Topic
Seismic
- 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
- 08
Lesson learned · Seismic
Rayleigh with a fixed β: every model in your database gets different damping
Copying the same damping coefficient into every model looks neutral, but it is not: a flexible structure ends up with 1.5% and a stiff one with 5%. I explain where that comes from and how to fix it.
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