PopSci's Best of What's New 2007

Engineering
Jacobs-Sverdrup and Thomas Jee and Associates Golden Gate Bridge Seismic Retrofit

NEW QUAKE-PROOFING FOR AN OLD BRIDGE

Following the 1989 Loma Prieta earthquake, studies showed that the Golden Gate Bridge needed a serious upgrade to survive another large seismic event. Now, thanks to a six-year-long project to bolster the southern approach, the 70-year-old bridge can withstand a magnitude-8.3 earthquake and support up to 220 percent of its weight laterally—up from 7.5 percent before the retrofit. The challenge was reinforcing the iconic bridge without changing its look. Engineers modified the structures that connect the steel beams to the concrete pylons, giving the bridge an inch of vertical travel so that it will float instead of snap when shaken. To minimize destruction, contractors also installed metal plates that shear under stress at designated fail points. goldengatebridge.org

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