RICHMOND, California — Sure, earthquake engineers can now make bridges safe during even the biggest earthquakes, but they’re still rendered unusable in the key hours after a temblor.

Now, they have a new goal: building bridges that cars can keep driving over in the immediate wake of a quake. And they unveiled a set of technologies Wednesday at the Pacific Earthquake Engineering Research Center that may be able to make cities more resilient in the wake of a disaster.

“Can we design bridges to not just be safe but remain open after an earthquake?” asked Stephen Mahin, the director of the center.

Recent earthquakes in China and Haiti showed how vulnerable poorly designed buildings are, but in the rich countries around the quake-prone Pacific Rim like the United States and Japan, earthquake engineers have solutions to the basic architectural problem of keeping a building standing under extreme forces. Seismic isolators allow buildings to slide around a bit as a way to dissipate the energy of an earthquake. New ways of making and reinforcing concrete keep columns from cracking.

Now, though, engineers want to keep buildings not only intact, but functional. In the video above, engineer Kenneth Ogorzalek, a graduate student in civil engineering at the University of California at Berkeley, built a test railroad bridge complete with tracks on a shake table. To simulate the weight of the real thing, he used every scrap of lead the engineering center could muster. Thehttp://blog-admin.wired.com/wiredscience/wp-admin/edit.phpn, the movements caused by several earthquakes like 1989’s Loma Prieta quake were re-enacted by a series of actuators located underneath the floor of the experiment area.

You can see two systems at work in the video. First, there is a series of a new type of isolator called a “triple pendulum.” The isolator reduces the amount of force the bridge experiences by slowing down its acceleration. The triple pendulums are like nested bearings, so the bridge can respond appropriately to different-size quakes.

The other innovation is a way of coupling the sections of the bridge together. The idea is to make sure that even if the segments of a bridge move a little after a quake, they still form a straight line that can be used. The Segmental Displacement Control Isolation System was tested for the very first time Wednesday.

The new technology probably won’t be used for years, but Mahin said that his group was “doing research now to support what policymakers will want to do in 10 or 15 years.”

Posted in: