ABSTRACT
Cables structures are becoming more and more common in engineering practice. These structural systems include main elements of support for roofs, suspension bridges or alternatively, systems of retention of structures or structural components, for example, cable-stayed bridges.
The present studies are centered on the cable stayed bridge over the River Arade, in Portugal and consisted in the analysis of the static response of the cables subject to self-weight and evaluation of natural frequencies and modal shapes in order to indirectly extract the installed force.
The static and dynamic analysis of cables were developed in two forms, an analytical by the formulation presented by Caetano (2007) and numerically in ANSYS. The two approaches provided good correlation results and showed also very close results to experimental data in reports Freyssinet (2005) and Caetano, et al. (2007).
The application of the optimization methodology of the numerical model to estimate the tensions in cables based on the measurement of natural frequencies provides accurate estimation, with errors no greater than 4.13% for long cables and 4.91% for short cables, compared to experimental tests. For short cables, given the difficulty in evaluating the effect of bending stiffness, two stages of optimization were required, where the first consisted in identifying an optimal cable section and the second phase consisted in the identification of the tension.
Referring to the relative importance of natural frequencies, it could be concluded that the frequency of the 1st mode has a higher correlation with the load in the cable than the others frequencies. This emphasizes the importance of searching for the identification of the first frequency in the experiments, in particular when the force on the cable is estimated by frequency measurement.
As regards the choice of algorithms for the optimization process, it could be concluded that mode-FRONTIER showed smaller errors in the estimation of loads than the Design Exploration ANSYS, particularly in the testing of short cables, where errors are more pronounced. Cable 24S Correlation of the load and frequencies. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig328_1.tif"/>
Finally it can be concluded that by optimizing of the numerical model, it is possible to find the values of the stresses in the cables, and the accuracy is directly proportional to the installed load and to the number of response parameters used in the optimization process.
