1 General Provisions
1.0.1 This specification is formulated with a view to regulating the application of rebar mechanical splicing in concrete structure engineering, achieving safety and applicability, advanced technology, economy and rationality and ensuring quality.
1.0.2 This specification is applicable to design, construction and acceptance of rebar mechanical splicing in concrete structure in construction engineering.
1.0.3 Rebars used for mechanical splicing shall meet the requirements of current standards of the nation Steel for the Reinforcement of Concrete - Part 2: Hot Rolled Ribbed Bars (GB 1499.2), Remained Heat Treatment Ribbed Steel Bars for the Reinforcement of Concrete (GB 13014), Stainless Steel Rebar Used for Reinforced Concrete (YB/T 4362) and Steel for the Reinforcement of Concrete - Part 1: Hot Rolled Plain Bars (GB 1499.1).
1.0.4 Rebar mechanical splicing shall not only comply with this specification, but also comply with those in the current relevant standards of the nation.
2 Terms and Symbols
2.1 Terms
2.1.1 Rebar mechanical splicing
connection method of transmitting the force in one rebar to another through mechanical lock effect of rebar with connectors of mechanical splicing or other intervention materials or through pressure-bearing effect of rebar end face
2.1.2 Splice
shortened form of rebar mechanical splice, which is whole set for rebar mechanical splicing
2.1.3 Connectors of mechanical splicing
all components used for connecting rebar, including coupler or sleeve and other assemblies
2.1.4 Coupler or sleeve
steel sleeve used for transmitting axial tensile force or pressure of rebar
2.1.5 Rebar threaded sector
threaded segment of rebar end in splice
2.1.6 Length of mechanical splice
sum of length of splice connectors of mechanical splicing and that of the cross-section change segment of rebar on both ends of connectors of mechanical splicing, i.e., the exposed threaded sector and the upsetting transition section of threaded splice
2.1.7 Tensile strength of splice
maximum tensile stress value reached by splice sample in the process of tensile test
2.1.8 Residual deformation of splice
deformation of splice sample measured within specified gauge length, after loading and unloading are carried out according to specified loading system
2.1.9 Total elongation of splice sample at maximum tensile force
total elongation of splice sample at maximum force which is measured within specified gauge length
2.1.10 Area percentage of splice
area percentage of mechanical splice of longitudinal load-bearing rebar within the same connection segment is the ratio of the cross-sectional area of longitudinal load-bearing rebars with mechanical splice to that of all longitudinal rebars within the segment; in case connection is carried out between rebars with different diameters, it shall be calculated according to the area of rebar with smaller diameters
2.2 Symbols
Asgt——the total elongation of splice sample at maximum tensile force;
d——the nominal diameter of rebar;
fyk——the standard value of rebar yield strength;
fstk——the standard value of ultimate tensile strength of rebar;
f0mst——the measured tensile strength of splice sample;
p——the thread pitch;
u0——the residual deformation of splice sample within specified gauge length after the splice sample is loaded to 0.6 fyk and then unloaded;
u20——the residual deformation of splice sample after being subjected to 20 times of tension-compression repeatedly under high stress according to loading system in Annex A of this specification;
u1——the residual deformation of splice sample after being subjected to 4 times of tension-compression repeatedly with large deformation according to loading system in Annex A of this specification;
u8——the residual deformation of splice sample after being subjected to 8 times of tension-compression repeatedly with large deformation according to loading system in Annex A of this specification;
εyk——the strain where rebar stress reaching standard yield strength value.
3 Performance Requirements of Splice
3.0.1 Splice design shall meet the requirements of strength and deformation performance.
3.0.2 Coupler or sleeve used for rebar connection shall meet the relevant requirements of the current professional standard Couplers for Rebar Mechanical Splicing (JG/T 163); in case cold-drawn or cold-rolled precision seamless steel pipe made of No.45 steel was adopted as raw materials of coupler or sleeve, steel pipe shall be subjected to annealing treatment and shall meet the relevant requirements of the current professional standard Couplers for Rebar Mechanical Splicing (JG/T 163) on strength limit value and elongation after fracture of steel pipe. Bar or seamless steel pipe with the same material as the rebar base material should be adopted as the raw material of stainless steel rebar connecting coupler or sleeve, and the appearance and mechanical performance shall meet the requirements of the current national standards Stainless Steel Bars (GB/T 1220) and Seamless Stainless Steel Tubes for Structure (GB/T 14975).
3.0.3 Splice performances shall include uniaxial tension, repeated tension-compression under high stress, repeated tension-compression under large deformation and fatigue performance; corresponding inspection items shall be selected according to splice performance grade and application scenario.
3.0.4 Splice performances may be classified into Grades I, II and III according to tensile strength, residual deformation, total elongation at maximum tensile force as well as repeated tension-compression performance at high stress and with large deformation; the performances shall comply with the requirements specified in 3.0.5 ~ 3.0.7 of this specification respectively.
3.0.5 Tensile strength of Grade I, II or III splice must be in accordance with those specified in Table 3.0.5.
Table 3.0.5 Tensile Strength of Splice
Splice grade Grade I Grade II Grade III
Tensile strength f0mst≥fstk Rebar tensile failure
or f0mst≥1.10fstk Damage of connectors of mechanical splicing f0mst≥fstk f0mst≥1.25fyk
Notes:
1 Rebar tensile failure refers to the break at rebar threaded sector and rebar upsetting transition section at rebar base material and outside coupler or sleeve;
2 Damage of connectors of mechanical splicing refers to break at coupler or sleeve, longitudinal crack of coupler or sleeve or extraction of rebar from coupler or sleeve as well as damage of other connected components.
3.0.6 Grade I, II or III splice shall be able to withstand the circulation of specified high stress and repeated tension-compression under large deformation; after withstanding the tension-compression circulation, the tensile strength shall still meet the requirements specified in 3.0.5 of this specification.
3.0.7 Deformation performance of Grade I, II or III splice shall be in accordance with those specified in Table 3.0.7.
Table 3.0.7 Splice Deformation Performance
Splice grade Grade I Grade II Grade III
Uniaxial tension Residual deformation (mm) u0≤0.10 (d≤32)
u0≤0.14 (d>32) u0≤0.14 (d≤32)
u0≤0.16 (d>32) u0≤0.14 (d≤32)
u0≤0.16 (d>32)
Total elongation at maximum tensile force (%) Asgt≥6.0 Asgt≥6.0 Asgt≥3.0
Repeated tension-compression under high stress Residual deformation (mm) u20≤0.3 u20≤0.3 u20≤0.3
Repeated tension-compression under large deformation Residual deformation (mm) u4≤0.3 and u8≤0.6 u4≤0.3 and u8≤0.6 u4≤0.6
3.0.8 As for structural members directly bearing repeated load, anti-fatigue performance of splice shall be proposed in design according to rebar stress amplitude. In case there is no specific requirement in design, the fatigue stress amplitude limit value of rib-stripped rolling straight thread rebar splice, upsetting straight thread rebar splice and squeezed coupler or sleeve splice of ribbed steel bar shall not be less than 80% of that of ordinary rebar specified in current national standard Code for Design of Concrete Structures (GB 50010).
3.0.9 Rebar splicing by grout-filled coupling sleeve shall meet the relevant requirements of the current professional standard Application Technical Specification of Rebar Splicing by Grout-filled Coupling Sleeve (JGJ 355).
4 Splice Applications
4.0.1 Selection of splice grade shall meet the following requirements:
1 Concrete structure parts requiring to give full play to rebar strength or with high ductility requirements shall select Grade II or I splice; in case the area percentage of rebar splice within the same connection segment is 100%, Grade I splice shall be selected.
2 Concrete structure parts with relatively high rebar stress while with low ductility requirements may select Grate III splice.
4.0.2 Concrete protective cover thickness of connectors of mechanical splicing should comply with the relevant requirements of the current national standard Code for Design of Concrete Structures (GB 50010) and shall not be less than 0.75 times the minimum rebar protective cover thickness or 15mm (whichever is the larger); anti-rust measures may be taken for connectors of mechanical splicing, if necessary.
4.0.3 Splices of longitudinal load-bearing rebar in structural members should be mutually staggered. Splicing segment length of rebar mechanical splicing shall be calculated according to 35d; in case of splicing of rebars with different diameters, calculation shall be carried out based on the one with smaller diameter. Area percentage of rebar mechanical splice within the same splicing segment shall meet the following requirements:
1 Splice should be arranged at the part of structural members with relatively small tensile rebar stress; in case parts with high stress are arranged with splice, in the same splicing segment, the area percentage of Grade III splice shall not be greater than 25 %, and that of Grade II splice shall not be greater than 50 %. Area percentage of Grade I splice may be limited by no provision, exempt for Items 2 and 4 of this subclause.
2 Splice should be kept away from stirrup densified area at beam end and column end of frame with seismic fortification requirements; in case it is inevitable, Grade II or I splice with the area percentage not greater than 50% shall be adopted.
3 As for parts with relatively small stress of tensile rebar or longitudinal tensile rebar, the area percentage of splice may not be limited.
4 As for structural members directly bearing repeated load, the area percentage of splice shall not be greater than 50%.
4.0.4 As for structure directly bearing repeated load, certified splice with type inspection report on fatigue performance shall be selected.
5 Type Inspection of Splice
5.0.1 In case of one of the following conditions, type inspection shall be carried out:
1 Where splice performance grade is determined;
2 Where coupler or sleeve material or specification or splice machining technique changes;
3 Where the period from issuance of type inspection report exceeds 4 years.
5.0.2 The splice samples for type inspection shall meet the following requirements:
1 As for rebar mechanical splice of each type, grade, specification, material and process, the quantity of sample for type inspection shall not be less than 12 pieces, thereinto, the quantity of sample for tensile strength of rebar base material shall not be less than 3 pieces, that for uniaxial tension shall not be less than 3 pieces, that for repeated tension-compression under high stress shall not be less than 3 pieces, and that for repeated tension-compression under large deformation shall not be less than 3 pieces;
2 All rebar samples shall be taken from the same piece of rebar;
3 Splice sample shall be installed in accordance with those specified in 6.3 of this specification;
4 Pre-tensioned sample shall not be adopted for type inspection.
5.0.3 Splice type inspection shall be carried out in accordance with those specified in Annex A of this specification; in case the test result complies with the following specified requirements, it shall be regarded as qualified:
1 Strength test: measured strength value of each splice sample shall meet the strength requirements of corresponding splice grade in Table 3.0.5 of this specification;
2 Deformation test: the average values of residual deformation and measured total elongation at maximum tensile force of 3 samples shall meet those specified in Table 3.0.7 of this specification.
5.0.4 As for type inspection, parameters of connectors of mechanical splicing and splice shall be recorded in detail, and test report and assessment conclusion in the format specified in Annex B of this specification should be issued.
5.0.5 Where splice is used for member directly bearing repeated load, fatigue performance test shall be carried out according to those specified in Table 5.0.5 and those specified in Annex A of this specification during splice type inspection.
Table 5.0.5 Stress Amplitude and Maximum Stress for Fatigue Performance Test of HRB400 Rebar Splice
Stress group Ratio of minimum stress to maximum stress ρ Stress amplitude
(MPa) Maximum stress
(MPa)
Group I 0.70~0.75 60 230
Group II 0.45~0.50 100 190
Group III 0.25~0.30 120 165
5.0.6 Type inspection on fatigue performance of splice shall meet the following requirements:
1 6 pieces of splice samples shall be made by rebar with diameter not less than 32mm, which are classified into two groups , with 3 pieces in each group;
2 Two groups of stresses in Table 5.0.5 of this specification may be randomly selected for test;
3 In case no sample is damaged after all samples are loaded for 200 million times, this lot of samples for type inspection on fatigue shall be regarded as qualified.
Foreword i
1 General Provisions
2 Terminologies and Symbols
2.1 Terminologies
2.2 Symbols
3 Performance Requirements of Splice
4 Splice Applications
5 Type Test of Splice
6 On-site Machining and Installing of Splices
6.1 General Requirements
6.2 Machining of Rebar Threaded Sector
6.3 Installing of Splices
7 On-site Inspection and Acceptance of Splices
Appendix A Test Methods for Splice Samples
Appendix B Report Format of Type Test for Splice Sample
Explanation of Wording in This Specification
List of Quoted Standards
