ABSTRACT
The measurement of the cable tensions of a cable-stayed bridge during the tensioning process is of great interest, because this value is critical to the correct distribution of internal forces in the finished bridge. But this is not an easy task, especially when it is not possible to use load cells. In this case, it is necessary to use indirect measurements, such as strain, elongation and vibration techniques, among others.
This paper shows a case study of a curved in plan cable-stayed bridge placed in Oviedo (Spain). This bridge is composed by a total of 21 suspension cables, 26 supporting cables and 2 loops. The loops collect the tensions from both the supporting and suspension cables and carry them to a retaining wall and an inclined pylon. General view of the cable-stayed bridge during the tensioning process. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig320_1.jpg"/>
All cables are Full Locked Coil Strand, and they are provided by Fork Socket. This system makes impossible the use of load cells to measure the tension of the cable. As consequence, it is necessary to use alternative measure techniques to get the tension force, such as 2 mm-length strain gages glued to some of the wires of the cable, vibrating wire extensometers, transducer displacements, which measures the elongation of the cable between two different cross-sections, and accelerometers, to obtain the tension through the natural frequency.
Environmental conditions during the tensioning process (daily thermal variations, rain, etc) have a significant influence on the measurement.
The different techniques above mentioned are compared, in terms on measurement quality, linearity response, feasibility, robustness under environmental agents, cost of implementation, etc.
