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Code for construction and acceptance of reinforced concrete silos
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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.
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