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GB 50669-2011 English PDF (GB50669-2011)

GB 50669-2011 English PDF (GB50669-2011)

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GB 50669-2011: Code for construction and acceptance of reinforced concrete silos

This code is formulated with a view to improving the construction level of reinforced concrete silo works, regulating the quality acceptance of reinforced concrete silo works and achieving advanced technology, reliable quality, safety, usability, economy and rationality.
GB 50669-2011
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
UDC
P GB 50669-2011
Code for Construction and
Acceptance of Reinforced Concrete Silos
ISSUED ON: FEBRUARY 18, 2011
IMPLEMENTED ON: MAY 1, 2011
Jointly issued by: Ministry of Housing and Urban-Rural Development of
the People's Republic of China;
General Administration of Quality Supervision,
Inspection and Quarantine of the People's Republic of
China.
Table of Contents
Foreword ... 4
1 General Provisions ... 8
2 Terms ... 9
3 Basic Requirements ... 11
4 Foundation Works ... 14
4.1 General Requirements ... 14
4.2 The Ground and Pile Foundation Work ... 14
4.3 Earth and Foundation Pit Works ... 15
4.4 Reinforcement Works ... 15
4.5 Formworks ... 16
4.6 Concrete Works ... 16
5 Cylinder Structure ... 18
5.1 General Requirements ... 18
5.2 Reinforcement Works ... 20
5.3 Formworks ... 21
5.4 Concrete Works ... 22
5.5 Prestressed Works ... 23
5.6 Liner Works ... 25
6 Silo-bottom and Internal Structure Works ... 27
6.1 Silo-bottom Structure & Filling Works ... 27
6.3 Hopper Liner Works ... 28
7 Silo-top Works ... 30
7.1 Silo-top Steel Structure Works ... 30
7.2 Silo-top Concrete Structure Works ... 31
8 Ancillary Works ... 33
9 Seasonal Construction ... 34
9.1 General Requirements ... 34
9.2 Construction in Winter or Rainy Season ... 34
10 OHS and Environmental Protection ... 35
10.1 Occupational Health & Safety ... 35
10.2 Environmental Protection ... 36
11 Quality Acceptance ... 38
11.1 Classification of Quality Acceptance ... 38
11.2 Acceptance of Project Quality ... 39
11.3 Inspection and Evaluation of Project Quality ... 41
Appendix A -- Testing of Cylinder Structure ... 44
Appendix B -- Verticality Test of Cylinder Structure ... 46
Explanation of Wording in This Code ... 51
List of Quoted Standards ... 52
1 General Provisions
1.0.1 This code is formulated with a view to improving the construction level of reinforced concrete silo works, regulating the quality acceptance of reinforced concrete silo works and achieving advanced technology, reliable quality, safety, usability, economy and rationality.
1.0.2 This code is applicable to the construction and quality acceptance of circular or polygonal cast-in-place reinforced concrete silos storing bulk materials and compressed air mixing silo of mixed powders.
1.0.3 The requirements for construction quality acceptance in the contract agreement document and engineering technical document adopted for the
construction of reinforced concrete silo works shall not be less than the requirements of this code.
1.0.4 New technologies, new processes, new equipment and new materials
shall be popularized in the construction of reinforced concrete silo works. 1.0.5 The construction of reinforced concrete silo works shall comply with the management provisions of relevant OHS and environmental protection.
1.0.6 This code shall be used together with the current national standard ?€?Unified Standard for Constructional Quality Acceptance of Building
Engineering?€? GB 50300.
1.0.7 The construction and quality acceptance of reinforced concrete silo works shall not only comply with this code but also comply with those in the relevant current national standards.
2 Terms
2.0.1 Reinforced concrete silo
The circular, square, rectangular, polygonal and other geometric shape upright reinforced concrete vessels storing bulk materials are referred to as silos; the part holding materials is the silo body.
2.0.2 Silo-top
The structure to seal the top surface of the silo body.
2.0.3 Silo-wall
The vertical wall of silo body directing contact the stored material and bearing the its lateral pressure.
2.0.4 Supporting wall
The vertical wall with same plane as the silo body and supporting the silo body. Silo-wall together with supporting wall is called cylinder.
2.0.5 Silo-bottom structure
The concrete structure on silo body bottom to support cone, filler, stored material and form a hopper.
2.0.6 Cone
The conical structure inside the silo body to homogenize and decompress the stored materials.
2.0.7 Hopper
The vessel at the lower part of silo body to discharge the stored materials. 2.0.8 Filler
The filler material used to form the discharging slope at the silo-bottom. 2.0.9 Liner
The structural layer used for the protection and abrasion resistance of parts directly contact with stored materials, such as silo-bottom, hopper, silo-wall, etc., and helping for the flow of discharged materials.
2.0.10 Bulk material
4 Foundation Works
4.1 General Requirements
4.1.1 The foundation works construction must be provided with engineering geology investigation data. Before construction, detailed distribution conditions of engineering geology, underground pipelines, underground obstructions and cultural relics shall be grasped and the type, distribution and structure of adjacent buildings and underground facilities shall be learnt about.
4.1.2 The foundation pit supporting form shall be determined comprehensively by combining the factors such as hydrological geology conditions, ground load, construction duration, etc. During the construction, the foundation pit side slope shall be monitored according to the requirements and any discovered abnormal condition shall be treated timely.
4.1.3 Special job file shall be compiled for the construction of pile foundation works; in the complex geological areas, the engineering geology investigation data required for construction should be supplemented according to the actual demand to determine the reasonable comprehensive piling construction
scheme.
4.1.4 Quality inspection shall be carried out for non-natural foundations, such as pile foundation, composite foundation, artificial replacement foundation, etc., according to the design requirements and the relevant requirements of current national standard ?€?Code for Acceptance of Construction Quality of Building Foundation?€? GB 50202.
4.1.5 If abnormal condition of foundation occurs during the construction process, it shall be treated according to the relevant requirements of the current professional standard ?€?Technical Code for Ground Treatment of Buildings?€? JGJ 79.
4.2 The Ground and Pile Foundation Work
4.2.1 Foundation subsoil must be inspected for foundation treatment works and composite foundation; and concealment acceptance procedures shall be
handled before the construction of replacement layer and foundation works. 4.2.2 The pile shall be tested before the construction of pile foundation according to the engineering design requirements and the requirements of the current professional standard ?€?Technical Code for Testing of Building
Foundation Piles?€? JGJ 106.
4.2.3 As for the pile foundation works adopting pile driving (sinking) process for replacement of reinforcement.
4.4.2 The position, spacing, connection mode and anchoring length of
reinforcement shall meet the design requirements as well as the relevant requirements of current national standard ?€?Code for Acceptance of
Constructional Quality of Concrete Structures?€? GB 50204.
4.4.3 The protective layer cushion blocks of foundation reinforcement shall be placed uniformly and possess sufficient compression strength; its strength shall not be less than the design strength level of the foundation concrete.
4.4.4 Upper layer reinforcement of foundation shall be provided with sufficient quantity of support brackets in the structural form and layout complying with the rigidity and global stability requirements. Where the support brackets are placed on the bottom, their vertical pole shall be provided with water-stop and anti- seepage measures.
4.4.5 The layout pattern and anchoring length of foundation steel dowel must meet the design requirements and be provided with reliable positioning
measures.
4.5 Formworks
4.5.1 The support system of foundation formwork shall possess sufficient strength, rigidity and stability. Special construction scheme shall be compiled for large foundation formwork.
4.5.2 Before concrete pouring, acceptance shall be carried out for the formwork; During concrete pouring, the formwork and its support system shall be inspected and any discovered abnormal condition shall be treated timely.
4.6 Concrete Works
4.6.1 Special technical scheme shall be compiled for the construction of foundation mass concrete.
4.6.2 Cement with low hydration heat and coarse aggregates with large grain size and good gradation should be adopted for the construction of foundation mass concrete, meanwhile, measures reducing the hydration heat, such as addition of fly ash, milling of slag powder and high efficiency water reducer should be adopted.
4.6.3 The concrete reinforcing strip should be arranged reasonably for large silo foundation.
4.6.4 Comprehensive temperature control measures shall be taken for the curing of foundation mass concrete; the internal and external temperature 5 Cylinder Structure
5.1 General Requirements
5.1.1 During the cylinder structure construction, slipform, lifting form, reversed form, creeping formwork, incremental slipforming with sliding frame and other specialized construction technology may be selected according to the
construction features and conditions. As for the silos arranged with several structural layers under the silo-bottom, the supporting structure of silo bottom should be poured by formwork support method.
5.1.2 The load-bearing capacity, rigidity and stability design calculation shall be carried out for the formwork and its support system, which shall be easy for assembly/disassembly, safe and reliable, and convenient for operation and maintenance. During the construction process, the application safety of formwork support system of cylinder structure shall be monitored and any discovered abnormal condition shall be treated timely according to the
construction technology scheme.
5.1.3 The cylinder formwork construction shall meet the following requirements: 1 The cylinder structure construction shall select the stereotyped
assembled steel slipform and steel frame bamboo (wooden) formwork according to the construction features, construction technology, economical rationality, safety and reliability.
2 Cambered surface formwork should be adopted for circular silo cylinder; where straight surface formwork is adopted, the width of single formwork shall meet the those specified in Table 5.1.3:
Table 5.1.3 -- Width Limit of Single Straight Surface Formwork of
Circular Silo
No. Silo diameter D (m) Width of single formwork Maximum width limit of single formwork (mm) 1 D < 20.0 ??? D/50 ?€?
2 20.0 ??? D < 40.0 ??? D/80 ?€?
3 D ??? 40.0 ??? D/100 600
3 The dismantle sequence and methods of formwork and its support system must be implemented according to the special construction scheme for
formwork.
5.1.4 The cylinder reinforcement construction shall meet the following
requirements:
1 Other accessories shall not be welded on the cylinder horizontal
5.2 Reinforcement Works
5.2.1 The variety, specification, space and connection mode of cylinder horizontal reinforcement must meet the design requirements.
5.2.2 The horizontal reinforcement should adopt bound connection joint with the overlapping length not less than 50 times of reinforcement diameter. Where construction quality is assured, the horizontal reinforcement may also adopt end lap weld. The two welded reinforcements shall be at the up and down positions respectively and welding procedure qualification and acceptance shall be carried out before construction. The effective weld length of the joints shall not be less than 12 times of reinforcement diameter; appearance quality shall be carried out with total inspection and specimens shall be cut from the
engineering part to perform mechanical property inspection as required. The joint of horizontal reinforcement shall be staggered. The stagger distance in horizontal direction shall not be less than one overlapping segment and shall not be less than 1.0 m. And it shall not be more than one joint as for every other three reinforcements on the same vertical section.
5.2.3 The cylinder arc-shaped horizontal reinforcement shall be molded in mechanical way. The reinforcement radian shall be even without any obvious warping at ends.
5.2.4 The blanking length of vertical reinforcement shall be confined in 4 m ~ 6 m. The vertical reinforcement should adopt mechanical connection or welded connection and Article 5.2.2 of this code shall be followed where end lap weld is applied. Where bound connection is adopted, the overlapping length of plain reinforcement shall not be less than 40 times of reinforcement diameter (hook is not included); the overlapping length of reinforcement with rib shall not be less than 35 times of reinforcement diameter. The joints shall be arranged in a staggered way. The percentage of joints in the same connection segment shall meet the design requirements; where there is no requirement in the design, 25 % should not be exceeded.
5.2.5 The horizontal reinforcement shall be in close contact with vertical reinforcement; interface points shall be bound in full and the tail end shall be back on to formwork face.
5.2.6 The tie bar and welded frame reinforcement shall be arranged between the reinforcements at internal and external sides of cylinder. The inclined angle from vertical reinforcement of variable section cylinder to circle center shall be provided with limit measures.
5.2.7 At least one bound horizontal reinforcement shall be retained on each concrete lift.
shall be strengthened to ensure the bearing capacity of support bar and the stability of slip form system.
7 Each machine shift shall exam the formwork system and hoisting system at least once. Once deformation and instability are observed, strengthening treatment shall be conducted immediately and record on monitoring in
construction shall be kept.
5.3.3 The following requirements shall be followed where reversed form, lifting form and creeping formwork are adopted in construction:
1 The dismantled cylinder formwork shall be adjusted and maintained prior to use again.
2 The specification and form, arrangement, of split bolt and the disposal of screw rod end shall meet the requirements of construction design.
3 The triangular frame of reversed form should be 3 layers. The support of reversed form shall be integrated at vertical and horizontal directions. 4 Special acceptance shall be carried out on the direct supporting members after each installation of cylinder formwork.
5 Where reversed form is adopted in construction, the concrete shall be carried out with partial pressure-bearing calculation. If the strength of concrete reaches above 6.0 MPa, the under formwork and support may be dismounted. 5.3.4 Vertical construction seam should not be retained in construction of silos in line and group silos. However, if seam is a necessity, it shall be arranged beyond 250 mm at the outside of conjoined part of silo body and reliable measures shall be taken to ensure the proper position of reinforcement and the concreting quality. The additional reinforcement of the connecting part of silo body shall have adequate anchorage length at both sides of construction joint. 5.4 Concrete Works
5.4.1 The water cement ratio of cylinder structure concrete shall be strictly controlled; measures for enhancing compactness shall be taken; additive with chloride shall be strictly prohibited.
5.4.2 The concrete of cylinder structure shall be placed layer by layer. Where slipforming process is adopted in construction, the concreting height each time should not be greater than 250 mm; where reversed form and any other
processes are adopted, the concreting height each time should not be greater than 500 mm; the concreting shall be conducted continuously. The concretes at both sides of preset hole and door and window opening shall be placed in a symmetrical and balanced way.
machine; the adoption of electric arc cutting is strictly prohibited.
5.5.4 The steel wire (bundle) or steel strand adopted by prestressed tendon shall be free from dog leg or the dog leg must be cut off. The adding of prestressed tendon shall be carried out with special connector.
5.5.5 The pore passage of post-tensioning bonded prestressed tendon and unbonded prestressed tendon shall be reliably fixed by positioning supports and shall be smoothly laid. Moreover, measures shall be taken to prevent the displacement and deformation in process of concreting.
5.5.6 The connection of pipe laid in pore passage of bonded prestressed tendon and the connection of pipe and bearing plate at end shall be firm and tight, without any grout leakage. The buried pipes may be connected by welding, bushing and pipe joint. The buried annular prestressed tendon pipe shall be bent according to the radius of design requirements and the bent steel pipe shall be free from crack and dog leg.
5.5.7 The concrete at the prestress tensioning end shall be provided with crack resistance strengthening measures. The length of straight segment at annular prestressed tendon end should not be less than 400 mm and shall be in
tangency with the prestressed steel ring.
5.5.8 If required in the design, pore passage friction loss test shall be carried out before the formal tensioning of prestressed tendon. The pore passage for test shall be randomly chosen or taken as designed.
5.5.9 In tensioning of prestressed tendon, the strength of concrete shall meet the design requirements. If the prestressed tendon exceeds 25 m, both ends should be tensioned; if the length exceeds 50 m, the prestressed tendon should be tensioned and anchored in sections. The tensioning sequence shall be in accordance with the design requirements and technical scheme; intermediate inspection and acceptance on concrete construction quality shall be carried out before construction.
5.5.10 After the tensioning of prestressed tendon, the anchorage zone shall be protected promptly. As for strand tapered anchorage, the surplus part of exposed unbonded prestressed tendon shall be cut away first and then be bent; the anchorage and bearing plate shall be blocked.
5.5.11 The concrete casted later and grouting material used in anchorage zone must not use additive containing chloride ion or corrosive to the prestressed tendon, anchorage and cladding.
measures and duration shall be determined according to the meteorological conditions as well as the technical requirements of sticking materials. The curing duration should not be less than 7 days.
5.6.7 The construction of mortar and concrete wear layer shall meet the following requirements:
1 The cementitious material should adopt ordinary portland cement with
strength grade not less than 42.5 MPa and the water cement ratio shall not be larger than 0.50. The wearproof aggregate size of mortar shall be 0.5 mm ~ 5.0 mm; and the wearproof aggregate size of concrete should be 5 mm ~ 20 mm. Cement dispersing agent should be added in wear resistance concrete.
2 The wearproof mortar bottom shall be carried out with texturing treatment and the thickness (excluding grout surface and wearproof mortar) should not exceed 40 mm. The thickness and evenness of wearproof mortar shall be
controlled by dotting screeding; the motor shall...

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