Study On Influence Factors Of Bending Capacity Of RC Beams Strengthened With NSM Prestressed CFRP Strips

With the fast development of highway constructions over the past few decades,the focus of transportation business will transform from construction tomaintenance and rehabilitation. In the near future, many existing bridges willbecome dangerous and need maintenance and reinforcement, even demolishmentand reconstruction. The technology of strengthening reinforced concrete beamswith Near-Surface Mounted(NSM) Pre-stress CFRP strips has many advantagesincluding good durability, light mass, short construction period, little trafficinterference, and aesthetic appearance, similar to the traditional strengtheningtechnology with external bonded CFRP. In addition, the technology has specialadvantages: good overall performance, convenient operation, saving CFRP material,and being suitable for the flexural strengthening in the negative moment region. Ithas a bright application future for such advantages.This paper conducted a series of research work on the flexural strengtheningtechnology with NSM pre-stress CFRP strips as follows:(1) To study the influence of different factors on the bending capacity and failuremodes of the strengthened beams, including bonding length, anchoring measure atthe end of the bonding area, CFRP amount, concrete strength, the distance betweemthe groove and edge of the beam, grooving method, and steel reinforcement ratio,four-point bending tests were performed on 8 beam specimens including 7strengthened RC beams with NSM pre-stress CFRP strips and 1 normal RC beam.(2) The test results showed that the parameters including bonding length, CFRPamount, concrete strength, and steel reinforcement ratio had influence on thebending capacity of the strengthened beams. An appropriate anchoring measure atthe end of the bonding area could change the failure mode of the strengthened beam,and can increase the carrying capacity and utilization ratio of CFRP strength.(3) A 3-D finite element modal was presented. The parameters including thecracking load, the failure load, the ultimate load, the displacement, and the stressdistribution of the CFRP strips of the strengthened RC beams can be predictedaccurately. The 3-D finite element modal can be a quantitative analysis tool forverifying experiments and further research work.