Derek Larsen's Activities

Code Minimum Steel in Ram Concept for PT Slab

Derek Larsen — Tue, 11 Oct 2022 18:21:11 GMT

I am trying to understand how Ram Concept applies the code section ACI 318-14 section 8.6.2.3, which simply calls for 0.00075 x Acf.

Here is the cross section in question from the "Audit Cross Section" tool. Acf in this direction is 3205 inches squared, which I take no issue with. 0.00075 x 3205 inches square = 2.41 inches squared = (8) #5's

The program actually picks out (13) #5 bars, so I tried to figure out where that comes from by the Audit Cross section tool:

This shows a number called Acf(Parallel) and they call it span section area. I have no idea what this area is or where it is in the ACI code. This is a much larger area than the cross section in the longitudinal direction. Could you clarify where this area is coming from?

Thanks,

Ram Structural System with Ram Concept - LLR Parameters

Derek Larsen — Fri, 25 Mar 2022 23:07:49 GMT

So I am entering the LLR Parameters manually in a 3 over 1 Podium building and am trying to get the Live Load reduction to work. On my job, I have (3) levels, so I thought if I input an area for one level, and then input the total number of levels, that the program would then do the live load reduction based on 3 times the input area. I just went through the latitude design strips, and input the area of each design strips (taken directly from a plan where "Visible Objects:LLR Parameters" is turned on). I input that area in both the Trib Area and Influence Area values on the LLR tab of the design strip settings dialog. I then input the number of levels as 3. The 'LLR Levels' didn't appear to make any changes to how the program calculated the LLR.

As an example, 1 bay of a continuous design strip that I have has LLR Parameters area of 681 sf. It is roughly 28'-0" long by 24'-0" wide so that area appears correct. I have the LLR Calculations set to the 2018 IBC. I went through and input manually that the "LLR Levels" = 3 and the Trib Area = 681 sf, and the program calculates a 17.5% reduction. This 17.5% reduction is what you would calculate by IBC 2018 Equation 16-23 for a 681 square foot area and a Kll = 1.0 for a two way slab.

I thought the whole reason to have the LLR Levels input was so I wouldn't have to calculate by hand the area is 3 times the area that I input (when you have dozens of bays in two directions, and you are inputting the areas manually, adding a calculation to it would be even more cumbersome). So what is the point of the LLR Levels line? What am I doing wrong?

Problem with Ram Concept Version 3 - Mat Foundations

Derek Larsen — Mon, 31 Jan 2022 23:43:25 GMT

A co-worker was using Ram Concept Version 3 to design some Mat Foundations, and it wasn't reporting any bearing pressures for the purely gravity load load cases (D+S, D+L, D, etc). So I opened one of my old files in Ram Version 2, got the bearing pressures for those gravity load cases. Then I upgraded to Version 3, opened the same file, ran it, and did not calculate any bearing pressures for the gravity load cases. Just curious if this is a bug or if there is some new settings we are not aware of.

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Tue, 18 Jan 2022 02:33:25 GMT

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Does Ram Structural system allow you to adjust the in-plane base fixity of shear walls when they are tilt-ups without holdowns?

Derek Larsen — Tue, 18 Jan 2022 02:32:56 GMT

For modeling tilt-up walls in Ram Structural system, we were curious as to the proper base fixity when holdowns are not used on the wall. It seems that a fully fixed in-plane stiffness would not be appropriate, but we were unable to find any way to modify its in plane stiffness.