Experimental modal analysis and finite element model updating of a historical masonry arch bridge

This paper presents the experimental test campaign to calibrate a finite element model intended to evaluate the seismic vulnerability of the SS Filippo e Giacomo historical masonry arch bridge in Ascoli Piceno (Italy). The bridge has undergone very complex vicissitudes related mainly to exceptional river floods; it was partially rebuilt twice and other strengthening works were carried out over the time. The bridge, which is almost completely built with travertine blocks, has a total length of 146 m and follows a slightly curved path. Six arches, the main of which is semi-circular with span of 25 m and the others are lancet arches with span of about 8 m, support the carriageway that is about 8 m wide. The piers and abutments are founded on the bedrock and consequently some piers are deeply embedded in the sandy gravel deposit. A campaign of experimental tests was executed encompassing onsite measurements of stresses and modulus of elasticity, as well as laboratory measurements on specimens taken from the structures. Vibration tests were also carried out to evaluate the modal properties of the bridge. The acquired experimental data were used to calibrate a 3D Finite Element Model that has been developed considering the complex geometry of the bridge also including the deformable soil deposit. A very good consistency was achieved between experimental and theoretical behaviours.