Civil Engineering March 2021 | Vol 29 No 2

supports. The beams therefore had a vari- able cross section over their length, which had to be considered with the design software. Using SOFiSTiK, the beam was mod- elled using a parametric function which added a vertical curve to vary the cross section over its length. The results were checked against several spreadsheets and hand calculation techniques. The out- come is a visually appealing, structurally robust beam element. FOUNDATION CONDITIONS Due to limited space available in the road reserve, and the positioning of the pier foundations in proximity to the edge of the N2 roadway and existing embank- ments, sheet piling was used to preserve the layerworks and integrity of the embankment. The beams and slab elements were manufactured offsite at the Cape Concrete yard to very strict tolerances and brought to site prior to launching. BEAM LAUNCHING Part of the N2 highway at Broadway Boulevard Bridge had to be closed in order to place the precast beams. The contractor was allowed a 19-hour window over a weekend to launch the 12 precast beams. This resulted in two night launches of 10 and 9 hours each, for Saturday and Sunday night respectively. This accounted for the time required to transport the beams from the concrete yard, and the re-positioning of the crane truck on either side of the bridge. The inbound carriageway was closed on the Saturday night, and the outbound carriageway the Sunday night, and all the beams were successfully placed within the stipulated hours. TRAFFIC ACCOMMODATION To minimise traffic congestion due to the closure of the N2, traffic was directed to detours through intersections at Victoria Road / N2 intersection; Macassar Road Exit Ramp / N2; and through the Broadway Boulevard (R44) / N2 inter- change via the exit ramps back onto the N2. This was achieved with careful inter- action between the construction team and local traffic control authorities.  Micro piling at the northern abutment (Credit: W Scheepers) Completed piers (Credit: W Scheepers) Night launch of precast beams over the N2 (Credit: N De Mink) Civil Engineering March 2021 19 Placing of precast concrete slabs (Credit: N De Mink)