Prestressed Concrete

Prestressed Concrete

BC 1704.4

1704.4 Concrete construction. The special inspections and verifications for concrete construction shall be as required by this section and Table 1704.4.

Exception: Special inspections shall not be required for the following when specifically exempted on the approved con­struction documents:

  • Concrete placement of less than 50 cubic yards (38 m3)‡ provided that the concrete is nonstructural and is not subject to the durability requirements of Section 1904. In such case, testing may be waived by the reg­istered design professional who prepared the struc­tural construction documents.
  • Nonstructural concrete slabs supported directly on the ground, including prestressed slabs on grade, where the effective prestress in the concrete is less than 150 psi (1.03 Mpa).
  • Concrete foundation(s) for lightweight fences and recreational equipment.
  • Concrete patios, site furnishings, garden walls, drive­ways, sidewalks and similar construction.
Special Inspection: Prestressed Concrete
Code Section(s): BC 1704.4
Minimum Qualifications: Primary Inspector or Inspection Supervisor. 
a. PE- Civil/ Structural; and
b. 1 year relevant experience
Supplemental Inspector (Alternative 1),
a. Bachelor’s degree in engineering; and
b. ICC Certification as Prestressed Concrete Special Inspector; and
1 year relevant experience
Supplemental Inspector (Alternative 2)
a. ICC Certification as Pretested Concrete Special Inspector; and
b. 3 years relevant experience

Inspection Task: Inspection Interval (Continuous/Peri odic) NYC Construction Code Reference Section Reference Standard (e.g. ASTM X1234) Baseline Document (Approved plans, Shop Drawings, Manufacturer’s Instructions, etc.) Comments (e.g. needs test performed by Approved Testing Agency)
1. Inspection of reinforcing steel, including placement, for both prestressing steel and ordinary reinforcing steel. Verify type, hook dimensions, cover requirements Periodic. BC 1704.4

Table 1704.4

BC 1903.5

BC 1907.1

BC 1907.7

ACI 318:3.5.6

ASTM A421 (wire)

ASTM A421 (low-lax wire)

ASTM A416 (strand)

ASTM A722 (bar)

• Shop/Manufacturer’s drawings approved by design professional Recommendation: For shop cast items, Special Inspection agency may rely on report of testing/ inspection agency local to the plant
2. Verify presence of solid safety shields behing jacking equipment Periodic- prior to tensioning of prestressing steel BC 1906.6.7 Recommendation: While not defined in code, safety shields should be of contained sand or other material capable of absorbing the energy of a jack propelled by total failure of the strand being tensioned
3. If pre-tensioned, verify application of required pre-stressing force in each strand/tendon Continuous Recommendation: For shop cast items, Special Inspection Agency may rely on report of testing/inspection agency local to the plant
4. Verify use of required design mix Periodic See Concrete Inspection See Concrete Inspection • Approved specifications and material submittals
5. Concrete placement to be inspected as per concrete inspection Continuous See Concrete Inspection See Concrete Inspection See Concrete Inspection
6. Inspection for maintenance of specified curing temperature and techniqures Periodic BC 1905.11

BC 1905.13

BC 1914.9

ACI 318 5.11-5.13
7. Verify strength of in-situ concrete prior to application of pre-stress Periodic BC 1906.2 ACI 318: 6.2
8. For post- tensioned applications, verify application of required pre-stress force in each strand/tendon Continuous ACI 318:18.20

ACI 318:18.18.4

Verify calibration of jack, and/or minimum elongation of strand/ tendon
9. Grouting of bonded pre-stressing in seismic systems Continuous ACI 318:18.20

ACI 318:18.18.4

10. Erection of precast members Periodic ACI 318 Chapter 16