JGJ/T 231-2021 PDF in English
JGJ/T 231-2021 (JGJ/T231-2021, JGJT 231-2021, JGJT231-2021)
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Technical standard for safety of disk locksteel tubular scaffold in construction
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Standards related to (historical): JGJ/T 231-2021
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JGJ/T 231-2021: PDF in English (JGJT 231-2021) JGJ/T 231-2021
UDC JGJ
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
P JGJ/T 231-2021
Replacing J 1128-2021
Technical standard for safety of disk lock steel tubular
scaffold in construction
ISSUED ON: JUNE 30, 2021
IMPLEMENTED ON: OCTOBER 01, 2021
Issued by: Ministry of Housing and Urban-Rural Development of the People's
Republic of China
Table of Contents
Foreword ... 4
1 General provisions ... 7
2 Terms and symbols ... 7
2.1 Terms ... 7
2.2 Symbols ... 9
3 Basic requirements ... 12
4 Loads ... 13
4.1 Load classification ... 13
4.2 Characteristic value of loads ... 14
4.3 Subentry coefficient of loads ... 16
4.4 Combination of loads effects ... 17
5 Structural designs ... 18
5.1 General requirements ... 18
5.2 Foundation bearing capacity calculation ... 20
5.3 Calculation of shoring scaffold ... 21
5.4 Calculation of operation scaffold ... 23
5.5 Calculation of component ... 26
6 Construction requirements ... 27
6.1 General requirements ... 27
6.2 Shoring scaffold ... 27
6.3 Operation scaffold ... 32
7 Installation and disassembly ... 34
7.1 Preparation for construction ... 34
7.2 Construction scheme ... 35
7.3 Ground and foundation ... 35
7.4 Installation and disassembly of shoring scaffold ... 36
7.5 Installation and disassembly of operation scaffold ... 37
8 Inspection and acceptance ... 39
9 Safety management and maintenance ... 41
Annex A Calculating Coefficients of Wind Load ... 43
Annex B Design parameters ... 45
Annex C Stability coefficients for axial compression components... 46
Annex D Construction acceptance record sheets for scaffold ... 48
Explanation of wording in this Standard ... 52
List of quoted standards ... 53
Technical standard for safety of disk lock steel tubular
scaffold in construction
1 General provisions
1.0.1 This Standard is formulated to ensure that the design, installation, dismantling,
use and management of disk lock steel tubular scaffold are technologically advanced,
economically reasonable, safe and applicable.
1.0.2 This Standard applies to the design, installation, dismantling, use and management
of disk lock steel tubular scaffold in construction and municipal engineering.
1.0.3 In addition to complying with this Standard, the design, installation, dismantling,
use and management of disk lock steel tubular scaffold shall also comply with the
provisions of relevant national standards.
2 Terms and symbols
2.1 Terms
2.1.1 disk lock steel tubular scaffold
According to the purpose of use, it can be divided into shoring scaffold and operation
scaffold. A structural frame that can withstand corresponding loads and has operational
safety and protection functions, in which the standards are connected by outer tube or
inner tube, ledgers and diagonal braces are snapped into the connecting plate by the use
of rod end ledger or diagonal brace end, connected with wedges, is referred to as a
scaffold.
2.1.2 shoring scaffold
It is a disk lock steel tubular scaffold that is supported on the ground or structure and
can withstand various loads. It has safety protection functions and provides support and
working platform for building construction. It includes shoring scaffold and structural
erection supports for concrete construction.
2.1.3 operation scaffold
It is a disk lock steel tubular scaffold that is supported on the ground, buildings or
attached to engineering structures to provide a working platform and safety protection
for construction.
FR - Design value of vertical force acting on the connecting plate;
MR - Anti-overturning moment of the scaffold under the design load;
MT - Overturning moment of the scaffold under the design load;
Mw - Bending moment due to wind load design value;
Mwk - Bending moment caused by characteristic value of wind load;
N - Design value of standard’s axial force;
N0 - Axial force generated by the out-of-plane deformation of the scaffold due to the
constraints of the anchoring;
Nk - Standard combination value of the axial force transmitted from the standard to the
top surface of the foundation;
Nl - Design value of axial force of anchoring;
Nlw - Design value of axial force of anchoring s caused by wind load;
∑NGk - Sum of the axial force of the standard generated by the permanent load
characteristic value;
∑NQk - Sum of the axial force of the standard generated by the variable load
characteristic value;
Pk - Average pressure at the bottom of the standard’s foundation corresponding to the
standard combination of load effects
R - Design value of scaffold resistance;
S - Effect design value of scaffold calculated based on basic load combinations;
w0 - Basic wind pressure value;
wk - Wind load characteristic value.
2.2.2 Material properties and resistance
E - Elastic modulus of steel;
f - Design values for tensile, compressive and flexural strength of steel;
fa - Characteristic value of foundation bearing capacity;
Qb - Design value of connecting plate shear bearing capacity;
Rc - Design value of anti-slip bearing capacity of fasteners’
[v] - Allowable deflection.
2.2.3 Geometric parameters
A - Cross-sectional area;
Ag - Base bottom area corresponding to base jack;
An - Net cross-sectional area of anchoring;
a - Distance from head jack support point to center line of ledger;
Hl - Vertical spacing of anchoring;
h - Frame lift height (take the distance between connecting plate on the standard as the
modulus);
h’ - Top step distance of the frame (take the distance between connecting plate on the
standard as the modulus);
I - Sectional moment of inertia;
i - Radius of gyration of section;
Ll - Horizontal spacing between anchorings;
l0 - Calculated length of standard;
la - Vertical distance of standard;
W - Section modulus.
2.2.4 Calculation coefficients
k - Reduction coefficient for the calculated length of the cantilever end of the shoring
scaffold;
Φ - Windshield coefficient;
βH - Adjustment coefficient for the height of shoring scaffold of the shoring scaffold;
γ - Correction coefficient for the lift height of the top layer of the frame;
γ0 - Importance coefficient of scaffold structure;
γG - Permanent load component coefficient;
γQ - Variable load coefficient;
γR - Adjustment coefficient for bearing capacity design value;
arranged in a staggered manner with standards of different lengths. The bottom of the
standard shall be equipped with a base jack or pad.
6.3.4 When setting up a pedestrian passage with double rows of external work racks,
support beams shall be erected on the upper part of the passage. The size of the cross-
beam section shall be calculated and determined based on the span and the load it will
bear. Diagonal braces shall be added to the work racks on both sides of the passage. A
closed protective board shall be laid on the top of the opening. Safety nets shall be set
up on both sides. Safety warning and anti-collision facilities shall be installed at
openings where motor vehicles pass.
6.3.5 Vertical diagonal braces shall be installed on the outer facade of double-row work
racks and shall meet the following requirements:
1. At the corners of the scaffold and at the end of the open scaffold, diagonal braces
shall be continuously installed from the bottom to the top of the scaffold body.
2. A vertical or diagonal continuous diagonal brace shall be installed every no more
than 4 spans. When the height of shoring scaffold of the frame is above 24 m, a vertical
diagonal brace shall be installed every no more than 3 spans.
3. Vertical diagonal braces shall be set continuously from bottom to top between
adjacent standards on the outside of the double-row work rack (Figure 6.3.5).
6.3.6 The setting of anchoring shall comply with the following regulations:
1. The anchoring shall be rigid rods that can withstand tensile and compressive loads,
and shall be firmly connected to the main structure and frame of the building.
2. The anchoring shall be set close to the disk lock node of the ledger.
3. Anchorings on the same floor shall be on the same level. Horizontal spacing shall be
no greater than 3 spans. The cantilever height of the shelf above the anchoring shall not
exceed 2 steps.
4. The corners of the frame or the ends of open double-row scaffold shall be set
according to floors. The vertical spacing shall not be greater than 4 m.
operators shall be briefed on technical and safety operations in accordance with the
requirements of the special construction plan.
7.1.3 Components and parts that have passed the acceptance inspection shall be
classified and stacked according to varieties and specifications. Quantity and
specification nameplates shall be attached. The storage area for components and
accessories shall have smooth drainage and no accumulation of water.
7.1.4 The installation of embedded parts such as anchoring, brackets, cantilever beam
fixing bolts or lifting rings of the operation scaffold shall be embedded in accordance
with the design requirements.
7.1.5 The scaffold erection site shall be flat, solid, and have drainage measures.
7.2 Construction scheme
7.2.1 The special construction scheme shall include the following contents:
1. Compilation basis: relevant laws, regulations, normative documents, standards and
construction drawing design documents, construction organization design, etc.;
2. Project overview: overview and characteristics of hazardous sub-projects,
construction layout, construction requirements and technical guarantee conditions;
3. Construction plan: including construction progress plan, material and equipment plan;
4. Construction technology: technical parameters, process flow, construction methods,
operating requirements, inspection requirements, etc.;
5. Construction safety and quality assurance measures: organizational guarantee
measures, technical measures, monitoring and control measures;
6. Construction management and operation personnel allocation and division of labor:
construction management personnel, full-time safety production management
personnel, special operations personnel, other operations personnel, etc.;
7. Acceptance requirements: acceptance standards, acceptance procedures, acceptance
content, acceptance personnel, etc.;
8. Emergency response measures;
9. Calculations and related construction drawings.
7.3 Ground and foundation
7.3.1 The scaffold foundation shall be constructed according to a special construction
plan. It shall be inspected and accepted according to the foundation bearing capacity
7.4.3 The base jack shall be placed on the alignment line and shall be kept level. If a
backing board needs to be laid, it shall be flat and without warping. Do not use cracked
wood backing boards.
7.4.4 When supporting frames are installed continuously on a multi-story floor, the
supporting standards of the upper and lower floors shall be on the same axis.
7.4.5 After the shoring scaffold is installed, the frame body shall be inspected for
acceptance. It shall be confirmed that the requirements of the special construction plan
are met before proceeding to the next construction process.
7.4.6 After the base jack and head jack are installed, the outer surface of the standard
shall match the adjustable nut. The difference between the outer diameter of the
standard and the inner diameter of the nut step shall not be greater than 2 mm.
7.4.7 After the installation of the ledger and diagonal brace wedge is completed, the
hammering method shall be used to spot-check the wedge. The amount of continuous
subsidence shall not be greater than 3 mm.
7.4.8 When the frame is hoisted, standard connectors shall be added to the connections
between standards.
7.4.9 During the erection and dismantling of the frame, small components such as the
base jacks, head jacks, and base collars shall be transferred manually. The hoisting
operation shall be directed by a dedicated person, and no collision with the frame shall
be allowed.
7.4.10 After the scaffold is erected, the vertical deviation of the standard shall not be
greater than 1/500 of the total height of the shoring scaffold, and shall not be greater
than 50 mm.
7.4.11 Dismantling operations shall be carried out according to the principle of
installation first and then disassembly, and then assembly and disassembly first. It shall
be dismantled starting from the top floor and working down layer by layer. Do not work
up and down at the same time. Shall not be thrown.
7.4.12 When sections or facades are demolished, the technical treatment plan for the
boundary shall be determined. The frame body shall be stable after segmentation.
7.5 Installation and disassembly of operation scaffold
7.5.1 The operation scaffold standards shall be accurately positioned and erected in
accordance with the construction progress. The height of shoring scaffold of the double-
row external work rack shall not exceed two steps of the uppermost anchoring at one
time. The free height shall not be greater than 4 m.
7.5.2 The anchoring of the double-row external operation scaffold shall rise with the
height of the scaffold. Synchronize settings at specified locations. Delayed installation
and arbitrary dismantling are not allowed.
7.5.3 The operation layer settings shall meet the following requirements:
1. Scaffold boards shall be laid all over;
2. Foot guards and protective railings shall be installed on the outside of the double-
row outside operation scaffold. The protective railing can be arranged with two ledgers
at the 0.5 m and 1.0 m connecting plates of the standards on each floor of the working
surface. Dense-mesh safety nets shall be hung all over the outside;
3. The gap between the working layer and the main structure shall be equipped with a
horizontal protective net;
4. When steel decks are used, the hooks of the steel decks shall be securely fastened to
the ledgers. The hook shall be in the locked position.
7.5.4 Reinforcements and diagonal braces shall be erected simultaneously with the
operation scaffold. When fastener steel pipes are used as reinforcements and diagonal
braces, they shall comply with the relevant provisions of the current industry standard
"Technical code for safety of steel tubular scaffold with couplers in construction" JGJ
130.
7.5.5 The height of the outer protective railings on the top floor of the work rack above
the top work floor shall not be less than 1500 mm.
7.5.6 When the standard is in tension, the casing connection extension of the standard
shall be connected with bolts.
7.5.7 Operation scaffolds shall be erected and used in sections. They shall be inspected
and accepted before use.
7.5.8 The operation scaffold can only be dismantled after the unit's project leader
confirms and signs a dismantling permit.
7.5.9 When the operation scaffold is dismantled, a safe area shall be marked out.
Warning signs shall be set up. Special personnel shall be assigned to monitor it.
7.5.10 Before dismantling, the scaffold shall be cleaned of utensils, excess materials
and debris.
7.5.11 The operation scaffold shall be dismantled according to the principle of first
installation and then disassembly, and then installation and first disassembly. Do not
work up and down at the same time. The anchoring of the double-row external scaffold
shall be dismantled layer by layer along with the scaffold. The height difference for
segmented demolition shall not be greater than two steps. When working conditions are
limited and the height difference is greater than two steps, additional anchoring shall be
shall comply with the provisions of Articles 6.2.4 and 6.2.5 of this Standard;
4. The wedges of the ledger or diagonal brace end and the connecting plate shall be
tightened.
8.0.4 When one of the following situations occurs, the operation scaffold shall be
inspected and accepted:
1. After the foundation is completed and before the operation scaffold is erected;
2. When the height of the first section reaches 6 m;
3. When the frame is raised layer by layer as the construction progresses;
4. After the height of shoring scaffold reaches the design height;
5. Discontinue use for more than 1 month before resuming use;
6. After encountering strong winds of level 6 and above, heavy rain and frozen
foundation soil thawing.
8.0.5 The inspection and acceptance of operation scaffolds shall meet the following
requirements:
1. The erected frame shall meet the design requirements. The installation of diagonal
braces or scissor braces shall comply with the provisions of Chapter 6 of this Standard;
2. There shall be no uneven settlement of the standard’s foundation. The contact
between the base jack and the foundation surface shall not be loose or suspended;
3. The setting of anchoring shall meet the design requirements and shall be reliably
connected to the main structure and frame;
4. The outer safety vertical net, the inner horizontal net between layers, and the
installation of protective railings shall be complete and firm;
5. Before use, the scaffold structure accessories used for turnover shall be visually
inspected and recorded;
6. The construction records and quality inspection records of the erection shall be timely
and complete;
7. The wedges of the ledger, diagonal brace end and the connecting plate shall be
tightened.
8.0.6 When the shoring scaffold needs to be preloaded, the following regulations shall
be met:
1. A special shoring scaffold stacking preloading plan shall be prepared. Safety
technical briefing shall be conducted before preloading;
2. The preload load arrangement shall be graded by simulating the actual load
distribution of the structure. Symmetrical preloading, preloading monitoring and
loading classification shall comply with the relevant provisions of the current industry
standard "Technical specification for preloading in full scaffold construction" JGJ/T
194.
8.0.7 Records shall be formed after the acceptance of the shoring scaffold and operation
scaffold. The record sheet shall comply with the requirements of Annex D of this
Standard.
9 Safety management and maintenance
9.0.1 Scaffold erection workers shall wear safety helmets, safety belts and non-slip
shoes correctly.
9.0.2 The requirements of the construction plan shall be implemented and the scaffold
installation and removal process shall be followed.
9.0.3 The use of scaffold shall be managed by designated personnel.
9.0.4 The construction load on the working layer shall be controlled and shall not
exceed the design value.
9.0.5 If preloading is required, the load distribution shall be consistent with the design
plan.
9.0.6 During the loading process of scaffold, it shall be carried out according to the
principles of symmetry, layering and grading. There shall be no centralized loading and
unloading. Special personnel shall be assigned to monitor the working status of the
scaffold in the safe area.
9.0.7 During the period of use of the scaffold, it is not allowed to dismantle or modify
the structural components of the scaffold or add other facilities to the scaffold body
without authorization.
9.0.8 Excavation operations shall not be carried out within the scope of influence of the
scaffold foundation.
9.0.9 When performing electrical welding operations on scaffold, fire prevention
measures and dedicated supervision shall be taken.
9.0.10 Scaffold shall be kept at a safe distance from overhead power lines. When
erecting scaffold in open areas, lightning protection measures shall be installed in
accordance with the relevant provisions of the current industry standard "Technical
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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