New York's Metropolitan Transportation Authority is digging an artificial cavern for a future Second Avenue Subway stop below 86th street. Patrick Cashin is photographing the massive operation. Fortunately, the tunnel has been blessed by a Catholic priest. Check out more of Cashin's photos on Flickr and a brief riff on the project by Geoff Manaugh at BLDGBLOG.
San Francisco will get a new Bay Bridge this summer. The New York Daily News has an interesting story about that bridge's creation — and the earthquake-resistant engineering behind it. — Maggie
Remember when you had to build a bridge out of popsicle sticks in high school science class? The goal was to construct the miniature bridge that could withstand the most physical stress. Your materials were just sticks and glue. So the real challenge was to find strong shapes.
On the day of testing, we all learned very quickly what those shapes were. Bridges built out of lots of squares collapsed almost instantly. Bridges built out of triangles made the finals.
This is a pretty basic lesson, but it's not one that the global construction industry has learned yet, says the US Geological Survey's Ross Stein. Last week at the meeting of the American Geophysical Union, he began a talk on "Defeating Earthquakes" by demonstrating the difference between the cube-centric structures we build all over the world and how much stronger those structures can be if you just add triangles in the corners. It's a powerful demonstration of how simply having the technology to solve a problem isn't enough. You have to get people to use it.
This whole video is worth watching and easy for laypeople to follow. And it's just one of a huge collection of lecture videos from AGU 2012 that are now available online. They cover everything from the chemistry of lighting to the geology of volcanoes to the effects of space storms and solar flares. Very cool stuff!
How do engineers know that the pillars supporting a bridge can withstand the force of thousands of cars driving over them for decades? How do we know what would happen to that bridge during an earthquake? What about an earthquake in winter?
Buildings, roads and bridges are all designed with a buffer of safety—basically, engineers round up on the numbers, a lot, and design these things to be far more sturdy than they actually have to be. But to make those decisions, they first have to know the physical limits of the materials they're working with. The best way to do that: Take a scaled version of a girder, pillar, or concrete slab and push it past the breaking point. Yes, this is, in fact, as awesome as it sounds.
The Constructed Facilities Laboratory at North Carolina State University is one of the places in the United States where this kind of research happens. In this lab, engineering researchers shake, bend, freeze, and crush the stuff that supports our world. I got to take a tour of this lab back in January, led by lab manager, Greg Lucier.
The videos here will take you through the 4500-square-foot lab and introduce you to the equipment these engineers use—from giant compression machines to something called a "Thermotron environmental chamber."
We'll start with a quick spin around the lab, just to get acquainted with the space. Then, you'll learn how some of the systems you see here work and why they're so important. Finally, you'll get to watch the lab in action.
Read the rest
Anechoic chambers are pretty damn awesome. Basically, they're rooms designed to be sound-proofed against outside noise, while, inside, sound is prevented from bouncing off the walls. There's no echo. There's a number of ways you can build this, but one system at the University of Salford in England, is actually a room within a room, with the innermost chamber actually mounted on springs, rather than the floor of the outer room.
Anechoic chambers are often used to test out audio equipment or to get accurate audio measurements on systems that are supposed to operate very quietly.
Minnesota Public Radio recently went inside the room that holds the title for world's quietest—an anechoic chamber at Orfield Laboratories in Minneapolis.
To get into the anechoic chamber, you go through two bank vault-like doors. The floor in the room is mesh like a trampoline so there's nothing on the floor for the sound to bounce off of. The walls are lined with sound-proofing wedges that are a meter long so they absorb the sound.
...A typical quiet room you sleep in at night measures about 30 decibels. A normal conversation is about 60 decibels. This room has been measured at -9 decibels.
Listen to the rest of the story at Minnesota Public Radio's website.
Read about the history of anechoic chambers.
Image: Photo of an anechoic chamber taken at the Kyushu Institute of Design's anechoic chamber by Alexis Glass. Free to use under GDFL.