It is no surprise that there is a massive push in the AEC industry to build more sustainable projects. To facilitate this push towards sus - tainability, engineers and researchers are turning to new, alternative materials. One of the most promising amongst these new materials has been in the engineers’ repertoire for thousands of years: wood. Today’s engineers are not using our ancestor’s wood, however; they are using mass timber products. Mass timber products are created when layers of wood are glued, nailed, or doweled together. This process results in strong and versatile structural panels, beams, and posts. In addition to strength and versa - tility, mass timber products carry a significantly lower carbon footprint compared to building materials such as steel and concrete. One firm leading the way in mass timber projects is Arup who is cur- rently serving as Project Engineer for Washington DC’s first mass timber overbuild project: 80 M Street SE. This commercial office building is the first in Washington DC to feature additional floors en- tirely constructed using mass timber. Additionally, 80 M Street SE is currently on pace to be the first high rise overbuild timber structure in North America. The property is owned by Columbia Property Trust; who were looking to add rentable square footage to maximize the allowable height limit for the site without having to reinforce the existing structure or founda - tions. Working with the project architect Hickok Cole, Arup proposed using mass timber to reduce the weight on the existing structure. Not only would using mass timber achieve the goals of reduced weight and sustainability, it would also create a distinctive facade. There are several advantages to using mass timber, from both a sus - tainability and building perspective. As a renewable resource, mass timber products inherently carry a significantly lower carbon footprint compared to steel and concrete. According to Matt Larson, Arup’s Buildings Practice Leader and Associate Principal, many develop - ers “shy away” from using mass timber on their projects due to cost, building code restrictions, and lack of policy incentives. However, Larson believes that mass timber’s sustainable, low carbon benefits can outweigh these issues. One of the biggest challenges for firms looking to build using mass timber in North America is contending with current building codes. In most of the United States, the adopted version of the International Building Code (IBC) limits the height of timber buildings to 85 feet. The team at Arup was prepared to overcome these challenges. Lar - son believes they were well equipped to handle coding modifications based on previous joint-research completed with the project’s architect, Hickok Cole. According to Larson, this research, “[allowed] the teams Reinventing the Past: Timber is Making a Comeback By Luke Carothers
to align closely on the project’s vision and serve as the basis for the design concept proposed to Columbia Property Trust.” After the Columbia Property Trust accepted the design concept, the project then had to be submitted to Washington D.C. Code Authority for approval and vetting. To prepare for and maneuver through this process, the team at Arup leveraged its extensive knowledge of code consulting and timber structures, working closely with the Department of Consumer and Regulatory Affairs to receive a code modification for the use of mass timber on a high rise building. The code modifica- tions required for the project required taking a multidisciplinary ap- proach. After early meetings with the chief building official, the code consulting team determined that this multidisciplinary approach must
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csengineermag.com
November 2021
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