Structural health monitoring of Artemio Franchi Stadium in Florence, Italy: measurement using interferometric radar

The “Artemio Franchi” Stadium in Florence, Italy, designed by Pier Luigi Nervi in 1929, was built from 1930 to 1932. The stadium has a reinforced concrete structure and it is composed by 24 stands, a 50-meter tower (“Maratona” tower) and a cantilever roof. In occasion of the World Cup in 1990 the stadium was renovated by adding seats at the ground level as retrofit. A study for seismic requalification is in progress and an interferometric radar has been used for monitoring the architectural complex. In particular, the radar monitored the “Maratona” tower and some of the stands. In this paper, the experimental results of this preliminary measurement campaign are reported. The interferometric radar is a remote sensor for monitoring large structures. When the structure under test is excited by external actions (i.e. wind, vehicular traffic, vibrodyne), the interferometric radar is able to detect the displacements of the structure and to measure its natural frequencies. The wind action was exploited to test the “Maratona” tower. The tower is a 30-meter tower located on a reinforced-concrete slab placed in the middle of the grandstand on the east-side of the Stadium, close to one of its well-known spiral stairs. Inside the tower an elevator is hosted. This measurement was performed both with an interferometric radar and a seismic accelerometer. The radar was installed close to an entrance of stadium, the seismic accelerometer was installed on the tower’s attic. Natural frequencies were measured for these structures with both instruments, and the results were in good agreement. The stands are too rigid to be appreciably excited by wind or vehicular traffic, hence the measurements were performed during football matches. The supporters’ movements were used as input action to measure the dynamic properties of stands. Unfortunately, this input was not enough wide to allow the measurement of the natural frequencies of all the stands. The experimental results of stands have been compared with a numerical model.