Concurrent multi-scale modeling of a transmission tower structure and its experimental verification

The interruption of electrical service due to failure of transmission tower structures can have devastating economic and social consequences. The current method for analyzing transmission tower structures is often to treat the angle members of the tower as either pin-ended truss elements or fix-ended beam elements. This approach ignores the effects of joint flexibility, local geometric and material nonlinearity, bolt slippage and deformation, making the structural analysis and design of the tower inadequate. In an effort to improve the structural analysis of transmission tower structures, this study aims at developing a multi-scale modeling method for transmission tower structures, in which critical joints of the tower are modeled using solid elements in a great detail while other members are modeled with common beam elements. The critical joint model includes gusset plates, angle members and bolts. The effects of local geometric and material nonlinearity and the contact problem between the bolts, plates and angles are all taken into consideration. New multi-point constraints for beam-to-solid connections at interface developed by the authors are used to couple the critical local joint model with the beam elements to form a multi-scale model of the tower. To verify the multi-scale modeling method, a physical model of a transmission tower structure was constructed and tested. The displacement and strain response of the tower model measured from the static tests are compared with the numerical results. The dynamic characteristics of the tower model identified from the dynamic tests are also compared with the numerical results. The comparative results show that the multi-scale modeling method is feasible and accurate for simultaneously predicting both global and local responses as well as estimating dynamic characteristics of the transmission tower structure.