1 General Provisions
1.0.1 This specification is formulated with a view to reasonably applying the anchorage, grip and coupler for prestressing tendons in the prestressed structure engineering, ensuring the safety and reliability of anchorage zone and anchorage joint, and ensuring quality.
1.0.2 This specification is applicable to the application of anchorage, grip and coupler for prestressing tendons in such engineering as prestressed concrete structure, building prestressed steel structure, rock anchor and ground anchor.
1.0.3 Application of anchorage, grip and coupler in the prestressed structure engineering shall not only meet the requirements of this specification, but also comply with those in the current relevant ones of the nation.
2 Terms and Symbols
2.1 Terms
2.1.1 Anchorage
It refers to the permanent anchor device used to maintain the tensile force of prestressing tendon and transfer it to the structure in the post-tensioning structural member.
2.1.2 Grip
In the production process of pre-tensioning prestressed concrete member, it refers to the instrumental anchor device used to maintain the tensile force of prestressing tendon and fix it on the production pedestal (or equipment); in the prestressing tendon tensioning process of post-tensioning structure or member, it refers to the instrumental anchor device used to clamp the prestressing tendon on the tensioning jack or equipment.
2.1.3 Coupler
It refers to the device used to connect the prestressing tendon.
2.1.4 Prestressing tendon
It is the general term of single or bundled steel wire, steel strand or prestressed twisted reinforcement (referring to fine rolling twisted reinforcement) used to establish prestress in the prestress works.
2.1.5 Prestressing tendon-anchorage (grip) assembly
It refers to the load carrying unit assembled with prestressing tendon and anchorage (grip) at the end, hereinafter referred to as anchorage (grip) assembly.
2.1.6 Prestressing tendon-coupler assembly
It refers to the load carrying unit assembled with prestressing tendon and coupler, hereinafter referred to as coupler assembly.
2.1.7 Ultimate tensile force of tendon-anchorage (grip, coupler) assembly
It refers to the maximum tensile force reached by the tendon-anchorage (grip, coupler) assembly in the process of static load anchoring performance test.
2.1.8 Efficiency factor of prestressing tendon
It refers to the factor subject to such factors as influence of number, test device and initial stress adjustment of prestressing tendon, in consideration of the uneven tensile stress of prestressing tendon.
2.1.9 Draw-in
It refers to the retraction phenomenon of prestressing tendon due to the relative displacement between parts of anchorage or between anchorage and prestressing tendon in the anchoring process of prestressing tendon. Draw-in includes anchorage deformation, clip displacement and prestressing tendon retraction.
2.1.10 Bearing plate
It refers to the component used to bear the pre-applied force transferred by the anchorage and transfer it to the concrete in the post-tensioning prestressed concrete structural member. Bearing plate may be divided into ordinary bearing plate and casting bearing plate.
2.11.11 Anchorage zone
It refers to the zone used to bear the pre-applied force transferred by the anchorage and make the member section concrete stress uniform in the post-tensioning prestressed concrete structural member; the zone thereof directly enclosed with prestressing anchor device and strengthened with reinforcement is referred to as partial anchorage zone.
2.1.12 Anchorage joint
It refers to the partial structural stressed component used to bearing the pre-applied force of prestressing tendon (or cable) in the prestressed steel structure.
2.1.13 Load transfer test
It refers to the test for verifying the load transfer performance in the partial anchorage zone.
2.1.14 Prestress loss due to friction at anchorage device
It refers to the prestress loss of prestressing tendon due to friction at the horn mouth corner of anchorage and bearing plate at the tensioning end. Where the clip-type anchorage is tensioned by the limit self-anchoring process, prestress loss caused by prestressing tendon reversely scratched by clip also belongs to prestress loss due to friction at anchorage device.
2.1.15 Prestress loss due to friction at deviated device
It refers to the prestress loss of prestressing tendon due to friction at the inner corner of deviated device.
2.2 Symbols
Ap1——Nominal sectional area of single prestressing tendon;
Ap——Sum of nominal sectional area of each prestressing tendon in the prestressing tendon - anchorage (or grip) assembly;
Ep——Elastic modulus of prestressing tendon;
——Measured compressive strength mean of concrete cube specimen cured under the same conditions in the load transfer test in the anchorage zone;
fcu,k——Standard value of concrete cube design compressive strength, also known as grade value of concrete compressive strength;
fptk——Standard value of prestressing tendon tensile strength;
fpm——Ultimate tensile strength mean of prestressing tendon for test use (section is counted by Ap1);
Fapu——Ultimate tensile force of prestressing tendon-anchorage assembly;
Fgpu——Ultimate tensile force of prestressing tendon-grip assembly;
Fpm——Average ultimate tensile force of prestressing tendon, determined by breaking force mean of prestressing tendon specimen;
Fptk——Standard value of prestressing tendon tensile force;
Fu——Ultimate load in load transfer test in the anchorage zone;
Ncon——Tensioning control force of prestressing tendon;
Np——Design value of pre-applied force on the bearing plate;
△a——Relative displacement between prestressing tendon and anchorage (or coupler and grip);
△b——Relative displacement between parts of anchorage (or grip and coupler);
△l——Theoretical elongation value of prestressing tendon between working anchorage at the tensioning end and jack tool anchorage under the tensioning control force;
εapu——Total strain of prestressing tendon where the prestressing tendon-anchorage assembly reaches the ultimate tensile force;
ηn——Efficiency factor of anchorage determined in the static load anchoring performance test of prestressing tendon-anchorage assembly;
ηg——Efficiency factor of grip determined in the static load anchoring performance test of prestressing tendon-grip assembly;
ηp——Efficiency factor of prestressing tendon.
3 Performance Requirements
3.0.1 Basic performance of the anchorage, grip and coupler for prestressing tendons shall meet the requirements of the current national standard "Anchorage, Grip and Coupler for Prestressing Tendons" GB/T 14370.
3.0.2 The static load anchoring performance of anchorage shall be determined according to the efficiency factor (ηa) of anchorage measured through the static load test of prestressing tendon-anchorage assembly and the total strain (εapu) of the prestressing tendon in the assembly when reaching the ultimate tensile force. Efficiency factor (ηa) of anchorage shall not be less than 0.95; total strain (εapu) of prestressing tendon shall not be less than 2.0%. Efficiency factor of anchorage shall be determined according to the test results and calculated according to the following formula:
