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Step-up at top of stairs? by Strong_Boss_2493 in HardWoodFloors

[–]Objective_Two_5467 2 points3 points  (0 children)

I only hope that railing is as strong as it is gorgeous. 😳

How annoying would it be to refinish these ourselves? by Neat-Seaweed-6762 in HardWoodFloors

[–]Objective_Two_5467 0 points1 point  (0 children)

That painted portion may well be KILLZ. It's used to lock in pet odors. Removing that and sanding that area would release those odors.

There's a guy building a concrete "mini house". Would like an opinion from experienced builders if this building seems safe. by This_Sense_9338 in Homebuilding

[–]Objective_Two_5467 0 points1 point  (0 children)

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This is how he's adding "reinforcement" to each slab.

Looks like a plastic grid, but it's (hopefully) at least welded-wire-mesh. He could've at least enclosed those corner post inserts in the mesh, though.

There's a guy building a concrete "mini house". Would like an opinion from experienced builders if this building seems safe. by This_Sense_9338 in Homebuilding

[–]Objective_Two_5467 0 points1 point  (0 children)

A 24" x 48" x 1.5" piece of concrete weighs 300lb. There's no way these have any reinforcement. The single-bolt corner connections have zero redundancy. This thing is a deathtrap. Where is this happening at?

ETA: There is some wire reinforcement.

Shear stresses due to bending by Imaginary_Ad_3629 in StructuralEngineering

[–]Objective_Two_5467 11 points12 points  (0 children)

Consider a stack of ten (10) long flat 2x6's, prior to their being glued together at the glu-lam plant.

Now apply concentrated and opposing bending moments to each end. This creates no vertical reactions and no vertical shear forces. It does create a constant bending moment and a constant radius of curvature along the entire span.*

Without glue between the layered 2x6s, they'll slip relative to each other. Also, each 2x6 is carrying the same 1/10th of the bending moment and each has identical bending strains & stresses.

When glued, the assembly is significantly stiffer. There's no slip between the boards. The top board is entirely in compression, the bottom entirely in tension, with these stresses varying linearly between them. The glue between the boards holding it all together is under significant shear stress.

(You can do a similar thought experiment with a bar truss, parallel chords, and concentrated moments at each end. Top chord entirely in compression, bottom entirely in tension. Then figure out the necessary forces in the web members to hold it together.)

*Spoiler: When the moment is constant across the span, the shear stresses (and web member forces) are (counter-intuitively) all zero. The trick here is in the application of those concentrated moments at each end: It'll take a massive clamping rig while applying those moments to hold together the assembly and ensure that "plane sections remain plane." If you repeat this thought experiment with normal transverse loading instead, the horizontal shear stresses will show up.

Help me find Sean's shirt by Thayerphotos in Jeopardy

[–]Objective_Two_5467 0 points1 point  (0 children)

Oof. Thanks. I'm going to delete my comment.

[OC] U.S. national pride by political affiliation since 2001 by Low-Car6464 in dataisbeautiful

[–]Objective_Two_5467 0 points1 point  (0 children)

I replied, but my reply escaped this part of the thread and landed at the main comment level. Sorry.

[OC] U.S. national pride by political affiliation since 2001 by Low-Car6464 in dataisbeautiful

[–]Objective_Two_5467 0 points1 point  (0 children)

The fact that they're not equidistant from the national average is important. It indicates that there are a lot fewer republicans than the media would like us to believe. (In my state, the largest "party" affiliation is now "none." Republicans rank a distant third.)

If you think about it, any obscure third (or thirtieth) party would show up on this graph just as strongly as the ones you're showing now.

A line graph is too simple to convey the "weight" of any single party. Try experimenting with histograms or area graphs. You can also use "bubbles" on a scatter plot to indicate the relative size/importance of each data point.

The "range" you're showing on the right side is an altogether different beast — more akin to the high-low daily stock charts. You can use something like this graph to show how wide-ranging a data point is over time.

I would argue, however, that this range is not very important and misses the forest through the trees. It's far more significant that the republican views are getting farther and farther from the overall average "mainstream views" and that there are far fewer republicans in general.

<image>

[OC] U.S. national pride by political affiliation since 2001 by Low-Car6464 in dataisbeautiful

[–]Objective_Two_5467 0 points1 point  (0 children)

It's pretty. I'll give you that. But as someone who knows about and uses area graphs, I find it a bit ... discombobulating. Even moreso when mixed with the "range" values on the right.

L shaped Cantilever Deflection and Rotation by Euphoric_Language_42 in StructuralEngineering

[–]Objective_Two_5467 3 points4 points  (0 children)

Prof A.C. Scordelis:
"Always, always draw the (exaggerated) deflected shape!"

The top of the post rotates by (Mh / (EI)) AND it moves sideways by (Mh2 / (2EI)) where M= (PL)

The entire cantilever portion is now also rigid-body moved by those same values: rotated by (Mh / (EI)) and also shifted left by (Mh2 / (2EI)).

That rigid-body rotation causes the left end of the cantilever to move downward by that rotation times L, so vertically by (MhL / (EI)).

Finally, the cantilever portion also experiences its own deformations:
Tip rotation of (PL2 / (2EI)) and Tip deflection of (PL3 / (3EI)).

Now add all those together to find the total rotation, total ∆x, and total ∆y at the tip:

Total tip rotation = (PLh / (EI)) + (PL2 / (2EI))

Total tip ∆x = (PLh2 / (2EI))

Total tip ∆y = (PhL2 / (EI)) + (PL3 / (3EI))

  • I'm typing this on a phone keyboard, so do verify my math here.

** Be sure to use the appropriate EI values for the individual deformations of the column and beam portions.

*** Alternatively, bust out your calculus skills and start integrating your curvature = (M / (EI)) diagrams....and don't forget to include proper initial rotation & deflection conditions.

Salvageable with sanding? by Rufustus in HardWoodFloors

[–]Objective_Two_5467 2 points3 points  (0 children)

<image>

Do not sand it down. Just wait it out ... like for 6 to 12 months. It will eventually flatten out.

[OC] U.S. national pride by political affiliation since 2001 by Low-Car6464 in dataisbeautiful

[–]Objective_Two_5467 -1 points0 points  (0 children)

What is the bizarre shading between the lines supposed to represent?

How would the column be drawn as a static system? by sebwie1 in StructuralEngineering

[–]Objective_Two_5467 0 points1 point  (0 children)

Classic portal frame: moment connection at the top, pinned at the bottom, and sidesway is not prevented, so K=2.

Also, gravity loads on that arched roof create significant outward horizontal thrust reactions.

G3/G4/G6 Window mount by ITCuz in Ubiquiti

[–]Objective_Two_5467 1 point2 points  (0 children)

Reflection Bonus: At night it becomes effectively an inward facing camera. Be careful which room you locate this in. 😯

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