On the fundamental natural frequency of bridge decks: review and applications

The fundamental frequency of vibration of a bridge deck is a key parameter that represents the dynamic characteristics and the condition of the superstructure. This paper reviews the different empirical and/or theoretical formulae that have been proposed in the past. The classical vibration theory of beams and plates was simplified in order to clarify and review the general philosophy behind the previously proposed formulae. On the basis of the results obtained from limited dynamic tests performed by the authors on a number of reinforced concrete bridges and the results of limited tests conducted by other researchers, a formula for the first bending natural frequency of a bridge deck was derived. Moreover, as new applications, new practical formulae are introduced that can be used for estimating the initial dimensions of a deck cross-section for simple span bridges, which are particularly suited to bridge-widening projects. The first bending natural frequency/period of the bridge deck and its corresponding cross-sectional properties are considered here as functions of the bridge main span length.