They did that in San Fran and it took just one earthquake to pancake the upper and lower lanes.
Yes NathanR, but if you look at the way they constructed them, it’s no wonder.
There were cement risers every so often that resembled large posts. The whole freeway shifted the length of the stretch of freeway.
If you put cross bracing in, that stops.
I don’t know how they ever got a permit to do what they did. I’m not in the industry, and it looked very flimsy to me.
In all fairness, the joint connections of the ‘Cypress Structure’ column-to-deck needed more joint reinforcement to insure stability; but, the placement of the elevated freeway on landfill was the first error. The second contributing factor was that the Cypress was at the convergence zone for two propagation paths of seismic waves, originating from the Loma Prieta quake.
Before the quake, if caught in rush hour stoppages on the lower deck, thumps and vibration could be felt every time truck traffic passed on the roadway above. On first acquaintance with this quirk, one might easily have believed another vehicle was providing the jostle.
That’s because the concrete pilings for the Nimitz freeway were not reinforced properly for earthquakes. They were simply reinforced with vertical rods. I saw an analyisis on TV once that indicated that if the pilings had also been reinforced with circular horizontal rods, they would have held up.