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This specification is a revision task issued to Shenzhen Construction Bureau by Guangdong Provincial Department of Construction's Notice on assigning the task of revising the provincial standards for engineering construction in Guangdong Province in 2003 (first batch) (YUANJIANKEHAN [2003] No.122). According to Shenzhen Construction Bureau's Notice on assigning the Revision Plan for ‘The specification for design and construction of concrete structure with cold-rolled deformed bars’ (SHENJIANKE [2003] No.8), the Civil Engineering and Architectural Society of Shenzhen organized relevant scientific research, design and enterprise units to revise the original provincial standard of Guangdong DBJ/T 15-7-92 The specification for design and construction of concrete structure with cold-rolled deformed bars, and changed its name to DBJ/T 15-7-2007 Technical specification for concrete structure member with cold-rolled deformed bars to form this specification.
During the revision process, the specification revision team carried out various special studies and extensive investigation and analysis, summarizing the practical experience of design, construction and acceptance of concrete structure members with cold-rolled deformed bars in China in recent years, coordinating with relevant standards and codes, and comparing them with and making reference to international advanced standards and codes. On this basis, the team solicited the opinions of relevant units extensively in various ways to correct the main problems repeatedly, and eventually finalize the final draft after examination.
This specification mainly covers: materials, basic design rules, member design, detailing, member regulations, construction and acceptance regulations with respect to concrete structure with cold-rolled deformed bars and relevant annexes.
In order to improve the quality of the specification, all units are requested to sum up experience in combination with engineering practice in the process of implementing the specification, and feed back the opinions and suggestions to the Civil Engineering and Architectural Society of Shenzhen [Room 2012, Shenzhen Design Building (Zip Code: 518031)] for reference in future revision.
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Contents
1 General provisions 1
2 Terms and symbols 2
2.1 Terms 2
2.2 Symbols 2
3 Materials 4
3.1 Concrete 4
3.2 Cold-rolled deformed bars 4
4 Basic design requirements 6
4.1 General requirements 6
4.2 Requirements for calculation of bearing capacity limit state 6
4.3 Requirements for checking of serviceability limit states 6
5 Member design 8
5.1 General requirements 8
5.2 Calculation for bearing capacity of normal section 8
5.3 Calculation for bearing capacity of inclined section 8
5.4 Checking of serviceability limit states 8
6 Requirements for detailing and members 9
6.1 Concrete cover 9
6.2 Anchorage of cold-rolled deformed bars 9
6.3 Connection between cold-rolled deformed bars 10
6.4 Minimum reinforcement ratio of concrete structure members with cold-rolled deformed bars 10
6.5 Member regulations 11
7 Construction and acceptance regulations 14
7.1 General requirements 14
7.2 Raw material 14
7.3 Steel bar processing 15
7.4 Steel bar connection 15
7.5 Installation of steel bars 16
7.6 Steel bar replacement 17
Annex A Main technical characteristic indexes of cold-rolled deformed bars 18
Annex B Steel bar replacement table 20
Explanation of wording 29
1 General provisions
1.0.1 This specification is formulated with a view to using cold-rolled deformed bars in concrete structures, so as to achieve economic rationality and safety & serviceability, and ensure quality.
1.0.2 Cold-rolled deformed bars are mainly applicable to slab members with mainly flexural capacity in industrial and civil buildings and general structures.
1.0.3 This specification is developed according to GB 50010-2002 Code for design of concrete structures. The contents not listed in this specification shall still conform to the current specifications on design and construction acceptance.
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2 Terms and symbols
2.1 Terms
2.1.1 cold-rolled deformed bar
deformed bar in the shape of a twist formed by cold rolling or cold twisting of an ordinary low carbon hot rolled steel bar (coiled wire or steel rod)
2.1.2 marked diameter
diameter of raw material (parent metal) of a cold-rolled deformed bar before cold rolling
2.1.3 nominal diameter
diameter of a circle with its sectional area equal to that of a cold-rolled deformed bar
2.1.4 concrete structure member with cold-rolled deformed bars
concrete member equipped with cold-rolled deformed bars
2.2 Symbols
2.2.1 Properties of materials
Es——the elastic modulus of cold-rolled deformed bar;
fyk——the standard strength of cold-rolled deformed bar;
fy——the design tensile strength of cold-rolled deformed bar;
f′y——the design compressive strength of cold-rolled deformed bar;
ft——the design axial tension strength of cold-rolled deformed bar
2.2.2 Effects of actions
wmax——the maximum crack width calculated according to the standard combination of load effects and with the long-term effects taken into account.
2.2.3 Geometric parameters
d——the nominal diameter of a cold-rolled deformed bar;
dm——the marked diameter of a cold-rolled deformed bar;
c——the thickness of concrete cover;
b——the breadth of section;
h——the height of section;
h0——the effective height of section;
la——the anchorage length of a longitudinal tensile bar;
las——the anchoring length of lower longitudinal cold-rolled deformed bar extending into the beam support;
x——the depth of concrete compression zone;
As——the sectional area of a cold-rolled deformed bar;
As1——the sectional area of HPB235 steel bar;
As2——the sectional area of HRB335 steel bar;
Asw——the sectional area of CDB-W500 steel bar;
AsD——the sectional area of CDB-D460 steel bar.
2.2.4 Calculated coefficients and others
ξb——the boundary depth of the compression zone;
α——the shape coefficient of a cold-rolled deformed bar;
ρsmin——the minimum reinforcement ratio of longitudinally tensile cold-rolled deformed bars;
vi——the relative bonding characteristic coefficient of cold-rolled deformed bars.
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3 Materials
3.1 Concrete
3.1.1 The concrete strength grade for concrete structures with cold-rolled deformed bars shall not be lower than C20, and that for concrete structure members in Class II and III environments shall not be lower than C30.
3.1.2 The concrete strength grade, standard strength, design strength and elastic modulus of concrete structures with cold-rolled deformed bars shall be in accordance with the relevant requirements of GB 50010-2002 Code for design of concrete structures, 4.1.
3.2 Cold-rolled deformed bars
3.2.1 There are two types of cold-rolled deformed bars: D-type and W-type ones, both with ordinary low-carbon steel bars (coiled wires or steel rods) used as the parent metal.
D-type cold-rolled deformed bars are formed by the parent metal being cold-rolled, flattened and then twisted into a twist shape, with its cross section in a rectangular shape, and coded as CDB-D.
W-shaped cold-rolled deformed bars, also known as "cold-rolled winged bars", are formed by the parent metal being twisted into a twist shape at a single time, with its cross section in an S shape (thick in the middle and thin on the sides) with winged edges, and coded as CDB-W.
3.2.2 The main technical characteristic indexes of cold-rolled deformed bars shall meet the requirements of Annex A.
3.2.3 Technical indexes such as the marked diameter dm, nominal diameter d, sectional area AS and theoretical weight of cold-rolled deformed bars shall be in accordance with Annex A-3.
The formula for calculating the sectional area As of cold-rolled deformed bars is:
As=πd2/4 (3.2.3)
As for the diameter of cold-rolled deformed bars, except that the nominal diameter d shall be used during the calculation of the sectional area, the marked diameter dm shall be used in the other calculations.
3.2.4 The standard strength of cold-rolled deformed bars shall be determined by their yield strength and shall be guaranteed not to be less than 95%.
The standard strength fyk, design tensile strength fy and design compressive strength f′y of cold-rolled deformed bars shall be in accordance with those specified in Table 3.2.4.
Table 3.2.4 Standard and design strengths of cold-rolled deformed bars (N/mm2)
Code Symbol Material dm (mm) fyk fy f′v
CDB-D460 φD Q235 5.5~12 460 360 360
CDB-W500 φW Q235 5.5~14 500 400 400
3.2.5 The elastic modulus Es of cold-rolled deformed bars shall be 1.9×105N/mm2.
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4 Basic design requirements
4.1 General requirements
4.1.1 The requirements on structural reliability design and limit state design methods in GB 50010-2002 Code for design of concrete structures, 3.1.1~3.1.8 shall be observed during implementation of this specification.
4.1.2 Plastic internal force redistribution may be considered in the internal force calculation of continuous concrete slabs with cold-rolled deformed bars, and the moment amplitude modulation of its support should not be greater than 15% of the calculated elasticity.
4.2 Requirements for calculation of bearing capacity limit state
4.2.1 The bearing capacity design for application of concrete slab members with cold-rolled deformed bars shall conform to the limit state design expression given in GB 50010-2002 Code for design of concrete structures, 3.2.3.
4.3 Requirements for checking of serviceability limit states
4.3.1 The checking of serviceability limit states shall meet the requirements of GB 50010-2002 Code for design of concrete structures, 3.3.1.
4.3.2 The maximum deflection of slab members shall be calculated according to the standard combination of load effects and with the long-term effects taken into account. The calculation model shall reflect the actual supporting condition and stress state of the slabs, and the calculated results shall not exceed the deflection limits specified in Table 4.3.2.
Table 4.3.2 Deflection limits of slab members
Member span Deflection limit
l0<7m l0/200 (l0/250)
7m≤l0≤9m l0/250 (l0/300)
l0>9m l0/300 (l0/400)
Notes:
1. l0 in the table is the calculated span of the member;
2. The values in parentheses in the table are applicable to members that require higher deflection;
3. If the member is pre-arched during manufacturing and allowable during using, the arch camber may be subtracted from the obtained deflection when the deflection is checked;
4. during calculation of the deflection limit of the cantilever member, the calculated span shall be taken as twice the actual cantilever length.
4.3.3 The crack control level III shall be applied to members with cold-rolled deformed bars in Classes I, II and III environment. When the maximum crack width wmax is calculated according to the standard combination of load effects and with the long-term effects taken into account, its calculated value shall not exceed 0.3mm in Class I environment and 0.2mm in Classes II and III environment.
1 General provisions
2 Terms and symbols
2.1 Terms
2.2 Symbols
3 Materials
3.1 Concrete
3.2 Cold-rolled deformed bars
4 Basic design requirements
4.1 General requirements
4.2 Requirements for calculation of bearing capacity limit state
4.3 Requirements for checking of serviceability limit states
5 Member design
5.1 General requirements
5.2 Calculation for bearing capacity of normal section
5.3 Calculation for bearing capacity of inclined section
5.4 Checking of serviceability limit states
6 Requirements for detailing and members
6.1 Concrete cover
6.2 Anchorage of cold-rolled deformed bars
6.3 Connection between cold-rolled deformed bars
6.4 Minimum reinforcement ratio of concrete structure members with cold-rolled deformed bars
6.5 Member regulations
7 Construction and acceptance regulations
7.1 General requirements
7.2 Raw material
7.3 Steel bar processing
7.4 Steel bar connection
7.5 Installation of steel bars
7.6 Steel bar replacement
Annex A Main technical characteristic indexes of cold-rolled deformed bars
Annex B Steel bar replacement table
Explanation of wording
