Spaghetti Bowl quake repairs to take one night, $20,000
The earthquake damage that closed a Spaghetti Bowl ramp as Memorial Day travelers were coming into and getting out of town will take one night and cost $20,000 to repair.
The dislodging of protective rubber encasing a bridge seam on the ramp connecting southbound U.S. Highway 95 to southbound Interstate 15 was the only highway bridge damage resulting from Friday’s 4.8-magnitude quake centered near Caliente just before noon.
The Nevada Highway Patrol closed the ramp after discovering what appeared to be earthquake damage. The Nevada Department of Transportation concurred with the decision to do further inspection. The ramp was closed about four hours.
Inspectors wouldn’t speculate whether the earthquake shook the rubber cushioning loose or whether a quake of equal or greater magnitude would result in the same outcome.
“The entire replacement process will take place within 24 hours,” Transportation Department spokesman Tony Illia said. “The work will be performed at night in order to minimize traffic disruptions. In addition, nighttime work provides a cooler ambient temperature for concrete curing.”
The joints are engineered to fill a seam with a rubber cushion for gaps of 1 to 20 inches. The damaged seam had a gap of 6 inches that department officials said “made it look much worse that it was in reality.”
The department has determined that the ramp is safe for use and most motorists probably don’t even realize where the joint is when driving over it.
Normally, the gap isn’t the problem; it’s when the gap fills with dirt and road debris that problems can occur.
“(The rubber) helps keep dust, dirt and debris out of the joint gap; it’s an important function because if the gap gets filled in, then the bridge’s ability to properly flex, expand and move is greatly reduced leading to possible product failure,” Illia said.
The rubber cushions on the Spaghetti Bowl bridge joints were due to be replaced during the Project Neon construction program that begins next year. There’s no set replacement cycle for the cushions because their durability is based on weather conditions and wear from vehicle use. The redesigned Spaghetti Bowl bridge joints have been in place for about 15 years.
District Engineer Mary Martini said the old bridge expansion joint would have to be fully removed by saw-cutting the surrounding concrete to pry out the joint. The replacement joint will be moved into place and new concrete will be poured around the joint, embedding it into the deck.
“A chemical additive helps the concrete cure quickly, reaching serviceable strength within hours as opposed to a month,” Martini said.
The concrete will achieve about 75 percent of its final design strength of 5,000 pounds per square inch before being opened to traffic. It’s a job that will require the ramp to be closed overnight to minimize traffic disruptions on the state’s busiest freeway interchange. The department expects to take the project to bid and award it next month.
The Transportation Department inspects all of its 1,100 bridges statewide a minimum of once every two years as required by federal law. Inspectors will take a closer look at a bridge or road if there has been a crash or an extraordinary incident, such as the earthquake.
The Caliente earthquake was relatively shallow which resulted in there being less damage to structures closest to the epicenter.
Contact Richard N. Velotta at rvelotta@reviewjournal.com or 702-477-3893. Find him on Twitter: @RickVelotta.
