Vertical Shear Contour Plot in RAM Concept

RE: Vertical Shear Contour Plot in RAM Concept

Seth Guthrie — Tue, 04 Aug 2015 17:58:39 GMT

It's just a vector product (SRSS) since the X and Y shears are 90 degrees to each other (that's also mentioned in Section 50.1.3 "Out of plane behavior"). My example was a standard result, no patterns involved.

RE: Vertical Shear Contour Plot in RAM Concept

Lim Sam Adiputra — Tue, 04 Aug 2015 17:30:08 GMT

Hi Seth,

Thank you for the example. It helps clarify what Vx and Vy is.

One follow up question with the Max context:
Why does it do a square root of the sum of Vx and Vy to come up with the magnitude?
(e.g. 9.09 = sqrt(8.83^2+2.07^2) on the lower left column).

Section 30.2.2 talks about doing this for different loading patterns, but there is no patterned loading in this case.

Thanks,
Sam

RE: Vertical Shear Contour Plot in RAM Concept

Seth Guthrie — Tue, 04 Aug 2015 17:06:08 GMT

Let's try an example. The top is a slab spanning between two walls, essentially a pure one-way behavior. The bottom is a slab on four columns, but with a wide aspect ratio, mostly two-way behavior.

Here's a plot of the Shear in the X axis context along with a couple of slices:

Notice for the top slab that there is a nearly linear change from left to right with 0 shear at mid-span like you would see for a beam in classical theory. Furthermore, any horizontal slice would show basically the same results. The bottom slab at the columns has a similar lok, but the shear spikes near the point support. This is one of the key reasons why designers always integrate results across some width when designing concrete structures. To design for the point stresses would be overkill.

Here's a plot of the Shear in the Y context:

Notice that there is very small, almost 0, shears for the one-way slab panning left right. The two-way slab still shows shear near the columns.

Finally, here the Max axis context which is a combination of the X and Y results.

RE: Vertical Shear Contour Plot in RAM Concept

Lim Sam Adiputra — Mon, 03 Aug 2015 22:11:04 GMT

Hi Seth,

Could you define what is defined by Slab - Shear -(Mid-Depth) X/Y?

Thanks,
Sam

RE: Vertical Shear Contour Plot in RAM Concept

Seth Guthrie — Mon, 03 Aug 2015 17:56:30 GMT

Yes, the "Shear" output is for out-of-plane unit forces. "IP Shear" is the option for in-plane shear unit forces.
For a technical explanation of how out-of-plane shell stresses are derived, see program manual section 50.1.3 Out-of-plane behavior.

RE: Vertical Shear Contour Plot in RAM Concept

Lim Sam Adiputra — Mon, 03 Aug 2015 17:36:14 GMT

Hi Seth,

thank you for the reply. I will keep that in mind.

So are you confirming that the Slab - Shear -(Mid-Depth) Max/Min are showing vertical shear?
Could you define what is defined by Slab - Shear -(Mid-Depth) X/Y then? Is it showing vertical shear also?

Thanks,
Sam

RE: Vertical Shear Contour Plot in RAM Concept

Seth Guthrie — Mon, 03 Aug 2015 17:14:47 GMT

I would normally recommend plotting Slab - Shear - (Mid depth) Max (and Min) for this, though you will get a warning like this for any Rule Set:

---------------------------Slab Plot Accuracy---------------------------

The selected slab plot may contain errors due to the max/min force enveloping being performed based on values about the x- and y- axes.

So I would usually recommend doing this for each single form load combination.

Keep in mind, instantaneous though shear is not something the program designs for. It designs for vertical one-way shear on sections (including strips) and punching shear on columns only.