JGJ 12-1999 Code for Design of Lightweight Aggregate Concrete Structures JGJ12-99
Some standard content:
Industry Standard of the People's Republic of China
Specification for Design of Lightweight Aggregate Concrete Structures
Specification for Design of Lightweight Aggregate Concrete StructuresJGI12—99
Editor: China Academy of Building ResearchApproving department: Ministry of Construction of the People's Republic of ChinaEffective date: October 1, 1999
3—5—1
Notice on the Issuance of the Industry Standard "Specification for Design of Lightweight Aggregate Concrete Structures"
Jianbiao [1999] No. 63
In accordance with the requirements of the "Notice on the 1986 Plan for the Formulation and Revision of Standards, Specifications and Regulations" ([86] Chengke No. 263) issued by the former Ministry of Urban and Rural Construction and Environmental Protection, the "Specification for Design of Lightweight Aggregate Concrete Structures" edited by the China Academy of Building Research has been reviewed and approved as a mandatory industry standard, numbered JGJ12—99, and will be implemented on October 1, 1999. The original Ministry Standard "Design Code for Reinforced Lightweight Aggregate Concrete Structure" JGJ12-82 is abolished at the same time.
3——5—2
This standard is managed by the China Academy of Building Research, the technical unit responsible for building engineering standards of the Ministry of Construction, and is specifically interpreted by the China Academy of Building Research. It is published by the China Building Industry Press organized by the Standard and Quota Research Institute of the Ministry of Construction.
Ministry of Construction of the People's Republic of China
March 17, 1999
Symbol.
2.1 Actions and effects of actions
2.2 Material properties
2.3 Geometric parameters
2.4 Calculation coefficients
3 Materials-
3.1 Lightweight aggregate concrete
3.2 Steel bars
4 Basic design regulations
4.1 General regulations
4.2 Calculation regulations for components of prestressed lightweight aggregate concrete structures…
5 Ultimate limit state calculation of bearing capacity
5.1 Calculation of normal section bearing capacity.
5.2 Calculation of bearing capacity of inclined section.
Calculation of bearing capacity of twisted section
5.4 Calculation of shear bearing capacity….
5.5 Calculation of local compressive bearing capacity
6 Verification of limit state for normal use
6.1 Verification of crack resistance
Verification of crack width
Verification of deflection of bending member
7 Structural provisions
-General provisions
Structural provisions of prestressed lightweight aggregate concrete structural members
Provisions for structural members
: 3~5—4
3—5—5
3—5—4
3—5—6
5—13
3—5-17
3—5—20
3—5—-22
3—5—23
. 3-5—23
3—5—23
3—5—24
3--5—25
3—5—26
3—5—26
5—27
-5—28
8.4 Shear wall
8.5 Corbel
8.6 Joints and lifting rings of precast components·
Reinforced lightweight aggregate concrete structural components
Seismic design
General provisions
9.2 Materials·
9.3 Frame beams
9.4 Frame columns·
9.5 Frame nodes·
9.6 Shear wall||t t||Lightweight aggregate plain concrete structure
Appendix A
Member calculation
General provisions
A.2 Compression members
A.3 Flexural members
A.4 Local structural reinforcement
A,5 Local compression
3--5—33
3-—5—34
-5—34
-5—35
-5—35
-5—37
-5—38
3--5—-40
3--5—-40
... 3-5--40
.... 3-5—41
3—5—41
3—5—-41
Appendix B Calculation method for the cross-sectional area of the longitudinal tensile reinforcement of reinforced light aggregate concrete rectangular cross-section flexural members·
.. 3-5--41
Appendix C Approximate calculation method for the bending bearing capacity of the normal section of reinforced light aggregate concrete bidirectional flexural members……
. 3—5--42
....... 35--42
Plastic coefficient of section resistance moment
Appendix D
Calculated cross-sectional area and
Appendix E
Nominal mass
Appendix F
Terms used in this code
Additional explanation
3-5--43
3—5—— 3
1 General
1.0.1 This code is formulated to implement the national technical and economic policies in the design of lightweight aggregate concrete structures, to achieve advanced technology, economic rationality, safety and applicability, and to ensure quality. 1.0.2 This code is applicable to the design of reinforced lightweight aggregate concrete, prestressed lightweight aggregate concrete, and lightweight aggregate plain concrete load-bearing structures for industrial and civil buildings and general structures.
1.0.3 For the design of lightweight aggregate concrete structures, in addition to the provisions of this code, the provisions of the relevant current national standards shall also be met. 2 Symbols
2.1 Actions and effects of actions
2.1.1 In the design of lightweight aggregate concrete structures, the symbols representing actions and effects of actions shall be adopted in accordance with the following provisions: N
Design value of axial force;
Axial force value calculated according to the combination of short-term effects of loads;Axial force value calculated according to the combination of long-term effects of loads;-The resultant force of prestressed steel bars and non-prestressed steel bars in post-tensioning members;
The resultant force of prestressed steel bars and non-prestressed steel bars when the normal prestress of lightweight aggregate concrete is zero;
Design value of bending moment:
Bending moment value calculated according to the combination of short-term effects of loads:Bending moment value calculated according to the combination of long-term effects of loads;Bending moment value of the positive load surface of a flexural member;
Design value of the flexural bearing capacity of the positive section of the member;Design value of torque;
Design value of shear force;
Design value of shear bearing capacity of lightweight aggregate concrete and stirrups on the inclined section of a member;
Normal stress of lightweight aggregate concrete at the edge of cracking verification under the combination of short-term effects of loads;
Normal stress of lightweight aggregate concrete at the edge of cracking verification under the combination of long-term effects of loads;
Normal stress of lightweight aggregate concrete caused by prestressing;
-Principal tensile stress in lightweight aggregate concrete;
Principal compressive stress in lightweight aggregate concrete;
Stress of longitudinal ordinary steel bars in the calculation of normal section bearing capacity;
Stress of longitudinal prestressed steel bars in the calculation of normal section bearing capacity;
-Tension control stress of prestressed steel bars;
3-5— 4
Longitudinal tensile reinforcement stress or equivalent stress calculated according to the combination of short-term effects of loads;
Prestress loss value of prestressed reinforcement in the tension zone at the corresponding stage;
Prestress loss value of prestressed reinforcement in the compression zone at the corresponding stage;
Prestressed reinforcement stress when the normal stress of lightweight aggregate concrete at the combined force point of prestressed reinforcement is equal to zero; Effective prestress of prestressed reinforcement;
Shear stress of lightweight aggregate concrete;
Maximum crack width considering the influence of uneven crack width distribution and the combination of long-term effects of loads;
B--Section stiffness of flexural members.
2.2 Material properties
When designing lightweight aggregate concrete structures, 2.2 represents the material properties.1
Symbols shall be used in accordance with the following provisions:
-elastic modulus of lightweight aggregate concrete;
G. --shear modulus of lightweight aggregate concrete;
-Poisson's ratio of lightweight aggregate concrete;
-elastic modulus of steel bar;
-standard value of axial compressive strength of lightweight aggregate concrete; f
design value of axial compressive strength of lightweight aggregate concrete; fank
standard value of bending compressive strength of lightweight aggregate concrete; -design value of bending compressive strength of lightweight aggregate concrete; -standard value of axial tensile strength of lightweight aggregate concrete; -design value of axial tensile strength of lightweight aggregate concrete; -means that the standard value of cube strength is 25N/mm2 Strength grade of lightweight aggregate concrete;
fa-compressive strength of lightweight aggregate concrete cube with a side length of 150mm;
standard value of compressive strength of lightweight aggregate concrete cube with a side length of 150mm;
standard value of ordinary steel bar strength;
-standard value of prestressed steel bar strength;
design value of tensile strength of ordinary steel bars;
design value of compressive strength of ordinary steel bars;
-design value of tensile strength of prestressed steel bars;
-design value of compressive strength of prestressed steel bars.
2.3 Geometric parameters
2.3.1 In the design of lightweight aggregate concrete structures, the symbols representing geometric parameters shall be adopted in accordance with the following provisions:
--the distance from the resultant force point of the longitudinal tension reinforcement to the near edge of the section; aw
α--the distance from the resultant force point of the longitudinal compression reinforcement to the near edge of the section; as
the distance from the resultant force point of the longitudinal non-prestressed tension reinforcement to the near edge of the section;
--the distance from the resultant force point of the longitudinal non-prestressed compression reinforcement to the near edge of the section;
the distance from the resultant force point of the longitudinal prestressed reinforcement in the tension zone to the near edge of the section;
the distance from the resultant force point of the longitudinal prestressed reinforcement in the compression zone to the near edge of the section:
--the width of the rectangular section, T-shaped and I-shaped sections Web width;
Flange width of the tension zone of the T-shaped or I-shaped section; Flange width of the compression zone of the T-shaped or I-shaped section; d-diameter of the circular section or diameter of the steel bar; thickness of the lightweight aggregate concrete cover;
-distance from the point of action of the axial force to the resultant force point of the longitudinal tension steel bars;
distance from the point of action of the axial force to the resultant force point of the longitudinal compression steel bars:
eccentricity of the axial force to the center of gravity of the section;
additional eccentricity;
initial eccentricity;
h-section height;
effective height of the section:
hFlange height of the tension zone of the T-shaped or I-shaped section: hFlange height of the compression zone of the T-shaped or I-shaped section; radius of gyration:
r. Radius of curvature;
- minimum anchorage length of longitudinal tensile reinforcement: ta
- calculated span or calculated length;
spacing of transverse reinforcement or spacing of stirrups along the axis of the member;
height of compression zone of lightweight aggregate concrete;
- distance from the centroid of the converted section to the calculated fiber; yo
- distance from the centroid of the net section to the calculated fiber; yh
distance between the resultant force point of longitudinal tensile reinforcement and the resultant force point of compression zone of lightweight aggregate concrete;
member cross-sectional area;
- member converted cross-sectional area;
- member net cross-sectional area;
A- cross-sectional area of longitudinal non-prestressed reinforcement in tension zone; A
cross-sectional area of longitudinal non-prestressed reinforcement in compression zone Area; - cross-sectional area of longitudinal prestressed steel bars in tension zone; cross-sectional area of longitudinal prestressed steel bars in compression zone; cross-sectional area of single-leg stirrups in shear calculation; cross-sectional area of single-leg stirrups in torsion calculation; total cross-sectional area of vertical stirrups of each leg in the same section;
total cross-sectional area of horizontal stirrups of each leg in the same section;
- cross-sectional area of non-prestressed bent steel bars in the same bending plane;
- cross-sectional area of prestressed bent steel bars in the same-- bending plane;
elastic moment of resistance at the tensile edge of the section:
elastic moment of resistance at the tensile edge of the converted section; W.- elastic moment of resistance at the tensile edge of the net section; I
moment of inertia of the section;
- converted moment of inertia of the section;
- moment of inertia of the net section.
2.4 Calculation coefficient
2.4.1 In the design of lightweight aggregate concrete structures, the symbols representing the calculation coefficients shall be adopted in accordance with the following provisions:
Linear expansion coefficient of lightweight aggregate concrete:
Tensile stress limitation coefficient of lightweight aggregate concrete; α
ratio of the elastic modulus of steel bar to the elastic modulus of lightweight aggregate concrete;
Plastic influence coefficient of lightweight aggregate concrete in tension zone; Shear span ratio of calculated section;
Reinforcement ratio of longitudinal tensile steel bars;
Volume reinforcement ratio of stirrups;
Stability coefficient of axially compressed members;
Influence coefficient of the combination of long-term effects of loads on the increase of deflection;
Strain unevenness coefficient of longitudinal tensile steel bars between cracks; Seismic adjustment coefficient of bearing capacity.
3.1 Lightweight aggregate concrete
3.1.1 Concrete made of light coarse aggregate, light fine aggregate or ordinary sand, cement and water, with a dry apparent density not exceeding 1950kg/m2, is called light aggregate concrete. This specification is applicable to fly ash ceramsite concrete, clay ceramsite concrete, shale ceramsite concrete, pumice or volcanic slag concrete, self-igniting coal grinding stone concrete and expanded slag bead concrete.
3.1.2 The concrete strength grade of reinforced light aggregate concrete structure should not be lower than CL15; the concrete strength grade of prestressed light aggregate concrete structure should not be lower than CL25. The concrete strength grade of reinforced light aggregate concrete and prestressed light aggregate concrete components used for self-bearing and heat insulation can be appropriately reduced.
3.1.3 Lightweight aggregate concrete is divided into two grades according to its dry apparent density. The density standard value of a certain density grade of light aggregate concrete and reinforced light aggregate concrete should be adopted according to Table 3.1.3. 3.1.4 Standard strength values of lightweight aggregate concrete shall be adopted according to Table 3.1.4. 3.1.5 Design strength values of lightweight aggregate concrete shall be adopted according to Table 3.1.5. 3-5-5
Density grade
Lightweight aggregate concrete and steel bars
Standard density values of lightweight aggregate concrete
Standard density values (kg/m2)
Lightweight aggregate concrete upper and lower apparent
Density variation range
(kg/m2)
760 850
860950
960 -- 1050
1060 -- 1150
1160--1250
12601350
1360~1450
14601550
1560~1650
16601750
1760~1850
1860 - 1950
Lightweight aggregate
Concrete
Reinforced light aggregate concrete
: 1. The standard value of density of reinforced lightweight aggregate concrete can also be determined according to actual conditions;
2. For precast components that are hoisted immediately after steaming, the standard value of density should be increased by 100kg/m during hoisting verification.
Standard value of strength of lightweight aggregate concrete (N/mm2) Strength type symbol:
Strength grade of lightweight aggregate concrete
aL7.5CL10CL15CL20|C125CL30cL35CL40CL45CL50Axial compression
Flexural compression
6.710.013.517.020.023.527.029.532.07.511.015.018.522.026.029.532.535.0Tension tk0.750.90|1.20|1.501.752.00|2.252.45|2.602.75Note: ". The standard value of tensile strength of pumice or volcanic slag concrete should be multiplied by the value in the table. With a coefficient of 0.8;
2. The standard value of tensile strength of self-igniting coal-ground stone concrete should be multiplied by a coefficient of 0.85 according to the value in the table.
Strength type symbol,
Lightweight aggregate concrete strength design value (N/mm2) Lightweight aggregate concrete strength grade
7.50|52025L30CL35CL4045L0
3.75.07.510.0|12.515.0|17.519.521.523.5Axial compression f.
Flexural compression fam
4.5.58.511.0|13.516.519.021.523.526.0Tensile strength 0.550.650.901.101.301.501.651.801.902.00 Note: 1. The tensile strength design value of pumice or volcanic slag concrete shall be multiplied by the coefficient of 0.8 according to the value in the table;
2. The tensile strength design value of self-burning coal-ground stone concrete shall be multiplied by the coefficient of 0.85 according to the value in the table;
3. When calculating the axial compression and eccentric compression components of cast-in-place reinforced lightweight aggregate concrete, if the long side or diameter of the section is less than 300mm, the strength design value of lightweight aggregate concrete in the table shall be multiplied by the coefficient of 0.8; when the quality of the component (such as concrete molding, section and axis size, etc.) is guaranteed, it is not subject to this limitation. bZxz.net
35— 6
3.1.6 The elastic modulus Ec of lightweight aggregate concrete under compression or tension can be adopted according to Table 3.1.6.
Table 3.1.6
Elastic modulus Ec of lightweight aggregate concrete
(×10°N/mm2)
Grade8090000000200130014000016007001800|900CL7.54.24.75.2 5.76.26.77.27.7 8.2CL10
6.06.67.27.88.49.09.610.2
8.89.510.210.911.612.313.0| |tt||11.912.713.514.315.1|15.9
14.215.116.016.917.8
16.5|17.5 |18.5|19.5
18.0|19.0|20.0
18.519.520.5
20.0|21.0
Note: 1. When there is a test basis, the elastic modulus value can also be determined based on the measured data;
2. For concrete using expanded slag beads or self-igniting coal-ground stone as coarse aggregate, its elastic modulus can be increased by 20% compared with the values listed in the table. The shear modulus Gc of lightweight aggregate concrete can be calculated as follows: 3.1.7
Poisson's ratio of lightweight aggregate concrete. 0.2(3.1.7)
3.1.8 When the temperature is in the range of 0℃ to 100℃, the linear expansion coefficient αc of lightweight aggregate concrete can be adopted according to Table 3.1.8. Table 3.1.8
Linear expansion coefficient αc of lightweight aggregate concrete Density grade
αc (per degree Celsius)
0.7×10 5
1.0×10-5
Note: The αc value of the intermediate density grade is determined by linear interpolation. 3.2 Steel
Reinforced lightweight aggregate concrete structures and prestressed lightweight aggregate concrete3.2.1
Reinforcement of soil structures should be selected according to the following provisions: Ordinary steel bars should be Grade I, II, III steel bars and 3.2.1.1
LLS50 grade cold-rolled ribbed steel bars, and cold-drawn Grade I (d≤12mm) steel bars and Grade B cold-drawn low-carbon steel wires can also be used. 3.2.1.2 Prestressed steel bars should be carbon steel wire, notched steel wire, steel strand and heat-treated steel bars, as well as cold-drawn Grade II, II, IV steel bars. 3.2.1.3 For prestressed steel bars in medium and small components, LL650 or LL800 grade cold-rolled ribbed steel bars should be used, and Class A cold-drawn low-carbon steel wires can also be used. Carbon steel wires should be used for post-tensioned components. Note: 1. Ordinary steel bars refer to steel bars used in reinforced lightweight aggregate concrete structures and non-prestressed steel bars in prestressed lightweight aggregate concrete structures;
2. Carbon tangled steel wires and notched steel wires refer to the smooth and notched high-strength round steel wires that have been stress-relieved in the national standard "Steel Wire for Prestressed Concrete" GB5223. The standard strength value of steel bars should have a guarantee of not less than 95%. 3.2.2
The standard strength values of ordinary steel bars and prestressed steel bars should be adopted according to Table 3.2.2-1 and Table 3.2.2-2. Standard value of steel bar strength (N/mum2)
Table 3, 2.2-1
fkfpyk
orfask
T grade (Q235)
Ⅱ grade (20MnSi, 20MnNb (b))
Grade (20MnSiV, 20MnTi, K20MnSi)IN grade (40Si2MnV.45SiMnV.45Si2MnTi)[Grade (d12)
Ⅱ grade d≤25
d = 28 40
Cold rolled strip
Ribbed steel bar
Heat treatment
LL550 (d = 4~ 12)
LL650 (d= 4, 5, 6)
1.L800 (d = 5)
40Si2Mn (d=6)
48Si2Mn (d = 8.2)
[45Si2Cr (d=10)
Note: Grade II K20MnSi steel bars are residual heat treated steel bars. Table 3.2.2-2
Standard values of steel wire and steel strand strength (N/mm2)
47, 8, ↓9
Grade A:
Grade B:
#3～±5
Fstk or Jpuk
1770, 1670, 1570, 1470
1670, 1570
1570, 1470
1570, 1470
1860, 1820, 1720
Note: 1. The diameter d of steel strand refers to the diameter of the circumscribed circle of the steel strand cross section, that is, the nominal diameter De in the steel strand standard GB5224-95; the calculated cross-sectional area and nominal mass of the steel strand are shown in Appendix E; 2. The standard strength value of Grade A cold-drawn low-carbon steel wire used as prestressed steel bars should be reduced by 0N/mm2 after mechanical straightening. 3.2.3
The design value of steel bar tensile strength f, or f and steel bar compressive strength f, or factory w shall be adopted according to Table 3.2.3-1 and Table 3.2.3-2 respectively.
Table 3.2.3-1
Design value of steel bar strength (N/mm2)
Grade 1 (Q235)
Grade II (20MnSi, 20MnNb(b))
Hot-rolled grade (20Mnsiv, 20MnTi, K20MnSi)
Grade V (40Si2MnV.45SiMnV,
45Si2MnTi)
Grade 1 (d12)
d - 28 40
LL550(d = 4~ 12)
Ribbed LL650 (d = 4.5.6)
L1800 (d = 5)
40Si2Mn (d = 6)
48S2Mn (d = 8.2)
45Si2Cr (d = 10)
, or f, or f
Note: 1. In reinforced lightweight aggregate concrete structures, when the design value of the tensile strength of the steel bars of axial tension and small eccentric tension members is greater than 310N/mm2, it should still be taken as 310N/1mm2. When the design value of the tensile strength of the steel bars of other members is greater than 360N/mm2, it should still be taken as 360N/mm2. For Grade 1 steel bars with a diameter greater than 12mm, if they are cold drawn, the strength after cold drawing shall not be used;
2. When reinforced lightweight aggregate concrete When the strength grade of lightweight aggregate concrete in concrete structure is CL10, the strength design value of smooth steel bar shall be 190N/mm2, and the strength design value of deformed steel bar shall be 230N/mm2; 3. After mechanical straightening of LL550 grade cold-rolled ribbed steel bars supplied in coils, the design value of tensile strength shall be reduced by 20N/mm2, and the design value of compressive strength shall not be greater than the corresponding design value of tensile strength; 4. When different types of steel bars are provided in components, each type of steel bar shall adopt its own strength design value according to its stress conditions. Table 3.2.3-2 Design values of steel wire and steel strand strength (N/mm2 Type
Carbon steel wire ±4~±9
Notched steel wire! $5, #7
Cold drawn low
Carbon steel wire
Fpc = 1770
fpck = 1670
fu = 1570
fpk = 1470
fak = 1570
fok = 1470
For welding skeletons
and welding meshes
For tying skeletons
and tying meshes
f, or y
,Or
Group 1 Group II
460430
430400
3—5—7
Steel strand
ok=1720
Fak=1720
Fpk=1860
Ppk= 1820
Fptk = 1720
f, or foy
f, or f
Note: 1. When cold-drawn low-carbon steel wire is used as prestressed steel bar, it shall be inspected coil by coil according to the standard value of steel wire strength specified in Table 3.2.2-2, and its strength design value shall be adopted according to Grade A; Grade B cold-drawn low-carbon steel wire can be inspected in batches and is suitable for use as welded skeletons, welded meshes, frame reinforcement, stirrups and structural reinforcement;
2. After mechanical straightening, the tensile strength design value of Grade A cold-drawn low-carbon steel wire used as prestressed steel bar shall be reduced by 30N/mm2, and the compressive strength design value shall not be greater than the corresponding tensile strength design value: 3. When the strength standard value of carbon steel wire, notched steel wire and steel strand does not meet the requirements of Table 3.2.2-2, its strength design value shall be converted,
3.2.4 Elastic modulus E of steel bar. It shall be adopted according to Table 3.2.4. Table 3.2.4
Elastic modulus of steel bars (N/mm2)
Grade I steel bars, cold-drawn grade I steel bars
Grade II steel bars, grade II steel bars, grade V steel bars, heat-treated steel bars, carbon steel wire, cold-drawn low-carbon steel wire
Cold-rolled ribbed steel bars
Cold-drawn grade II steel bars, cold-drawn grade II steel bars, cold-drawn grade IV steel bars, notched steel wire, steel strands
Note: When necessary, the elastic modulus of steel strands can be measured. 4 Basic design provisions
4.1 General provisions
4.1.1 This code adopts the limit state design method and uses the design expression of partial factors for design.
4.1.2 Structural members shall be calculated and verified in accordance with the following provisions according to the requirements of the ultimate state of bearing capacity and the limit state of normal use:
4.1.2.1 Bearing capacity and stability: All structural members shall be calculated for bearing capacity (including compression instability), and the overturning and sliding of the structure shall be verified when necessary; for structures in the ground exhibition area, the anti-capacity bearing capacity of the structural members shall also be calculated.
4.1.2.2 Deformation: Structural members whose deformation values need to be controlled according to the use conditions shall be verified for deformation.
4.1.2.3 Crack resistance and crack width: For members that are required not to crack during use, the tensile stress of lightweight aggregate concrete shall be verified; for members that are allowed to crack during use, the crack width shall be verified. 4.1.3 The load design value shall be used for the calculation of the bearing capacity (including compression buckling) and the verification of tilting and sliding of structural components; the corresponding representative load value shall be used for the verification of deformation, crack resistance and crack width. Prefabricated components shall also be verified during the construction phase according to the load design values during manufacture, transportation and installation. For the verification of the hoisting of prefabricated components themselves, the deadweight of the component shall be multiplied by the dynamic coefficient. The dynamic coefficient is generally taken as 1.5, but it can be appropriately increased or decreased according to the stress conditions when the component is hoisted. For cast-in-place structures, verification during the construction phase shall be carried out when necessary. When structural components are designed for seismic resistance, the load design value and the seismic action design value shall be adopted in accordance with the provisions of the current national standard "Code for Seismic Design of Buildings" GBJ11.
4.1.4 When the reinforcement percentage of longitudinal force reinforcement is less than that specified in Article 7.1.10 of this Code, reinforced lightweight aggregate concrete and prestressed lightweight aggregate concrete structural members shall be considered as lightweight aggregate plain concrete structural members and calculated in accordance with the provisions of Appendix A of this Code. 4.1.5 The maximum deflection of flexural members shall be calculated according to the short-term effect combination of loads and taking into account the influence of the long-term effect combination, and the calculated value shall not exceed the allowable value in Table 4.1.5.
Table 4.1.5 Allowable values of deflection of flexural members
Member type
Roof, floor and staircase members:
When lg<7m
When 7≤10≤9m
When l0>9m
Suspended wall panels (calculated out of plane):
When lg≤7.5m
When lo>7.5m
Suspended wall panels (calculated in plane):
When l≤7.5m
When (o>7.5m
Allowable values of deflection
I to/200 (to/250)
to/250 (to/300)
to/300 (to/400)
to/200
2o/250
to/600
to/800
Note: 1. If the member is pre-arched during manufacture and it is allowed in use, the calculated deflection value can be subtracted from the arch value when checking the deflection. For prestressed lightweight aggregate concrete members, the anti-arch value caused by the prestress can be subtracted;
2. The values in brackets in the table are applicable to members with higher requirements for deflection in use;
3. The allowable deflection value of cantilever members should be taken by multiplying the corresponding value in the table by a coefficient of 2.0;
4.1o To calculate the span.
4.1.6 When designing structural members, different crack control levels should be selected according to the use requirements. The classification of crack control levels should comply with the following provisions:
-For members that are strictly required not to crack, when calculated according to the combination of short-term load effects, the lightweight aggregate concrete on the tensile edge of the member should not produce tensile stress;
Level 2-
For members that are generally required not to crack, when calculated according to the combination of long-term load effects, the lightweight aggregate concrete on the tensile edge of the member should not produce tensile stress, and when calculated according to the combination of short-term load effects, Lightweight aggregate concrete is allowed to produce tensile stress at the tensile edge of the member, but the tensile stress should not exceed αf;
Level 3-1 - For members where cracks are allowed to appear, the maximum crack width is calculated based on the short-term effect combination of the load and the influence of the long-term effect combination, and the calculated value should not exceed the allowable value. 4.1.7 The crack control level, tensile stress limitation coefficient α of lightweight aggregate concrete and prestressed lightweight aggregate concrete structural members should be adopted according to Table 4.1.7 based on the working conditions of the structural members and the type of steel bars. For structures with special requirements for crack control Parts, the values specified in Table 4.1.7 should be appropriately reduced: When there is reliable engineering experience, the crack resistance requirements for prestressed lightweight aggregate concrete components can be appropriately relaxed.
Table 4.1.7
Crack control level, lightweight aggregate
Concrete tensile stress limit coefficient and maximum crack width allowable value Reinforced lightweight aggregate
Concrete structure
Reinforcement type
Structural component
Factory. Working conditions
I grade steel bar
II grade steel bar
Field grade steel bar
Prestressed lightweight aggregate Concrete structure
Cold drawn II grade steel bars
Cold drawn III grade steel bars
Cold drawn V grade steel bars
Cold rolled ribbed steel bars
General components
Indoor
Roof beams,
Normal environment
Roof trusses,
Open air or indoor
High temperature environment
Carbon steel wire
Notched steel wire
Steel strand
Heat treated steel bars
Cold rolled ribbed steel bars
Cold drawn low carbon steel wire
αet =0.3
Note: 1. Components belonging to the column of open air or indoor high humidity environment refer to: components directly exposed to rain; components frequently exposed to rain in houses without enclosure structures; indoor components frequently exposed to steam or condensed water (such as bathrooms, etc.); components in direct contact with soil; 2. For bending components in areas where the annual average relative humidity is less than 60%, and the ratio of the standard value of variable load to the standard value of constant load is greater than 0.5, the maximum allowable crack width may adopt the number in brackets; 3. For general prestressed lightweight aggregate concrete components and roof beams equipped with cold-rolled ribbed steel bars and cold-drawn low-carbon steel wires, the crack control requirements shall comply with the relevant provisions of special regulations;
4. For chimneys, silos and components under liquid pressure, the crack control requirements shall comply with the relevant provisions of the current special specifications; 5. The tensile stress limit coefficient and maximum allowable crack width of lightweight aggregate concrete prestressed structural components in the table are only applicable to the verification of the normal section, and the verification of the inclined section shall comply with the provisions of Chapter 6 of this Code. 4.2 Calculation regulations for prestressed lightweight aggregate concrete structural components 4.2.1 In addition to the calculation of bearing capacity and deformation, crack resistance, crack width and stress verification according to the use conditions, prestressed lightweight aggregate concrete components should also be verified according to the specific conditions during the construction stages such as production, transportation, and hoisting.
4.2.2 The tension control stress value αam of prestressed steel bars should not exceed the value in Table 4.2.2.
Allowable tension control stress value
Carbon steel wire, notched steel wire, steel strand
Heat-treated steel bars, cold-rolled ribbed steel bars, cold-drawn low-carbon steel wire
Cold-drawn steel bars
Tensioning method
Pre-tensioning method
Post-tensioning method
0.70f ock
Note: 1. The standard value of the strength of prestressed steel bars shall be adopted in accordance with Article 3.2.2 of this Code:
2. The tension control stress value of carbon steel wire, notched steel wire, steel strand and heat-treated steel bar shall not be less than 0.4fpk; the tension control stress value of cold-rolled ribbed steel bar and cold-drawn low-carbon steel wire should not be less than 0.4fik; the tension control stress value of cold-drawn steel bar should not be less than 0.5fpyk4.2.3 When prestressing is applied, the compressive strength of lightweight aggregate concrete cube shall be determined by calculation, but should not be less than 75% of the designed standard value of lightweight aggregate concrete cube compressive strength.
4.2.4 The normal stress of lightweight aggregate concrete caused by prestressing and the stress of prestressed steel bars at the corresponding stage can be calculated according to the following formulas:
(1) Pre-tensioned member
Normal stress of lightweight aggregate concrete caused by prestressing (4.2.4-1)
Effective prestress of prestressed steel bars at the corresponding stage OEO
Ope = αn —
(4.2.4-2)
Prestressed steel bar stress when the normal stress of lightweight aggregate concrete at the combined force point of prestressed steel bars is zero
= on )
(4.2.4-3)
(2) Post-tensioned member
Normal stress of lightweight aggregate concrete caused by prestressing Op=
Ne+ Npem
Effective prestress of prestressed steel bars at the corresponding stageae
(4.2.4-4)
(4.2.4-5)
Prestressed steel bar stress when the normal stress of lightweight aggregate concrete at the prestressed steel bar resultant point is zero
O = Gn - Oi + aEdp
where Ao
(4.2.4-6)
converted cross-sectional area (including the total cross-sectional area of lightweight aggregate concrete excluding weakened parts such as channels and grooves, and the cross-sectional area of all longitudinal prestressed steel bars and non-prestressed steel bars converted into the cross-sectional area of lightweight aggregate concrete; for sections composed of different lightweight aggregate concrete strength grades, the cross-sectional area should be converted into the cross-sectional area of the same lightweight aggregate concrete strength grade according to the ratio of the elastic modulus of lightweight aggregate concrete); - net cross-sectional area (converted cross-sectional area minus all A.
cross-sectional area of longitudinal prestressed steel bars converted into the cross-sectional area of lightweight aggregate concrete);
Io——converted moment of inertia of section;|| tt||- Net section inertia moment;
The distance from the centroid of the converted section to the combined force point of the prestressed steel bars and non-prestressed steel bars shall be calculated in accordance with the provisions of Article 4.2.5 of this Code;
The distance from the centroid of the net section to the combined force point of the prestressed steel bars and non-prestressed steel bars shall be calculated in accordance with the provisions of Article 4.2.5 of this Code;
-The distance from the centroid of the converted section to the calculated fiber;-The distance from the centroid of the net section to the calculated fiber;Yn
-The prestress loss value at the corresponding stage shall be calculated in accordance with the provisions of Articles 4.2.6 to 4.2.11 of this Code;The ratio of the elastic modulus of steel bars to the elastic modulus of lightweight aggregate concrete;αE=E./E., where E shall be taken according to Table 3.2.4 of this Code, E. It can be used according to Table 3.1.6 of this Code:
The resultant force of prestressed and non-prestressed steel bars of pre-tensioned components shall be calculated according to the provisions of Article 4.2.5 of this Code; the resultant force Np
of prestressed and non-prestressed steel bars of post-tensioned components shall be calculated according to the provisions of Article 4.2.5 of this Code. Note: In formulas (4.2.4-1) and (4.2.4-4), the second term on the right side takes a positive sign when the stress direction is the same as the first term, and a negative sign when the stress direction is opposite. Formulas (4.2.4-2) and (4.2.4-6) are applicable to the case where α is compressive stress. When it is tensile stress, it should be replaced by a negative value. 4.2.5 The resultant forces of prestressed and non-prestressed steel bars and the eccentricity of the resultant force points (Figure 4.2.5) can be calculated according to the following formulas: (1) Pre-tensioned members
Nn = amA, + opA,-asA, - GisA.(4.2.5-1)
Apyp - apA,y, - QisAsys + aisA.y,GA,+ dpA,- 015As - 01SA,
(4.2.5-2)
(2) Post-tensioned members
Np = apA, +opeA, -- OisA, - oiA,(4.2.5-3)
OxApypn diApypn - 015Asysn + 0isAsymem=
OpeA, + opeA, - OisA, - OisA, (4.2.5-4)
Wu Zhong o
Prestressed steel bar stress at the resultant point of prestressed steel bars in the tension zone when the normal stress of lightweight aggregate concrete is zero;
Prestressed steel bar stress at the resultant point of prestressed steel bars in the compression zone when the normal stress of lightweight aggregate concrete is zero;
Effective prestress of prestressed steel bars in the tension zone; 3—5-10
Effective prestress of prestressed steel bars in the compression zone; Cross-sectional area of prestressed steel bars in the tension zone: Cross-sectional area of prestressed steel bars in the compression zone; - Cross-sectional area of non-prestressed steel bars in the tension zone; Cross-sectional area of non-prestressed steel bars in the compression zone; Distance from the resultant point of prestressed steel bars in the tension zone to the centroid of the converted section:
Distance from the resultant point of prestressed steel bars in the compression zone to the centroid of the converted section;
-Non-prestressed steel bars in the tension zone The distance from the centroid of the reinforcement to the centroid of the converted section;
The distance from the centroid of the non-prestressed reinforcement in the compression zone to the centroid of the converted section;
The prestress loss value caused by shrinkage and creep of lightweight aggregate concrete at the resultant force point of the prestressed reinforcement in the tension zone shall be calculated in accordance with the provisions of Article 4.2.9 of this Code;is-The distance from the resultant force point of the prestressed reinforcement in the tension zone to the centroid of the net section;
ypn
The distance from the resultant force point of the prestressed reinforcement in the compression zone to the centroid of the net section;
The distance from the centroid of the non-prestressed reinforcement in the tension zone to the centroid of the net section;
y-The distance from the centroid of the non-prestressed reinforcement in the compression zone to the centroid of the net section.
Note: When A=0 in formula (4.2.5-1) to (4.2.5-4), αs=0 can be used in the formula.
Converted heat mass gravity center sugar
Net two gravity centers sugar
Figure 4.2.5 Position of combined force of prestressed steel bars and non-prestressed steel bars (a) Pre-tensioned member; (b) Post-tensioned member 4.2.6 The prestress loss value in the prestressed steel bars can be calculated according to the provisions of Table 4.2.6. When the calculated total prestress loss value is less than the following value, the following value shall be used:
Pre-tensioned member
Post-tensioned member| |tt||Table 4.2.6
130N/mm2
110N/mm2
Prestress loss value (N/mm2)
Factors causing loss
Deformation of tensioning anchorage
and rebar shrinkage
Pre-tensioned components
Calculate according to the provisions of
4.2.7 of this Code
Post-tensioned components
|Calculate the factors causing the loss according to the provisions of Article 4.2.8 of this Code. |Friction between the prestressed steel bars and the wall of the duct |Friction at the turning device of the prestressed member |Friction of the prestressed member at the turning device |During the heating and curing of lightweight aggregate concrete, the tensioned steel bars | |tt|| and the temperature difference between the equipment under tension
stress relaxation of prestressed steel bars
shrinkage and creep of lightweight aggregate concrete
according to the actual situation
post-tensioned components
according to the provisions of Article
of this Code
cold-drawn steel bars, heat-treated steel bars:
one-time tensioning 0.05acm
over-tensioning 0.035cm
Carbon steel wire, notched steel wire, steel
stranded wire:
General relaxation
Here:
Super tension
One tension
Low relaxation
When αcm≤0.7fpk
0.125(cmm-0.5)aom
When 0.7fork
0.20(con -0.575)cam
Cold-rolled ribbed steel bars, cold-drawn low-carbon
steel wire:
Prestressing 0.08gcm
Calculate according to the provisions of Article 4.2.9 of this code
Sweat: 1. 2t in the table is the temperature difference between the tensioned steel bars and the equipment bearing the tension during the heating and curing of lightweight aggregate concrete (); 2. When the stress relaxation loss value of the super-tensioning in the table is taken, the tensioning procedure shall comply with the requirements of the current national standard "Concrete Structure Engineering Construction and Acceptance Code" GB50204;
3. For carbon steel wire, notched steel wire, and steel strand, when αcm/fpk≤0.5, the stress relaxation loss value of the prestressed steel bar shall be equal to zero. 4.2.7
The prestress loss u (N/mm2) of prestressed straight steel bars due to anchor deformation and steel bar shrinkage can be calculated according to the following formula: YE
The anchor deformation and steel bar shrinkage value at the tensioning end should be taken according to α
4.2.7 in the table;
The distance between the tensioning end and the anchorage end (mm). Table 4.2.7
Anchor deformation and steel bar shrinkage value α (mm) Anchor with nut (including tapered screw anchor of wire bundle, barrel anchor, etc.):
Nut gap
Gap of each rear pad
Swept head anchor of wire bundle
Steel tapered anchor of wire bundle
JM12 anchor: When the prestressed tendon is steel bar When the prestressed tendon is steel strand
Tapered anchor clamp for single cold-rolled ribbed steel bar and cold-drawn low-carbon steel wire
Note: 1. The anchor deformation and steel bar shrinkage values in the table can also be determined based on measured data;
2. The deformation and steel bar shrinkage values of other types of anchors should be determined based on measured data.
4.2.8 The prestress loss value a of the prestressed curved steel bars of the post-tensioned components due to the deformation of the anchors and the shrinkage of the steel bars, as well as the prestress loss 012 caused by the friction between the prestressed steel bars and the channel wall, can be adopted in accordance with the provisions of the current national standard "Code for Design of Concrete Structures" GBJ10.
4.2.9 The prestress loss 015 and ai5 (N/mm2) of the prestressed steel bars in the tension zone and the compression zone caused by the shrinkage and creep of lightweight aggregate concrete can be calculated according to the following formula:
d1s = α1α2
'is = α1α2 1+ 15p
(4.2.9-1)
(4.2.9-2)
Cube formula of lightweight aggregate concrete when prestressed
Compressive strength;
Normal compressive stress of lightweight aggregate concrete at the combined force point of prestressed steel bars in the tension zone;
Normal compressive stress of lightweight aggregate concrete at the combined force point of prestressed steel bars in the compression zone;
Reinforcement ratio of prestressed steel bars and non-prestressed steel bars in the tension zone ;
Reinforcement ratio of prestressed steel bars and non-prestressed steel bars in compression zone;
Calculation coefficient shall be taken according to Table 4.2.10-1 of this Code;
Calculation coefficient shall be taken according to Table 4.2.10-1 of this Code;
-Environmental humidity influence coefficient shall be taken according to Table 4.2.10-2 of this Code;
α2--Volume surface area ratio influence coefficient shall be taken according to Table 4.2.10-3 of this Code.
The normal compressive stress αc and αp of lightweight aggregate concrete at their respective combined force points of prestressed steel bars in tension zone and compression zone shall be calculated according to the provisions of Articles 4.2.4 and 4.2.5 of this Code. At this time, the prestress loss value only considers the loss of lightweight aggregate concrete before prestressing (the first batch), and the stress 015 and αs in its non-prestressed steel bars shall be taken equal to zero, and the value shall not be greater than 0.5f; when. When the stress is tensile, the x in formula (4.2.93-5--11
2) should be taken equal to zero. The influence of self-weight can be considered when calculating according to the manufacturing conditions of the components.
The reinforcement ratios p and β of prestressed steel bars and non-prestressed steel bars in the tension zone and compression zone can be considered according to the following conditions: For pre-tensioned components, β=(A,+A)/Ao, '=(Aβ+A)/Ao; For post-tensioned components. p= (A,+A,)/An, p'= (A',+A')/An For components with symmetrically configured prestressed steel bars and non-prestressed steel bars, β=β is taken. At this time, the reinforcement ratio should be calculated based on half of the cross-sectional area of the steel bars.
When the component is steam-cured at normal pressure, Q15 and α'1s should be multiplied by the reduction factor 0.85.
When the time for a component to bear external loads can be determined in advance, the influence of time on the shrinkage and creep loss values of lightweight aggregate concrete can be considered. At this time, αis and 1s can be multiplied by a coefficient β that shall not be greater than 1. The coefficient β can be calculated according to the following formula:
βaa+r
(4.2.9-3)
wherein - the time (d) for the structural component from prestressing to bearing external loads;
time influence coefficient, which shall be adopted according to Table 4.2.10-4 of this code;
- time influence coefficient, which shall be adopted according to Table 4.2.10-4 of this code.
, when calculating the prestress loss of prestressed steel bars, the influence coefficients of various 4.2.10
factors shall be taken into consideration and can be used according to the provisions of the following tables: Table 4.2.10-1
Prestressing method
Post-tensioning method
Table 4.2.10-2
Shrinkage and creep influence coefficients (N/mm2)
Aggregate types
Self-burning coal grinding stone| |tt||Self-ignited coal gravel
Environmental humidity influence coefficient
Environmental humidity conditions
Dry conditions
Normal conditions
High humidity conditions
Table 4.2.10-3
Volume-surface area ratio influence coefficient
Volume-surface area ratio (V/S) (mm)
Note: In the table, V is the volume of the component, and S is the surface area of the component exposed to the air.
3--5--12
Table 4.2.10-4
Concrete types
Ceramic aggregate concrete
Self-ignited coal-grinded stone concrete
Pumice concrete
Time influence coefficient
4.2.11 The prestress loss values of prestressed components at various stages can be combined according to the provisions of Table 4.2.11.
Table 4.2.11
Combination of prestress loss values at each stage
Combination of prestress loss values
Loss of lightweight aggregate concrete before prestressing
(First batch)
Loss of lightweight aggregate concrete after prestressing
(Second batch)
Pre-tensioned components
011 + 012 + 013 + 014
Post-tensioned components
di4 + ais
, when calculating the bending bearing capacity of the normal section and inclined section of the anchorage zone at the end of the prestressed lightweight aggregate concrete member, the design value of the tensile strength of the prestressed steel bars in the anchorage zone may be taken according to the following provisions: zero at the anchorage starting point, "w" at the anchorage end point, and the value may be taken by linear interpolation between the two points.
For prestressed members using cold-drawn Grade II and Grade III steel bars and cold-rolled ribbed steel bars, the design value of the tensile strength of the prestressed steel bars in the anchorage zone may not be reduced.
The anchorage length of the prestressed steel bars 1. shall be taken according to Table 4.2.12. Table 4.2.12
Anchorage length of prestressed steel bars (mm)
Lightweight aggregate concrete Concrete strength grade
Notched steel wire (45)
Stranded steel wire
Cold-drawn low-carbon steel wire
≥CL40
Note: 1. When the construction process of suddenly relaxing prestressed steel bars is adopted, the starting point of the anchorage length should be 0.251 from the end of the member, and the prestress transfer length 1 of the prestressed steel bars should be taken according to Table 6.1.5; 2. The standard values of steel bar strength in the table are: notched steel wire 1570N/mm2; stranded steel wire 1860N/mm2; cold-drawn low-carbon steel wire 700N/mm2. When the strength standard value is other values, the anchorage length increases or decreases according to the strength ratio.
Prestressed lightweight aggregate concrete components in production, transportation and installation 4.2.13
The verification calculation in the installation stage shall comply with the relevant provisions of the current national standard "Concrete Structure Design Code" GBI10.
4.2.14 For pre-tensioned and post-tensioned lightweight aggregate concrete components, in the calculation of bearing capacity and crack width, the resultant force N of the prestressed steel bars and non-prestressed steel bars when the normal prestress of the lightweight aggregate concrete is equal to zero and the eccentricity e of the corresponding resultant force point shall be calculated according to formulas (4.2.5-1) and (4.2.5-2) of this code. At this time, the stress 0 and α of the prestressed steel bars of the pre-tensioned and post-tensioned components shall be calculated according to the provisions of Article 4.2.4 of this code.
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