Local buckling of side plated reinforced concrete beams. I: theoretical study

Steel plates can be bolted to the sides of reinforced-concrete beams to both strengthen and stiffen them. When these side-plated beams are subject to their intended design actions, compression, bending, and shear stresses are produced in the steel plates and this can lead to instability by local buckling of the plates. This type of buckling problem is known as a contact problem, since the plate is constrained to buckle in only one lateral direction. The paper presents a Rayleigh-Ritz method of the local buckling analysis of rectangular unilaterally restrained plates in compression, bending, and shear. Polynomials are used to define the displacement function, while the restraining medium is modeled as a tensionless foundation. The method is shown to be very efficient computationally, and elastic local buckling coefficients are presented for a variety of restraint cases for various plate aspect ratios, in terms of interaction diagrams. The buckling model is shown to be in good agreement with experimental results from the full-scale testing of two side-plated reinforced-concrete beams, as presented in a companion paper.