High Strength Prestressing Screw Thread Steel Bars

High Strength Prestressing Screw Thread Steel Bars

High strength prestressing screw thread steel bars for concrete, also called finished deformed bars, it is straight reinforcing bar with discontinuous external screw threads on surface, in big outside diameter, high strength, and high dimension precision. The rebar can be connected by screwing connectors with internal threads or screwed nuts with threads at any cross section for anchoring. Prestessing screw thread steel bars is graded by yield strength with, and its code name is "PSB" plus the specified minimum yield strength. P, S and B are the first English letters of Prestressing, Scres-thread and Bars respectively. E.g., PSB830 indicates steel bars with yield strength standard value of 830MPa.
We give more information about high strength prestressing screw thread steel bars as below:
A.Base circle area-----Area of steel bar section without thread

B.Effective section coefficient-----The ratio of the base circle area of steel bar section to the area with threads (i.e. nominal section area)

C.Dimension ----- The nominal diameter of steel bars ranges from 18 mm to 50 mm.

D. For Nominal cross-sectional area and theoretical weight of finished deformed bar, please refer to table below:
Nominal OD /mm Nominal cross-sectional area/mm2 Effective section coefficient Theoretical cross-sectional area/mm2 theoretical weight(kg/m)
18 254.5 0.95 267.9 2.11
25 490.9 0.94 522.2 4.10
32 804.2 0.95 846.5 6.65
40 1256.6 0.95 1322.7 10.34
50 1963.5 0.95 2066.8 16.28

E.Shape of High strength prestressing screw thread steel bars---- in thread shape without longitudinal connection, in addition the two sides threads are in one same helix.

F.Allowed Deviation ----- the prestressing screw thread steel bars are usually delivered as per fixed length, the specific delivered length shall be described in the contract. When delivered in fixed length or double ruler fixed length, the allowed deviation for length shall be in range 0~+50mm.

G.Bending Degree and the Ends: The bending degree of reinforcing bars shall not affect the normal use. The bending degree per meter of reinforcement shall not be greater than 4mm, and the total bending degree shall not be greater than 0.4% of the total length of reinforcing bars. The ends of reinforcing bars shall be flush, so as not to affect the passage of connectors.

H.Weight and Allowed Deviation: The finished deformed bars are delivered as per actual weight or theoretical. The difference for actual weight and nominal weight shall be more than ±4% of nominal wight.

More information Table
Standard GB/T 20065-2006
Grade PSB500, PSB785, PSB830, PSB930. PSB1080
Size 18mm, 25mm, 32mm, 40mm, 50mm
Length 4 to 12m or as per clients request
Technical Request Chemical composition S≤0.04%, P≤0.04%,
  Smelting Method Steel is smelted by oxygen converter or electric furnace
  Delivery condition In hot rolled condition; rolled residual heat treatment condition; or annealed condition in straight form
  Surface quality There shall be no transverse cracks, scars and folds on the surface. Defects that do not affect the mechanical properties and connection of steel bars are allowed.
  Dimension check In addition to dimension measurement and inspection, special connectors are also used to inspect the precession of steel bars
Test Needed Tensile Test Tensile test shall be carried out with full section size steel bar specimen. It is not allowed to reduce the cross-section of the sample by machining.  For lot quantity more than 60tons, 3 tensile test samples shall be selected.
  Bending Test After bending test specimens are bent according to regulations, cracks shall not occur on the surface of the bent parts.
  Relaxation Test 1. During the test, the ambient temperature of the sample should be kept within 20℃± 2℃. 2. Test gauge length shall not be less than 60 times of nominal diameter. 3. No heat treatment or cold working shall be carried out after sample preparation. 4. The initial load shall be uniformly applied within 3 min ~ 5 min, and the relaxation value shall be recorded after holding the load for 1min. 5. It is allowed to calculate the relaxation rate value of 1000h from the test data of at least 100h
  Fatigue Test With the consent of both the supplier and the supplier, fatigue test can be carried out. The rebar shall withstand 2×106 cycles of cyclic stress without fracture, and vibrate up and down when the maximum stress is 70% of the nominal tensile strength. The rebar stress amplitude is equal to 195MPa.
Packing Packed in bundle, standard seaworthy package or customers’ requirements.
Application large bridges and slope anchoring projects of expressways and high-speed railways.
Advantage simple connection and anchorage, strong adhesion, safe and reliable tension and anchorage, convenient construction, etc

Mechanical Property Table
Grade Yield Strength MPa Tensile Strength MPa Elongation at Failure A% Uniform Elongation
PSB500 ≥500 ≥630 ≥10 ≥2.5
PSB785 ≥785 ≥980 ≥7 ≥3.5
PSB830 ≥830 ≥1030 ≥6  
PSB930 ≥930 ≥1080 ≥6  
PSB1080 ≥1080 ≥1230 ≥6