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GB 50669-2011: Code for Construction and Acceptance of Reinforced Concrete Silos
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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 and 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 and 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 ...