Bridges: Bissone

Case study: SOFO System

Concrete bridge refurbishment
Deformation monitoring during added concrete setting
Hold-new interaction evaluation

Project Description

Summary: Deformation monitoring during added concrete setting, old-new interaction evaluation

Clients: Ticino Canton

Place: Ticino Canton (Switzerland)

Period: 1996 - N/A

Installation: IMM SA

Structure's short description: This thirty years old road bridge was refurbished due to the concrete damage produced by ageing. The degraded concrete was hydro-demolished and a new concrete layer was added.

Aim of monitoring: Two 1.5 m long SOFO sensors were installed in the new concrete to evaluate the adhesion between the hold and the new concrete. One sensor was placed in the vicinity of the old concrete, while the other was installed near the surface.

Number of sensor: 2

Main Results: The results of the SOFO sensors were compared to the ones obtained with the surface mounted mechanical gauge and with measurements performed on a concrete prism preserved in controlled temperature and humidity conditions. The figure compares the results obtained with these different methods. The prism shows larger values because its shrinkage is not hindered by the old concrete. The mechanical gauge and, to a lesser extent, the B SOFO sensor show important oscillations due to the environmental humidity and temperature changes (sun, rain, wind,...). The A SOFO sensor, installed near the old concrete surface, shows a much smaller shrinkage indicating a good adhesion between the two materials. This application shows the interest of internal deformation measurements for the evaluation of the material quality.

Deformatins recorded on the two sensors, on a cancrete sample and on the surface

Sensor emplacement in the beam cross-section

Bibliography:

Bridge monitoring by interferometric deformation sensors , D. Inaudi, S. Vurpillot, N. Casanova, Conference on Laser Optoelectronics and Microphotonics: Fiber Optic Sensors, Beijing, invited paper, SPIE, Vol 2895, p 34-45, 1996

Development and laboratory tests of deformation fiber optic sensors for civil engineering applications, L. Vuillet, N. Casanova, D. Inaudi, A. Osa-Wyser, S. Vurpillot, SPIE, International Symposium on Lasers, Optics and Vision for Productivity in Manufacturing, Besan?n, France, Vol 2782, p 97-108, 1996

Structural monitoring with embedded and surface mounted fiber optic sensors , N. Casanova, D. Inaudi, Inspection and monitoring of the architectural heritage, Bergamo, Italy, p 25 - 332, 1997

Deformation monitoring during bridge refurbishment under traffic , D. Inaudi, N. Casanova, S. Vurpillot, B. Glisic, P. Kronenberg, S. Lloret, 16th Congress of IABSE, Luzern, Switzerland, on CD, 2000