CCEER-95-8: Full-Scale Field Resonance Tests of a Railway Bridge

Abstract

Field dynamic resonance tests of the Strawberry Park Underpass, a two span simply supported railway bridge located in Los Angeles, were performed by using an eccentric mass dynamic shaker. The east span of the structure and the adjacent roadbed were instrumented with twenty four FBA-11 accelerometers. The bridge was shaken in both the longitudinal and the transverse directions. To identify the influence of the rails, the tests were performed initially with the rails in place and then with the rails cut at the abutments. The natural frequencies and the corresponding modal damping values of the first and second transverse, the first longitudinal and the first vertical modes were calculated. Significant participation of the adjacent roadbed, indicating a strong interaction between the structure and the soil, was also observed. A three dimensional finite element program was developed, in order to predict the experimentally developed results. These predictions were reasonably accurate. This model will be the first step towards further analytical studies, which are currently under development. This report describes the experimental procedures, the analysis of the data and its results and the development of the analytical model (Abstract by authors).