Demo, hold the dust
Safer, smarter practices in demolition
Sometimes, before a new building can go up, an old one must tumble down. Whether it’s fallen into disrepair and been deemed unsafe, or a new development can’t feasibly incorporate the old, some structures end up on the wrong end of a wrecking ball.
But modern demolition entails more than just smashing things or blowing them up. Complicated layouts such as aging power plants and bridges present unique challenges. Asbestos or other hazards might well lurk. And to be green, reusing and recycling are de rigueur. Let’s explore a new wave of innovation in the art and science of deliberate destruction.
Hats off for the hat method
Three rival Japanese firms manage to demolish high-rises without smashing or blowing up anything at all. Across the nation, hundreds of towers more than 100 meters (328 feet) tall were erected four or five decades ago. Most aren’t up to the nation’s current, more stringent earthquake codes. That means a big demand is nigh for efficient, environmentally responsible demolition that doesn’t disturb the neighbors. (In densely-built Tokyo, as in many cities, there’s hardly even room to swing a wrecking ball today.) To meet that demand, the Taisei, Takenaka, and Kajima corporations are in a race to perfect a technique whereby a building is dismantled floor by floor.
In the Taisei and Takenaka systems, a protective “hat” or “capping” hangs from a high-rise’s roof. Covering the top three floors, this suspended scaffolding is covered with dust and noise barriers. Inside, crews cut holes in the floors and install temporary columns and giant hydraulic jacks. Then with jackhammers and excavators, they break apart the floors and walls. A ceiling traveling crane brings the refuse to an opening where a telpher crane lowers it to the ground floor. There, workers load the broken-up concrete and steel onto trucks that ferry it to a recycling center.
Once a floor is demolished, the jacks lower the capping, and the cycle repeats. In this way, Taisei shrunk the 139-meter (456 feet) Old Grand Prince Hotel Akasaka by two floors every 10 days.
That project was covered by Wired and other American outlets. However, the Italian engineering firm Despe has been taking down buildings in a similar manner for years. They call their method Topdownway:
Taisei takes the method further by using a telpher crane that actually generates electricity. Though the crane itself uses electrical power, the motion of the crane dropping and rising creates energy that is captured and stored in a battery. The new energy powers lights and fans inside the capping.
Kajima’s demolition method is similar, using giant hydraulic jacks to shrink a building, but they dismantle from the bottom. The Kajima Cut and Take Down Method takes inspiration from a Jenga-like traditional Japanese game, Daruma Otoshi. See the time-lapse video of a Kajima project:
Cons and pros of these seemingly painstaking methods? It takes months to deconstruct a building, and it isn’t cheap. But Taisei estimates it reduces carbon emissions by 85 percent, noise levels by 20 decibels, and dust by 90 percent. Despe says its system contains 100 percent of the dust. Plus, the Italian company provides clients with advertising space on its highly visible protective tent.
Work in the enclosed space is not subject to the whims of weather. And best of all is the safety benefit. Whether inside the “hat” or operating from the ground floor, there’s no danger of debris or equipment falling on workers or passing pedestrians.
When failure begets success
Even the more dramatic form of demolition—using explosives to effect a controlled implosion—can be done in a smarter, more efficient way. A new entity in the UK offers a streamlined, tech-enhanced process, using robotics as well as explosives honed in the military.
The Atom Project comprises three firms that came together in the wake of tragedy. In February 2016, the conventionally planned demolition of the UK’s Didcot Power Station went awry when the building partially collapsed, killing four workers. For months, it wasn’t even safe to enter the teetering ruin to retrieve the workers’ bodies.
The power plant owners fired the previous demolition contractor and brought in Arcadis, AR Demolition and Alford Technologies to collaborate on a solution. Pooling their experience, they used point cloud laser surveys to assemble a 3D model of the site to plan the number, placement, and strength of explosives. Top-of-the-line Kiesel demolition robots—capable of switching attachments in minutes—rolled in to cut and remove anything that could be salvaged.
The robots then placed linear cutting charges in the planned locations. These are explosives engineered to blast a knife-like cut into steel or concrete. They’re common in the military, but not yet in commercial demolition. “There’s a reticence about adopting the technology,” Alford Technologies Managing Director Roland Alford told the Construction News, “but it is totally reliable.”
The effort succeeded in bringing down the rest of the power plant—entirely remotely. The three companies decided to continue their partnership. Alford declared, “This is the iPhone moment for demolition,” a potential sea change in the way demo is done.
Rise of the “robots’” relevance
Of course, demolition robots themselves are not new. Swedish-based Brokk sold its first such vehicle in 1976. But their use is growing, for safety and cost reasons. Although they’re not, strictly speaking, robots.
“‘Demolition robots’ is the generally accepted term,” said Peter Bigwood, VP of sales and marketing for Brokk’s North American division. “It sounds cooler and trips off the tongue better than the more accurate nomenclature, which would be ‘remote-controlled demolition machines.’”
Human technicians operate electric-powered Brokk and similar machines from a safe distance—as much as 100 yards away if need be. At trade shows, Bigwood will ask potential customers, “And would you like Brokk binoculars with that?”
Bigwood says several factors explain why his company is selling more Brokks than ever before—even with new competition from Husqvarna, suggesting “the pie is bigger,” he said.
“It’s really hard to get labor in construction,” Bigwood said. “There are parts of the country where you won’t find a guy who’ll operate a jackhammer.” Those who will are aging. “The spirit is willing, but the flesh is weak. They hurt their back or shoulders,” and that leads to expensive workman’s compensation claims. “If a robot costs 150 grand, that might be cheaper than a couple shoulder operations.”
Added to that, Bigwood said, is “a greater emphasis in the industry on safety, which as a human being I welcome wholeheartedly.” Hammering from afar using a remote control box means “keeping your workforce safe so they can go home at night.”
Oftentimes, smart demolition is simply a matter of smarter planning. Derrick Chery, project manager on a Suffolk job in East Boston, worked with JDC Demolition to demolish a smokestack. Before imploding it, the team calculated the radius of the area that would be filled with smoke and dust; they then flooded the area to drastically reduce the dust.
“It’s not common to do a takedown that way, but it saved us a lot of time,” Chery said. “A few mini-excavators picked up all the brick and it took us only a couple hours to get it cleaned up,” versus the delays in a dust cloud scenario.
ENR recently reported on an innovative approach to a complex project, the dismantling of an abandoned sugar factory in Colorado. The team there used careful planning and asbestos-proofed trucks in order to defer the asbestos abatement to an outside facility.
And for complexity, you can’t beat the San Francisco–Oakland Bay Bridge. In three sections—two suspension bridges and a cantilever bridge—this 1930s structure stretched four and a half miles across the bay. With the opening of a new and more quake-resistant Bay Bridge, the old bridge has been under deconstruction since March 2015. The gargantuan effort includes cutting, imploding, and shipping away trusses on barges. Essentially, crews are taking the bridge apart in the reverse order of how it was built.
What happens to the materials?
Many in the Bay Area have wondered, what’s to become of the 167,100 tons of steel that made up the Bay Bridge? Most of it will be sheared to size and reused in construction projects across the country.
But much of the steel has been set aside for public art. For example, AECOM—an architectural firm that has been a frequent collaborator with Suffolk—will turn some of the salvaged steel into stylized benches and planters along a new river walk called Clipper Cove Promenade. Pedestrians will be able to stop and relax on pieces of the old bridge as they take in views of the new.
Recycling can happen on a smaller scale, too. A Suffolk project team in southern Florida found 16 pallets of unused paint in a site slated for demolition. “It’s amazing that much paint was sitting around,” said Suffolk Senior Virtual Design & Construction Manager Kyle Goebel.
Rather than pay for disposal (or worse, cart it off to a landfill), Goebel arranged to donate the paint—all $25,000 worth—to the local Habitat for Humanity. Soon Habitat’s volunteers will be painting the walls of affordable homes in the region. “The cost of living is always an issue here,” said Goebel. “The fact that we were able to salvage this material efficiently and for a good cause was a great use of resources.”
Crash, boom, bang
Of course, recycling, robots, giant jacks and noise barriers, and all these innovative demo methods do lack one thing: the satisfying punch of a wrecking ball or dynamite implosion. So in case you need to scratch that itch, we’ve put together this little montage. Enjoy!
This post was written by Suffolk Content Writer Patrick L. Kennedy. Video edited by Suffolk Content Marketing Manager Zachary Leighton. If you have questions, Patrick can be reached at PKennedy@suffolk.com. You can connect with him on LinkedIn here or follow him on Twitter at @PK_Build_Smart. You can reach Zach at ZLeighton@suffolk.com or connect with him on LinkedIn here.