Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/699963
EquipmentWorld.com | July 2016 53 with an airport job completed in 2001, and a highway project in 2003. The first published research on stringless paving, issued in 2003, covered a project in Iowa. Multiple impacts Stringless paving eliminates several factors affecting smoothness that are connected to using stringlines. These include sag associated with stringline expansion in hot weather, push up from improperly tensioned sensors, deviations from the loss of contact, bumps from knots and/ or splices and the human factor of the crew making touching sensor controls too often. Stringless systems control hori- zontal and vertical curves to be more accurate to the plan, with a series of arcs (the curved part of a circle) paved rather than a series of cords. In geometric terms, think of a circle, with the curved part as an arc, and a cord as a straight line along the arc. By paving as an arc/ curve instead of a series of straight lines roughly forming a curve, a 3D system creates a more accurate and smooth surface. This means more precise machine control to smaller increments in a digital format. That precision translates to improved and consistent ride quality, control of material quantities and lower yield loss, which helps lower costs. Efficiencies also come in the form of man hours, as contractors gain productivity and time efficiency with these systems. They can re- duce their field surveying and elimi- nate stringline surveying for hubs and stakes. Crew members establish a control network that consists of control points that are created from the field survey work. These control points are tied to known bench- marks positioned out of the way of operations and the public. As a re- sult, crew members also spend less time on overall grade preparation. Safety is also improved with these systems. Trip hazards are reduced and site access is improved, particu- larly for inspectors and testing tech- nicians. There also are fewer back- up hazards and paving at night and in tight areas is less complicated. Stringless methods also allow crews to work in a more compact space, since they require less than half the clearance on each side of the paver than that of stringline operation. Systems designed for efficiency Brian Lingobardo, systems manager of 3D Road Construction for Top- con Positioning Systems says the No. 1 benefit of stringless paving can be simply pulled from its name. "No stringline reduces material A total control station from Topcon. Image: Topcon