Tuesday, May 30, 2017
Solving the wobbly dock spur problem
Our marina has put in docks like this, with a main runner, and spurs for boat access. Trouble is that these spurs are connected with hinges, so that they can take the big waves. These hinges have a give which translates into a wobble at the end of about 2 cm either way. There is no damping, so the velocity is about 10 cm/s. So a displacement of 2 cm with 10 cm/s is a good earthquake. People are going nuts!
This ground motion, just like an earthquake, makes people think they are going to dump into the lake. But you really need a displacement of 20 cm to lose your balance, and probably 50 cm/s. That's a damaging earthquake!
Nevertheless, these dock earthquakes are a bad feeling. You need to dampen the torsion of the spurs. Basically, I am thinking about rubber at the inside corners. I was looking at an inside corner docking bumper, but they don't have those. Probably just heavy dock bumper strips bent at a 50 cm radius on the inside corner will do.
ps. I really like recycled rubber crumble stuff. The damping coefficient must be huge.