African Design Magazine November 2015 - Page 28

the support tower then moved on wheels to the next truss. Once all the trusses had been erected, the mobile tower was then incorporated into the permanent works. “The design of the boxed trusses was a complex process that required careful consideration of erection safety and stability,” Tim Dubber, principal technologist: structures at Hatch Goba in the Eastern Cape, comments. The springing of each truss consisted of a double pin support, thereby providing sufficient lateral stability to individual trusses, even without lateral bracing. The design and detailing of the bolted and welded connections using square hollow sections meant that special attention had to be paid to the higher design and fabrication complexities of the connection type. Another design and detailing challenge was posed by the wind load transfer from the door pockets to the arch, given the load magnitude, arch geometry and bracing stiffness required. An innovative lateral bracing system was introduced that involved the use 28