Flexural Behavior Of Stone Beams/Slabs Reinforced With Prestressed NSM CFRP Bars

Stone is a type of traditional material and was suitable for building importantconstructions in ancient times. The advantages of stone include excellent durability, highcompressive strength, low water absorption, and elegant appearance. There are still numerousstone buildings distributing all over the world. Unlike compressive members like stone walls,flexural members like stone beams and stone slabs will collapse once cracking occurs on thetension side. The brittleness of this material suppresses the further application of stonestructures. As a result, to overcome the problem of brittle failure and increase the bearingcapacity and deformation capacity is the key research point of inheriting and developing thestone architectural culture.A technique for reinforcing stone beams and stone slabs with prestressed near-surfacemounted (NSM) carbon fiber-reinforced polymer (CFRP) bars was proposed in thisdissertation. The following studies were carried out:(1) An innovative clamping anchor for CFRP bars was proposed. Pull-out tests wereconducted on forty CFRP-anchor assemblies to study the anchoring performance of theclamping anchor. The test parameters included the bonded length, the pre-tightening forcesand number of bolts, and the surface characteristics of CFRP bars. Test results showed that,the maximum anchoring efficiency coefficient of the anchor was larger than95%, and theCFRP slip under the peak load was relatively small. Increasing the bonded length, thepre-tightening forces or number of bolts led to a higher bearing capacity. The anchoringmechanism of the clamping anchor was analyzed, and a model to predict the bearing capacitywas proposed. The recommended configuration of the clamping anchor and the pre-tighteningforces of the bolts were also provided.(2) Fifteen pull-out tests were carried out on stone blocks with NSM CFRP bars to studythe interfacial bond behavior. The test parameters included the bar diameter and the bondedlength, and the bonding agent was the cement-based mortar. All specimens failed by pullingout the CFRP bars, accompanied by the stone cracking near the groove. Test results showedthat, increasing the bar diameter and the bonded length led to a higher bearing capacity and alower average bond strength. By comparing test results with the existing experimental data, itwas indicated that the bearing capacity as well as the average bond strength of the specimensusing cement-based mortar was lower than those of the specimens using epoxy adhesive asthe bonding agent. The bonding mechanism was analyzed and a bond-slip model wasestablished. (3) Fourteen stone beams and six stone slabs were reinforced with prestressed NSMCFRP bars and tested under monotonic loading. Test parameters included the amount of NSMCFRP reinforcements and the prestressing forces. Test results showed that, the bare stonebeams and slabs ruptured under a small deflection. The use of prestressed NSM CFRP barschanged the failure mode of stone beams and slabs from abrupt fracture to a more ductilemode, and the bearing capacity was significantly increased. The load-deflection curves of thereinforced stone beams and slabs exhibited a three-stage response which was similar to that ofthe reinforced concrete beams. The prestressing force increased the cracking load andimproved the utilization of the CFRP reinforcements, and delayed the formation of newcracks.(4) CFRP-strip wrapping was applied in the flexural-shear region of the reinforced stonebeams. Monotonically loading tests were carried out on four reinforced stone beams toinvestigate the effect of CFRP-strip wrapping on the shear strength of specimens. Test resultsconfirmed the effectiveness of the technique. The shear-resistant mechanism of thestrengthened specimens was analyzed, and a model to predict the shear capacity wasestablished.(5) Full-progress sectional analysis of the stone beams and stone slabs reinforced withprestressed NSM CFRP bars was conducted, and the models to predict the cracking load, thepeak load, the stress of the CFRP bars and the stone, the balanced reinforcement ratio, and theminimum reinforcement ratio were proposed. Also proposed were the models to predict theaverage crack spacing and the crack width, and the bending stiffness and the load-deflectioncurve for the reinforced stone beams and slabs.(6) Simulative study on the flexural behaviour of the stone beams and stone slabsreinforced with prestress NSM CFRP bars was performed. Based on the verification of themodel, parametric studies were carried out to further investigate the flexural behaviour of thereinforced stone beams and slabs under more parameters.