Thursday, July 8, 2010

What's wrong with this picture


My wife and I visited friends over the July 4th weekend. On our way home on I-65 (somewhere between Indianapolis and Chicago) we exited the interstate to fill our car's gas tank. That's when I noticed something odd about the first gas station we passed (see the picture above).

Can you guess what's wrong?

Hint #1: Gasoline burns when exposed to fire

Hint #2: Fireworks are small explosives


Not wanting to risk our safety, we returned to the interstate to fill-up at a gas station 10 miles away. Why? It takes one idiot with a lighter to trigger an explosion at a combination fireworks/gas station and we did not want to be around for the show.

Did anyone else question the safety of the combination fireworks/gas station or was common sense also on holiday over the July 4th weekend?


-Dr. Dave

Tuesday, July 6, 2010

Expanding concrete! Really?!?


A portion of Chicago's famous Lake Shore Drive (LSD in local parlance) was closed due to buckled concrete (see the photo from the Chicago Tribune).

Why did this occur? It's simple: the heat.

In grade school science class, kids are taught the concept of thermal expansion: the phenomenon where high temperatures cause materials to expand and cold temperatures cause materials to contract.

Everything undergoes thermal expansion. In fact, some materials noticeably expand or contract with only a small change in temperature. Engineers must factor in thermal expansion of different materials when constructing roads, bridges, and buildings.


Why? Let's take the buckled LSD concrete as an example:

Under normal circumstances, roadways are designed to accommodate thermal expansion and contraction to certain design limits.

The weather over the past few days in Chicago has been anything but normal and likely exceeded the design limits. Unusual warmth both day and night, prevented the concrete sections from cooling and contracting sufficiently. While the concrete was able to withstand several warm days and nights in a row, the intense heat on Monday was the final straw for the section in question. As the concrete expanded beyond engineering limits, several slabs pushed against the other with great force. The only way to relieve strain was to move in the direction with the least resistance (upwards), which is what happened.

Considering the length of Lake Shore Drive, I'm impressed only one section buckled.

Some may ask, why not construct the roadway with greater high temperature tolerances? Since the road way must be used year-round, engineers must also consider the opposite problem of thermal contraction during the winter. If the roadway was only designed with tolerances for the heat of summer, it is likely there would be gaping cracks in the concrete during the cold winter temperatures.

Oh, I forgot to mention that temporary repairs were made overnight to the section of buckled concrete. Thank you City of Chicago Department of Transportation road repair crew!

-Dr. Dave

Friday, July 2, 2010

Time for a change

I started www.drdavescience.com for my then 10 year-old cousin. He'd always ask me how everyday things work (e.g., airplanes, microwave ovens) and I would do my best to explain so he could understand. I must have done something right because I received requests from kids and adults around the world a few months later.  And so I wrote. And wrote.

Writing simple and accurate responses to complicated questions is both challenging and time consuming. In the beginning, blogging was a welcome distraction from the monotony of chemistry graduate school. Yes, the science was fascinating but the daily routine of experimentation and failure wore me down. Blogging kept my spirits up and my mind sharp.

After graduating with my Ph.D. in chemistry, blogging also helped me land a job as a science writer! Amazingly I used the same skills I developed while blogging to write and review scientific documents for pharma companies. Unfortunately my job leaves little time to think about blogging about how things work. But I still want to write! What to do?

Well, I finally decided that this blog will no longer be a how-does-it-work site. Rather, I will write about things I've learned, thoughts about whatever is on my mind, and funny and not-so-funny incidents I've experienced while trying to navigate the worlds of science and business.

And with that, I start new.

Best,
Dr. Dave