DYNAMIC PROPERTIES OF BEAM-SLAB HIGHWAY BRIDGES (ABRIDGMENT)

The natural vibration periods of the designs of varying dimensions and stiffness properties of eighteen simple-span beam-slab bridges with prestressed concrete I-beams and without skew were determined using the finite element method and compared with those predicted by the equivalent-beam approach where natural vibration period is a function of beam mass per unit length, beam length, beam modulus of elasticity, and beam moment of inertia. It was found that the first period is predominantly dependent on span length (in fact, it does not vary substantially from a given span length) that the dynamic characteristics of bridges vary as bridge configurations change that the equivalent beam approach yields an accurate estimate of the first natural vibration period of a structure but poor ones for all the other dynamic properties, and the contribution of the slab should be included in the estimation of the dynamic characteristics of bridge superstructures.