شبیه سازی عددی رفتار سازه برج های انتقال

Transmission towers are a vital component and management needs to assess the reliability and safety of these towers to minimise the risk of disruption to power supply that may result from in-service tower failure. Latticed transmission towers are constructed using angle section members which are eccentrically connected. Factors such as fabrication errors, inadequate joint details and variation of material properties are difficult to quantify. Consequently, proof-loading or full-scale testing of towers has traditionally formed an integral part of the tower design. The paper describes a nonlinear analytical technique to simulate and assess the ultimate structural response of latticed transmission towers. The technique may be used to verify new tower design and reduce or eliminate the need for full-scale tower testing. The method can also be used to assess the strength of existing towers, or to upgrade old and aging towers. The method has been calibrated with results from full-scale tower tests with good accuracy both in terms of the failure load and the failure mode. The method has been employed by electricity utilities in Australia and other countries to: (a) verify new tower design; (b) strengthen existing towers, and (c) upgrade old and aging towers.

Overhead transmission lines play an important role in the operation of a reliable electrical power system. Transmission towers are a vital component and management needs to assess the reliability and safety of these towers to minimise the risk of disruption to power supply that may result from in-service tower failure. One of the problems facing tower designers is the difficulty in estimating wind loads as they are based on a probabilistic approach. Another is tower strength, which in contrast, could be deterministic provided a proven-reliable analytical tool is available for the specified design load conditions. In practice, factors such as fabrication errors, inadequate joint details and variation of material properties are difficult to quantify and they are often used to justify the use of full-scale tower testing. Strictly speaking, however, test results are only valid for the particular tower under the particular test loading conditions, and they may not predict exactly how a tower may behave in practice under different loading conditions. This paper describes a computer simulation technique for predicting the ultimate structural behaviour of self-supporting and guyed latticed transmission towers under static loading. The technique can predict accurately the failure load and the failure mode of towers, and may thus be used to replace or reduce the need to carry out full-scale tower testing. The method has been employed by electricity utilities in Australia and other countries to: (a) verify new tower design; (b) strengthen existing towers, and (c) upgrade old and aging towers. Three case studies are presented: (i) a calibration case study, (ii) a case study involving the strengthening of existing towers, and (iii) a case study involving upgrading old towers. For commercial reasons, ownership of the towers will not be revealed.

The paper describes a nonlinear analytical technique for simulating the ultimate structural response of latticed transmission towers. Accurate structural analysis of towers is complicated because the structure is three-dimensional and comprised of angle section members eccentrically connected. The influence of geometric and material nonlinearities plays a very important role in determining the ultimate behaviour of the structure. The proposed technique may be used for verifying new tower design thereby reducing or eliminating the need for full-scale tower testing, in addition to providing a degree of design confidence. It can also be used for assessing strength of existing towers, or upgrading old and aging towers. Three case studies have been reported. In the first case, the technique was used to verify design prior to full-scale tower testing which included loading the tower to failure. The method has been shown to predict accurately both the failure load and the failure mode. In the second case, the technique was used to strengthen existing towers and in the third case, the technique was employed to upgrade the capacity of towers that were 45 years old. In Case Studies 2 and 3, proof-loading of the towers would have been very difficult, if not impossible.