Potential impact of the code of practice revisions on the structural adequacy of existing structures

Abstract

In this study, we delve to assess the potential impact of the TIA 222 standard revisions on the structural adequacy of existing lattice or self-supporting tower structures in Uganda. Three lattice towers of slightly varying heights and base width were selected for this study. The main objective of this project is to evaluate the potential impact of the TIA standard revisions of TIA 222F, TIA 222G and TIA 222H on the structural adequacy of selected existing lattice tower sites in the ATC Uganda portfolio. In addition, to understand structural condition of the selected lattice towers when subjected to wind loads to determine if they can take on extra loading due to the infrastructure sharing modal.

The parameters considered for the study were noticed changes in the transitions between TIA 222 standard revisions of TIA 222F, TIA 222G and TIA 222H that were Wind speed and environmental categorizations of tower sites. The data needed to complete this project was gathered from American Tower Company Uganda and Ugandan Authorities. For example, the wind map was obtained from the Uganda National Meteorological Authority and Uganda Civil Aviation Authority. The noticed changes in the TIA 222 standard transitions helped in selecting the three appropriate towers that were used this study. The main loads acting on the towers were self-weight, wind loads and antennae loads. The lattice towers structures were analyzed and designed using TnX Tower software. Environmental categorizations were noticed using Google Earth pro along with site visits in the Tower Mapping activity.

A reduction in the member capacities as we transited from TIA 222F to TIA 222H was noticed, which was because of the change from Allowable Stress Design (ASD) to Limit State Design (LSD) design Philosophy, introduction of more realistic factors of exposure, and topographic categories that reduced on the velocity pressure reaching the towers. From analysis and design it is recommended that enough attention is given to how wind affects the changes in the bracing types chosen by designers. In this one should check on the effects of the mentioned structural irregularities of (mass, torsion and stiffness) on the member sections and bracing types chosen by designers. A seismic design study is recommended too to check on how different seismic loads affect the structural adequacy of lattice towers in the different wind zones of Uganda.