Field tests on two structures to assess integrity, efficient maintenance strategy, soil/structure interaction, risk profile, and seismic response.

The approach of using ambient excitation from natural sources to establish a baseline signature for the structure is shown to be both viable and allows advantages for understanding structural behavior. The baseline consists of an estimate of all aspects of the response of the structure that are necessary to define it mathematically. The baseline signature enabled the identification of the major modes of vibration, their frequencies of resonance, the associated damping ratios (energy dissipation) and the deformed shapes under resonance conditions. The excitation source was purely generated from ambient sources (breezes and human activity) as well as light traffic, and this paper considers their use on two buildings. Examples of how these techniques were used on data collected from two buildings in the field are presented in this paper, and these are analyzed so as to assess the integrity of the structures.