Structural EIT. I feel exactly the same way. But, even with tensile forces neglected, grouting the entire wall will lower axial stress significantly over 16" on center, so also this agrees with your extra masonry to end up with a higher capacity. However, the lower allowable due to the...
There is also the debate about what qualifies as eccentricity. I have always allowed for eccentricity for all conditions, as a minimum of 2", even for a full bearing beam on top of a pilaster. I think that the contractor will miss it, beam will be too short, etc. Would you agree or disagree...
So I just read something. That Pe for unreinforced masonry is 0.25 because of the reduced moment of inertia and inherent eccentricity due to the cracked section. The Pe is not something checked in ACI 530 section 2.3. Can anyone verify this?
I too am in ACI 530-05, maybe equation numbers are different in other versions.
JAE- why no check of Pe in h/r less than 99? If you do check it, then P for 8" o.c. would be less than Pa. From the Pe equation for 8" o.c. I get 7648 lb/lf with E=1350000, In=443,e=2, h=12'. And 8782 lb/lf for...
Great discussion. My design is working out fine with the lower buckling stress for 8" on center, so I'm going with the reduced load based on 1/4 Pe.
Ok, MSJC 2.2.3.1 equations 2-10 and 2-11 are for all members subject to axial compression and/or flexure. Only Fa is different depending whether...
For an interior wall with 5 psf load (dealing with stack bond here so it is a little different than running bond). Allowable Pe is 1/4Pe I get the following
8" 16"
Pa=approx 11,000plf Pa=approx 7250plf
Peallow=6370plf Peallow= 7320plf
So yes, the fa (therefore Pa)...
r=(I/A)^0.5
At 8" o.c. At 16" o.c.
Aavg=91.5 Aavg=65.8
Iavg=443.3 Iavg=387.1
r=2.2 r=2.43
Although the I increases 14%, the A increases 40%, driving down the r.
At 8" centers, Pe=25470#/lf
at 16" centers, Pe=29300#/lf
at 32" centers, Pe=32900#/lf
Anyone have any...
Ok, calculators out!
Contrary to what I believe, apparently, a solid grouted masonry wall buckle at a lower load than one with grout at 16" on center. ACI 530, Equation 2.2.3-d with the following values:
8" wall
h= 12'
e= 2"
E= 1125000
Wall Properties
8" on center 16" on center
r= 2.2...
Thanks to everyone for the comments. I understand this is a difficult issue. Lb being the primary problem. Is it reasonable to use the following: For the first third, Mn based on Lb is 30' for the unreinforced beam, for the middle third, Mn is based on Lb of 30' for the reinforced section.
Can anyone explain to me how a allowable shear and moment diagram will look like for a steel beam that is partially reinforced with a C on top? The Lb is the length of the beam, the beam in reinforced in the middle third. Will the moment capacity of the unreinforced section be based on the...
There are inward forces and outward forces, tie beams across the building seem more appropriate. I was considering that the building might try and move laterally with wind, with the tie beam soil friction and footing overturning/sliding keeping the building in place. If the above is not...
New pre-engineered metal building with no slab, 100' clear span. The contractor wants tie beams, not large footings. I'm thinking that dead-men along the tie beams will put the thrust back into the ground. Any other ideas????
A tie rod cannot be used at this point, a thrust block is required. My problem is that it is relatively shallow so develops a low passive pressure. Making it deeper is more economical, but puts a couple into the block from the column thrust at grade level, to the center of reaction of passive...
My solution was a thrust block in the form of a grade beam, this keeps it close to the building, but involves more re-bar than a true thrust block. It's looking like it will use less concrete though. The contractor wants to look at alternatives, I'm guessing to save some steel. Any ideas on how...
