PRECAST ARCH SYSTEMS

The use of Techspan precast arch system eliminates the time and cost of erecting formwork, curing, striking, and scaffolding. In most cases TechSpan can be installed without disrupting the flow of traffic under the arch, or redirecting watercourses.

 
The TechSpan arch is created by assembling prefabricated concrete segments. Each element consists of a half section of arch varying in length to suit each individual project. The base of each element is placed on a simple foundation and the elements support each other by pressing against each other at the crown. This procedure allows rapid installation as shoring of the units is not required. A team of four operatives can install 15 to 20 linear metres of arch per day without the need for scaffolding or expert assistance.
Each foot of the arch may be supported on independent strip footings or a concrete raft foundation. The foundation size will depend on soil conditions, structure size and loading above the arch. The arch segments are placed in 100mm deep keyways cast into the foundations, these locate the arch feet and aid alignment during construction.
The first segment is placed into the keyway. In place, but still held by the crane, the first element will act as the support for the second segment which can now be positioned using a second crane. Simultaneously, both cranes bring the top of the TechSpan elements together so they interlock at the top. The second element is aligned with the first element in a staggered fashion by ½ the panel width plus joint. By staggering the elements, each subsequent element will bear against the previously placed element. Once the first four units are in place, their alignment verified, the second crane may be released and construction may proceed using one crane until completion of the TechSpan arch.
The TechSpan elements are then grouted into position at the footing keyway, a small beam is cast at the crown to provide a longitudinal tie between the segments, at this stage a waterproofing membrane or geotextile lining may be applied to the joints.

Approved backfill material is placed around the arch such that the differential level between opposite sides of the TechSpan structure does not exceed 500mm. At this point, Reinforced Earth Headwalls and wingwalls can be constructed as they coincide with the arch backfilling sequence.
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