Shear displacement in open-sandwich reinforced concrete beams

Synopsis The deflections of open-sandwich, reinforced concrete beams under load are analysed to verifv that shear deformation of the adhesive layer between the concrete beam and its steel reinforcing plate does not cause an unacceptable loss of structural interaction. The cumulative effect of the shear deformation, i.e. the ‘shear displacement’, is loosely analogous to the slip of steel bars in a conventionally reinforced concrete beam. The partial interaction theory introduced by Newmark et al and extended by Goodman and Popov and others is further extended to include thermal expansions, cracked concrete, and unsymmetrical loading. The accuracy of the resulting analysis is assessed by comparisons with finite element predictions and with experimental results. It is found that thin layers of adhesives with a large shear modulus are preferable from an in-service structural point of view. They lead to small shear displacements and to good control of the influence of flexural cracks.