huangyhg

wind load on elevated structures?
which asce section applies on houses that are only a few feet above the ground?
find a job or post a job opening
assuming you are referencing asce 7....all of them.
the wind speed calculated in asce-7 chapter 6 is a 10 meter height (or below).
ron, thanks for the wakeup call.
my project is a beach front house. it will be elevated 4 feet above the ground. the site is flat.
the question is what is the effect of elevating the structure 4 feet on wind load? and where is that covered in asce 7
seanan...thanks for the clarification. you will have wind flowing under and around the building, so you can get uplift potential on the floor area, similar to an overhang condition.
wind flowing under the house will cause negative pressure under the house and positive pressure inside the house. this will cause the house to pull down toward the ground. the load is downward. not uplift
the wind flowing over the house has a larger distance to travel, therefore less velocity.
bernoulli's equation tells us that the pressure above the house will be less than below... which causes uplift.
the same is the case for airplane wings, the top of the wing is longer than the bottom, creating uplift, that's how planes fly...
not to mention automobiles... the top of the car is obviously longer than the bottom, which causes uplift due to air velocity, so the closer to the ground the car is, the less air can go under the car resulting in less uplift.
i'm not a physicist.. but i'm pretty sure that's how it works.
air going under the car causes a drag not uplift!!
i'm with bridgebuilder on this one. the wind will cause an uplift which needs to be checked per the overhang section in asce-7
not to point this thread towards cars, but like you said it does cause drag, but also uplift. have you ever watched gt racing? there are plenty of instances... take a look.
"air going under the car causes a drag not uplift!!"
check out f1 cars ... their underbodies are carefully designed to maximise downforce from airflow under the car's body.
the point is the aerodynamics are way too confused to say upforce or downforce will be generated ... ground effects, local trees, landscaping, etc all have an effect. i think the code provided a conservative solution and as an alternative you could spend a tonne of money modelling and analyzing your specific design to prove that in no case is uplift generated ... but it'd be way easier to work with the code, no?

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