ACI-318-05 (Section 11.6.3a) û Torsional Moment Strength

[eeedesign]

Hello Fellow Engineers!

Anybody can suggest solution and practical ideas if the stresses in Torsion + Shear exceed the limit by the Code stated above without increasing the section of the concrete beam?

Your comments and suggestions is really appreciated. Thanks guys....

 

[JedClampett]

Have you maxed out the reinforcing?

 

[eeedesign]

Thanks JedClampett. Reinforcement is not an issue since i can still go with the requirements, but i am just worried about the capacity of my concrete because it exceeds as per code requirement.

 

[BAretired]

You can add ties as required. What is the problem?

BA

 

[JedClampett]

Are you exceeding the limits set in ACI 318 Chapter 11.5.3?
Those limits are pretty high. I wouldn't exceed them.

 

[jsha811]

Post tensioning is a way to solve the problem.

Moment curvature analysis,reinforced concrete column design and prestressed concrete pile design at

http://www.structurexpress.com

 

[eeedesign]

Yes JesClampett and that is the issue i need to solve without increasing the section of my beam (above Aci code is 2005 which u can find in Chapter 11.6.3, chapter 11.5.3 in Aci 2008 as you mentioned). Thanks jsha811 but Prestress is not allowed as an alternative due to un availability of such system in the area and beam section limitations.

Here's the forces for your checking:
Beam section/dimension is limmited to b=400mm H=700mm
Mu = 795kN.m
Vu = 460kN
Tu = 180kn.m
Fc' = 40MPa
Fy = 460MPa
Fyt = 420Mpa

 

[JedClampett]

I'm kind of flailing, but can you go to a higher strength concrete?

 

[RFreund]

Not sure if this is even possible but maybe encased steel tube?


EIT

http://www.HowToEngineer.com

 

[PUEngineer]

This isn't coming from compatibility, correct?

 

[cliff234]

Can you re-frame your floor to eliminate the torsion? I try to avoid torsion whenever possible. I like to keep things simple. Why do you have torsion in the beam?

 

[eeedesign]

JedClampett: i tried to increased the concrete to higher strength same as the columns (fc,=50MPa) but still failure occured. So it means that Aci 318 Chapter 11.5.3 shall be satisfied only by increasing the section, am i correct?

Thanks Cliff234, i'll try to reframe the structure in a way to reduced the stresses. [sub][/sub]

 

[hokie66]

eeedesign,
Please answer PUEngineer's question. He (and I) are suspicious as to what kind of torsion you have. If you would describe the structure or show us a plan of the structural element in question, we could assist further.

 

[eeedesign]

Hi PUEngineers: Yes, it is a compatibility torsion.

 

[eeedesign]

hokie66,

Since it is compatibility torsion, i changed the torsional modifier (J) to 0.01 and got a smaller torsion effect. Am I going ryt for the solution? please advise. Thanks