Structural Effect on Columns of Existing Low-Rise Buildings due to Installation of Rooftop Towers - A Case Study

Telecommunication towers are vital components of any telecommunication network, as the last-mile connectivity of any wireless network is usually provided by these towers. The amount of expenditure, regulatory constraint and construction related challenges for a construction of a green field tower is usually high, hence telecommunication operators started to construct towers as an alternative for greenfield towers, especially in urban areas. However, ensuring the structural stability and integrity of the host structure is essential when installing rooftop towers, as almost all such buildings have not been initially designed considering additional loads from a roof top tower. In case of occurrence of a major structural issue of a building after installing a rooftop tower would lose the advantage of rooftop towers over green field towers as a sustainable alternative. Very limited scientific research on rooftop towers and the effects of rooftop tower installation on existing structures have been carried out in Sri Lanka as well as in global context. Accordingly, this study was undertaken to study structural effects on columns of existing low-rise buildings due to installation of a rooftop tower through a case study selected based on a field survey of buildings having rooftop towers. By Computer Aided structural modelling of the selected building while changing the location of the rooftop tower on the rooftop, effects of physical location of tower on structural performance of relevant columns were studied. According to this study, it was found that the tower location of a rooftop tower is highly influential on additional stresses in columns and would exceed the design capacities of columns especially when the tower is located close to a corner or edge of a rectangular building. Further, relevant to the selected case study, it was found that cracks reported in columns in this particular case would be most likely due the overstressing of columns, and immediate retrofitting and strengthening of defective columns would be required.