DC Southwest Library

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.

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.