“Truss Tuesday”, as it is dubbed by the project team, marked a major milestone for the Milwaukee Bucks Arena. On May 2 JP Cullen ironworkers placed the first half of a long-span steel truss weighing 24 tons. It will be followed by six other long-span trusses and two smaller ones to form the arena’s roof, which will be complete by early Fall.
Steel erection for the arena was kicked off on November 7, 2016 when the first of the 358 steel columns were set in place, coming in at 36-feet tall and 10,700 pounds each. The project includes 7,673 main structural steel pieces, and 6,000 additional miscellaneous structural steel pieces – such as angle braces and stub columns. In its entirety, the structure will have over 8,000 tons of structural steel!
With the roof trusses being erected inside of the arena bowl, it makes for pretty tight quarters for all of the crews, material and equipment. These conditions could adversely impact the safety of tradespeople with this high-risk activity, as well as the laydown and work area for the crews. Extensive planning, sequencing, and coordination are a must to ensure success.
Another challenge is the sequencing and delivery of the steel to keep the entire project on schedule. Steel schedules are critical to all other activities following it on construction projects, so creating a reliable fabrication and delivery schedule in order to maintain the supply of material needed to support the onsite erection operation is crucial.
Weather – including the wind speed – could become an issue if it would shut down the crane, thus impacting the schedule. If the anemometer on the crane measures the wind speed over 30 miles per hour, the lifting of the roof trusses would have to be stopped until it fell below the threshold.
This job is a high risk activity that requires a lot of planning from the very start. In fact, the team has been preparing for this for nearly a year now. Planning includes discussions on: how the team is going to accomplish this process safely, what the site is going to look like, and what equipment the team needs on site.
This type of planning required engineering and the use of Building Information Modeling (BIM). BIM allowed the team to create a 3D model of the site long before this week for site planning, including details like where the cranes and truss rack should be placed. By the time the first truss arrived on site, the team had been preparing to set it for months.
The trusses come to the site as individual pieces, and the team uses a truss rack to build the truss on the ground. Once assembled on the rack the truss is erected. Two cranes are required to erect each truss half: the first crane picks and sets the actual truss, while the other crane is used to set infill steel (secondary trusses and beams) to stabilize the truss. The process of setting the half truss including all of the secondary infill steel needed to stabilize the truss is a day long process, however still much safer and efficient than trying to build the truss piece by piece in the air, which would take weeks and introduce many safety concerns that are eliminated by the process of assembling each truss on the ground.
The structural steel erection is currently underway and will be complete by early Fall 2017. Check back for the results of this critical activity for the Milwaukee Bucks Arena project!