Output-Only Modal Identification on Multi-Span Continuous Viaducts

Abstract

This paper calls the attention to a type of civil engineering structures – multi-span continuous viaducts – that can have natural vibration modes with very close frequencies, which are as close as greater is the number of spans. This, off course, creates difficulties in what concerns the experimental evaluation of the dynamic properties of that type of structures, especially when using natural input testing and output-only modal identification methods. In the paper, a brief review is made of a few aspects concerning the dynamic properties of multi-span continuous beams with constant cross section. The tests and modal properties extraction analysis performed in two highway viaducts with continuous decks (with 4 and 16 spans) are also presented. Considering the data from those tests, the performance of an output-only modal identification method is analyzed and the identified dynamic characteristics are compared with the ones computed with finite element models of the viaducts.