METHODS OF ANALYSIS AND DESIGN OF CONCRETE BOX BEAMS WITH SIDE CANTILEVERS

After a survey of some 500 references, two methods have been selected for the analysis of rectangular, single-cell, straight boxbeams. That originally due to Vlasov, and reformulated by Kollbrunner, Hajdin and Heilig, treats torsional warping effects adequately, while the beam-on-elastic-foundation analogy is used for distortional warping and transverse bending effects. Only a slide-rule or programmable desk calculator is needed for the calculations, which have been verified by experiment on Perspex models. If an electronic computer is used, a few seconds suffice to obtain the maximum stresses, These methods of analysis do not discritize the structure, and therefore reduce very considerably the requirement for computer capacity. A parameter study of 864 single-span boxbeams has been performed by the above methods, and information obtained on the significance of warping and distortion under eccentric HB loading, as affected by changes in cross-sectional geometry, for spans of 30, 50 and 70 m. It is shown in numerical examples that serious underestimates of stress can arise in certain cases by using simplified analyses which neglect warping, distortion or shear lag.