After the completion of construction on a commercial building in Kampala Central business district, there was a need to provide vehicular access to the building from the city centre, across the Nakivubo channel. Therefore, to address this need, a bridge was designed to span over the 13-meter-wide drainage channel. Somers Engineering was appointed to design, detail, and install the post-tensioning system. Post-tensioning technology was best suited for this application – to span longer with comparatively thinner concrete members.
For the bridge foundation, micro-piles were preferred due to limited space as they cause minimal disturbance to the surrounding infrastructure. The piling work included the installation of 14 No. 210mm diameter micro piles to provide support for the bridge decking. The micro piles were then driven into the foundation as per the design load capacity. The bridge precast beams were then cast in molds, cured, and post-tensioned on-site in readiness for erection across the channel. The beam size was 600×200 spanning 13.0m with a spacing of 600mm centre to centre. After the erection of the bridge girder beams, 150mm of concrete was cast on the bridge deck as a surface course.
Post-tensioning is a method of prestressing concrete that employs the use high strength steel tendons that are stressed after concrete placement. Post-tensioning allows for the creation of longer, slender spans with fewer supports hence allowing for thinner slabs thereby reducing material quantities and facilitating the design of aesthetically pleasing structures
Post-tensioning offers direct cost reduction over conventionally reinforced members primarily by reducing concrete and rebar material quantities as well as rebar installation labor. Typically, savings between 10% -20% indirect costs are achieved.
If you are in need of a bridge (vehicular or pedestrian), do not hesitate to call Somers Engineering Ltd. We specialize in the execution of post-tensioning for bridges and other applications such as multistorey buildings, storage, and containment structures.