LONG BEACH, Calif. (AP) – A replacement bridge under construction at the nation’s second-busiest port isn’t just a crucial route for cargo trucks and Southern California commuters – it’s a concrete-and-steel science experiment for engineers and seismologists. The new Gerald Desmond Bridge stretching over the Port of Long Beach is being built with about 75 seismic sensors called accelerometers. They’ll measure the forces imparted on the bridge during an earthquake. It’s slated to open next year. California’s bridges and other infrastructure have been outfitted with quake sensors since the 1970s. But the new Long Beach span marks the first time they’ve been incorporated into the design of a bridge from Day One.