What Is SpeedCore Construction and How Does It Affect Welding?

Photo 1 courtesy of Level 10 Construction. Photo 2 courtesy of Schuff Steel. 

A construction method for high-rise erection projects that can save significant time and money — in addition to having other benefits — is gaining interest across the industry. 

Learn more about the SpeedCore construction technique and how it affects the welding operation, project timelines and results. 

What is SpeedCore construction?

SpeedCore is a concrete-filled composite steel plate shear wall (CF-CPSW) core used in multi-story steel structures. With this system, erection can be completed much faster. In one recent project, it took 43% less time to erect the entire structure compared to using a traditional cast-in-place reinforced concrete core, according to the American Institute of Steel Construction (AISC). 

One common way to build a multi-story or high-rise structure is to first erect a concrete core. This core acts as the lateral force (e.g., load from the wind or an earthquake) resisting system. It often houses such building necessities as elevator shafts or stairwell systems. Once the concrete goes up, contractors integrate either concrete flooring or steel framing around it. Because the concrete needs time to cure to reach full strength, this can hold up erection projects. A reinforced concrete core typically takes from three to five days per floor to construct.

SpeedCore uses prefabricated, panelized modules consisting of outer steel plates spaced some distance apart that form the inner and outer parts of the wall and are connected to one another by regularly spaced round steel bars. These modules are then shipped to the site, stacked atop one another, spliced together (typically with field-welded joints), and filled with concrete every few stories as they are erected. The outer steel plates act as permanent formwork — reinforcement to the concrete — and also provide enough structural integrity so that the core erection remains a continuous operation synchronized with the steel framing that then connects into it. This eliminates the time-consuming operation of field rebar work and reliance on concrete curing to reach strength and leads to significant time savings. 

Because it’s an open-source, non-proprietary technology, it can be used by any engineer for designing the core of a structure. AISC promotes it as a way for contractors to speed up project timelines. 

“We're looking to promote technologies that better the steel industry,” says Brian Raff, AISC vice president for Market Development, Marketing Communications and Government Relations. “We want to make sure that we support open technologies so that all of our member fabricators can take advantage of them.”

When is SpeedCore a good fit?

Any project that uses a core wall system would be a good candidate to consider for SpeedCore. But the number of stories in the building is a key factor in evaluating the economics of the process. SpeedCore has been considered and used for buildings five stories and taller. Some two-story projects are considering the technology because of the more precise tolerances steel can achieve (plus or minus 1/16 inch is readily achieved with SpeedCore construction) compared to typical concrete construction. To date, two projects have used the SpeedCore system: the 850-foot-tall, 58-story Rainier Square Tower in Seattle and 200 Park in San Jose, California, at 19 stories and 300 feet in height. 

“SpeedCore is not the easy-button solution for every single building. It depends on the set of circumstances and criteria,” Raff says. “It lends itself to larger projects, but there have been plenty of examples where SpeedCore, even on a smaller scale, could make sense.”

What are the benefits of SpeedCore? 

The method can deliver several benefits that help save time and money for owners and contractors. These include: 

• Time savings: Projects to date have reduced erection time by at least 40% when compared to reinforced concrete wall systems. For example, the Rainier Square project showed a 43% reduction in erection time compared to concrete core systems, with a similar reduction realized for the 200 Park project. Erection times vary using a reinforced concrete core, but a pace of three to five days per floor is common. With SpeedCore, contractors can build four floors (two tiers) in a week. 

• Cost savings: Time savings in the field also translate into reduced costs. Project owners save on financing (loan interest) and general condition costs. Reducing construction cycle length also allows owners to collect rent sooner. Contractors can finish projects faster and move on to other jobs. On the 200 Park project, the team shaved three months off the schedule and saved $10 million (about 5% to 7%) of the structural cost compared to using a steel frame with a concrete core. 

• Safety: In projects that use a traditional concrete core, the concrete tradespeople are working overhead of the steel erectors and others on the jobsite. This presents a hazard of dropped objects if not properly mitigated. With SpeedCore, the modules are erected in sequence with the steel framing and floor system. As such, no tradespeople are working above the ironworking operation. The metal decking of the floor system (installed shortly after the steel framing is erected) protects people working below. 

• Optimized wall thickness: On 200 Park, located in a region with very high seismic activity, the overall wall thickness was reduced by 30% (6 inches) by using SpeedCore instead of a reinforced concrete wall system in the 19-story building. This opened up more leasable space and allowed more architectural freedom in building design. 

• Other benefits: The numerous other benefits associated with SpeedCore include increased blast resistance, minimal construction tolerance issues and dimensional conflicts compared to concrete wall systems, as well as added flexibility for adaptive reuse. In fact, the system acts as one giant embedded plate, eliminating the risk of misaligned connections.

What is the impact on the welding operation? 

The majority of SpeedCore modules are fabricated in a shop environment. Those modules are then stacked and welded together in the field. The system can require a lot of larger welds depending on erector preference. These can include butting half-inch plates together and completing long, horizontal fillet welds or full-depth welds. 

The construction of a building using SpeedCore technology is a real paradigm shift in conventional construction methodology — placing a higher emphasis on the need for atypical structural welding, both in the fab shop and in the field. 

In the shop, modules require welding of cross ties, shear studs and boundary and connecting core sections. An estimated 500,000 fillet welds for 250,000 cross-ties were completed on the Rainier Square project. Varying levels of automation can and have been used for these highly repeatable welding operations on the two SpeedCore projects completed to date. In the field, welding the stacked steel modules together is the most extensive welding on these projects in terms of weld metal deposited. However, these welds are done in the horizontal position and specified to reduce inspection requirements (e.g., the use of full-depth partial penetration welds). Other field welding included the outrigger sections (when applicable), column splices and multitude of fill hole covers used to cap areas where concrete is pumped into the core. 

“I think SpeedCore certainly could be a potential boom for the welding industry,” Raff says. “It’s much more sophisticated than typical traditional building framing.”

Innovations like SpeedCore provide tangible cost savings in the form of schedule reductions. In a similar fashion, contractors can realize cost savings of their own when they invest in new welding technologies. Using a remote-control solution such as ArcReach® technology from Miller Electric Mfg. LLC is a good example of a technology that could be implemented to significantly improve welding efficiency. Using standard weld cables, operators can remotely adjust and change all weld settings at the point of work. Therefore, they never need to make unnecessary trips to and from equipment that may not be easily accessible.

What are common roadblocks to using SpeedCore? 

Because the system is relatively new, many engineering firms may not be experienced in designing buildings in this fashion. Prescriptive requirements for designing with SpeedCore are forthcoming in the 2022 Specification and Seismic Provisions. A departure from the status quo is likely a hurdle in adopting this construction method. Most firms are much more familiar designing traditional steel framing and concrete core structures. 

Depending on project location, it may also be difficult to find a fabricator that can take on a project of this magnitude. Because it deviates from traditional steel fabrication, it may require investment in new technology. 

In locations where SpeedCore isn’t already in building codes, it may require extra steps for permitting and approval. 

“There’s been a lot of progress in getting SpeedCore into building codes,” Raff says.”

The future of SpeedCore construction 

Industry interest in this construction method is growing, according to Raff. The 200 Park project was the first SpeedCore project in California. It was the first of four buildings using SpeedCore planned for that site. A SpeedCore project is being planned for Boston; it would be the first on the East Coast, according to Raff. 

“I would say over the last few years we’ve seen an almost meteoric rise in interest and in application,” Raff says. “We have five or six projects in the planning stages looking at SpeedCore, which I think is really encouraging.”

AISC encourages members to consider the method for projects because of the potential time and cost savings and safety benefits. 

“There are very real advantages to SpeedCore, both from a structural perspective and also economically,” Raff says. “As more designers get familiar with using SpeedCore and more fabricators cut their teeth on putting the modules together, we are going to reach a critical mass where you will see a big explosion of using SpeedCore.”