Review of advanced modelling methods for lattice steel towers

Abstract : The analysis of transmission line steel lattice towers is usually performed with simplified linear numerical methods. However, the actual behaviour of bolted lattice towers is complex and may be affected by different factors such as rotational stiffness of connections, bolt slippage, eccentricities at the connection, initial deformations of the members, etc. For this reason, most utilities perform full-scale tests for the qualification of new design of steel lattice transmission towers. These tests are expensive and add delays in the planning of the construction of new transmission lines. Advanced numerical methods were developed over the years and they may effectively provide more insight into the force distribution scheme and loading condition of individual members found in the steel structure and hence, help to optimize the use of full-scale experimental tests. The objective of this paper is to review the main strategies that were identified in order to model accurately the behaviour of steel lattice towers. It reviews a number of documents that were published on this subject and presents recent advances made with research projects performed at Université de Sherbrooke. First, the choice of elements is reviewed and traditional methods using truss elements, beam elements, or a combination of truss and beam elements are discussed. The possibility to use shell and 3D elements is also evaluated. Second, the behaviour of bolted connection is studied and strategies for including the effect of slippage, rotational stiffness and eccentricities are discussed. Third, a review of research works using static and dynamic analyses is presented. Finally, a novel hybrid simulation method combining experimental tests with numerical modelling is explained. In summary, many options are available for improving modeling of the complex behaviour of steel lattice towers. One needs to select hypotheses carefully to make sure that the model is compatible with the problem studied and that its complexity is minimized. Future works needed include the simplification of model building methods, further development of hybrid testing techniques, and validation of modeling techniques with full-scale lattice tower tests