Bending and time-dependent responses of RC beams strengthened with bonded carbon fiber composite laminates

Externally bonded carbon fiber reinforced polymer (CFRP) sheet has shown excellent performance to repair, restore and increase the load-carrying capacity of RC structures. In this paper results of an experimental test are presented in which fourteen RC beams strengthened with CFRP epoxy bonded sheets in flexure and time-dependent tests are subjected to four-point bending and sustained load respectively. The test variables included different degrees of strengthening scheme and two types of sustained load for both un-cracked and cracked beams. For flexural strengthening, the increase of ultimate strength provided by CFRP was assessed by varying the layers of laminates and incorporating end anchorage. In time-dependent test, deflection reduction coefficient in concrete tension stiffening model is proposed to evaluate the stiffness of the section after cracking for RC beams. It is found that the analytical values based on effective modulus method (EMM) are in general gives conservative estimates of the experimental results.

Graphs showing the comparison between the experimental and analytical values with and without modified tension stiffening of time-dependent deflection performance of 1-layer and 3-layer carbon fiber strengthened cracked RC beam respectively.Figure optionsDownload as PowerPoint slideHighlights▸ This study presents the behaviour of multi-layered CFRP strengthened RC beams. ▸ Significant increase in the ultimate capacity was noted for end anchorage beams. ▸ Attachment of CFRP sheet is effective in controlling time-dependent deflections. ▸ Modified tension stiffening gives conservative estimate with experimental deflection.