DC Southwest Library
Engineer-Build
Pavilion on the Park
The new DC Southwest Library brings a sustainable and unique design to replace the previous outdated library. Needed by the community was a Library that could provide State of the Art Technology, a place for training education and work force development, and vitality. The Design Build Team engaged the community at many levels to obtain crucial feedback that informed and inspired the design solution.
Comprised of a mass timber structure, this innovative building involves such elements as a highly unique timber folded plate roof using Dowel Laminated Timber. Supporting the steel and timber lateral system were glulam beams and columns with detailed timber-to-steel connections. The Library achieved LEED Platinum Status, implementing sustainable strategies such as regionally sourced material, solar panels on the green roof, and timber throughout.
In addition to our EOR services, StructureCraft provided fabrication and installation for the superstructure, including the folded plate DLT (dowel-laminated timber) roof supported by a Glulam / steel substructure and a hybrid timber and steel braced frame. We are delighted to see Perkins & Will's beautiful design vision realized for this warm, inviting community space.
An emphasis on connection to the surrounding community has shaped the design development process. The library’s design strives to highlight the new park adjacent to the project, provide a sense of arrival, feature a flexible pedestrian plaza, offer a sustainable site, maximize connection to the outdoors, and allow ample natural light. - Perkins + Will
Engineering Process
The library’s distinctive form is capped with a roofline inspired by the bold mid-century shapes found in DC’s Southwest neighborhood. The “crinkle” folded plate bears similarities to historical cast-in-place concrete roof outlines of the 1950’s but without the burden of framework and with a nod towards modern connection technology and low-carbon materials. The result is a series of dowel laminated wood panels that create a unique building massing and a memorable space within.
The whole project team faced and overcame several key challenges throughout the design and construction process. Creating a beautiful timber structure on a tight budget meant that as Engineer of Record and a key member of the design team, StructureCraft needed to integrate an efficient foundation design with the timber superstructure to reduce overall project cost.
The innovative shape of the long-span folded plate roofs created a particular challenge for both the structural engineering and construction of these complex elements. The use of dowel-laminated timber in a folded-plate structure required complex non-linear finite element analysis to enable prediction of stresses and structural behavior of the folded plate.
Combining steel and timber braced frames to create a unique hybrid lateral force resisting system meant close analyzation of the different material strengths. The finished result was a minimal, aesthetic design that met the architectural vision while incorporating both materials.
Fabrication
BIM (Building Information Modeling) played a key role in the construction of the DC Southwest Library. This allows for a 3D fabrication model with a high level of detail to be used by both designers and constructors – the onsite team used it extensively. Also, BIM allows proactive clash detection and penetration coordination amongst all trades, which is particularly important in a prefabricated highly exposed timber structure. The BIM model drove the manufacturing of Glulam, DLT, and steel and produced detailed piece shop drawings for each element. Small chamfers were added to edges of the half modules fabricated in the shop to ensure the elements remained within legal width limits for trucking cross-continent.
It was a challenge to coordinate the job with all the other projects going through the StructureCraft shop simultaneously, but the fabrication itself was straightforward. The shop team created a jig to make sure the carriers (ridge beams and purlins) were in the correct positions for each half of the folded plate roof. Teamwork was crucial, as many in the shop aided the fabrication to provide a seamless fit for all components. The carriers had steel rods lengthwise that needed to be epoxied to join them together. In addition, jigs were fabricated for site assembly.
Erection
The erection of the timber structure was rapid, taking a small crew of timber specialists only a matter of weeks to erect the glulam and all sections of the DLT folded plate roof. Because of the extensive prefabrication, all the complex work was done off site, and elements were shipped ready to “click” into place.
Using a unique prefabrication plan, two halves of the up to 70ft long and 20ft wide gables were assembled into self-supporting sections of the folded plate, then erected as a single piece. At the intersection of the sloping folded roof plate and the flat DLT roof panels, angled notches allowed the flat portions to seamlessly be slid under the folded plate. These notches were also required around various columns and at steel brace frame connections.
From initial form and design to engineering, prefabrication, and installation, the entire team came together around this complex challenge and delivered successfully on the unique architectural form.