This truss footbridge spanning 25m crosses a busy road in Italy. The bridge is made of glass-FRP channel sections, with bolted connections consisting of stainless steel plates and bolts. The bridge rests on two concrete piers. The total mass of the structure is about eight tonnes. A few bridge photographs are shown in Figure 1. The testing and analysis of the structure was conducted in collaboration with Professor S. Russo and Dr G. Buscato of IUAV, Venice and A. Adilardi of Comune di Prato.

Modal testing

Ambient vibration tests were conducted to identify the dynamic properties. The peak-picking method and stochastic subspace identification approach were employed for modal parameter identification and produced consistent results. The first lateral flexural vibration mode was at 5.8Hz with damping ratio of 1.8%. The fundamental vertical flexural mode at 7.5Hz had damping ratio of 2.6% whilst the deck torsion was registered at 2.1Hz, accompanied by damping ratio of 1.6%.

Response measurements

Acceleration of the bridge was measured under single and multiple pedestrians walking as well as a person jumping on the bridge deck. In addition, vibration at the top of the piers was measured. Figure 2 shows some of these tests. The results have been reported in a conference paper, and will be a part of a journal paper that is currently under development.