USE OF CFRP ANCHORS TO STRENGTHEN LAP SPLICES OF RECTANGULAR RC COLUMNS

ABSTRACT

In many reinforced concrete structures built in the 1970’s and earlier, lap splices in column longitudinal reinforcement were based on compression loads only. The length of splice and the amount of transverse reinforcement are inadequate if the lap splices are subjected to different types of loading or if ductility is needed. If an earthquake occurs, performance of the structure may be less than desired. The jacketing of the reinforced concrete columns using Carbon Fiber Reinforced Polymer (CFRP) material may provide a solution for improving the lap splice behavior. However, the CFRP jacketing of rectangular reinforced concrete columns is not as efficient as it is for circular or square columns. While the corner bars in CFRP jacketed rectangular columns can benefit from the confinement provided by the CFRP jacket, the benefits of confinement may be marginal for bars not located at or near a corner. By providing CFRP anchors, the efficiency of the confinement provided by a rectangular CFRP jacket can be increased and the behavior of lap splices away from the corners can be improved. In addition, CFRP anchors may be used without CFRP jackets in strengthening lap splices in rectangular columns with walls. The objective of this study was to develop effective methods of strengthening deficient lap splices in rectangular reinforced concrete columns by a combination of CFRP jackets and CFRP anchors or using CFRP anchors only. Three rectangular (460 mm x 910 mm) columns were fabricated and strengthened by CFRP anchors with or without CFRP jackets. Column 1 was tested as-built under monotonic loading, and Column 2 and 3 were tested after strengthening with CFRP under cyclic loading.

Keywords 

CFRP anchor, CFRP jacket, lap splice, reinforced concrete column, seismic strengthening