Crews completed a permanent splice on the fractured Delaware River Bridge, which links Pennsylvania and New Jersey, one month early, allowing I-276 traffic to resume on March 9 for the first time since Jan. 20, when the crack was found on the 1.25-mile-long symmetrical truss bridge. Before it reopened, a series of load tests were successfully performed on the 61-year-old bridge, which carries about 42,000 vehicles a day. Brad Heigel, chief engineer for the Pennsylvania Turnpike Commission, said two “plug welds”—commonly used in the 1950s to fill mistakenly drilled holes—were the primary factors contributing to the fracture. The team found no other plug welds on the bridge after weeks of inspections, which included ultrasonic testing and metallurgical analysis. Heigel said the forensic team will determine whether other factors, such as air temperature, heavy truck loads or high winds, also led to the fracture. Media reports said the repair cost $12 million.
Because it can moderate the damaging effects of earthquakes, base-isolation is a technique used primarily in seismically active regions. ENR takes a look at some of the largest applications of base-isolation technologies in the world.