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Providing tower bracing is preferred but you certainly can do it. If the stringer is attached to a slab, you’ll only have a one bolt connection likely. Also you should play close attention to the flexibility of the stringer/tower connection. Another option is to provide a knee brace from...

I've never done this design before but you can Hilti those in by the development length and rely on shear friction for the shear at the joint. You might want to consider the cold joint at the sidewalk. Hilti has a guide with examples for slab extensions.

If you can get one stirrup near the top of pedestal (within the 5"), you can do a strut and tie check for the high shear load. Refer to PIP STEO5121. Alternately, you can check your concrete breakout strength and other anchorage requirements from your code.

@ ENGDM, exactly - it's great for that situation. Make sure you have torsional support at the support points.

Agree with Dave. If you need to squeeze more capacity out of an existing beam, you can add bottom flange braces or increase your Cb factor. See AISC commentary, section F1. There is a formula that allows you to make use of top flange support for negative bending.

Refer to Pip STE05121 for a guide on designing anchor reinforcement according to ACI. If breakout strength is insufficient you can rely on the pedestal bars by effectively “lapping” them with the anchor bolts. You need to provide sufficient development length above and below the breakout cone...

PCA "Concrete Floors on Ground" is a good reference.

Thanks Koot. Just lateral support of the top flange would be sufficient. Found this: https://www.youtube.com/watch?v=rNMX962XVsQ&t=2812s Skip to 33:00 min.

Hello, Would you consider new steel beams grouted under an existing slab to be fully supported? I saw an article once saying that the restoring torque from the slab reaction is sufficient in preventing lateral torsional buckling, but I can no longer track down the article. Does anyone have a...

If you neglect the St. Venant torsion, your warping moment will be higher, which will be conservative with respect to normal stress (in my experience normal stress usually controls in design, but not always). Neglecting St. Venant torsion can be done as per AISC design guide 9: Note that this...

You should have a panel point at the ridge to remove eccentricity in the top chord. Why are you placing your panel points in line with the end columns? There are requirements for stability type braces, however for a roof truss you should have higher forces from lateral loads.

DTS, table 22.9.4.4 has equations for the upper limit on interface shear strength (which are dependent on Ac). If Ac is taken as the area of the compression block then you will likely get a reduction in shear strength.

VT do you mind sharing the example from SE reference manual? Does it bother you that Hilti doesn't follow this method for Ac calculation?

VT17, I've battled with this question myself since ACI does not clearly define Ac. I generally agree with your approach. There are a few clues that lead me to believe ACI is referring to the entire shear plane and not just the area of the compression block. 1. The title of Table 22.9.4.4 -...

Thanks Geoff, that is helpful. Basically, for a flat bottom tank (with shell flaring out) you still load up the shell from the product weight on the upper portion - This is interesting, I hadn't though of this. For a standard flat bottom tank (with no flare), you ignore the product weight...

Geoff, the tank widens to 56 ft, there is no error in the loading. Yes, the 20300 includes both product weight and dead weight of shell. Yes, roughly 21" bolt spacing. We actually have a skirted tank, so there is no tension in the anchor bolts as per my calculation above. My question is...

OK thanks Geoff, in this case I am looking at the anchorage of the bolts though (pullout, side-face blowout, concrete breakout). For this part of the design, ACI or CSA A23 would apply.

The overturning moment is 65700 ft-kips, operating weight is 20300 kips, bolt circle is 34 ft, 60 anchor bolts. Using the PIP equation for bolt tension, you would get: Would it be applicable to use the equation as above? Or should I remove the dead load portion and design for 132 kips tension...

The tank is designed to API 650. I used the PIP guide just to estimate the anchor bolt tension (using applicable load cases from ASCE 7). The anchorage will be designed according to ACI.

Good morning Eng tippers, For flat bottom vessels, is it safe to rely on the operating dead weight to counteract seismic overturning moments, when looking at anchor bolt tension? I am concerned that the flexibility of the bottom plate will prevent the content dead weight from counteracting...