Dynamic characterization tests of the Tagus River suspension bridge

The Tagus River suspension bridge in Lisbon was recently subjected to strengthening construction works in order to add two railway tracks at the lower level of the stiffening truss and to widen the upper roadway deck. This paper describes the ambient vibration tests that were conducted on the Tagus River suspension bridge after completion of the strengthening works, as well as the techniques that were adopted in the analysis of the obtained acceleration records. The main purpose of the tests was to evaluate the dynamic characteristics of the first vibration modes of the bridge structure, like their frequencies, shapes and damping ratios. The values estimated from the tests are presented and compared with the ones evaluated with the finite element models used by the designers of the strengthening solution of the bridge.