Member with combined flexure and axial forces

[Awre]

AISC have a provision for members subjected to flexure and axial force given in Chapter H (H1.1)
The given formulas require that the combination of required strengths devided by the available strengths for both axial and moment not to exceed 1
Is there any allowance for slight overstress? (i.e. assuming the result is 1.04 or 1.09)
Some engineers accepts 5% more, some other say within 10% is OK (?) I am just trying to see if there is any standard/ practice that justifies any of these claims..

Thanks

 

[rb1957]

i'd've thought it'd've been 1.00 (assuming you're using plastic bending).

another day in paradise, or is paradise one day closer ?

 

[KootK]

There's no allowance. If you really want to make something work that's slightly overstressed, however, there's usually a way to make it work by sharpening your pencil rather than simply accepting the overstress. If I'm 5% over and I know that I've got some room with K or my loads, I'll just let it go rather than re-run my calc.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[RPMG]

You should have a justification other than 10% overstress is ok. KootK is right. Maybe you don't need 5 psf for piping and mechanical loads.

I don't have my manual with me, but the interaction formula allows for 8/9 x moment strength ratio for most columns.

Try putting a knee brace on your beam-column.

 

[wannabeSE]

In the specification, there is no allowance for overstress. Less than or equal to 1.0 is pretty clear. Someone could argue that only two significant digits are required - 1.04 rounds to 1.0. On the other hand, I have seen engineering judgment used to justify slight overstresses, particularly when evaluating existing structures.

 

[jayrod12]

If I'm 5-10% overstress in combined loading but each axial and bending alone both work I will usually just finesse the loading. More often than not I'm being slightly conservative on my loading and capacities. (I typically round up for all loading calcs and down for any capacities)

More often than not I can find enough just by tightening my belt. I don't blindly accept a value of 5-10% over (That's un-true, if I'm checking an existing structure and I get 5% overstress I call it good enough without a recheck).

 

[joengineering]

Try calculating based on ASD, it might give u a smaller dcr.