Prestressed Concrete Steel Bars

     Standards:

• GB/T 5223.3-2005 steel bars prestressed concrete
• GB/T 10120- stressed relaxation testing method for method
• ASTM 328 – stressed relaxation testing method for material and structure
• ISO 6934-3:1991 steel for prestressing of concrete-part 3: quenched and tempered wire, MOD,
• American standards: ASTM A416, ASTM A882/A882M-91,
• British standards: BS 5896
• Japanese standards: JIS G3536, JISG3137,
• Australia new standards: AS/NZS 4672
• Brizil standards: NBR -7483

    PCB steel bars for prestressed concrete:

   round steel bar for prestressed concrete,(P), helical grooved bar(HG), helical ribbed bar(HR), ribbed bar(R), quenched and tempered bar

Concrete centrifugal pipe pile, telegraph pole, viaduct pier, railway rolling pillow, and prestressed member.

    Calibration item and content for PC steel bar

    Tensile testing machine for steel bar

• Tensile strength of steel bar: carried out according GB/T 228. Adopting nominal section area of steel bar to calculating tensile strength.
• Nominal non-proportional Extension strength: carried out according to GB/T 228, nominal non-proportional extension strength R0.2 of steel bar is replaced by 1% stress R_ of nominal non-proportional extension strength. When Measuring Rw.zo, Pre-loading is 10% of nominal non-proportional extension loading.
• Elongation of steel bar: measuring max. Elongation according GB/T 228. Extension produced by pre-loading should be add to total extension, elongation should be round off 0.5%
• Measuring of elongation of steel bar fracturing: carried out according to GB/T 228, gauge length(L) is 8 times of nominal diameter of steel bar(Lo=8d).
• Scratching of guage should not lead to fracturing at scratching point, length of sample guarantee that distance between two clamper should be 50mm longer than nominal length.
• Usual testing adopting elongation after fracture, arbitration test is according to total elongation of Max. Loading, gauge length of elongation for Max. Loading = 200mm.

      Bending testing for steel bar:

   According to GB/T 238, repeatedly bending testing for steel bar(excepting ribbed and spiral groove steel bar) of nominal diameter less or equal 10mm. There relative specification for diameter of bending. Bending tstsing for Nominal diameter of steel bar (excepting ribbed and spiral groove steel bar) more than 10mm is according to GB/T232, diameter of bending mandrill is 10 times of nominal diameter.

     Stressed relaxation testing for steel bar:

• it carried out according GB/T 1012. Guage of temperature for envionment should be kept at 20℃±2℃, gauge length of sample should be not less or equal to 60 times of nominal diameter, sampel should not be heat treatment and cold working after preparation of sample.
• Initial loading should be completed in 3min to 5min, starting record after keeping loading for 1min.  Reckoning relaxation value for 1000h for testing data not less than 100h by linearity regression analysis.

      Fatige testing for steel bar:

• cuting fatige testing sample from steel bar, length of sample should be not less than 140mm between two clamplers.
• steel bar should be endure 2×106 times and pulsating loading of 0.7Fb to (0.7--2⊿Fa).Round steel bar: 2⊿Fa /Sg=200Mpa,Spiral groove and sprial ribbed steel bar and ribbed steel bar: 2⊿Fa /So=180MPa；Fb- nominal breaking loading of steel bar(N).2⊿Fa- equivalent value of stressed scope (2 times stressed amplitude).So nominla area of section for steel bar, (mm²)
• Max. keeping stressed of pulse-tension for static measuring precision should be 1±% in entire process of testing.
• circling frequency of stress should not exceed 120Hz
• all stress should be axial direction passed to sample without infulence of jaw and notch, with special device to control any sliding of sample.
• testing is invalid when sample is breaking in chuck or clamping area (twice of nominal diameter of steel bar) under infulence of notch and partial overheating.
• testing temperature should not exceed 40℃ in process of testing, envionmental temperature of laboratory should between 18℃and 25℃。