Ties that Bind A NATION

The final truss pick made by the Williams Steel Erection crew was made using the two 200-ton cranes. The Link-Belt HC-248H truck crane was able to narrowly fit into the opening next to the truss.

Atlantic Union Bank Center at James Madison University, Harrisonburg, Va. Structural Steel Class III ($1 millon to $2.5 million) Erector: Williams Steel Erection Co., Inc. Fabricator: Banker Steel Company, LLC Architect: Populous, Moseley Architects Structural Engineer: Walter P. Moore, Moseley Architects GC: S. B. Ballard Construction Company Contract Value: $2.4 million Tons of Steel: 2650 Topped Out: January 2020

COVER STORY By Tina Cauller

Ties that Bind A NATION

Erectors make their mark on iconic structures for church, state, military, and higher education

Common challenges faced by the 2022 Project of the Year award winners included tight working conditions, wind restrictions, the need for significant bracing, and tandem crane picks. Three projects in Class III ($1 million to $2.5 million) and Class IV (over $2.5 million) additionally required working adjacent to historic buildings. What’s more, those same three projects also dealt with working during the Covid-19 Pandemic.

The 2023 Project of the Year competition is open now. Members can submit for erection contracts that top out in 2021 or 2022. Submissions are due December 31, 2022. Look for more information at SEAA.net.

■ Structural Class III Winner: Expertise from the Get-Go

The project management team at Williams Steel Erection Co., Inc., provided its expertise on the erection of Atlantic Union Bank Center even before the steel fabricator or erector was selected. The company provided a proposed method of erection and sequencing, which assured the general contractor that the erection plan for the arena at James Madison University was feasible.

The building consisted of a 10,000-seat indoor arena bowl structure with two-deck seating covered by a roof structure. The structure is supported by eight trusses weighing up to 55 tons each with a maximum length of 230 feet. The structure was built into a steep hill and extends to the perimeter of the site on three sides.

A year of detailed planning was required. Steel erection activity had to be coordinated inside the tight bowl area alongside cast-in-place concrete retaining wall shoring and precast concrete seating riser erection. Compounding this, the main roof truss erection was completed from both ends of the building working towards the center. The middle truss had to be set last because limited access made it impossible to set the end truss last. Stability concerns were a result of setting the truss in the middle last.

“We bid the job based on the plan to exit out one end of the arena,” noted Art Williams. “Early on, the reality meant that we needed an alternative bracing plan. Our experience and knowledge of this type of project really helped. Our operations manager worked together with the engineer of record on an erection plan that was feasible given the challenges.”

Small space for laydown and cranes

Sequence plans were carefully designed to ensure structural stability while maintaining laydown space for as long as possible. The lower superstructure and auxiliary wings were erected first, followed by the first roof trusses.

All trusses were assembled on the ground, and then raised into place with two cranes. Due to the retaining walls that ran through the site, these first trusses required crawling the cranes forward while the suspended truss was positioned.

Since the trusses were supported by the outer perimeter columns, the perimeter had to be almost completely erected before the final trusses could be erected. There was only a narrow 30-ft opening into the bowl to accommodate three cranes—a 100-ton Link-Belt truck crane, 200-ton Link-Belt truck crane, and 200-ton Link-Belt crawler crane— as well as the 230 x 20-ft truss.

The permanent bracing configuration could not be counted on to fully support the structure until it was complete, so a complex bracing and guying plan was created and strictly followed. During erection of the first trusses, the cranes had relatively free room to swing, but the available space narrowed with each added truss. As each truss was erected, significant temporary bracing had to be installed to stabilize the structure.

The final truss

The final truss pick was made using the two 200-ton cranes. The Link-Belt HC-248H truck crane was able to narrowly fit into the opening next to the truss. The third crane, a Link-Belt HTC-86100 truck crane was staged in the bowl to assist with truss stabilization. During the lift, the Williams crews carefully guided the booms of the three cranes along with the truss itself into the 30-ft space between this truss and the next. The tight working path required both the LS-248H II crawler and HC-248H to position themselves less than two feet from each other to accommodate the final lift. It was determined that the crawler crane had to move to allow for the swing radius of the other crane. Extensive prelift communication with the rigging manager, the operations manager, and the superintendent ensured that the booms didn’t collide.

By the time the last center truss was erected, all remaining superstructure steel was in place except for a narrow 30-ft bay, which was left out to provide laydown area for the final truss. To accommodate this, the 20-ft-deep truss was assembled vertically, requiring careful planning and engineering analysis. Once the final truss was set, the cranes were disassembled in the arena bowl and the remaining infill bay was completed from the exterior of the building.

There was only a narrow 30-ft opening into the bowl of Atlantic Union Bank Center arena to accommodate three cranes — a 100-ton Link-Belt truck crane, 200-ton Link- Belt truck crane, and 200-ton Link-Belt crawler crane — as well as the 230 x 20-ft truss

■ Structural Class III Honorable Mention: Saving the Day

The Uptown Pearl is a sophisticated multi-family living and retail development in Denver’s vibrant Uptown neighborhood. This community features 316 luxury apartments and 12,000 square feet of retail space in a prime location near the city’s commercial business district.

Flawless Steel Welding was brought into the 10-story mixed-used apartment project to provide a turnkey solution when the previous subcontractor abandoned the jobsite.

Uptown Pearl, Denver, Colo. Structural Steel Class III Honorable Mention Erector & Fabricator: Flawless Steel Welding, LLC Architect: Shears Adkins Rockmore Structural Engineer: JVA, Inc. GC: SLC Commercial Construction, LLC Contract Value: $1.7 million Tons of Steel: 342 Topped Out: December 2020

Flawless Steel Welding was brought into the 10-story mixed-used apartment project to provide a turnkey solution when the previous subcontractor abandoned the jobsite. The project was behind schedule, but that didn’t worry Victor Garcia, President of Flawless Steel Welding. This is not the first time his company has saved the day. The company won a SEAA Project of the Year award in 2019 for a similar situation on a parking garage project in Overland Park, Kan.

“People sometimes fall into the trap of taking the low bid and then the project runs into trouble. I’ve built my business by finding opportunities in those situations. We aren’t always the lowest price but we offer expertise and value,” said Garcia.

The initial project included more than 400 balcony rails, each of which were field-verified, and more than 6,800 linear feet of brick relief angle, trellises, storefront frames, canopies, and five stairways. The Flawless team also completed the elevator divider steel, parapet steel, and davit posts.

Second Act

After impressive efforts to re-detail all connections of landing for post installation and account for previous inaccurate concrete embeds and anchor bolts, the company was awarded an additional scope to fabricate and erect the new Pearl Tavern. Developers, preservation groups, and planners wanted to retain the historic identity of the neighborhood and preserve the Tavern, an iconic feature of the 17th Avenue block. Flawless Steel Welding was tasked with erecting the building while leaving the original 50-year-old façade intact.

Once again, Flawless Steel Welding, created a plan to erect a structure accounting for existing conditions. Challenges were everywhere, but once the remaining structure was braced for the installation of the interior structural steel, the company got to work solving those challenges and gaining time on the schedule.

“Turning this job around gave us a chance to show off and make the client happy, which led to us being awarded three other projects,” said Garcia.

Flawless Steel was awarded additional scope to fabricate and erect the new Pearl Tavern, which required leaving the original 50-year-old façade intact.

A Spydercrane 295 mini crawler crane was used on the roof of the Uptown Pearl Tavern for lifting support.

■ Structural Class IV: A Temporary Home for an Iconic Structure

Atlantic Union Bank Center at James Madison University, Harrisonburg, Va.

The final challenge involved erection of the west side pipe buttresses ,constructed of 36-inch diameter pipe sections, designed primarily for axial load at a specific angle. Installation of the buttresses required a rigging plan that ensured connections were not overload when the buttresses were lifted in horizontal position then transitioned to placement at an angle.

Atlantic Union Bank Center at James Madison University, Harrisonburg, Va. Structural Steel Class III ($1 millon to $2.5 million) Erector: Williams Steel Erection Co., Inc. Fabricator: Banker Steel Company, LLC Architect: Populous, Moseley Architects Structural Engineer: Walter P. Moore, Moseley Architects GC: S. B. Ballard Construction Company Contract Value: $2.4 million Tons of Steel: 2650 Topped Out: January 2020

Deem Structural Services erected a temporary building enclosure to facilitate renovation of the iconic Cadet Chapel at the United States Air Force Academy. The chapel, originally built in 1962 and designated a National Historic Landmark, is undergoing extensive rehabilitation. All aluminum exterior cladding will be removed down to the basic structural steel and replaced. To protect the site from the weather, the chapel was enclosed in a temporary structure, which also supports the dynamic load of four overhead cranes being used to remove and replace the aluminum panels. The project demanded careful crew coordination and risk mitigation.

The enclosure has 40,000 sq ft of clear-span area with vertical truss columns that rise to a height of 173 ft. Deem proposed a vertical truss instead of joists, which made the job more erectable.

Complex bracing

The enclosure was designed to be self-supporting only when the structural system and roof diaphragm were complete. However, permanent bracing could not be complete until the next to the last transverse frame was erected. During most of construction, the temporary bracing system carried the horizontal loadings and provided stability for the incomplete structure. The temporary bracing acts as back-up for the permanent bracing system since the enclosure will be dismantled after the restoration is complete. As the construction process is reversed, the temporary bracing will again become the primary stability mechanism.

The design challenge of the temporary bracing system was that the load distribution of the forces changed as erection proceeded. The erection engineering design had to consider the loading forces at specific points in time during the erection process. In fact, some of the bracing in the first phase of the structure received more load as the second and third phases were constructed. Since the capacity of temporary bracing has practical limits, this resulted in the addition of other, seemingly redundant bracing.

In addition, the project’s location on the Front Range of the Rocky Mountains commonly experiences wind gusts of 60 - 70 mph. “We reviewed the weather history in this zone to predict the winds forces we might encounter. When the project was pushed back to later in the winter, we recalculated for snow loads. This info contributed to the temporary bracing planning,” said David Deem, President of Deem Structural Services.

Deem Structural Services erected a temporary building enclosure to facilitate renovation of the iconic Cadet Chapel at the United States Air Force Academy. The enclosure has 40,000 sq ft of clear-span area with vertical truss columns that rise to a height of 173 ft.

Two crews in tandem

Coordinating two erection crews working in tandem—each working on opposite sides of the structure—necessitated a defined schedule, and daily communication to make sure each phase was completed in unison. Deem also implemented a rigorous inspection protocol to ensure uniform erection of the shell.

Crews also had to be careful to protect the chapel during construction. No field welding was permitted to reduce risk of welding sparks catching the historic landmark on fire. But mechanical fastening comes with drop risk, so Deem Structural crews used tool lanyards. “In addition, we limited the quantity of bolts in the skip buckets that went up with ironworkers. Drop prevention was a daily reminder during site meetings,” said Deem.

What was most unusual was the need to use bolts to fasten the long span bridging. “We used Angel Wing baskets during that process to put ironworkers in the best position for the work,” he said. The good news, says Deem, is that when comes time to dismantle the structure, the exterior portion is outside the perimeter of the chapel.

Overhead crane erected from below

Adding to the project’s challenges, 50 ft runway beams for the overhead cranes could not be erected from underneath. “We had to remove part of the shell to fly runway beams in, install some decking to add additional bracing and roof diaphragm, then hang another runway. Decking had to be carefully coordinated and installed to the greatest extent possible to make sure everything was braced adequately. Finally, we cantilevered the last crane to bring it in through an opening in the roof, and then set it on the beams to finish the installation,” said Deem.

The final challenge involved erection of the west side pipe buttresses, constructed of 36-inch diameter pipe sections, designed primarily for axial load at a specific angle. This required a rigging scheme that allowed the buttress to lift at a slightly greater angle with the horizontal while ensuring that the buttress and its internal connections were not overloaded during the lifting transition from a horizontal position to the final placement angle. The buttress and the rigging were analyzed at numerous points during the lift to ensure that there would be no failure of the member or its connections and that the buttress would remain stable during the lift.

David Deem noted: “Everything about this job was unique. The bracing is still there and will remain until it’s time to take down the temporary structure. It is helping with stability of the structure even now.”

■ Structural Class IV Honorable Mention: Pandemic Perseverance

Virginia General Assembly Building, Richmond, Va. Construction of the General Assembly Building required a 300-ft concrete shear tower in the core that tied into all four sides, as well as building the frame out for the building’s multiple elevators.

Structural Steel Class IV Honorable Mention Erector: Mid Atlantic Steel Erectors, Inc. Fabricator: SteelFab of Virginia, Inc. Architect: Robert A.M. Stern Architects, LLP, Glave & Holmes Architecture Structural Engineer: Silman Engineering GC: Gilbane Building Company Contract Value: $3 million Topped Out: January 2021

Mid Atlantic Steel Erectors (MASE) overcame numerous obstacles—not all of which were construction related—in the erection of the 15-story, 420,000-sq ft General Assembly Building. The project incorporated the original 1912 façade of Virginia government building.

Limited working hours and weather-related delays were some of the more usual of the challenges. The company also navigated working during the height of the Covid-19 pandemic when masks and temperature scans were required, and workers were sent home for weeks to recover from illness. What’s more, at one point, riots led to police shutting down street access.

Limited laydown, low ground pressure

This job required a 300-ft concrete shear tower in the core that tied into all four sides, as well as building the frame out for the building’s multiple elevators. Situated on a single block in downtown on a main thoroughfare, the site constraints were significant. The laydown yard was a small strip on the same side of the building as the 110-year-old façade. MASE retrofitted window supports and placed reinforcing steel into façade, which was custom built on site. While tying the first six floors into the backside of the façade, MASE had to be careful flying steel around the stone part of the structure.

Low ground pressure requirements meant that MASE had to supply the smallest possible crane that could still reach the 9th floor. A 200-ton Liebherr LR 1160 crawler crane with luffing boom set the steel, while a second 550-ton Grove GMK-7550 truck crane was set up in the main thoroughfare to place a complex truss system and 140,000-lb girder beam. MASE fabricated and placed a three-story truss that support upper floors as it spanned the full basement and meeting rooms. For these phases, work was limited to weekends to meet the city’s requirements for street shutdown.

The Liebherr 630 EC-H tower crane was used for construction of the west half of the building and everything above the 10 th floor. The project faced more delays when winds in excess of 25 mph shut down the tower crane for periods of time.

Despite both usual and extraordinary circumstances, Mid Atlantic Steel Erectors sustained progress, completing the project without incident.•

Situated on a single block in downtown on a main thoroughfare, the site constraints were significant. MASE only had access to a small strip of space for a laydown yard on the same side of the building as the 110-year-old façade.

The project incorporated the original 1912 façade of the Virginia government building.