DTE Energy needed an analysis performed on the NE Substation communication tower to account for proposed changes in AT&T cellular equipment. Commonwealth was chosen to analyze the tower which also included existing DTE Energy and ITC equipment. The proposed AT&T equipment included standoff frame mounted antennas, additional TMA’s, coax cables, and a RET cable. The existing DTE Energy equipment was various standoff frame and leg mounted antennas and coax cables. The existing ITC equipment included an antenna and coax cable.
Commonwealth evaluated and analyzed the tower strength in accordance with the Telecommunications Industry Association standard, “Structural Standard for Antenna Supporting Structures and Antennas” (ANSI/TIA-222-G). The structural analysis was performed using PLS-TOWER. The wind load case was applied to the analysis in the worst case loading direction for the tower.
The analysis results indicated that the legs of the tower were overloaded which in turn may also be causing overstresses on the foundation. To remedy the overstresses, additional bracing would be necessary as well as full leg replacement to replace damaged members. Commonwealth did not recommend that the proposed AT&T equipment be installed. Additionally, Commonwealth recommended that for future upgrades to be achieved the tower should be replaced, be designed to the latest ANSI/TIA code and any future proposed loading at the site.