Modal Methods in Continuous Bridge Deck Statics

The growing use of continuous bridge decks, as a structural type, has demanded more sophisticated analytical methods to investigate static behavior under live loads. These methods are based, essentially for the beamand‐slab decks, on the analysis of computer aided equivalent grillages. Solutions in close form are not available since harmonic analysis is sound only for simply supported bridge decks. But, if a differential equation system describing deck behavior is studied by modal analysis techniques it is possible, in two limiting cases, to give a solution in close form made up of a set of uncoupled differential equations for a set of independent beams on elastic foundation. Then, it is easy to write compatibility equations for continuous decks. These two cases occur when longitudinal beams have either null or infinite torsional rigidity. Nevertheless they are of great interest in practice since the true cases can generally be, with enough accuracy, assumed as one or the other limiting case. A numerical example shows a continuous bridge deck analyzed by hand calculations.