Medical Building Challenges Concrete Pumping Contractor to Research a Pouring Scheme
Medical Building Challenges Concrete Pumping Contractor to Research a Pouring SchemeSTURTEVANT, Wis. (September 2004) – Sometimes building a facility to house biomedical research can be nearly as difficult as conducting the actual research.
To help take it to the forefront of expanding biomedical technology, Oregon Health & Science University (OHSU), Portland, Ore., is constructing a 274,000-square-foot research facility. To complete the facility, a Portland-area concrete pumping contractor had to research how to conduct a pour on a job site that would prove to be unique.
The building represents the first step in the university’s new research recruitment and expansion efforts. With 11 levels, four below grade and seven above, the structure will include a pediatric research center, an advanced imaging research center and state-of-the-art laboratories.
Not your typical construction job, planners called for the building to be positioned on the side of a steep grade, at basically a 45-degree angle. The unusual location was chosen so the structure could be joined to an existing cluster of buildings.
The project required building two shear concrete walls, with structural steel placed between the walls. Along with the complexities caused by having to carve out dirt from a mountainside, the virtual lack of access to the site added other challenges.
The working area was so tight that it was necessary to leapfrog all supplies, such as rebar and structural steel, up the mountain. This was accomplished with two cranes, situated about 300 feet apart.
The general contractor for the $113.4 million project was Hoffman-Andersen Joint Venture, Portland, Ore. Pence-Kelly of Salem, Ore. was selected as the concrete contractor.
Pence-Kelly crews quickly discovered that a truck-mounted concrete boom pump could not make the pour because of the restricted site access. Fortunately, an area pumping company, Lucht’s Concrete Pumping, Clackamas, Ore., helped develop an alternative method of placing the concrete.
A Putzmeister 36-Meter placing boom with a 105-foot horizontal reach was selected for handling the 4000-psi to 6000-psi concrete mix, which included special chemicals and additives. The placing boom was powered by a diesel power pack because three-phase, 440-volt power was not readily available onsite. The power pack, directly mounted on the boom’s pedestal, was equipped with a 56-hp, turbo-charged Kubota engine.
The placing boom was strategically positioned among three PM towers. Two towers were placed at opposite ends of the two L-shaped shear walls and one 40-foot tower, behind a shear wall for handling difficult perimeter pours.
Initially, the freestanding tower was elevated up to 80 feet from a mounting base, which was ballasted with 60,000 lbs. of counterweight. For the next 60 feet, the tower was tied off to the structure using custom tie-offs developed to handle the load factors. Eventually, the base was weighted down with 85,000 lbs. to help the PM tower reach its final 140-foot height.
“Free-standing a placing boom and tower on a mounting base at 140 feet is the tallest height ever accomplished in the Western Hemisphere,” said Tim Swindle, vice president of Lucht’s Concrete Pumping. “The Putzmeister base cross system is the top performer for this type of construction.”
Although the placing boom was detached from a 36-Meter truck, the truck wasn’t used to pump the concrete. Rather, a Putzmeister BSA 2110 HP-D trailer pump with a maximum 3190-psi (220-bar) pressure was chosen.
Steve Lucht, owner of Lucht’s said, “The 2110 trailer pump was insurance for us, as it’s better to have extra horsepower in reserve. There’s nothing worse than three-inch slump starting to set and no power to push it. The whole system could have been lost and that would have been disastrous.”
The added insurance provided by the correct selection of equipment paid dividends because on several occasions, the trailer pumps higher pressure capability was needed. Creating a pouring route from the trailer pump to the tower involved snaking the delivery line through a maze of obstacles using thrust blocks and Putzmeister hydraulic diversion valves.
It also involved routing the delivery line through a series of walls underground and in one location, the crew had to pour a pipeline inside a wall. At one stage, concrete had to travel more than 400 feet horizontally before reaching the PM tower, where it then had to flow another 200 feet vertically.
Although a high pumping pressure was critical, there was no need for high volume. Lucht said the Putzmeister trailer pump handled the average hourly output of 60 yards and the 3-inch and 4-inch slump without fail.
Because just one road provided a route to the job site and flagmen could halt traffic for only a limited number of minutes, two mixer trucks at a time waited to make their deliveries on a turnout along the access road.
Radio communications ensured mixer trucks would not block the road to emergency vehicles.
Lucht brought in two seasoned concrete pumping operators, both experienced with placing booms and tower climbing systems. Jim Hall of Denver, and Ian Bond of Houston – each with more than 10 years pumping experience – handled the daily complexities of placing concrete in the unusual work setting.
“The biggest factor about the job was the high intensity. It was challenging and we had to be extremely safety conscious beyond anything I’ve ever experienced,” Swindle said.
“For example, just to fly the boom 200 feet required a detailed, full-scale plan outlined in a written format. Then the entire job had to be completely shut down during the actual flying process.
“I’d say the best way to sum up the overall job was extensive and expensive.”
Construction started in January 2003 and should be finished by the fall of 2005 with slightly more than 10,000 yards of concrete poured in a challenging environment.
OHSU is the state’s lone health and research university and only academic health center. A nonprofit public corporation that is both a business and service partner of the state of Oregon, OHSU’s mission is to improve the well being of residents of the region. The facility provides care for more than 187,000 patients annually, employs 11,000 and has a student body of 3,500.
OHSU disclosed 89 scientific discoveries in the past year, or basically one every four days.
Architect: Zimmer Gunsul Frasca Partnership, Portland, Ore.
General contractor: Hoffman-Andersen Joint Venture, Portland
Concrete contractor: Pence-Kelly, Salem, Ore.
Pumping contractor: Lucht’s Concrete Pumping, Clackamas, Ore.
Ready-mix supplier: Ross Island, Portland
Equipment: Putzmeister 36-Meter placing boom, PM tower with outside climbing system and Putzmeister 2110 high-pressure trailer pump