*Scroll down to watch the quake and interviews with the researchers (Courtesy of UNR)
5:04 pm, October 17th, 1989. San Francisco. It’s just minutes before Game 3 of baseball’s World Series, and ABC sportscasters Tim McCarver and Al Michaels had just gone on the air.
McCarver: “…and he fails to get Dave Parker at 2nd base, so the Oakland A’s take the –”
Michaels: “I tell you what, we’re having an earth—”
(more static, then silence)
A section of the Bay Bridge collapsed in the Loma Prieta earthquake, as did freeways in Oakland and San Francisco. Five years later, in Northridge, another quake crumbled three busy Southern California freeways. In both cases, dozens died and thousands were injured. And major transit routes were cut off – not just for evacuating residents, but for emergency vehicles too.
But what if bridges and freeways were built so well that they could withstand a massive earthquake, or even a terrorist attack?
Saiidi: “You would not have any collapses and you would not have any major damage.”
Saiid Saiidi is a professor of civil engineering at the University of Nevada at Reno.
Saiidi: “You would have a quick inspection to make sure that you’re not missing anything. Then, you could leave it open to traffic. That’s really the goal.”
So Saiidi took a grant from the National Science Foundation and built a bridge. A big bridge. In UNR’s large structures lab, which looks like a giant, cavernous warehouse. And then, Saiidi tried to knock it down, using shake tables to simulate a series of earthquakes.
UNR professor Ian Buckle runs the lab.
Buckle: “This is pushing the state of the art of experimental work. No lab has done this before, and certainly, probably nowhere in the world has this been done on this scale before.”
How big? Try 100 feet of concrete, weighing 200 tons. The bridge isn’t life-size, but it’s as close as you could get for an experiment – after all, it’s not like you can just build a real bridge and wait for an actual earthquake. Three pairs of columns, or piers, held the bridge up – each using both conventional construction and new designs, intended to bend and sway, but not break. With nearly a hundred people looking on, Saiidi unleashed a test with twice the acceleration of the Northridge quake.
Reporter on scene: “And here we go, it’s simulating an 8.0 magnitude earthquake. The concrete bridge is swaying back and forth. There’s concrete starting to fall, and dust from Pier 1. And just like that, in about 10 seconds, it’s over!”
Saiidi: “This test went very well.”
The bridge stayed up, Saiidi says, and all the columns survived. And though it’ll take more research to be sure, Saiidi says two of the three designs – or details, as he calls them – appeared to hold up so well that they wouldn’t need any repairs.
Saiidi: “Had we used these innovative details both at the top and bottom of these columns, from what I can tell, they could easily go through something like a magnitude 8 earthquake – they could take that without collapsing, without falling apart.”
One of the people in the audience was Mike Keever, who oversees CalTrans’ earthquake division. He says CalTrans is very interested in the new designs.
Keever: “I think we’d be looking at all three in the report, and then going back and looking at where we could potentially apply these. It could be there are advantages for these different systems under different conditions or different bridge configurations.”
Saiidi hopes CalTrans will test the new designs by using them to build a real bridge within the next couple of years. Keever thinks such a pilot project might take a bit longer. But both were excited with the results – and said other states would be interested, too. Saiidi says he’ll release his final analysis in about a year.
Video credit: University of Nevada at Reno