When producers gather at the Third International fib (fédération internationale du béton) Congress and exhibition in Washington, D.C., the U.S. concrete industry will be able to learn how Europeans have weathered the global economy's slowdown.
Many European and North American applications and technologies are very similar. This includes one common goal: safety. Now, U.S. precast producers can benefit from research on jobsite safety by employing a new technology unveiled at World of Concrete early this year.
The Finnish government funded a special project in 2005-06 on Safe Erection and Design Methods on building sites. The study resulted in new jobsite safety standards, including clarification of tasks and responsibilities in design, training programs for installers, and new quality standards for building components, frame stability, connection design, and slim floor construction.
Engineers from Peikko Group, a Finnish manufacturer of fasteners for concrete structures, has incorporated these new standards to create products that promote safety at jobsites. Peikko developed the Delta Torsion Beam (DTB) system specifically to protect erection crews of precast panels.
The system works with the manufacturer's Deltabeam to prevent rotation of precast floor slabs and eliminate the need for support from below. The Deltabeam is a hollow, welded steel beam with holes running along each side. It can support hollowcore, composite, or in situ concrete slabs.
After concrete panels are installed, the holes in the beams are filled with concrete. The Deltabeam then becomes a steel-concrete composite beam, together with the hollowcore panels, once the concrete has hardened.
In addition to jobsite safety, benefits of the composite action include a material savings up to 30% and a fire rating up to R120 (two hours of fire resistance).
The DTB system was designed for tall structures where traditional propping solutions are costly and labor-intensive. Delta Torsion Beams provide extra support during erection by holding precast panels in place until concrete is added to the Deltabeams.
DTBs attach to Deltabeams at specific fixing points that are determined before installation. The configuration depends on the structure's design, including grid sizes and weight loads. The torsion beam extends out to brace against the top of the concrete panel.
Peikko recommends using three DTBs per beam span—one at each end and one in the middle. DTBs are available in different standard sizes. The equipment (steel beam, steel packs, bolts, nuts, and washer plate) can be reused.
After the Deltabeam's holes have been filled and the concrete has reached its required strength, installers remove the DTBs and repeat the process as they erect each floor of the structure. See Figures 1-4 for the step-by-step process.
Visit Peikko at booth #409 at the PCI Convention and at www.peikko.com.
More on Hollowcore...
The following hollowcore extruding and slipforming equipment is available to precast producers.
Versatile casting machines
Produce prestressed T-beams, lintels, solid panels, and hollowcore slabs from 2.4- to 20-in. thicknesses with standard Echo casting machines. Each machine is equipped with one stationary front concrete hopper, one hydraulic rear hopper, and two vibrator units with adjustable power. Machines are available in 4-, 5-, and 8-ft. widths. Echo Engineering. +32 11 60 08 00. www.echo-engineering.net
The Extruder E9 produces prestressed hollow-core slabs on long beds, with a variety of cross-sections available for various applications. It helps meet stringent strand location tolerances with an advanced strand guide, and saves material and finishing work by producing a flat slab top. A touch-screen interface provides access to historical data. Elematic Inc. 262-798-9777. www.elematic.com
PCI booths #312, 314
Powerful extrusion technology
The MAX-truder produces hollowcore floor slabs and wall panels in 12-, 24-, and 48-in. widths, and heights ranging from 3 to 20 in. with just a change of the compaction unit. It delivers up to 12,500 psi compressive concrete for long spans and high-load capacity. The MAX-truder can produce hollowcore panels with void volumes up to 50%, minimizing material consumption. Weiler GmbH. 613-878-3435. www.weilerprecast.com
Manufacture prestressed hollowcore slabs with the Dynaspan slipform system. The machine uses lightweight or normal weight concrete to create slabs in 4- and 8-in. widths or metric sizes. Dynaspan deposits, vibrates, and finishes a slab in a single operation, reducing pouring time. Prestressing strands in the top fibers of the slab are optional for cantilevered or wall panel applications. Dynamold Corp. 785-667-4626.