The　dynamic　behavior　of　a　butterfly-arch　stress-ribbon　pedestrian　bridge　located　in　Fuzhou,　Fujian,　China　was　investigated　under　ambient　excitation.　Highly　synchronous　tri-axial　wireless　sensors　were　used　to　get　an　estimate　of　the　model　parameters,　finding　eight　stable　modes　with　bending　and　torsional　deformations　in　the　frequency　range　3.59-14.92　Hz.　Different　finite　element　models　of　the　bridge　were　developed　and　a　parametric　optimization　process　with　a　sensitivity-based　algorithm　was　performed　to　achieve　the　best　model　which　could　be　used　as　baseline　for　a　long-term　monitoring　of　the　bridge.　(c)　2023　The　Authors.　Published　by　Elsevier　B.V.