513 EM 385-1-1 Chapters 23-29

Sections

27-8. General Requirements.

Post Tension Operations

Allow only essential employees behind jacks or end anchorages during post-tensioning operations.
Use signs and barriers to demarcate and limit access to the post-tensioning area during operations.

Formwork and Shoring Design and Construction

Ensure formwork and shoring are designed and constructed according to ACI 347R-14, capable of withstanding all applied loads.
Maintain on-site manufacturer’s specifications for fabricated shoring systems.
Avoid the use of single post shores or adjusting devices with structural damage or defects.

Base Support Requirements

Verify the strength of supporting ground or structures for formwork and shoring is adequate to bear vertical and lateral loads.
Ensure the soundness and load-bearing capacity of sills for shoring.
Prohibit overloading fabricated shoring beyond the manufacturer’s safe working load.

Single Post Shores Regulations

Require a structural engineer to design and inspect single post shore layouts used in multiple tiers.
Align and splice single post shores vertically to prevent misalignment.
Ensure single post shores are braced for stability in all required directions and secure posts near slab perimeters.

Tubular and Frame Shoring Standards

Use structural-grade materials for couplers in tube and coupler shoring, and maintain all components in good condition for tubular welded frame shoring.
Inspect shoring towers for adherence to design specifications and ensure proper coupling tightness.
Ensure locking devices on shoring frames are functional and brace spacing does not exceed design limits.

Vertical Slip Forms Management

Design and brace steel rods or pipes for jacks or forms lifting, ensuring equal distribution of vertical loads and provision of automatic holding devices for jacks.
Conduct jacking operations uniformly without exceeding safe rates, and maintain the form structure aligned and plumb.
Equip all vertical lift forms with fully encircling scaffolding or work platforms.

Removal of Formwork and Shoring

Allow removal of forms or shores only after the Competent Person (CP) for forming or shoring confirms the concrete's strength to bear its own weight and superimposed loads, based on plan stipulations or concrete testing results.

Knowledge Check Choose the best answer for the question.

27-6. Who is allowed to work behind jacks or end anchorages during post-tensioning operations?

Designated employees

Authorized employees

Essential employees

All employees

You forgot to answer the question!

EM 385-1-1 Paragraph 27-8 (d.–e).

27-8. General Requirements. (d.–e).

d.  Post Tension Operations.  (27-8.d)

(1)  Do not allow employees, except those essential to the post-tensioning operations, to be behind jacks or end anchorages during post-tensioning operations.

(2)  Erect signs and barriers to identify and limit employee access to the post- tensioning area during tensioning operations.

e.  Formwork and Shoring.  (27-8.e)

(1)  Formwork and shoring will be designed and planned according to ACI 347R-14 (see para 27-7.a).

(2)  Design, fabricate, erect, support, brace, and maintain formwork, shoring, and bracing so that it will safely support all vertical and lateral loads that might be applied until such loads can be supported by the structure.

(3)  When fabricated shoring systems are used, keep a copy of the manufacturer’s specifications for the system available at the work site during job planning and execution.

(4)  Do not use fabricated single post shores or adjusting devices if heavily rusted, bent, dented, re-welded, or have broken welds or other defects.  If they contain timber,
    they may not be used if the timber is split, cut, has sections removed, is rotted, or is otherwise structurally damaged.

(5)  Base Support.

(a)  Ensure supporting ground or completed construction upon which formwork and shoring is placed has adequate strength to carry the applied vertical and lateral loads.

(b)  Ensure sills for shoring are sound, rigid, and capable of carrying the maximum intended load.

(c)  Ensure base plates, shore heads, extension devices, or adjustment screws are in firm contact with the footing sill and form material and when necessary, are secured to them.

(d)  Design and construct splices to prevent buckling and bending.

(e)  Provide diagonal bracing in vertical and horizontal planes to provide stiffness and to prevent buckling of individual members.

(f)  Provide reshoring to safely support slabs and beams after stripping or where such members are subjected to superimposed loads due to construction.

(g)  Do not load fabricated shoring beyond the safe working load recommended by the manufacturer.

(6)  Single Post Shores.

(a)  A structural engineer must design and inspect the layout wherever single post shores are used in more than one tier.

(b)  Vertically align single post shores and splice them to prevent misalignment.

(d)  Do not adjust single post shores to raise formwork after the concrete is in place.

(e)  Drive home all nails used to secure bracing or adjustable timber single post shores and bend the point of the nail over, if possible (that is, clinch the nails).

(f)  For stability, brace single post shores in both the longitudinal and transverse directions.

(f-1)  Adequately brace single-post shores in two mutually perpendicular directions at the splice level.

(f-2)  Diagonally brace each tier in the same two directions.

(f-3)  Install bracing as the shores are erected.

(f-4)  Secure posts located near the slab perimeter during assembly and dismantling or reshoring to prevent the post from “fall out”.

(7)  Tube and Coupler Shoring.

(a)  Use structural type material (for example, drop-forged steel, malleable iron, structural grade aluminum) for the couplers.  Do not use gray cast iron or dissimilar metals.

(b)  Do not use couplers if they are deformed, broken, or have defective or missing threads on bolts, or have other defects.

(c)  When inspecting the erected shoring towers, do not exceed the spacing between posts from that shown on the designed layout drawings.  Inspect the interlocking of all tubular members and the tightness of the couplings.

(8)  Tubular Welded Frame Shoring.

(a)  All locking devices on frames and braces must be in good working order and all components must be in a condition similar to that of original manufacture.  Coupling pins must align the frame or panel legs and pivoted cross braces must have their center pivot in place.

(b)  Do not exceed the spacing between towers and cross brace spacing from that shown in the design. Ensure all locking devices are closed.

(9)  Vertical Slip Forms.

(a)  Design the steel rods or pipe on which the jacks climb or by which the forms are lifted specifically for that purpose.  Brace the rods and pipes where not encased in concrete.

(b)  Position jacks and vertical supports so that the vertical loads are distributed equally and do not exceed the capacity of the jacks.

(c)  Provide jacks or other lifting devices with mechanical dogs or other automatic holding devices to provide protection in case of failure of the power supply or the lifting mechanism.

(d)  Perform lifting steadily and uniformly.  Do not exceed the predetermined safe rate of lift.

(e)  Provide lateral and diagonal bracing of the forms to prevent excessive distortion of the structure during the jacking operation.

(f)  During jacking operations, maintain the form structure in line and plumb.

(g)  Provide all vertical lift forms with scaffolding or work platforms completely encircling the area of placement.

(10) Removal of Formwork and Shoring.  Do not remove forms or shores, except those on slab on grade and slip forms, until the CP for forming or shoring determines that the concrete has gained sufficient strength to support its weight and all superimposed loads. The CP must base the determination on one of the following:

(a)  Satisfaction of conditions stipulated in the plans and specifications for removal of forms and shores.

(b)  Concrete testing indicates that the concrete has achieved sufficient strength to support its weight and superimposed loads.