1 General Provisions
1.0.1 This specification is formulated with a view to implementing the national technical economy policies so that advanced technology, economy and rationality, safety and usability as well as quality guarantee are achieved in the design and construction of concrete structures reinforced with welded steel fabric.
1.0.2 This specification is applicable to the design and construction of concrete structures reinforced with welded steel fabric adopted in buildings, municipal works and general structures.
1.0.3 The design and construction of concrete structures reinforced with welded steel fabric shall not only comply with this specification, but also meet the requirements of the relevant national current mandatory standards.
2 Terms and Symbols
2.1 Terms
2.1.1 Welded fabric
A steel fabric welding, by resistance spot welding, all cross points of longitudinal and transverse steel bars of the same diameter or different diameters which are arranged vertically at a certain spacing.
2.1.2 Cold rolled ribbed steel wire
A steel bar from hot rolled disc bar which is subject to cold rolled reducing and forms crescent transverse rib on its three or two sides.
2.1.3 Cold drawn (rolled) plain steel wire
A plain round steel bar from hot rolled disc bar which is subject to cold drawn (rolled) reducing.
Note: The cold drawn (rolled) plain steel wire is hereinafter referred to as cold-drawn plain steel wire.
2.1.4 Hot rolled ribbed steel bar
A steel bar, subject to hot rolled forming and natural cooling, with round cross section as well as two longitudinal ribs on the surface and transverse ribs evenly distributed along the length direction.
2.1.5 Spacing
The distance between the central lines of adjacent steel bars in the welded fabric. For twin bars, the central line is the common tangent of the contact point of two steel bars.
2.1.6 Twin bars
Two steel bars of the same type and diameter parallelly close to each other in the welded fabric. Twin bars are only applicable to longitudinal bars.
2.1.7 Overhang
The length of the central line of transverse and longitudinal bar beyond the outermost of welded fabric.
2.1.8 Lap of welded fabric
In concrete structural members, the connection formed by superposing or inserting two fabrics where the length or width of welded fabric is insufficient.
2.1.9 Normal overlapping
An overlapping with one fabric overlaying the other fabric (Figure 2.1.9).
Figure 2.1.9 Normal Overlapping
1 - longitudinal bar; 2 - transverse bar
2.1.10 Nesting
An overlapping with the steel bars of one fabric inserting the other fabric so that the longitudinal and transverse bars of the two fabrics are on the same plane respectively (Figure 2.1.10).
(a)
Figure 2.1.10 Nesting
(a) Before Nesting; (b) After Nesting
1 - longitudinal bar; 2 - transverse bar
2.1.11 Back overlapping
An overlapping with one fabric backing the other fabric so that their transverse bars are on the same plane and their longitudinal bars on two different planes (Figure 2.1.11).
Figure 2.1.11 Back Overlapping
1 - longitudinal bar; 2 - transverse bar
2.1.12 Lap length of welded fabric
The distance between the ends of steel bars overlapped by two welded fabrics (welded fabric of ribbed steel bar), or the distance between the outermost transverse bars of two overlapping fabrics (welded fabric of plain steel wire).
2.1.13 Welded stirrup cage
A welded stirrup skeleton where the beam and column stirrup connected by additional longitudinal bar is first welded into plane fabric and then bended by a bar folder till the overall design dimension (Figure 2.1.13).
(a) (b)
Figure 2.1.13 Welded Stirrup Cage
(a) Stirrup Cage for Beam; (b) Stirrup Cage for Column
2.1.14 Bottom fabric
The bottom layer of fabric in case there are two layers of welded fabric or above.
2.1.15 Top fabric
The top layer of fabric in case there are two layers of welded fabric or above.
2.1.16 Bridge deck pavement
A cover paved with asphalt concrete, cement concrete and high polymer on a bridge deck so as to protect the bridge deck and distribute the concentrated load of wheels.
2.1.17 Reinforced concrete pavement
A cement concrete pavement reinforced with longitudinal/transverse steel bars or welded steel fabric.
2.1.18 Tunnel
A structure built to allow a road to pass through inside stratum or underwater.
2.2 Symbols
2.2.1 Action and action effect
M - the design bending moment;
Mk - the bending moment calculated according to the standard combination of load effect;
Mq - the bending moment calculated according to the quasi-permanent combination of load effect;
σsk - the longitudinal tension bar stress calculated according to the standard combination of load effect.
2.2.2 Material property
Es - the elastic modulus of steel bar;
fstk - the standard tensile strength of steel bar for cold-rolled ribbed (or cold-drawn plain) welded steel fabric;
fyk - the standard tensile strength of steel bar for hot-rolled ribbed welded steel fabric;
fy - the design tensile strength of steel bar for welded fabric;
f′y - the design compression strength of steel bar for welded fabric;
fc - the design axial compression strength of concrete.
2.2.3 Geometric parameters
as - the distance from the force concurrence point of longitudinal tension bar to the proximal edge of cross section;
a′s - the distance from the force concurrence point of longitudinal compression bar to the proximal edge of cross section;
b - the width of rectangular section and the web width of T-shaped and I-shaped section;
d - the bar diameter;
h0 - the effective height of section;
la - the minimum anchorage length of longitudinal tension bar;
x - the height of concrete compression zone;
As - the section area of longitudinal bar at tensile zone;
A′s - the section area of longitudinal bar at compression zone;
B - the section rigidity of flexural member;
Bs - the short-term rigidity of flexural member under the standard combination of load effect.
2.2.4 Calculation coefficient
ξb - the height of relative boundary compression zone;
αE - the ratio of elastic modulus of steel bar and the elastic modulus of concrete;
ρ - the reinforcement ratio of longitudinal tension bar;
ν - the relative bonding characteristic coefficient of steel bar;
ψ—the strain non-uniformity coefficient of longitudinal tension bar between cracks.
3 Materials
3.1 Welded steel fabric
3.1.1 Grade CRB550 cold rolled ribbed steel wire or Grade HRB400 hot rolled ribbed steel bar should be adopted to fabricate welded steel fabric; Grade CPB550 cold-drawn plain steel wire may also be adopted for such fabrication.
Note: the technical requirements of steel bar for welded fabric shall meet the requirements of "Welded Steel Fabric for the Reinforcement of Concrete" (GB/T 1499.3).
3.1.2 The welded steel fabric is divided into standardized welded fabric and customized welded fabric.
1 The bar spacing and diameter of standardized welded fabric in two directions may differ, but the bar in the same direction should have the same diameter, spacing and length.
The type of standardized welded steel fabric is detailed in Appendix A of this specification.
2 The shape and dimension of customized welded fabric shall be determined through negotiation between supplier and purchaser according to the design and construction requirements.
3.1.3 The specification of welded steel fabric should meet the following requirements:
1 Steel bar diameter: 4~12mm for cold rolled ribbed steel wire or cold-drawn plain steel wire; grading by 0.5mm may be adopted for cold-finished steel bar with 4~12mm diameter; 5~12mm should be adopted for stressed steel bar; 6~16mm should be adopted for hot rolled ribbed steel bar.
2 The length of welded fabric should not exceed 12m while its width should not exceed 3.3m.
3 The bar spacing in the fabrication direction of welded fabric should be 100mm, 150mm and 200mm; the bar spacing perpendicular to the fabrication direction should be between 100~400mm and should be an integral multiple of 10mm. Different kinds of steel bars may be adopted for the longitudinal and transverse bar for welded fabric. Where the double-layer reinforcement specified in Article 5.2.10 of this specification is adopted for the bottom fabric (or top fabric) of two-way slab, the spacing between non-stressed steel bars should not be greater than 1000mm.
3.1.4 The standard strength of steel bar for welded fabric shall have at least 95% assurance factor.
The standard strength of cold rolled ribbed steel wire and cold-drawn plain steel wire is determined according to ultimate tensile strength, expressed by fstk. The standard strength of hot rolled ribbed steel bar is determined according to yield strength, expressed by fyk.
The standard strength fstk and fyk of steel bar for welded fabric shall be selected according to those specified in Table 3.1.4.
Table 3.1.4 Standard Strength of Steel Bar for Welded Fabric (N/mm2)
Steel bar for welded fabric Symbol Bar diameter fstk or fyk
CRB550 cold rolled ribbed steel bar φR 5, 6, 7, 8, 9, 10, 11, 12 550
HRB400 hot rolled ribbed steel bar 6, 8, 10, 12, 14, 16 400
CPB550 cold-drawn plain steel wire φcp 5, 6, 7, 8, 9, 10, 11, 12 550
3.1.5 The design tensile strength fy and f′y of steel bar for welded fabric shall be selected according to those specified in Table 3.1.5.
Table 3.1.5 Design Strength of Steel Bar for Welded Fabric (N/mm2)
Steel bar for welded fabric Symbol fy f′y
CRB550 cold rolled ribbed steel bar φR 360 360
HRB400 hot rolled ribbed steel bar 360 360
CPB550 cold-drawn plain steel wire φcp 360 360
Note: In reinforced concrete structure, 300N/mm2 shall be still adopted where the design tensile strength of steel bar for axial tension members and small eccentric tension members is greater than 300N/mm2.
3.1.6 The elastic modulus Es of steel bar for welded fabric shall be selected according to those specified in Table 3.1.6.
Table 3.1.6 Elastic Modulus Es of Steel Bar for Welded Fabric (N/mm2)
Steel bar for welded fabric Es
CRB550 cold rolled ribbed steel wire 1.9×105
HRB400 hot rolled ribbed steel bar 2.0×105
CPB550 cold-drawn plain steel wire 2.0×105
3.1.7 The fatigue-stress ratio of steel bar for welded fabric shall be calculated according to the following formula:
Where, - during member fatigue checking, the minimum stress of steel bar at the same layer;
- during member fatigue checking, the maximum stress of steel bar at the same layer.
3.1.8 The cold-rolled ribbed welded steel fabric is used for slab-type flexural members under fatigue load; where the maximum stress of steel bar subject to fatigue checking is less than or equal to 280N/mm2 and its fatigue-stress ratio is greater than 0.3, the fatigue stress amplitude of steel bar shall be less than or equal to 80N/mm2.
3.2 Concrete
3.2.1 The concrete strength grade of concrete structures reinforced with welded steel fabric shall be greater than or equal to C20. For structural members in Class II and Class III environment, the concrete strength grade should be greater than or equal to C30 and the concrete durability design shall meet the relevant requirements of the current national standard "Code for Design of Concrete Structures" (GB 50010).
Note: The environment classification for concrete structures shall meet the requirements of the current national standard "Code for Design of Concrete Structures" (GB 50010).
3.2.2 The standard strength, design strength and elastic modulus of concrete as well as the design fatigue strength and fatigue-stress ratio of concrete shall meet the relevant requirements of the current national standard "Code for Design of Concrete Structures" (GB 50010).
3.2.3 The concrete strength index, elastic modulus and technical performance of reinforced concrete pavement and bridge deck pavement shall meet the relevant requirements of the current professional standards "Code for Design of Urban Road" (CJJ 37), "Code for Design of Ordinary Cement Concrete Pavements" (JTG D40) and "Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" (JTJ 023).
1 General Provisions
2 Terms and Symbols
3 Materials
4 Design Calculation
5 Structure Requirements
6 Construction
Appendix A Type of Standardized Welded Steel Fabric
Appendix B General Specification Sheet of Welded Steel Fabric for Bridge Deck Pavement
Appendix C Technical Requirements of Stirrup Cage
Appendix D Appearance Quality Requirement and Geometric Dimension of Welded Steel Fabric As Well As Permissible Deviation of Steel Bar Diameter
Appendix E Technical Performance Requirements of Welded Steel Fabric
Explanation of Wording in This Standard
