Hmmm....

Know how when you're getting a shot at the doctors or at the dentist and they always tell you to think of a happy place? What do people think of? I think most everyone probably thinks of Disneyland. When you're grown up they let you watch the needle, so that's what I do now.

ARG!

I think the second most stressful part of being a parent of small kids is getting them ready to go out the door (the worst stresser is waking up screaming at 2 am and then not going back to sleep). The getting-ready-to-go-out-the-door process exponentially complicates itself in the cold winter due to coats and shoes even though you might only be going 20 feet from your doorstep to the car, to another doorstep.

Late last night I was getting the three kids ready to leave my mom's house after the Jazz game. Maggie is at the age where she can dress herself 50 to 75% of the way, but then needs help with one thing or another. She was putting her coat on and had one arm in, but was struggling with the other. She was bending her arm back funny like happens sometimes and so she was missing the sleeve. She asked me for help, and silly mean old me, instead of having her readjust her arm, I just forced it until it went in the sleeve hole, at which point a loud pop was heard. She screamed "OWWW!!!" but didn't cry and her shoulder didn't look dislocated and she still had full range of motion, so being the proud, reassuring parent, I just rubbed it and said, you'll be OK.

So then this morning she was watching me put a coat on one of the twins. After I was done she said, "Good job brudder! Daddy not breaka your arm. Daddy breaka my arm Grandma's house." I had to laugh. She is a good sport. I am glad kids are made of rubber and they don't break that easily. I am surprised that none of them have had to have stitches yet. By the time I was their cumulative age (~6.5 years) I had had stitches at least 3 times.

Here are some pictures of the twins the Sunday before Christmas. Things started out good with a standoff-ish high five and went downhill from there.

 

Will is really good at arching his back. I think he will make a fine wrestler.

Engineering Tip #1

Since this is a blog devoted to the art and science of engineering, I decided I should post an engineering tip.

Today's tip is about broken back slopes. I know that sounds risque and improprietous, but it is not what you think, it is a real engineering term. Click here to google broken back slopes. We will break down a broken back slope to understand its features and then calculate an equivalent slope.

Everyone repeat out loud today's objective with me: We will break down a broken back slope to understand its features and then calculate an equivalent slope.

OK. Lets start by examining the case of a retaining wall. A retaining wall with an infinite slope is shown below. The wall height is H and the back slope rises from the horizontal at the angle B (beta). The angle of the backslope (beta) is used in a long equation ripe with trigonometry functions to calculate the active force coefficient of the retaining wall backfill soil that must retained. The equation is called Coulomb Active Pressure (click to see in Wikipedia - oh, and don't forget to donate).

Now we will look at a retaining wall with a broken back slope. If the horizontal distance of the slope to the point where the back slope breaks is less than 2 times H, we should calculate an equivalent back slope called B' (beta prime) to use in the Coulomb Active Pressure calculation. B' (beta prime) is the angle of a line extrapolated from the top of the retaining wall to a distance 2 times H behind the wall.

Please ask questions by clicking here.