Static and dynamic response analysis of stay cables using terrestrial laser scanning and vibration measurements

Nowadays, high accuracy measurements provided by terrestrial laser scanner and vision sensors allow to collect useful and exhaustive information about the conditions of the existing structures, useful to detect defects and geometry anomalies and to better understand their mechanical behavior. These avant-garde technologies were found to be particularly effective for the structural health assessment of the cable-stayed pedestrian bridge described in this paper. Considering a continuous mono-dimensional model of an inclined perfectly flexible cable, the axial tension is locally tangent to the cable profile. Thus, determining the cable static response under self-weight consists of a geometric shape-finding problem. Through terrestrial laser scanning, a 3D point cloud model of the bridge was acquired, including a data-abundant description of the actual static configuration of the stays. Therefore, cable configuration was no longer an unknown of the static problem, which can be inverted to assess the static tension. Furthermore, modal analysis was conducted also through image-based vibrations measurements to identify the fundamental frequencies of the cables. The independent identification of the axial forces from static (geometric) and dynamic (spectral) data provided results in good agreement.