What it takes to build supertall structures

In order to construct new supertall buildings, some new building techniques are used:

Wind is the “dominant force” in tall buildings, says Baker. Over time, engineers and architects have become more and more sophisticated when it comes to shaping a building to account for gusts that can, on very rare days, reach 100 miles-per-hour at the crown of a 90- or 100-story skyscraper. Early in the design process, different shapes for a proposed tower are workshopped and run through wind tunnel testing to determine which one is most efficient. Computer simulations for complex wind patterns still take a long time, so model testing often works best to determine factors such as lift and cross-breezes. Baker says, “the wind tunnel is a giant calculator.”

Skyscraper designers want to “confuse the wind,” says Baker. Air pushing against the surface of a tall tower creates vortices, concentrated pockets of force that can shake and vibrate buildings (the technical term is vortex shedding). The aim of any skyscraper design is to break up these vortices. Facades often have rounded, chamfered or notched corners to help break up the wind, and sometimes, open slots are grooves will be added to let wind pass through and vent, in effect disrupting the air flow…

To help counter the shifting and swaying of building, engineers also utilize dampers, massive devices that shift and help stabilize tall structures like counterweights. Think of them like the weights in a grandfather clock; engineers attach 300-800 ton pieces of steel or concrete on a floor near the top of a tower, tuning and adjusting chains to balance them so they move out of phase with local wind patterns, steadying the tower. Two main types of dampers are used today; tuned mass dampers, which function like swinging pendulums, and slosh dampers, or slosh tanks, large pools of water that help absorb vibrations. The technology isn’t new; it’s been used on buildings such as the Seagram Tower, completed in 1958. But it’s become more common and more sophisticated. Some tuned mass dampers even use actuators, or small motors, to shift and move in opposition to the wind. The engineers of the Shanghai Tower even devised a damper system with powerful magnets…

Even with carefully engineered facades and vibration-canceling technology, supertalls still need to support massive amounts of weight. While we haven’t moved past concrete and steel, technological advances means the elemental ingredients of skyscrapers can support much larger loads with much less material. “Concrete is amazing these days,” says Baker. “We should call it something new, since it’s so different than concrete from a few decades ago.” More workable and up to five times stronger, concrete today has gained these powers due to a more complex chemical composition. In many cases, industrial by-products, such as fly ash, slag from steel mills and microsilica left over from silicon manufacturing, are added to strengthen the mix, allowing it to be stiffer and support heavier loads.

That’s a lot of work and we would want to make sure this is done right from the beginning. (If people are worried about all the computer code in cars, imagine an article written from the angle of what could go wrong is building these tall structures.) Just putting all the appropriate pieces together – in addition to the new technologies that evolve to help make this possible – requires dealing with an impressive amount of complexity.

Just a reminder from a post earlier this year: the engineering can get us to even taller buildings (3,000-5,000 feet) but the economics haven’t caught up yet. Yet, with the luxury end of the market continuing to thrive, perhaps we aren’t that far away…

Would you rather have a wind farm or McMansions built nearby?

This is a choice I assume many homeowners would not want to make: would you rather have a wind farm or McMansions built nearby? Here is what one Montana resident had to say in response to plans for eight wind turbines on a nearby hill:

One man’s trash is another man’s treasure. Windmills are not ugly, they are neat. Whoever saw a postcard of a windmill in Holland as a kid and didn’t want to go there? So what’s the deal? Windmills in Holland are picturesque, but a windmill in Anaconda is ugly? It’s got nothing to do with ugly. You’re brainwashed if you believe that.

I’ll tell you what’s ugly. What’s ugly is a McMansion on the skyline in Montana. That’s ugly! McMansions, with those “grand entrances.” They ought to be outlawed. Revoke the insurance policies on them I say.

What would you rather see on the skyline, a windmill or a McMansion? How would you like to look up and see some fool’s mansion everyday looking down on you? Just rubbing it in? Huh? I’d move. I wouldn’t put up with it for a week.

— Oldie

This is a clear denouncement of McMansions, particularly in the context of considering another kind of development that many homeowners would not want. Apparently, McMansions have entrances that are too large, they should not be built in the first place, the ones that are built shouldn’t be allowed to have insurance, and they are even worse when built on hills to lord it over everyone else. Perhaps McMansions should primarily be built in valleys where other people can look down on them?

Note: the windmills in Holland do look a little different than modern wind turbines…

Complaints about wind turbines: noisy and more

A number of wind farms built in more populated areas have drawn complaints from nearby residents, including the noise generated by the spinning turbines:

The wind industry has long been dogged by a vocal minority bearing all manner of complaints about turbines, from routine claims that they ruin the look of pastoral landscapes to more elaborate allegations that they have direct physiological impacts like rapid heart beat, nausea and blurred vision caused by the ultra-low-frequency sound and vibrations from the machines.

For the most extreme claims, there is little independent backing…

Numerous studies also suggest that not everyone will be bothered by turbine noise, and that much depends on the context into which the noise is introduced. A previously quiet setting like Vinalhaven is more likely to produce irritated neighbors than, say, a mixed-use suburban setting where ambient noise is already the norm.

A number of lawsuits against the turbines are now working through the courts.

An acoustic expert in the article suggests a solution: simply build the turbines further away from residences. However, there is a well-documented issue of a lack of high-capacity transmission lines that affects a lot of energy plant building.

How much of this is simply American NIMBYism in action: while people might generally support greener energy, how many want such plants built nearby?

h/t The Infrastructurist