11,000 Yards of Concrete Used to Top Out 28-floor Bellevue Center November 1999

Putzmeister boom wall bracket eases use of self-climbing form system

Skip Gribble, owner of Ralph’s Concrete Pumping in Seattle, faced a challenge after pouring 2,750 cubic yards (2103 m3) of concrete last July for the foundation for the 28-story Three Bellevue Center — how to effectively pour the core of the building using a detachable boom pump without securing it to the formwork.

Put simply, the challenge was to secure the boom pump someplace other than the formwork around the structure in such a way that would allow the forms to be later jacked up without having to remove the pump.

He called Bill Carbeau, a sales manager at Putzmeister America for help. “When I explained the problem to Bill, he told me Putzmeister had the answer,” said Gribble.

“Bill came back to us with a platform on a bracket that keeps the boom about two feet away from the formwork,” said Gribble. The wall or “L” bracket provides a platform to place up to a 50-foot (15 m) freestanding Putzmeister tower anywhere off the side of a sheer concrete wall.

Putzmeister introduced the brackets last year. They make it unnecessary for a freestanding placing boom used on high-rise projects to be secured to the formwork. With the boom and tower attached to the wall of the core, away from the forms, the formwork can be easily moved up to the next level and put in place for new sections to be poured.

With the Three Bellevue Center job, Gribble also took advantage of another recent Putzmeister innovation. He used a detach boom kit introduced by the company last year that turns a truck-mounted concrete boom pump into a separate placing boom. For this project, Ralph’s used a boom from a Putzmeister 28-Meter truck-mounted pump.

A crane hoisted the detach boom to the area to be poured. It was then mounted on the platform attached to the side of the wall using the “L” bracket. During a six-month period, more than 11,000 cubic yards of concrete were poured for the core of the building. It took almost 1,300 ready-mix trucks to supply the concrete needed.

The concrete, 400 cubic yards (306 m3) per floor, was pumped from the ground through a 5-inch (13 cm) delivery pipe 315 feet (96 m) up to the top of the structure. The core of the 471,635-square-foot (143,754 m2) building was topped out ahead of schedule in October. Three Bellevue Center is expected to open its doors to business in May 2000.

Because of the ease of removing the placing boom from the bracketed platform, Gribble was able to take down the boom and use it with his 28-Meter pump on other jobs during the seven-day cycle of pouring, curing and setting up the formwork for the next floor.

“I was very pleased with the way the bracket and the detachable boom worked,” said Gribble, “and I guess the general contractor was, too, because he gave me another job right after we finished with the Bellevue Center.”

Job Specs: General contractor: Sullen Construction, Seattle Concrete contractor: Ralph’s Concrete Pumping, Seattle Ready-mix supplier: Stoneway Concrete, Renton, Wash. Equipment: Putzmeister 28-Meter Truck-Mounted Concrete Boom Pump