STUDY OF THE ANCHORAGE OF CARBON FIBER REINFORCING PLASTICS (CFRP) UTILIZED TO UPGRADE THE FLEXURAL CAPACITY OF VERTICAL R/C MEMBERS

摘要

The upgrading of the flexural capacity of reinforced concrete (R/C) vertical members with externally applied CFRP layers as means of tensile reinforcement is investigated. The specimens were designed that the flexural limit state would prevail in the form of a plastic hinge region near their joint with the foundation. They were subjected to simultaneous constant vertical load and horizontal cyclic displacements. This was applied prior to the application of CFRP layers and was repeated with CFRP layers attached to the damaged specimens. The upgrading of the flexural capacity in terms of ultimate overturning moment is presented and discussed. A critical point is the effective anchoring of the CFRP sheets for the transfer of tensile forces to the foundation. Three different anchoring arrangements are applied sequentially to specimens that have been subjected to a damaging loading process prior to their repair. The anchoring schemes were based on observations and numerical simulation processes aimed to optimize the behavior. After virgin specimens developed the expected flexural plastic hinge three different repair schemes were tried. These repair schemes introduced improvements to the CFRP bonding and improvements to the anchoring arrangements of the CFRP to the foundation. The improvement is judged on the basis of the upgrading of the flexural capacity and on the developing failure mode. The final repair scheme is more practical and was successful in mobilizing the available capacity of the CFRP layers; it resulted in approximately 100% increase in the flexural capacity when compared to the virgin specimen without CFRP layers.