Managing existing structures is one of the most frequent tasks for today’s structural engineer. In particular, he can be called to handle RC members whose flexural and/or shear strength is not sufficient for carrying the actual actions. One of the most effective ways for improving the flexural strength of RC members consists in bonding FRP laminates at their soffit in order to upgrade the existing tensile strength. This kind of strengthening can be necessary due to either a section reduction of the corroded steel bars or an increase of actions on the structure. For this reason, strengthening RC beams by Externally Bonded FRP laminates is getting more and more common and various Codes of Standards have been issued in Europe, United States and Japan. In particular, the most up-to-date document has been released in Italy one year ago. A key problem to be faced when managing FRP strengthened beams deals with the possible premature failure due to debonding between the adhesive layer and concrete, which can occur at the beam end (end debonding) or in the cracked zone (intermediate debonding). In the present paper, a mechanical model considering non-linear stress-strain relationships for concrete, steel and FRP-to-concrete interface is presented, with the aim of simulating the behavior of RC beams strengthened by externally bonded FRP plates. Some of the experimental results available within the scientific literature will be considered for carrying out an experimental-vs-numerical comparison in order to assess the ability of the proposed model to predict the behavior and the failure mode of FRP-strengthened beams in flexure. The axial strain developed in FRP at U.L.S. is one of the key parameters to be observed in the analyses; in fact, debonding can occur at the FRP-to-concrete interface reducing the beam bearing capacity with respect to the one obtained for FRP tearing-rupture. The mentioned numerical model is able to assess the FRP effective axial strain at debonding, allowing to point out the key parameters which controls debonding failure.
Formulation and Validation of a Theoretical Model for Intermediate Debonding in FRP Strengthened RC Beams / Faella, Ciro; E., Martinelli; Nigro, Emidio. - ELETTRONICO. - (2006). (Intervento presentato al convegno 2nd International fib Congress tenutosi a Napoli nel 5-8 June 2006).
Formulation and Validation of a Theoretical Model for Intermediate Debonding in FRP Strengthened RC Beams
NIGRO, EMIDIO
2006
Abstract
Managing existing structures is one of the most frequent tasks for today’s structural engineer. In particular, he can be called to handle RC members whose flexural and/or shear strength is not sufficient for carrying the actual actions. One of the most effective ways for improving the flexural strength of RC members consists in bonding FRP laminates at their soffit in order to upgrade the existing tensile strength. This kind of strengthening can be necessary due to either a section reduction of the corroded steel bars or an increase of actions on the structure. For this reason, strengthening RC beams by Externally Bonded FRP laminates is getting more and more common and various Codes of Standards have been issued in Europe, United States and Japan. In particular, the most up-to-date document has been released in Italy one year ago. A key problem to be faced when managing FRP strengthened beams deals with the possible premature failure due to debonding between the adhesive layer and concrete, which can occur at the beam end (end debonding) or in the cracked zone (intermediate debonding). In the present paper, a mechanical model considering non-linear stress-strain relationships for concrete, steel and FRP-to-concrete interface is presented, with the aim of simulating the behavior of RC beams strengthened by externally bonded FRP plates. Some of the experimental results available within the scientific literature will be considered for carrying out an experimental-vs-numerical comparison in order to assess the ability of the proposed model to predict the behavior and the failure mode of FRP-strengthened beams in flexure. The axial strain developed in FRP at U.L.S. is one of the key parameters to be observed in the analyses; in fact, debonding can occur at the FRP-to-concrete interface reducing the beam bearing capacity with respect to the one obtained for FRP tearing-rupture. The mentioned numerical model is able to assess the FRP effective axial strain at debonding, allowing to point out the key parameters which controls debonding failure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
