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This specification is formulated by Guangdong Provincial Academy of Building Research and Architectural Design and Research Institute of Guangdong Province together with relevant universities, scientific research institutes and production enterprises in accordance with the Document YUEJIANKEHAN ([2010], No. 416) issued by Guangdong Provincial Department of Housing and Urban-Rural Development.
In the process of formulating this specification, this specification has been finalized by the drafting group through extensive investigation and research, reference to and absorption of existing scientific research achievements at home and abroad, summarization of practical design and construction experience in Guangdong Province, experimental investigation and theoretical analysis on key issues and coordination of relevant Chinese standards based on repeated discussions and revisions.
Main technical contents of this specification: 1. General provisions; 2. Terms and symbols; 3. Materials; 4. Basic requirements; 5. Method of structural analysis; 6. Calculation of structure members; 7. Construction requirements; 8. Joints; 9. Construction and acceptance; Annexes A~F.
This specification is completed on the basis of the national professional standard JGJ/T 268-2012 Technical specification for cast-in-situ concrete hollow floor structure. The supplementary contents are as follows:
1. the requirement that cast-in-situ hollow slab and cast-in-situ solid slab may be arranged separately or in a mixed way in the same floor and roof structure is supplemented, see 4.1.5;
2. the requirement that the steel mold may be considered is added, see 4.1.6;
3. the requirements that hollow floor structures may be classified into thick hollow floor structure and thin hollow floor structure according to the thickness-span ratio of slab are added, see 2.1.6~2.1.11;
4. the requirements on applicable height of buildings with hollow floor structure are supplemented, see 4.3;
5. the requirements on seismic grade of buildings with hollow floor structure are supplemented, see 4.4;
6. the requirements on seismic design requirements for lateral resistant system of hollow floor structure are supplemented, see 4.5;
7. the bending moment of the section of span slab in beamless floor structure is proposed, and appropriate reduction of dome effect may be considered. When finite element method is used for analysis, the effects of supporting sections of column, column cap, wall etc. may be considered, and the peak bending moment may be appropriately reduced, see 5.1.6;
8. the equivalent space frame method is proposed, see 5.6;
9. the construction requirements on minimum slab thickness and reinforcement when hollow slab is adopted for the basement roof are supplemented, see 7.1.14;
10. the requirements on beam-column joints of hollow floor structure are supplemented, see Clause 8;
11. some hollow slab parameters are supplemented for reference in scheme design, see 5.1.3 and Annex F.
The provisions printed in bold type in 4.4.1, 7.4.2 and 8.3.2 are compulsory and must be enforced strictly.
Guangdong Provincial Academy of Building Research (Address: No.121 Xianlie East Road, Guangzhou City Guangdong Province; 510500) and Architectural Design and Research Institute of Guangdong Province (Address: No.97 Liuhua Road, Guangzhou City Guangdong Province; 510010) are responsible for the explanation of specific technical contents. Please mail the problems and opinions found by units concerned during use to the chief drafting organization of this specification or send them to the e-mail address (E-mail: kxlgbz@163.com).
Technical specification for cast-in-situ concrete hollow floor structure
1 General provisions
1.0.1 This specification is formulated to make the design and construction of cast-in-situ concrete hollow floor structure be technologically advanced, safe and applicable, cost-effective and reasonable, and to ensure the quality.
1.0.2 This specification is applicable to the design, construction and acceptance of cast-in-situ reinforced concrete and prestressed concrete hollow floor structures in general industrial and civil buildings and structures in Guangdong Province.
1.0.3 The design, construction and acceptance of cast-in-situ concrete hollow floor structure shall not only comply with this specification, but also comply with the current relevant standards such as GB 50010 Code for design of concrete structures, GB 50011 Code for seismic design of buildings and JGJ 3 Technical specification for concrete structures of tall building.
2 Terms and symbols
2.1 Terms
2.1.1 cast-in-situ concrete hollow slab
hollow slab formed by in-situ casting with embedded or exposed filler
2.1.2 cast-in-situ concrete hollow floor structure
floor structure formed by horizontal members such as cast-in-situ concrete hollow slab and supporting beam (or concealed beam)
2.1.3 rigid edge supported floor structure
floor structure with the slab supported vertically by a wall or a beam with large vertical rigidity
2.1.4 flexible edge supported floor structure
floor structure with the slab supported vertically by beam with small vertical rigidity
2.1.5 column supported floor structure
floor structure with a column as the vertical support of slab and with no rigid or flexible beam between supports
2.1.6 thick hollow floor structure
cast-in-situ concrete hollow floor structure with the thickness-span ratio of slab (depth-span ratio of frame rib) not less than 1/22
2.1.7 thin hollow floor structure
cast-in-situ concrete hollow floor structure with the thickness-span ratio of slab (depth-span ratio of frame rib) less than 1/22
2.1.8 thick hollow slab-column structure
column supported thick hollow floor structure, frame structure formed by frame ribs or partial frame beams, flat beams and columns
2.1.9 thick hollow slab-column-shear wall structure
slab-column-shear wall structure equipped with thick hollow floor structure, wherein, the slab-column part is a frame structure formed by frame ribs or partial frame beams, flat beams and columns
2.1.10 thin hollow slab-column structure
column supported thin hollow floor structure
2.1.11 thin hollow slab-column-shear wall structure
slab-column-shear wall structure equipped with thin hollow floor structure, i.e., the general slab-column-shear wall structure
2.1.12 filler
object permanently embedded in cast-in-situ concrete slab to replace part of concrete to reduce the dead weight of structure; it may be classified into filler tubes, filler rods, filler boxes, filler blocks and filler plates according to shapes and molding methods
2.1.13 embedded filler
filler embedded in cast-in-situ concrete slab with no exposed surface
2.1.14 exposed filler
filler embedded in cast-in-situ concrete slab, with upper and (or) lower surface exposed to the slab surface
2.1.15 volumetric void ratio
ratio of volume of filler in the grid of cast-in-situ concrete slab to the floor volume, wherein, the volume of filler includes the volume of filler material and that of internal cavity
2.1.16 apparent density
ratio of mass to volume of filler in natural state
2.1.17 rib; main-rib; frame rib; secondary-rib
rib: concrete area formed between the side surfaces or end surfaces of adjacent fillers in the same column grid
main-rib: rib formed between adjacent filler plates in cast-in-situ concrete hollow slab
frame rib: main-rib or solid concealed beam in hollow floor structure, which is arranged between vertical supporting members and forms a lateral resistant system with vertical members
secondary-rib: rib formed between adjacent lightweight core blocks in the filler plate in cast-in-situ concrete hollow slab
2.1.18 rib spacing
distance between centerlines of two adjacent ribs
2.1.19 flange depth
distance from the upper and lower surfaces of the filler to the top and bottom of the cast-in-situ concrete hollow floor respectively
2.1.20 analogue slab method
calculation method of internal force and deformation analysis by cast-in-situ concrete hollow slab which is equivalent to solid slab
2.1.21 analogue cross beam method
calculation method of internal force and deformation analysis of cast-in-situ concrete hollow slab which is equivalent to two-way cross beam system
2.1.22 empirical coefficient method
calculation method of bending moment in control section of cast-in-situ concrete hollow floor structure with bending moment distribution coefficient
2.1.23 equivalent frame method
calculation method for internal force analysis respectively for the column supported floor structure or flexible edge supported floor structure which is equivalent to a continuous frame centered on the column axis in two directions
2.1.24 equivalent space frame method
calculation method where the upper plate and mid-span slab on column of hollow floor structure are equivalent to multiple beams according to the analogue cross beam method, which, together with vertical members, participate in the overall internal force analysis under the combined action of horizontal action and vertical load
2.2 Symbols
2.2.1 Properties of materials
Ec——the elastic modulus of concrete;
Ecb——the elastic modulus of beam concrete;
Ecs——the elastic modulus of slab concrete;
Ecc——the elastic modulus of column concrete;
Ex——the x-direction elastic modulus of orthotropic slab;
Ey——the y-direction elastic modulus of orthotropic slab;
Gxy——the shear modulus of orthotropic slab;
gfil——the apparent density of filler;
vc——the Poisson’s ratio of concrete;
vx——the x-direction Poisson's ratio of orthotropic slab;
vy——the y-direction Poisson's ratio of orthotropic slab.
2.2.2 Actions and action effects
Gfil——the weight of filler in slab grid;
M0——the design total bending moment of the plate within one span in the calculation direction;
Mx1, My1, Mx1y1——the x-direction bending moment, y-direction bending moment and torque of equivalent isotropic slab;
Mx, My, Mxy——the x-direction bending moment, y-direction bending moment and torque of orthotropic slab;
q——the design vertical uniformly distributed load on the slab surface.
2.2.3 Geometric parameters
Aa, Ap——the longitudinal and transverse sectional areas of hollow slab of round-section filler;
b——the calculated unit width; calculated plate width; calculated width of equivalent frame beam; width of upper plate on column;
bb——the width of beam section; width of analogue cross beam;
bc——the width of column section;
bw——the calculated width of section rib;
c2——the width of column (column cap) perpendicular to l1 direction of slab span in equivalent frame method;
D——the diameter of round-section filler;
h——the thickness of slab;
h0——the effective height of slab section;
hc——the height of column section;
hcon——the converted thickness of hollow slab;
Il——the section inertia moment of beam slab at the edge of column (column cap) in equivalent frame;
I0——the calculated section inertia moment of solid slab with equal width of the unit;
Ia, Ip——the longitudinal and transverse section inertia moments of hollow slab of round-section filler;
Ic——the section inertia moment of column in calculation direction;
Kc——the flexural linear rigidity of column in equivalent frame method;
Kec——the flexural linear rigidity of equivalent column in equivalent frame method;
Kt——the torsional rigidity of torsional members on both sides of column in equivalent frame method;
l1——the span of slab in calculation direction in empirical coefficient method and equivalent frame;
l2——the span of slab perpendicular to calculation direction in empirical coefficient method and equivalent frame;
lx——the calculated x-direction span of orthotropic slab; the long span of rigid support two-way slab;
ly——the calculated y-direction span of orthotropic slab; the short span of rigid support two-way slab;
lx1, ly1——the x-direction and y-direction spans of equivalent isotropic slab;
ln——the net span of slab in calculation direction.
2.2.4 Calculation coefficients and others
C——the section torsional constant calculated by empirical coefficient method;
k——the ratio of y-direction elastic modulus to y-direction elastic modulus of orthotropic slab; the ratio of transverse inertia moment to longitudinal inertia moment of filler tube (rod) hollow slab;
α1——the ratio of flexural rigidity of beam section to that of slab section in calculation direction in calculation by empirical coefficient method;
α2——the ratio of flexural rigidity of beam section to that of slab section perpendicular to calculation direction in calculation by empirical coefficient method;
αEf——the ratio of elastic modulus of filler to that of concrete;
β——the adjustment coefficient of transverse shear capacity of filler tube (rod) hollow slab;
βb——the amplification coefficient of torsional rigidity in equivalent frame calculation;
βt——the torsional rigidity coefficient of empirical coefficient method;
ρvoid——the volumetric void ratio.
3 Materials
3.1 Concrete
3.1.1 The concrete strength grade for cast-in-situ concrete hollow floor structure should not be lower than C25 for reinforced concrete floor structure, while should not be lower than C40 and shall not be lower than C30 for prestressed concrete floor structure.
3.2 Ordinary reinforcement
3.2.1 HRB400, HRB500, HRBF400 and HRBF500 steel bars should be adopted, and HPB300, HRB335, HRBF335 and RRB400 steel bars may be adopted, as the ordinary longitudinal load-bearing bars of cast-in-situ concrete hollow floor structure.
3.3 Prestressing tendon and anchoring system
3.3.1 For prestressing tendons of cast-in-situ prestressed concrete hollow floor structure, high-strength and low-relaxation steel strands should be preferred, and where necessary, prestressing tendons with reliable performance, such as steel wire bundles and fiber prestressing tendons may be adopted, and their performance shall meet the relevant requirements of the current national standards GB/T 5224 Steel strand for prestressed concrete and GB/T 5223 Steel wires for prestressed concrete.
3.3.2 Technology systems such as bonded, unbonded and retard-bonded prestressing may be adopted, and their performance shall meet the relevant requirements of the current standards GB 50010 Code for design of concrete structures, JG 92 Technical specification for concrete structures prestressed with unbonded tendons and JG/T 369 Retard-bonded prestressing steel strand.
3.3.3 The prestressed anchoring system shall meet the relevant requirements of the current national standard GB/T 14370 Anchorage, grip and coupler for prestressing tendons.
3.4 Filler
3.4.1 For filler materials used for cast-in-situ concrete hollow floor structure, the total content of chloride and alkali shall meet the concrete material requirements in the current national standard GB 50010 Code for design of concrete structures; the limits of radionuclides shall meet the requirements of the current national standard GB 6566 Limits of radionuclides in building materials; when used in normal service environment, they shall not generate members that are harmful to human health and the environment, and in case of fire, they shall not generate toxic gases precipitated from the floor within the time required by fire protection level.
3.4.2 The specifications and dimensions of filler tubes and filler rods shall be determined according to the specific project requirements, wherein, the outer diameter may be 100~500mm, the permissible dimensional deviation shall meet the requirements of Table 3.4.2, and the inspection method shall be implemented according to the requirements of Annex A. The appearance quality of filler tubes and filler rods shall meet the following requirements:
1 the surface shall be flat, smooth and free of visible through cracks and holes;
2 the end of filler tube shall be blocked tightly and firmly;
3 the outer sealing layer (if any) of the filler rod shall be densely sealed and firmly adhered.
Table 3.4.2 Permissible dimensional deviation of filler tube and filler rod
Item Permissible deviation (mm)
Length (mm) L≤500 ±8
L>500 ±10
Cross-section dimension (mm) D≤300 ±5
D>300 ±8
Axial surface flatness (mm) L≤500 5
L>500 8
3.4.3 The specifications and dimensions of filler boxes and filler blocks shall be determined according to the specific project requirements, wherein, the side length may be 400~1,200mm. The permissible dimensional deviation shall meet the requirements of Table 3.4.3, and the inspection method shall be implemented according to the requirements of Annex A. When the short side of the bottom surface of the embedded filler box and filler block is longer than 600mm, a vertical through hole should be set in the middle. The appearance quality of filler boxes and filler blocks shall meet the following requirements:
1 the surface shall be flat, smooth and free of visible through cracks and holes;
2 the filler box shall be reliably sealed;
3 the side of the exposed surface of exposed filler box shall be reliably connected with the floor structure concrete.
Table 3.4.3 Permissible dimensional deviation of filler box and filler block
Item Permissible deviation (mm)
Side length +5, -8
Height +5, -8
Surface flatness 5
Length difference of two diagonals 10
3.4.4 The specifications and dimensions of filler plates shall be determined according to the specific project requirements, wherein, the side length may be 800~1,800mm, the thickness may be 80~500mm, the permissible dimensional deviation shall meet the requirements of Table 3.4.4, and the inspection method shall be implemented according to the requirements of Annex A. The appearance quality of filler plate shall meet the following requirements:
1 the surface of filler plate shall be flat and smooth, and the lightweight core blocks shall be arranged neatly;
2 the connecting net shall be free of falling off;
3 for the lightweight core block, its surface shall be free of obvious damage, and its size shall meet the requirements of concrete pouring and compaction.
Foreword i
1 General provisions
2 Terms and symbols
2.1 Terms
2.2 Symbols
3 Materials
3.1 Concrete
3.2 Ordinary reinforcement
3.3 Prestressing tendon and anchoring system
3.4 Filler
4 Basic requirements
4.1 Structural arrangement principle
4.2 Calculation of section properties
4.3 Applicable height of building
4.4 Seismic grade of buildings
4.5 Seismic design requirements of lateral resistant system
5 Method of structural analysis
5.1 General requirements
5.2 Analogue slab method
5.3 Analogue cross beam method
5.4 Empirical coefficient method
5.5 Equivalent frame method
5.6 Equivalent space frame method
6 Calculation of structure members
6.1 General requirements
6.2 Calculation principles for design
6.3 Calculation of bearing capacity limit state
6.4 Checking calculation of serviceability limit states
7 Construction requirements
7.1 General requirements
7.2 Flexible edge supported floor structure
7.3 Thin hollow floor structure
7.4 Construction requirements for frame rib of thick hollow slab structure
8 Joints
8.1 Beam-column joints of flexible edge supported floor structure
8.2 Slab-column joints of thin hollow floor structure
8.3 Frame rib-column joints of thick hollow slab structure
9 Construction and acceptance
9.1 Construction points
9.2 Material approach acceptance
9.3 Constructional quality acceptance
Annex A Inspection method of filler
Annex B Calculation of dead weight, converted thickness and volumetric void ratio of hollow slab
Annex C Equivalent isotropic slab method of orthotropic slab
Annex D Construction technological process
Annex E Filler quality acceptance forms
Annex F Parameter table of cast-in-situ hollow slab
Explanation of wording in this specification
List of quoted standards
