars are effective in shifting the plastic hinge regions in bridge columns while maintain the column's ductile response.