Monitoring of a Prestressed Segmental Box Girder Bridge During Strengthening

The Grand-Mere Bridge, a 285 m (935 ft) long cast-in-place segmental box girder bridge, experienced some distress which required strengthening by adding external prestressing equivalent to 30% of the remaining internal prestressing. An extensive research program was undertaken with the objectives of measuring the external prestressing effects on the existing bridge and validating several design assumptions. The testing program comprised various measurements. Instrumentation included electrical strain gauges, mechanical strain gauges, thermocouples, and surface and embedded vibrating wire gauges. One mobile and two permanent data acquisition systems were used, together with manual reading devices. This paper presents details of the instrumentation program. Some field measurements are presented and comparisons with several design assumptions are discussed. The technology gained from this project is also applicable to precast, prestressed concrete bridges.