IT Helps Build Bridge Over Colorado River

One construction project using new IT tools is the Hoover Dam Bypass Project, a 3.5-mile, $231 million roadway that crosses the Colorado River approximately 1,500 feet downstream of the Hoover Dam. First, laser scanning was used to build a very accurate contour map of the rugged, complex terrain. The map was used to search for geological flaws or faults that might affect construction, then as the underpinning for a 3-D landscape model on which construction alternatives could be sited and visually evaluated.

When the time came to build the bridge, engineers used a structural model of a fully trafficked causeway to calculate the optimum length of each stay and the exact degree of tension at which each needed to be set. This is often a tricky step as the load on a bridge during construction looks nothing like the load during actual use.

“In the old days, the guys in the field would cut stays according to a written procedure that was months old, and which could not readily account for actual field conditions that vary throughout erection,” says David Goodyear, senior vice president at bridge designer T.Y. Lin International of San Francisco. “Now the team assembling the bridge gets explicit instructions spelling out exactly how much tension to impose on each element.”

The design team, designated the Hoover Support Team, is a consortium headed up by HDR Engineering. Major partners are the Sverdrup Civil, an arm of Jacobs Engineering, and T.Y. Lin. An animated rendering of the construction can be seen at enr.construction.com/ features/technologyeconst/archives/030811.asp.