Section
Design log
- 09
Design log · Seismic
Springs in series: the bearing sets the period too
A bridge pier is not just a column: bearings sit on top and a foundation sits below, and all three deform. In a typical case, adding them takes the period from 1.3 s to 1.9 s.
5 min read
- 06
Design log · Dams
Koyna Dam, 1967: why a concrete dam cracks at the "neck"
In 1967 an earthquake cracked Koyna Dam, in India, right where its downstream face changes slope. I modeled it in OpenSees and the video shows how that damage appears, second by second.
3 min read
- 03
Design log · Seismic
You do not design the cap beam with the reduced force: capacity protection
In seismic design we choose which part of the bridge gets damaged, like a fuse. Everything else is designed for what that fuse can transmit. In a two-column bent, that is almost twice what the analysis says.
3 min read