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20m Span Floor I Beam VS Truss Beam

20m Span Floor I Beam VS Truss Beam

(OP)
I am designing a double story amphitheater and clear span of this structure is 20m ,so i am stuck in floor beam design , either it should be a simple I beam(Standard Sections) or i should go with hot rolled truss beam so any one can suggest for this type of clear span (20m) which option will be better???

Additional Information:
however the floor joist are UB Section @ spacing 1.2m and frame bay spacing is 5.5 m
floor live load is 5KN/m^2.
Floor Beam is supported by the UC column

RE: 20m Span Floor I Beam VS Truss Beam

What is a hot rolled truss beam?

RE: 20m Span Floor I Beam VS Truss Beam

Sounds like a truss is probably the way to go. You'd be looking at a pretty deep hot rolled beam and you probably wouldn't want to skimp on depth much as vibration control will be important.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: 20m Span Floor I Beam VS Truss Beam

(OP)

Quote (Sounds like a truss is probably the way to go. You'd be looking at a pretty deep hot rolled beam and you probably wouldn't want to skimp on depth much as vibration control will be important. )

after reading your comment some points comes in to my mind as mentioned below.

after initial design it comes know that UB762-267-197 section is enough for this span (max deflection is coming 50mm DL+LL) so the effect of vibration will be enough for this much deep beam if yes then how we can control the vibration any suggestion??

however truss depth is required 1150mm so my question is that does the vibration effect will be less in trusses as compare to I beam section??

one more option in my mind is that i run the main floor beam in shorter span (5.5m) and floor joist in longer span (20m) but i guess this will be an expensive option as a lots of splice connection involves due to transportation limitations??

RE: 20m Span Floor I Beam VS Truss Beam

How about multiple Main beams in 5.5m direction spaced apart to allow suitable timber joists over. Not sure of flooring that would span 1.2m over joists with 5kPa?

RE: 20m Span Floor I Beam VS Truss Beam

(OP)

Quote (What is a hot rolled truss beam?)

i mean truss beam is made from UB Section (Standard Sections).

RE: 20m Span Floor I Beam VS Truss Beam

Quote (shahg123)

then how we can control the vibration any suggestion??

You gotta do the math and get a good match between mass, stiffness, and excitation characteristics.

Quote (shagh123)

however truss depth is required 1150mm so my question is that does the vibration effect will be less in trusses as compare to I beam section??

Often stiffness is a big help with vibration. A deep truss will often be stiffer than a shallower beam.

Quote (shagh123)

one more option in my mind is that i run the main floor beam in shorter span (5.5m) and floor joist in longer span (20m) but i guess this will be an expensive option as a lots of splice connection involves due to transportation limitations??

that does sound promising. You'll have more splices but also a lot few pieces and connections overall to erect.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

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