Yee Associates/ Brown & Root
An aluminium truss kit was among the three solutions produced by the Yee Associates/ Brown & Root team and was the design about which team members were most enthusiastic.
Light, extruded aluminium components slot together to form easily-assembled 3m deep Vierendeel trusses to which sections can be added or subtracted depending on the width of carriageway. The truss can also be adapted to carry cantilevered signs.
Extruded elements, shaped to accommodate cable channels, form the bottom chord of the truss. They will also form the walkway for maintenance workers who will move about within the truss's inverted triangle cross section.
Transparent acrylic sheets form guarding for maintenance personnel. The acrylic material is intended to heighten the sense of lightness in the structure. The team is working on a way of etching patterns onto the acrylic to make it more translucent at close range. This is expected to ensure that motorists are not distracted by maintenance work.
The team also produced similar designs for gantries using steel cable stiffened spine trusses and Jumbo steel sections.
All the designs could be used with precast microsilica concrete or steel supports. For verge supports the team suggested a water reducing admixture capable of producing different coloured concrete depending on the surrounding environments. Precast elements are designed as folded plate sections to mask the access ladder and can be cast onto formica for a smooth, glassy finish .
The full carriageway width gantry acts as a propped cantilever. Central props for the aluminium and steel trusses are also designed to be sacrificial so they can be knocked out without causing the whole structure to collapse. These struts will stiffen the truss and restrain it horizontally and will need only minimal foundations in the central reservation.