Thank you for tolerating this question. I work in a steel frame, 10 story building constructed in 1979. On several occasions in 20 years this building has swayed just enough to notice during wind gusts of over 60 or 70 mph. While I know this structure was not designed with Northridge in mind, common sense tells me that some sway was built in, even on the east coast. It really scares people and I try to reassure them that we are not going over like a pine tree. If I know it was built to the AISC Manual of Steel Construction Type 2, and it has wind moment connections, what kind of broadside wind can a 1979 structure tolerate? I have access to the current manual, but I'm not an architect nor did I sleep at a Holiday Inn Express last night. Thanks for your simplified comments.
Non Sequitur
Oct 7, 16 1:55 pm
Wind design predates 1979 by several decades. It is reasonable to assume that at the very least, bracing was incorporated. It is however unlikely that any sort of sway damper was installed given the short height of the building.
I do find it odd that the "sway" is noticeable. 10 storeys is not that tall and a good part of the sway during high winds is a factor of the vertical length. As you sure it's not just people complaining because the windows are rattling?
Wood Guy
Oct 7, 16 3:50 pm
All buildings and their components have some amount of deflection under load. The trick is to design the structure so you don't notice the deflection, without wasting material. If each floor can move, say 1/4", that is well within the safety zone. Steel is not brittle. It's just that when that's multiplied over 10 stories, you feel the building sway more like 2-3", which is noticeable.
In certain situations, strong winds can set up harmonic vibration in the structure, which would greatly exaggerate the amount of movement, and could cause structural failure. That's when you need a tuned mass damper, as NS mentions. But 10 stories is not that tall, and it is most likely just a minor nuisance.
midlander
Oct 7, 16 7:49 pm
^they got it. but if you want to scare your colleagues a bit have them read through this one:
...nor did I sleep at a Holiday Inn Express last night? - what does that mean? is this some pop cultural reference that's totally gone over my head? should i avoid staying at HIE when I need a cheap room by the airport?
Thank you for tolerating this question. I work in a steel frame, 10 story building constructed in 1979. On several occasions in 20 years this building has swayed just enough to notice during wind gusts of over 60 or 70 mph. While I know this structure was not designed with Northridge in mind, common sense tells me that some sway was built in, even on the east coast. It really scares people and I try to reassure them that we are not going over like a pine tree. If I know it was built to the AISC Manual of Steel Construction Type 2, and it has wind moment connections, what kind of broadside wind can a 1979 structure tolerate? I have access to the current manual, but I'm not an architect nor did I sleep at a Holiday Inn Express last night. Thanks for your simplified comments.
Wind design predates 1979 by several decades. It is reasonable to assume that at the very least, bracing was incorporated. It is however unlikely that any sort of sway damper was installed given the short height of the building.
I do find it odd that the "sway" is noticeable. 10 storeys is not that tall and a good part of the sway during high winds is a factor of the vertical length. As you sure it's not just people complaining because the windows are rattling?
All buildings and their components have some amount of deflection under load. The trick is to design the structure so you don't notice the deflection, without wasting material. If each floor can move, say 1/4", that is well within the safety zone. Steel is not brittle. It's just that when that's multiplied over 10 stories, you feel the building sway more like 2-3", which is noticeable.
In certain situations, strong winds can set up harmonic vibration in the structure, which would greatly exaggerate the amount of movement, and could cause structural failure. That's when you need a tuned mass damper, as NS mentions. But 10 stories is not that tall, and it is most likely just a minor nuisance.
^they got it. but if you want to scare your colleagues a bit have them read through this one:
https://en.m.wikipedia.org/wiki/Citigroup_Center
...nor did I sleep at a Holiday Inn Express last night? - what does that mean? is this some pop cultural reference that's totally gone over my head? should i avoid staying at HIE when I need a cheap room by the airport?
wind moment connection?