Concrete is Key in Port Construction

Gulfport’s restoration and expansion

The Port of Gulfport, Miss., is in the midst of a multiphase restoration and expansion, initially prompted by damage from Hurricane Katrina in 2005, which will accommodate Post-Panamax container ships when it’s completed in 2015. The work includes deepening the channel and the construction of six berths, or about 6,000 linear feet of pier. The expanded concrete pier is supported on 3-foot-diameter precast prestressed concrete piles.

The project was designed by KPFF Consulting Engineers, Seattle, and is being built by L and A Contracting, Hattiesburg, Miss. KPFF Managing Principal Don Oates described some of the requirements and challenges that are involved: “What these new larger vessels are driving in terms of port infrastructure are increases in berth depth and crane width, because the cranes have to be able to reach across the ships to load and unload containers. Even sophisticated ports like the Port of Los Angeles don’t have many cranes with the outreach to span the width of 24 containers, which is 200-plus feet.

“When the cranes have to reach that far out, you have to reconfigure or reconstruct the crane rails. As the cranes get larger and the outreach gets longer, the weight, wind loads, and other forces get that much more substantial, and often the existing dock infrastructure can’t support them. The only recourse is to pull out the old and put in new. And the concrete beams supporting the crane rails are massive—at least 6X6 feet, with lots of steel reinforcement, all cast in place. It’s tough work, and because it’s over water, you have all the environmental controls and insurance costs the contractor has to pay for, which makes it very expensive. Working over water, we try to do as much as we can using precast elements to limit the amount we have to cast in place and help keep costs in line,” Oates says.

He continues, “These [crane rail modification] projects aren’t solely related to the canal expansion—they’ve been going on for years in a lot of areas. To accommodate the larger cranes, crane rails have been expanded from 50 gauge, to 100, or even 120 gauge (feet between the crane rails), but many port managers would rather see the cranes themselves modified so that the rails can stay at 100 gauge. That way they can potentially reuse at least the landside rail, and not take up so much valuable yard space.”

Long Beach prepares for tomorrow

The Port of Long Beach, Calif., is already the second-busiest container port in the U.S., and its deep-water main channel and terminal berths are already able to accommodate the newest, largest container ships now in use. Faced with increasing competition due to the Panama Canal expansion, Long Beach is taking steps to maintain its leadership position for the future.

Long Beach’s $1.31 billion Middle Harbor project includes upgrading wharves, water access and storage areas, and adding a greatly expanded on-dock rail yard. Construction of the Middle Harbor is being done by a joint venture of Manson Construction Co. and Connolly-Pacific, of Long Beach.

“We construct everything from the bottom up: we drive the piles, set the formwork, pour the concrete, and then place the secondary concrete with the bolts and other embedded items critical to the crane system,” says Rich Ferguson, project manager for Manson/Connolly JV. “We set and mount the crane rails, grout the rails, and usually subcontract the asphalt paving that serves as a wear deck for the wharf.

“Because of the new 120-gauge cranes, the Middle Harbor wharves are much larger than typical ones. They’re about 145 feet wide, 15 feet wider than wharves we’ve done in the past. Through the main section of the wharf, the finished concrete slab is 4 feet from the bottom of the beams to the top of the deck, with about 15 inches of concrete above the pan forms.

“The biggest challenge with the construction was designing the falsework soffit form system to hold the concrete loads up,” Ferguson adds. “We had to be able to set the formwork efficiently, and also get it stripped out from underneath after the concrete cured. Working over the water, all we had to support the formwork were the concrete piles, which are part of the structure. We like to use plywood forms, so when we strip them off, they’ll float rather than sink to the bottom.”

The crew used friction collars around the piles to support steel girders, extending perpendicular to the shoreline on both sides of each bent of piles. Then they set the plywood panels on the girders, filled in with plywood around each pile and between the panels, placed the rebar and side forms, and then the concrete. Once the soffit forms are in place, pan forms created the longitudinal and transverse beams.

“The concrete mix designs for this kind of work are complex,” Ferguson says. “This used a very complicated mix, with a lot of admixtures, some of which tend to counter each other. The challenge was to get enough workability for placement, while also getting enough cure strength fast enough so we could strip our forms out and keep the schedule rolling.”

Kenneth A. Hooker is a freelance writer based in Oak Park, Ill.