As the construction industry continues its journey into the 21st century, a number of transformations are taking place. From prefab to building information modeling (BIM), new tools are making it possible to turn architecture, engineering and construction (AEC) into a field that is predictable, timely and efficient.
Demonstrating this shift is Michigan-based construction firm Barton Malow, which has developed a unique workflow for the laying of reinforced concrete in a wide variety of projects. By combining BIM, GPS and prefabrication, Barton Malow is able to reinvent the very foundation of the firm’s construction projects.
Switching to BIM
Barton Malow has been involved in such large-scale projects as Daytona International Speedway, Penn State University, and Little Caesars Arena, used by the Detroit Red Wings and Detroit Pistons. Up until 2008, it pulled this off by relying primarily on 2D drawings in AutoCAD.
In an interview with engineering.com, Matt Hedke, Senior Virtual Design and Construction Manager, lamented that the level of detail in drawings has decreased significantly over the years. At the same time, schedules have become more condensed and costs more constrained. 2D drawings haven’t been able to communicate what’s necessary for a project to stay on schedule and under budget.
“The amount of information on a contract drawing isn’t as good as it was 15 years ago,” Hedke said. “The other issue we struggle with a lot is the fact that just because a design has been drawn in 2D on a piece of paper doesn’t mean it can get built.”
Hedke has played a crucial part in transitioning Barton Malow to the use of 3D modeling and BIM. His role is to examine all of the trades within Barton Malow and determine where new technology can make a difference. This can be as simple as an app for tracking superintendent dailies better for performing 2D drawings in the field. While the firm had long used Trimble’s BIM software, Tekla Structures, as a construction management tool, Hedke was curious about its potential to increase productivity and efficiency in resteel and concrete detailing workflows.
Designing for Construction
Barton Malow now uses the software to create what Hedke dubs “bundles,” that is, LEGO-like sets of prefab components for concrete reinforcement on large construction projects. Constructible kits are sent, with step-by-step instructions, to the job site where anyone on the team can follow each step and accurately install the necessary parts for the project.
To make these assemblies, Barton Malow begins by building a precise BIM model of a site’s concrete, reinforcing steel and formwork, sometimes down to the anchor bolts. This includes base plates and stirrups, columns and detailed slabs, rebar and any concrete forms that will be on site. By designing the foundation work in a data-rich and highly detailed Tekla Structures model, the team can ensure constructability and visualize how everything will fit together, be sequenced and address any clashes or interferences before construction begins.
Not only is every detail accounted for, but so is the order in which the parts will need to be installed. Key to the process is the use of templates to generate automated assembly tags that provide instructions on how to pre-tie a cage to improve rebar placement efficiency. The use of Tekla’s Rebar Release Manager also enables Barton Malow to track each release of rebar, linking it to a given concrete pour.
Once the virtual model of the site is designed, it is approved by the engineer and the VDC team visits it once again to estimate the exact material quantities they will need to order, such as the amount of reinforcing steel the project will require. The Tekla Structures model is tied to Barton Malow’s fabrication software, Shear97, which allows the team to automatically transfer production information from the model to the firm’s fabrication system and produce only what’s needed for the job.
“We’re using Tekla Structures to validate and visualize our plan and ensure that everything from estimating to design and fabrication results in a project that comes together in the right sequence, efficiently and with a high level of accuracy on site,” Hedke said. “We’ll fabricate the bar; it comes right out of the fabline and we’ll have guys in our office pre-tying it all and then shipping it out as assemblies.”
Constructible in Action
Wind turbines are massive structures that require significant foundation work before the windmills can be hauled in and erected into place. When it set out to prepare for the construction of the Echo Wind Farm for DTE Energy, Barton Malow’s constructible process was essential to keeping the project on track and as streamlined as possible.
“Everything was based on when the turbines would be delivered and when the towers were going to be stood up. We had to work backwards. The turbines were going to arrive on a certain day, which gave us ‘X’ amount of time to get our foundation in,” Hedke said.
The foundation area of each turbine consisted of a massive octagon of approximately 50ft x 50ft, with another 11ft below ground. Crews had to excavate extra working room around the perimeter and create the two roads leading up to the actual wind farm construction site.
“We were pouring two of the foundations each day, with anywhere from 50 to 60 tons of reinforcing steel, which left no time for mistakes,” Hedke explained. “If there had been a hiccup, it would have had a ripple effect on the entire project because we had to pour two foundations each day to stay on schedule. After the first foundation went in and feedback from the field positive, the process was duplicated for the remaining foundations, saving time and helping Barton Malow finish the project on schedule.”
To tackle the job, the engineering team first designed the windmill foundation, before Barton Malow’s VDC team modeled in the rebar, concrete and anchor bolts. With the use of Tekla Structures, the team was able to model 144 individual anchor bolts located four inches apart, along with a top mat, and then use the software to find any potential clashes that might occur.
Upon catching any interference, the team was then able to quickly modify the plan to correct for the errors. Once everything was approved by the engineer, the Barton Malow VDC team could bundle the steel for on-site distribution.
“We built this entire constructible model virtually before we went into the field. The model allowed us to be very specific about how and when the materials would be installed so that we didn’t end up with 50 tons of reinforcing steel arriving in a random order dictated by the fabricator,” Hedke said. “To achieve this, we worked with our placing team and fabricator to bundle and group bars based on the build sequence, similar to the concept of an assembly line.”
Remote Excavation
All of this elaborate setup would be useless, however, without the proper execution. At the build location, each crew had 2D drawings of their specific work area, including spacing and the order of operations. Thanks to the use of Trimble Total Stations, this data was all rooted in the physical location of the site on the globe, including elevation and topography.
Anchoring the model with real-world data ensured that the virtual model lined up identically with the physical world, but, perhaps more interestingly, it also allowed Barton Malow to control the construction equipment remotely. The team leveraged Trimble Business Center to perform GPS-based control on the heavy machinery—from the blade on a bulldozer to the bucket on an excavator—to dig holes, grade the site, and push the dirt around down to the inch.
Constructible Efficiency
Hedke pointed out that with this extensive preplanning and remote management of equipment, what would normally be a three-person job was done by two people. The crewmember who would have been staking out the site and shooting elevation could then move onto another task.
“Your excavator is a huge capital expense and if you only have one or two people that are really your best, then there’s a chance that your expensive excavator could be sitting there waiting for the highly qualified operator,” Hedke said. “We can make it easier for someone that has potentially less experience to produce as well as the most experienced person on the team.”
Barton Malow believes that streamlining the foundation work alone resulted in efficiency gains of 15 percent. And, while the software Barton Malow is now using has a learning curve, Hedke believes the process is worth it, both because of the improved efficiency and democratization of information that BIM allows.
“What we’re doing is blue-collar BIM. We’re not only creating, managing and sharing models that are accurate and rich with data, we’re sending those models to superintendents and foremen in the field so they can visualize their work as it is getting built, look at a model on a tablet and do their jobs more efficiently,” Hedke said. “They say a picture is worth a thousand words, but I say that a model is worth a thousand pictures.”
Trimble sponsored this article but had no influence on its content. All opinions are mine unless stated otherwise. —Michael Molitch-Hou