Within a very tight schedules, a 1.5 km of bridge parapets had to be constructed, but, using advanced equipment, this was no problem for the Sangamo Construction Company.
Stringless Construction Of Parapets
Based in Springfield, Illinois, Sangamo Construction had been contracted to build several bridges including the parapets required: five bridges in central Illinois with a combined length of some 850 m plus another 700 m in the southern part of the state.
The parapets were 1 m high, 48 cm thick at the bottom, tapering to a width of just under 27 cm at the top, and had a perpendicular rear wall. As much as 260 m3 of concrete were processed just for the construction of the four 150 m long parapets on the twin bridges on Interstate Highway 55 near the small town of Lincoln.
The paving work was performed by a Wirtgen Slipform Paver SP 15i with AutoPilot which Sangamo had purchased from the North American Wirtgen Group along with an extra mould for parapets and another for curb and gutter profiles.
We have been in the concrete construction business for a long time and are particularly experienced in the field of bridge construction,
reports John Jilg, Project Manager at the Sangamo Construction Company.
In the past, a small team constructed the sidewalks, curbs and gutters and then Sangamo concluded a contract for a number of smaller repair jobs in urban areas.
Once we knew that we would be carrying out these tasks in addition to our bridge construction work – which always includes safety barriers in the form of bridge parapets – we decided to purchase a slipform paver,
The three crawler tracks and the possibility of mounting the moulds on either side of the machine are huge benefits,
explains the Project Manager. He felt that a larger model with four crawler tracks would not have been the right choice, particularly for work on narrow roads, which are often obstructed by parked cars in urban areas. This would disrupt the flow of traffic too much. But with its SP 15i, Sangamo is always flexible.
We have used the slipform paver to construct curbs and gutters in Springfield, but we can also use it to build 1 m high parapets,
Stringline-Free Paving Technology
The possibility of stringline-free paving was another key aspect in plant selection Developed by Wirtgen, the AutoPilot is a cost-effective 3D control system for offset applications and the construction of monolithic profiles such as concrete safety barriers, curbs, gutters and channels.
The GPS based system ensures maximum precision and efficiency, not only when creating straight or complex curved concrete profiles, but also when constructing closed configurations. There is no need for a digital terrain model, as the profile path or configuration is programmed on the spot.
The Autopilot permits fully automated top-quality paving in radii down to as small as 600 mm. The time-consuming and labour-intensive surveying, installation and removal of stringlines can now be completely dispensed with.