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GB 50669-2011: PDF in English

GB 50669-2011 NATIONAL STANDARD OF THE PEOPLE’S 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 be bladed and compacted by sections; the primary grout shall be pressed and finished. Where the thickness of wear layer is more than 30 mm, anchorage shall be set at the bottom, steel mesh with the specification above ø3 or reinforcing mesh with the specification above ø4 shall be suspended additionally and the mesh dimension should not be greater than 150 mm × 150 mm. 3 The wear resistance concrete shall be placed by formwork support method and anchored reinforcement shall be retained at the bottom course. 4 The curing duration for wearproof mortar and concrete shall not be less than 10 days. 5.6.8 The installation of metal plate liner shall meet the following requirements: 1 The dimension of installation unit of metal plate liner shall be determined comprehensively according to the design requirements and the construction & installation conditions. The splicing seam of interior lining panel shall be fully welded. 2 Before the installation of metal plate liner, pre-assembly shall be carried out to ensure an accurate dimension. 3 Where steel rail is adopted as the shock-resistant wear layer, the steel rail shall be installed in synchronization with the construction of concrete for major structure. Reliable positioning and anchoring measures shall be taken for the installation of steel rail. 7 Silo-top Works 7.1 Silo-top Steel Structure Works 7.1.1 The installation of silo-top steel structure works may adopt techniques of hoisting, slipform prefabrication and erection etc. The stress and deformation of steel structures during the process of depositing, assembling, hoisting and positioning etc. shall be analyzed and calculated. 7.1.2 When installing the silo-top steel structure according to the hoisting technique, it shall meet the following requirements: 1 The concrete strength of supports shall meet the design requirements and it shall not be less than 75 % of the designed strength grade. 2 Before installing the steel structure, production quality acceptance and components, accessories previewing shall be carried out. 3 Concrete construction joints of the support shall be processed and twice pouring shall be guaranteed. 4 Silo-top of arch truss structure and dome structure shall be adopted the approach of subdivision and symmetry when installing and reliable measures to guarantee stability of the central temporary support pillar. The temporary support pillar shall be uninstalled by times. 5 After hoisted the main components, the secondary components and stabilizing components shall be installed timely. 7.1.3 Where slipform process is adopted for the construction of cylinder, the integral positioning and installation of the silo-top steel structure should be carried out by slipform prefabrication and erection technique. The slipform prefabrication and erection shall meet the following requirements: 1 The design, calculation and installation of the slipform prefabrication and erection system shall meet the requirements “Technical Code of Slipform Engineering” GB 50113 and “Code for Design of Steel Structures” GB 50017. 2 According to the form of silo-top steel structure to carry out integration design of the tow devices, towing support, support system and slipform construction. When towing the space vault structure, a horizontal thrust balancing device (Figure 7.1.3) shall be installed. 8 Ancillary Works 8.0.1 The manufacture and installation of metal components in and out the silo, such as steel ladder, steel platform and steel handrail shall meet the national current standard specified in “Code for Acceptance of Construction Quality of Steel Structures” GB 50205 and “Technical Specification for Welding of Steel Structure of Building” JGJ 81. 8.0.2 The installation embedded parts of steel ladder and steel support shall be retained along with the construction of principal part of the project and it must not be omitted. The installation method of embedded parts installed by the methods of post-installed anchors must meet the design requirements and make a pull out test. 8.0.3 The lightning protection downlead of silo works shall be arranged out of the cylinder and it is strictly forbidden of using a vertically stressed reinforcement as the downlead. 8.0.4 The laying depth of earthing device shall meet the design requirements and shall not be less than 600 mm. The earth electrode of the earthing device shall be installed before back-filling of the foundation pit. After the installation of earthing device, the earthing resistance shall be tested and the resistance must meet the design requirements. 8.0.5 The earthing device, lightning protection downlead, ring conductor and lightning arrester (network) shall be mutually connected in order to form an access. 8.0.6 Deformation observation marks shall be arranged on silo works according to the design requirements and the number of single silo shall not less than 4. 9 Seasonal Construction 9.1 General Requirements 9.1.1 Special construction plan of the seasonal construction shall be formulated according to construction progress, construction layouts and weather conditions. 9.1.2 During the seasonal construction, weather information shall be collected and monitored and the construction operation shall be reasonably arranged according to meteorological conditions. 9.2 Construction in Winter or Rainy Season 9.2.1 Anti-typhoon action plan and measures shall be made when constructing at the coastal area. 9.2.2 Temporary lightning protection earthing device of the cylinder and construction facilities shall be arranged and the value of earthing resistance shall not be greater than 10 Ω. 9.2.3 When carrying out silo works slipform construction in winter, reliably heat preservation, anti-freezing measures and technical measures which guarantee the quality of concrete structures shall be made out. Without those measures and the when temperature is lower than −20 °C, it is unsuitable to carry out the slipform operation and construction. 9.2.4 The maintenance of cylinder concrete in winter shall use the combined method of brushing conservation liquid and suspending curtain. When the temperature is much lower, insulation measures of thermal resistance, electrical heating and steam curing shall be taken. the voltage of movable lighting facilities shall not be greater than 36 V. 10.1.10 Smoking is strictly prohibited at the places of exit passageway, vertical lift and operation platform. Inflammables and explosives shall not be stored on the construction platform. Adequate and applicable fire extinguisher or other fire-fighting equipment shall be arranged on the operation plane. Measures of fireproofing shall be provided at the influence area of electro-gas welding and the fire-use license be applied, motoring personnel be arranged. 10.1.11 To install and remove the scaffold, bearing support, special construction facilities and construction devices of the silo works shall according to procedures and methods determined by special program. The operating personnel must be an examination qualified professional worker and the special operation personnel shall have certificate. Carrying out demolition works, safety warning line shall be defined and operating supervisors shall be arranged for whole process supervising. 10.2 Environmental Protection 10.2.1 Silo works construction shall take technologies and con...... ......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.