Synergy between prefabrication and advanced design tools

BIM Insights

• Prefabrication, which is often used in manufacturing, has many benefits for building information modeling (BIM) because it can give design engineers a better idea of what is required for a project and cut down on labor requirements.
• The construction industry is dealing with labor and cost challenges like many industries and technologies such as BIM, prefabrication and many others can reduce some of the upfront and long-term costs associated with a project.

The ability to incorporate technology has major implications for the construction industry, which is struggling with rising construction costs and labor shortages. Industry leaders who leverage building information modeling to maximize prefabrication will stay ahead of the curve and create significant value for all stakeholders throughout a project’s life cycle.

Prefabrication and BIM have altered not only how we think about the stages of design, but also the process in which buildings are constructed. By employing BIM, users can generate complex, detailed 3D modeling and documentation of a building or facility’s physical and functional characteristics before it’s built. When manufacturing methods and assembly are based on digital component models, a major part of the construction process can be brought into a factory environment through prefabrication.

Harris prefabricated large riser racks to distribute HVAC and plumbing utilities to the various floors and concourse areas at Allegiant Stadium. Incorporating unified prefabricated mechanical systems components allowed Harris to maximize efficiencies for the arena. Courtesy: Harris

While prefabrication and modularization have been used in manufacturing, widespread use in the construction industry is more recent. Before 3D modeling, prefabrication was more about taking simple duct and pipe spool of a building’s mechanical systems and constructing as much as possible off-site in a shop. Input from models was limited. As the trade labor shortage became more prominent over the last several years, the industry shifted and innovative companies started looking at better ways for project teams to come together and maximize opportunities for prefabrication. BIM became heavily relied upon as did the use of modular coordination and standardization to industrialize the construction process. Labor hours began to shift from on-site to fabrication facilities.

BIM makes it much easier to identify opportunities to maximize prefabrication and modularization as the building itself can be seen virtually and visualized much earlier in the process and the need for field allowances is essentially eliminated. BIM allows the advantages of prefabricated components to be seen at a granular level.

With advanced modeling tools, buildings can be designed with prefabrication in mind. All components should be considered, even something as simple as adding an elbow off a piece of copper pipe. Can it be assembled in a shop? From something that basic to a large multi-trade rack with duct and pipe, electrical components, building automation components and fire protection — the potential range for prefabrication and modularization is very broad.

Constructing materials before they hit a job site can improve operations. When prefabricating to the fullest extent, more labor hours are moved into a shop where the environment is controlled and predictable. Field installation time decreases, quality and safety increases and the amount of wasted materials is reduced. Budgets and schedules become more accurate as specifiers can procure project materials earlier in the process. Those systems and components that cannot be prefabricated can often be kitted and delivered just-in-time to ensure field labor maximizes productivity and efficiency.

Prefabrication methods

Harris uses a hub-and-spoke prefabrication strategy with the hub being the project site and the spokes branching out to its designated prefabrication shops across the country, as well as to co-fabrication sites on-or-near the project. In this process, bulk materials are fabricated in a main facility and then flat-packed and shipped to a co-fabrication site. Final assembly is completed and the prefabricated components and modules are delivered to the building and immediately installed.

With the hub-and-spoke method, air isn’t shipped as much, which is often the case when dealing with large duct systems and pipe. Collaboration between MEP trades and the overall workflow is heightened and schedules are optimized as multiple building systems integrate.

Consider this example: Harris was enlisted to build the mechanical and plumbing systems for the new Allegiant Stadium in Las Vegas, home of the NFL’s Las Vegas Raiders. In the more than 70,000 hours of fabricated plumbing, piping and ductwork assemblies, crews constructed 72-foot rack sections (two 36-foot sections each) to distribute HVAC and plumbing utilities to the various floors and concourse areas. Because there was no overhead steel or floor to support the risers, engineers needed to come up with an alternative way to support the rack modules.

The answer was constructing a partial gravity and partial friction support. BIM played a crucial role, helping to analyze constructability, configure the modules and detail structural attachments. Of the eight riser racks built, six were constructed in a prefabrication facility then delivered to the site where they were lifted off trucks and set in place. While the risers built conventionally took about 2,000 hours, the prefabricated risers took about 520 hours each — with only 70 hours of on-site installation.

Harris prefabricated large bathroom water in-wall modules, water heater skids, pump skids, sump racks, piping distribution racks and plumbing fixture assemblies as part of its mechanical systems work for Allegiant Stadium. The components were delivered just-in-time, distributed to the appropriate level and set in place. Courtesy: Harris

The racks also eliminated the need to work in an enclosed shaft with limited access. The Allegiant Stadium project also included prefabricating large bathroom water in-wall modules, water heater skids, pump skids, sump racks, piping distribution racks and plumbing fixture assemblies. The units were prefabbed and stored off-site, delivered just-in-time, distributed to the appropriate level and set in place in an efficient manner.

Looking ahead at best practices for the construction industry, prefabrication, BIM and data will continue to play a critical role — not only in how buildings are constructed, but also in how building systems are maintained. As businesses turn toward enterprise resource planning to integrate the processes necessary to run a company — including planning, purchasing inventory, sales and more — there is a great deal of potential having ERP and BIM models working together. Resources could be more properly channeled, necessary raw materials could be better analyzed and cost estimates could be more accurate.

Courtesy: Harris

Whether it’s using a BIM model for tracking productivity on the fly or improving quality prefabrication, technology innovations will continue to be a key factor in construction processes.

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