Feature
Steel Awards 2015
placed at the most efficient structural support positions.
Where it was not possible to avoid a particular tree, it
was either allowed to pass through the structure, or
was tied back to ensure that it experienced minimum
interference from the structure.
The spine of the structure, a single tube section, forms
the bottom chord of a truss. The box section handrails
double as the top chords of the left and right trusses.
Ribs cut from 8mm plate at 1m centres serve both as
stanchions and as the vertical elements of the trusses.
The ribs are made up of three parts bolted together
below the deck. This ensures efficient use of material;
facilitates handling in the confined areas between trees;
and limits the use of heavy equipment in this sensitive
area.
All components were pre-assembled in the workshop
and when installed on site everything fitted perfectly,
with no on-site cutting or welding being required.
Since being opened to the public, the Boomslang has
proven to be extremely popular. The increase in gate
income from more visitors allowed the capital costs of
the bridge to be recovered within one year of it being
opened.
This fact influenced the judges who said: “The project
not only met the professional team’s requirements and
was aesthetically and practically outstanding, but it also
increased the numbers of visitors to the Gardens by over
30% thus making it a resounding commercial success. It
thoroughly deserved the Bridge category award.”
PROJECT TEAM
CLIENT: SANBI (South African National Biodiversity Institute)
ARCHITECT: Mark Thomas Architects, in association with
Christopher Bisset
STRUCTURAL ENGINEER: Henry Fagan & Partners
QUANTITY SURVEYOR: Bernard James & Partners Quantity
Surveyors
MAI 8