SHEAR AND PEELING STRESSES AT THE INTERFACE OFFLEXURE-STRENGTHENED RC BEAMS BY PLATE BONDING

摘要

Plate bonding technique is now universally accepted as a repair technique for thestrengthening of shear and flexure deficient RC beams. This technique may be defined as the one inwhich a steel plate of relatively small thickness is bonded with an epoxy adhesive to a RC beam toimprove its structural behaviour and strength. The plate bonding technique has become increasinglypopular in recent years because of its various advantages, which include: minimum increase in the size ofthe member, minimum site disruption, and minimum strengthening time. A lot of research has been doneon this technique and it has been used extensively in the field for the strengthening of concrete beams andslabs in flexure. The shear and peeling stresses at the interface of flexure-strengthened RC beams aremainly controlled by the geometry of the bonded plate and the strengthened RC beam, and shear andnormal stiffness of the epoxy layer. The design of the plate is controlled by the magnitude of the shear andpeeling stresses at the interface. Various numerical and analytical procedures have been developed forthe determination of shear and peeling stresses at the interface of flexure-strengthened RC beams.This paper presents a computer program for the determination of shear and peeling stresses at theinterface of the flexure-strengthened RC beams under more general loadings, using partial interactiontheory. The procedure presented herein is based on linear behaviour of steel plate and concrete beam. Anexisting analytical model for the partial interaction theory, for studying the behaviour of composite beams,was used for this purpose. The differential equations of the model were converted to algebraic equationsusing central finite difference. After applying the boundary conditions, the algebraic equations were solvedfor the unknowns. The program was verified with the existing solutions of the composite beams. Then theprogram was modified to include the curtailment of the bonded plate before the supports. The curtailmentof the bonded plate was modelled numerically, by assuming the shear and normal stiffness of theadhesive at the interface of the bonded steel plate and the strengthened RC beam to be zero, andassuming the moment of inertia of the plate to be zero, in the region between the supports and the point ofcurtailment. The shear and peeling stresses were found maximum at the point of curtailment of the plates.Distribution of shear and peeling stresses at the interface obtained by this program shows very goodagreement with the existing analytical solutions.