27.B.03 Post-tensioning operations.
Post tensioning is a technique for reinforcing concrete. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed.
- No employee (except those essential to the post-tensioning operations) must be permitted to be behind jacks or end anchorages during post-tensioning operations.
- Signs and barriers must be erected to limit employee access to the post-tensioning area during tensioning operations.
27.C Formwork and Shoring.
27.C.01 Formwork, shoring, and bracing must be designed, fabricated, erected, supported, braced, and maintained so that it will safely support all vertical and lateral loads that might be applied until such loads can be supported by the structure.
27.C.02 Planning and design.
- The planning and design of formwork and shoring must be in accordance with provisions of American Concrete Institute (ACI) Publication 347.
- The design of the shoring must be prepared by a QP (designer) and the Erection and Removal Plan for Formwork and Shoring must be submitted for review to the GDA. The erected shoring must be inspected by an engineer qualified in structural design.
- The manufacturer's specifications for fabricated shoring systems must be available at the job site during job planning and execution.
27.C.03 Base support.
- Supporting ground or completed construction upon which formwork and shoring is to be placed must be of adequate strength to carry the vertical and lateral loads to be imposed.
- Sills for shoring must be sound, rigid, and capable of carrying the maximum intended load.
- Base plates, shore heads, extension devices, or adjustment screws must be in firm contact with the footing sill and form material and when necessary, must be secured to them.
27.C.04 Splices must be designed and constructed to prevent buckling and bending.
27.C.05 Diagonal bracing must be provided in vertical and horizontal planes to provide stiffness and to prevent buckling of individual members.
27.C.06 Inspection.
- Shoring equipment must be inspected prior to erection to determine that it is as specified in the shoring design. Any equipment found to be damaged must not be used.
- Erected shoring equipment must be inspected immediately prior to, during, and immediately after the placement of concrete. Any shoring equipment that is found to be damaged, displaced, or weakened must be immediately reinforced or re-shored.
27.C.07 Re-shoring must be provided to safely support slabs and beams after stripping or where such members are subjected to superimposed loads due to construction.
27.C.08 Fabricated shoring must not be loaded beyond the safe working load recommended by the manufacturer.
Knowledge Check Choose the best answer for the question.
27-3. What must be accomplished prior to, during, and immediately after the placement of concrete?
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