The Rio Puerco bridge consists of three spans, with four girders in each span. Girders are precast prestressed I-beams, approximately 30 m long. They support on-site cast monolithic concrete decks (see Figure 2). The girders were fabricated in the open-air plant. The work forms of four girders, with the rebar cages and strands, were aligned, the strands were put in tension and the concrete was cast. The girders were then steam cured at temperatures in the range of 60°C to 90°C. Three days after the pouring, the strands were cut and prestressing force was introduced into the girders. Approximately three months later, the girders were transported on site and the deck was poured.
Aim of monitoring:
The main aim of the project has been to monitor prestress losses over the whole life of the bridge, including the early age of girders. For this purpose, four girders were equipped with Smartec SOFO sensors and thermocouples as shown in Figure 3. Each girder has contained 10 SOFO sensors and 6 thermocouples. This configuration of sensors allows monitoring of deformation and curvature and determination of thermal influences. Using appropriate algorithms it is possible to determine prestress losses in girders. Only four girders are selected due to the symmetry of the bridge (see Figure 2). All sensors were installed before the pouring. Details from the installation phases are presented in Figure 4.
Measurements started immediately after the pouring. In this way, the early and very early age deformation was recorded during the first three days. The deformation is later recorded during the prestress phase after each strand was cut. Thus, the real initial strain state of the girders was stored. Followed the period of continuous monitoring before transportation on-site, during transportation, and the pouring of the deck. At present, long-term monitoring is carried on. The results helped compare with different theoretical models and confirmed the very good condition of the bridge after construction.
|INSTALLATION PERIOD||TYPE OF SENSORS||NUMBER OF SENSORS|