STRUCTURAL HEALTH MONITORING OF A LATTICE TOWER

Abstract

Structural health monitoring of a lattice tower is presented. This research was prompted by the requirements of the Nigerian Communications Commission (NCC) that all masts should be checked for their structural health status every five (5) years. However, In the bid to cut down maintenance costs, some telecommunication network providers have adopted tower sharing without checking their structural health status to ensure their capability of bearing extra load from additional equipment, consequently creating an upsurge in the construction and maintenance of telecommunication towers. In this study, a lattice tower with the weakest parameter was selected: a 45m tower, with three (3) legs, erected over nine (9) years and shared by three (3) telecommunications operators in the Federal Capital Territory (FCT), Nigeria. The tower’s structural stability and utilization percentages were determined. The auditing of the tower and foundation was also carried out. There were no twisted or missing members on the tower and no visible crack or blister on the three (3) stub columns. The average compressive strengths of the stub columns determined using the Proceq digital Schmidt hammer were 25.1, 25.9 and 25.9 N/mm 2 for legs A, B and C, respectively. From the structural analysis of the lattice tower using the Effective Projected Area (EPA) model, the tower utilization percentage was found to be at 59% after optimization. While results obtained from the STAAD pro. V8i analyses show that the utilization ratios (actual ratio to allowable ratio) of the tower members are less than one (≤ 1) and there was no failed member identified after the structural analysis. The lattice tower can be said to be stable and fit for continuous use. However, the tower paint needs repainting, and it is recommended that structural status be checked whenever additional telecommunication antennas are to be installed on the tower by telecommunications network providers to prevent structural damage and consequent collapse of the tower.