Dynamic characterisation of an IPC pedestrian bridge

This paper reports on the experimental analysis of a pedestrian bridge made of Inorganic Phosphate Cement material. Experiments are made within the framework of a complete dynamic characterisation of the bridge, in order to evaluate the evolution of its dynamic parameters when it is subjected to progressive damage. Damage is induced by a four-point bending test in 8 different steps (static test). After each static loading step, the bridge is unloaded and dynamic measurements performed (experimental modal analysis). The results of the static test reveal a linear behaviour of the bridge until its Serviceability Limit State; this shows a good correspondence between the experimental results and the design calculations. From the dynamic analysis, six eigenmodes are well identified in the frequency range from 5 Hz for the first bending mode, to 36 Hz for the fourth bending mode. The obtained results show that, in general, all the eigenfrequencies are affected by the structural modification of the bridge engendered by static loading: they increase or decrease according to the static loading level reached and the eigenmode considered.