REPAIR OF DAMAGED PRECAST BRIDGE COLUMNS WITH GROUTED SPLICE SLEEVE CONNECTIONS USING CFRP SHELLS AND PLASTIC HINGE RELOCATION

A repair technique has been developed to relocate the column plastic hinge of severely damaged precast reinforced concrete (RC) bridge columns. The technique utilizes a combination of a prefabricated carbon fiber-reinforced polymer (CFRP) shell with additional wet layup CFRP layers, epoxy anchored headed mild steel bars and nonshrink concrete. Undamaged columns with two different mechanical connector systems were initially tested to failure using cyclic quasi-static lateral loads. One connection system was used to connect a RC bridge pier cap to a column and a second connection system was used to connect a RC footing to a column. Failure of the two original specimens occurred at drift ratios between 6% and 7% with longitudinal bars fracturing in the column plastic hinge region. Subsequently, the column plastic hinge region was repaired by increasing the column cross-section from an octagonal section to a circular section and thus enlarging the column size from 53 cm to 76 cm up to a height equal to 46 cm. The repair was constructed using a prefabricated CFRP shell with additional wet layup CFRP layers. Headed mild steel bars were epoxy anchored into the pier cap and footing inside the CFRP shell. Nonshrink concrete was used to fill the void between the original columns and CFRP shell. Compared to the undamaged assemblies, the repaired specimens failed at the same drift ratio and at greater ultimate lateral loads. The plastic hinge was successfully relocated at the column section adjacent to the repair and the failure mode was bar fracture in the relocated plastic hinge region. The method is a viable technique for seismic repair or seismic retrofit of precast assemblies with severe damage in column to footing or column to pier cap connections.