It is a well-established fact that built-up compression members exhibit extra flexibility than their equivalent solid members due to the shear action which effects the overall stability. This is usually taken into consideration by using a modified slenderness ratio for buckling modes that involve relative deformation of the interconnectors. Built-up members are often used as space truss members in communication towers. When modeling communication towers in structural analysis programs like SAP2000, the built-up member is usually defined as a single member element with a double section cross section. This does not catch the increase in deflection in the member due to the shear effect on the interconnected main members. To investigate the effect of this extra flexibility of built-up members on the overall side-sway of a communication tower, the single member element can be replaced by two elements with a variable number of interconnectors. The nonlinear analysis of the tower with a single element representing the built-up member was compared with the nonlinear analysis of the tower using two elements to represent the built-up member. Communication towers with a height of 22 m, 50 m, and 100 m were investigated to see the accuracy of the results obtained by modeling built-up compression members as a single member. Recommendations are made for the correction of the side-sway of communication towers modeled using single elements to represent built-up members.
El-Mahdy, G.M. and Alawamry, A.A., Modeling Considerations for Built-Up Compression Members in Communication Towers. (2021). Proceedings of the 2021 SSRC Annual Stability Conference, Online Event, 12-16 April 2021.