Chilean Bridges: Vespucio Norte POC

Speaking of earthquakes, we saw a few pedestrian overcrossings (POCs) that had collapsed during the February 27th earthquake in Chile. The superstructures were attached to the piers with two 5/8" rods that broke during the shaking.

This damage to the POC that went across the Vespucio Norte Expressway (the ring road around Santiago) was fairly typical. Of course, once it fell, it closed traffic on the expressway below (and was a hazard) until it was moved. Luckily the earthquake occurred at 3 AM.

Stronger connections between the girders and the piers and a global analysis to account for the complicated behavior of POCs when they are shaken should be routinely done to protect pedestrians and the traffic below POCs.

Chilean Bridges: Vespucio Norte POC by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Chilean Bridges: Concepcion POC with Spiral Ramps

Just a couple more pedestrian overcrossings (POC) and then we'll move on to something else.

I like the spiral ramps on this POC, although I'm surprised there is sufficient headroom for an adult. I noticed that they also provide a regular sloping ramp on one side of the road. Maybe they didn't have room to provide a sloping ramp on the other side? I also wonder if the columns for the spiral ramps are hollow and if they have a roof?

I remember there was a POC with spiral ramps near the beach in Santa Monica that was closed because of concerns how it would perform during an earthquake. However, this POC seems to be a more modest structure and the central column probably provides more stability.

Chilean Bridges: Concepcion POC w/ Spiral Ramps by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Chilean Bridges: Pan American Highway POC

There are so many concerns besides load carrying capacity when designing a pedestrian bridge. If the structure goes over a highway, you have to wrap the pedestrians in a cocoon of wire mesh to protect the drivers below. I think these fences are aesthetically displeasing and they seldom work well with the structure.

This tied arch over the Pan American Highway includes a tunnel of fencing, which does a good job of protecting drivers but it stick out unpleasantly past the arch. I suppose it's possible to make the fencing work with the arch, but I've never seen a satisfactory solution.

Chilean Bridges: Pan American Highway POC by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.