Strength Evaluation of Shear Deficient RCC Beams Strengthened With Fiber Reinforced Polymer

Strength Evaluation of Shear Deficient RCC Beams Strengthened With Fiber Reinforced PolymerGroup MembersKOMAL CHAUDHRY 11-CE-83HINA ZAIB 11-CE-09SHAGUFTA 11-ce-78Project SupervisorMaam Mehwish AsadContentsAbstractIntroductionObjectivesLiterature ReviewBeam DesignMethodologyProcedureResults and DiscussionsConclusionsAcknowledgementsReferences

AbstractThe objective of this thesis is to investigate experimentally the behavior of reinforced concrete beams in shear, laminated with CFRP, in order to arrive at a working model and equation for predicting the shear strength of these structural members. Structures that are deficient due to either a structural flaw or deterioration can be brought to a useful capacity using CFRP. The research program consists of 3 RCC beams of different depths. The effects of different depths on the shear strength of beams is investigated by experimental procedure. The beams are tested until their structural failure is achieved. CFRP lamination will then be applied on the failed area of beams. It is expected that the application of fiber wax leads to a significant improvement in the shear strength of the specimens.

IntroductionShear deficient reinforced concrete beams can be effectively strengthened using external fiber reinforced polymer (FRP) lamination. Due to the presence of the external elastic straps, a strengthened beam can continue to carry significant load beyond the stages of crack plane slipping and internal shear stirrup yielding, and the concrete is subjected to high tensile strain levels.

ObjectivesThe main objectives of current research areTo study the structural behavior of reinforced concrete shear deficient beams under static loading condition. To study the contribution of reinforced polymers on shear behavior of reinforced concrete beams.To examine the effect of different fiber orientations, number of layers etc. on the response of beam in terms of failure modes, enhancement of load carrying capacity and load deflection behavior. To investigate the effect of a new anchorage scheme on the shear capacity of beam.

Fiber Reinforced PolymerFiber Reinforced Polymers(FRP) are a particular typology of composite materials, made of high resistance fibers impregnated with polymeric resins. The mixing result is a material with properties between fiber and resin.FRP materials are distinguished by excellent tensile strength properties in the direction of the fibers and by negligible strength in the transverse to the fibers; this illustrates the anisotropic nature of these materials. FRP composites do not yield, but instead are elastic up to failure and they are also characterized by relatively low modulus of elasticity in tension and low compressive properties.

Carbon Reinforced FiberThe organic materials which contain a substantial amount of carbon are headed to produce fibers such as ryon, polyacrylonitrile (PAN), or pitch (a black residue from distillation of petroleum) in an inert environment. This kind of fiber is the strongest, stiffest and most durable. They are more expensive than glass fibers but offer an excellent combination of strength, low weight, and high modulus and fatigue properties.

Contd.Advantages of FRPThe general advantages of FRP reinforcement compared to steel are:Durability in aggressive environmentsHigh strength-to-durability ratioMagnetic and electric neutralityLow specific weightLow axial coefficient of thermal expansion

Beam detailsThree beams were tested of different depths i.e. 12, 15 and 18. They were entitled the IDs of SDS, SDM and SDD respectively. Their details are given as below:Groupof BeamCross-SectionSDS9x12SDM9x15SDD9x18Mix Design ratio: 1:2:4.28 days concrete cylinder strength: 3500 psiAll beams were designed with zero shear reinforcement in shear span to assess the shear failureTo provide sufficient flexure capacity, reinforcement ratio was kept nearly maximum and constant in all beams.Beam Structural Design MethodologyProcedureThe beams specimens were tested under the application of symmetric loading at the centerline of two bearing plates through hydraulic system, transferring the load through calibrated proving ring, to evaluate the shear behavior of beams.The loads were gradually increased and cracks developed in the beam specimens were closely observed. The loads and deflections of a beam corresponding to these cracks were also recorded.The cracked beams were wrapped using CFRP lamination. After treatment, beams were again tested under static gradually increasing loading. Deflection was recorded and cracks observed.

CFRP Repaired Beams

Results Beam deflections to the corresponding loads were recorded. Strain has been calculated for each beam against those displacements.Following are the graphs plotted for load against strain.Beam #1 : SDS

Load on a point (kN)Beam Response1071st diagonal crack on one side1131st diagonal crack on both sides122.49Beam failure

Load on a point(kN)Beam responses138 1st diagonal crack on one side146 1st diagonal crack on both sides168.969Beam failure

Load on a point(kN)Beam responses169 1st diagonal crack on one side177 2nd diagonal crack on both sides192.66 Beam FailureComparison of Load and corresponding strains of all Beams

Strain for beams against subjected loading after CFRP lamination, is shown in tabular form below

SDSSDMSDDOriginal BeamStrengthened BeamOriginal BeamStrengthened BeamOriginal BeamStrengthened Beam0.0310.0190.02240.01940.01660.0106ConclusionsIn this research, we presented the results of an experimental investigation carried out on beams reinforced by CFRP sheets and finalized to evaluate the ultimate shear capacity of these elements and the composite contribution to the shear strength. Following were concluded from experimental resultsCracked beams achieve 93% of the strength (on average) when laminated with CFRP. For beams with larger depth to span ratios, laminated beams showed greater recovery in strength as compared to those with lesser depth to span ratio. Failure mode is de-bonding of CFRP laminate.Strain was overall reduced for beams strengthened with CFRP.

AcknowledgementThe work described has been realized with the co-operation of the Concrete Laboratory staff and Lab Engineers. The financial assistance by University of Engineering & Technology Taxila , is gratefully acknowledged. We are highly grateful to our project supervisor Engr. Mehwish Asad

RecomendationIt has been recommended for future studies to investigate the orientation and quantity of lamination to strengthen RC beams. Also to increase the reliability of experimental results, it is required to test beams with greater depths. It can help in developing relationships between quantity of CFRP against different depths.

ReferencesCatalin Andrei Neagoe, Concrete Beams Reinforced with CFRP Laminates, Department of Strength of Materials and Structural Engineering, Polytechnic University of Catalonia. Ahmad Sabry Farghaly and Brahim Benmokrane, Shear Behavior of Concrete Deep Beams without Web Reinforcement, Journal of Composites for Construction. doi:10.1061/(ASCE)CC.1943-5614.0000385C.A. Zeris, Experimental Investigation Of Strengthening Of Non Ductile RcBeams Using FRP, Proceedings of the 8th U.S. National Conference on Earthquake Engineering, San Francisco, California, USA