91视频

Construction of District Office, a six-story, 90,400-square-foot mixed-use building on the rise at Southeast Martin Luther King Jr. Boulevard and Stark Street, began in May 2018 with demolition of the former home of Portland Music Co. One year later, crews are installing cross-laminated timber elements.

The building will feature a structural framework of glulam columns and beams and CLT floor panels around a pair of concrete building cores. One level of below-grade parking is topped with a post-tensioned concrete deck, but then it’s all wood until rough-in.

鈥淭here was a lot of conversation early on about trying to do them at the same time as we do timber,鈥� Andersen Construction project manager Katie Hoyt said. 鈥淏ut the cores require so much of (a) crane that you really have to dedicate the crane to them.鈥�

Andersen Construction is building District Office for Beam Development and Urban Development + Partners. Hacker designed the building to hold five stories of creative office space above ground-floor retail space. The exterior will feature brick cladding, fiberglass windows and aluminum storefronts at the main entry fronting Southeast Martin Luther King Boulevard.

District Office is one of a growing number of mass-timber buildings in the Portland area. The structural component has continued to gain acceptance among both builders and, more importantly, the International Building Council. Its code now makes provision for mass-timber construction up to 18 stories.

One of the biggest advantages of mass-timber construction is the time saved via use of prefabricated beams, columns or panels 鈥� or all three together. In the case of District Office, DR Johnson of Riddle manufactured every single beam, column and CLT floor panel before a single piece arrived at the job site. This allowed truckloads of columns and beams to arrive on-site to be installed immediately by a small crew of carpenters from Timberland Inc. Then 42-foot-long CLT floor panels are flown into place with the tower crane.

鈥淭he whole building is fabricated, and a small part of it is here and the rest is in Riddle,鈥� said Brad Nile, a project executive with Andersen Construction. 鈥淚t’s pre-cut and ready to go.鈥�

A three-inch concrete topping slab will add support on each floor once mass timber is in place. Gaps between CLT floor panels will facilitate other work.

鈥淭he intent is that all mechanical (systems), be it electrical or whatever, fit in those gaps to keep it clean,鈥� Hoyt said. 鈥淚t’s all open and accessible.鈥�

This is the first mass-timber project Hoyt has managed. The biggest difference between a traditional concrete-and-steel-framed structure and a mass-timber one, she said, is the savings of time and manpower that come from prefabrication.

鈥淏asically, it’s a whole, complete system that when it all goes and clicks together you’ve created a floor in a pretty quick time frame,鈥� she said. 鈥淭hey fabricated it from the top down and put it into storage, and as they pull it out it comes out from the bottom up in order.鈥�

Significant time was also spent modeling shipments three-dimensionally to ensure efficient delivery to the job site. Once on site, materials are lifted straight from the delivery truck to where they need to go.

鈥淵ou have to strategically place materials on the truck so they come off in somewhat of an order,鈥� Hoyt said.

The use of mass timber is only likely to grow, Nile said, but added that a maturation process is necessary.

鈥淲e need scale and efficiency and just the supply chain growing up to the point where it’s real,鈥� he said. 鈥淚t’s been a lot of work to get here. It’s all 3-D models, and every component is analyzed so you can do all this off-site fabrication very accurately. And it’s a fun way to build, but I think the supply chain needs to grow up a bit. It’s much more mature in Europe.鈥�

Construction of District Office is expected to finish by the end of 2019.