Dynamic characterization of slab on steel stringer bridges: Fid-Bau Portal

Dynamic characterization of slab on steel stringer bridges

Wang, X. / Kangas, S. / Swanson, J.A. / Helmicki, A.J. / Hunt, V.J.

A parametric study of critical dynamic characteristics of steel stringer highway bridges is presented in this paper. In the modal testing of highway bridges, it is very important to distinguish different mode types and compare the same type of modes between analytical models and experiments. The selection of modes for analysis is based on the truncation study of the first thirty modes. For three dimensional, three span symmetric, four span symmetric and four span asymmetric bridge models, four modes contribute over 80 % of the whole response. For a three span symmetric bridge model, three flexural modes and three torsional modes appear alternately before three consecutive butterfly modes appear. For a four span symmetric or asymmetric bridge model, four flexural modes and four torsional modes appear alternately before one butterfly mode appears. The naming system is accurately and efficiently applied to the analysis of dynamic characteristics of a set of calibrated three dimensional finite element bridge models. As opposed to the hypothetical bridge models, the calibrated bridge models have different combinations of physical properties. As a result, the mode types for the bridge models may appear in different order. Some limited number of modes may contribute most to the total modal response. In addition, a statistical comparison of fundamental frequency versus maximum span length shows that the analytical data match the results calculated by Cantieni's rule reasonably well. Another application of the database of dynamic characteristics is to make reasonable estimates of the frequencies and contribution coefficients for a bridge, which is instructive to field testing.