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GB 4623-1994 Annular prestressed concrete poles

Basic Information

Standard ID: GB 4623-1994

Standard Name: Annular prestressed concrete poles

Chinese Name: 环形预应力混凝土电杆

Standard category:National Standard (GB)

state:Abolished

Date of Release1994-01-02

Date of Implementation:1995-08-01

Date of Expiration:2006-12-01

standard classification number

Standard ICS number:Building materials and buildings>>Building materials>>91.100.30 Concrete and concrete products

Standard Classification Number:Building Materials>>Building Materials Products>>Q14 Concrete Products

associated standards

alternative situation:GB 4623-1984; replaced by GB/T 4623-2006

Publication information

publishing house:China Standards Press

other information

Review date:2004-10-14

Drafting unit:Suzhou Concrete Cement Products Research Institute

Focal point unit:National Technical Committee for Standardization of Cement Products

Publishing department:State Bureau of Technical Supervision

competent authority:China Building Materials Industry Association

Introduction to standards:

This standard specifies the product classification, technical requirements, test methods, inspection rules, marking and factory certificate, storage and transportation of annular prestressed concrete poles. This standard applies to poles, lighting pillars and signal poles for power, communication and overhead contact lines. It does not include other components of the pole, such as crossarms, chucks, chassis and other accessories. GB 4623-1994 Annular prestressed concrete poles GB4623-1994 standard download decompression password: www.bzxz.net

Some standard content:

National Standard of the People's Republic of China
Circuiar prestressed concrete pole
Circuiar prestressed concrete pole1Subject content and applicable range
GB4623--94
Replaces GB4623:94
This standard specifies the product classification, technical requirements, test methods, inspection rules, marking and factory qualification certificate, storage and transportation of circular prestressed concrete poles.
This standard applies to poles, lighting pillars and signal poles for power, communication and overhead contact lines. It does not include other components of the bracket, such as cross arms, chucks, chassis and other accessories. 2 Reference standards GB 175 Portland cement, ordinary Portland cement GB 109 GB 700 GB 1344 Rapid hardening Portland cement Carbon structural steel Hot rolled low carbon steel disc Sulfate resistant Portland cement Slag Portland cement, pozzolanic Portland cement and fly ash Portland cement GR 1499 CB4463 GB 5223 GB 5224
GB807G
Reinforced concrete steel bars
Heat-treated steel bars for prestressed concrete
Steel wire for prestressed concrete
Steel strand for prestressed concrete
Concrete admixtures
GB/T 14684
GB/T 14685
GB J81
GBJ107
GBF204
GBJ321
Sand for construction
Pebbles and crushed stones for construction
Specification for design of concrete structures
Test methods for mechanical properties of ordinary concrete
Standard for inspection and evaluation of concrete strength
Specification for construction and acceptance of reinforced concrete projects
Standard for quality inspection and evaluation of prefabricated concrete parts JGJ63 Standard for water used in concrete mixing
3 Terminology
3.1 Prestressed concrete pole (Y)
The main load-bearing steel bars of the pole are prestressed steel bars. The allowable value of the crack resistance inspection coefficient is 71.0. 3.2 Partially stressed concrete pole (BY) The main load-bearing steel bars of the pole are composed of prestressed steel bars and non-prestressed steel bars, or all of them are prestressed steel bars. The allowable value of the crack resistance inspection coefficient is [.--0. 8.
Approved by the State Administration of Technology on December 22, 1994 and implemented on August 1, 1995
3.3 Standard test load (P)
Normal short-term load test value.
3.4 ​​Standard test bending moment (M)
GB 4623-94
Test value of bending moment at the test section of the pole under the standard test load. 3.5 Bearing capacity test bending moment (M.)
Test value of bending moment at the test section of the pole under the bearing capacity test load. 3.6 Cracks
There are cracks on the surface of the pole that extend into the concrete. 3.7 Leakage
The cement slurry on the surface of the pole is lost, exposing sand and stone. 3.8 Exposed Rebar
Rebar inside the pole is exposed and not covered by concrete. 3.9 Collapse
The inner wall of the pole is condensed and falls off in blocks.
3.10 Debris
The surface of the concrete is exposed due to leakage or lack of cement mortar. 3.11 Pockmarked
Micropores on the surface of the pole.
3.12 Sticky
The cement slurry layer on the outer surface of the pole is stuck away, revealing an uneven structural layer. 3.13 Cracking
The surface of the pole has a turtle-back pattern, without neat edges and obvious depth. 3.14 Water Mark
When the concrete is immersed, fine lines are visible on the surface, and the lines disappear after the water evaporates. 4 Product classification
4.1 According to the appearance, the product can be divided into two types: tapered pole (taper is 175) and equal diameter pole, as shown in Figure 1. According to the different allowable values ​​of crack resistance test coefficient, it can be divided into prestressed concrete pole and partially prestressed concrete pole. Shape F
1—Pole length: L—Load point height: L:—Support point height/L.—Pin to load point limit (0.25m)\—Root diameter or diameter + d—Pin diameter 8 Seat thickness 4.2 Chain poles have whole poles and assembled poles. The rod segment series of the tapered rod is shown in Figure 2. 4.3 The tip diameter (or occupied diameter), length, standard test load and standard test bending moment of the electric shrimp are shown in Tables 1, 2 and 3178
Length of support segment, m
Diameter of rod segment, om
-+ 230
Figure 2 Rod segment series of tapered rod
6.0(length m)
(pin diameter, mm)
(pin diameter, mm)
Standard load production
9813.563.56
15:1.1 2.583.863.86
8.00 6.451.30
8.506.851.40
10. 008.05
13.008.85 7.90
12.009.752.00
13. 0410. 55 2. 20
15.0012.25:2.50
1.846.458.059
Table 1 Standard test bending moment of whole tapered rod
19. 3011.55
9,7111.1a12.4913.8&
6818019.6xh0
Diameter, mm
9. 71 11. 1d13. 88
11.2512.9014.5116.1219.3211.292.9016.12P
h0. 5018. 1221.725. 3814. 5016.65
3.50.4.00 :.00:5.006.09
21.7525.3829.0036.25
.2814.0816.101R.L20.1224.1514.0816-1020.1224.1528.1816.1920.1224.152. 0813.
Note: (D standard push test moment is the support point break and the bending range, and the lower standard Ya test load multiplied by the height of the load point. The pole bearing capacity test bending moment Mu-EPuMkLu bearing capacity comprehensive test system is divided into 2.1?Q..Q, ABC)... is a code for the same standard test and simple cutting. It can also produce other poles with other bearing capacity test bending moments through the agreement of the supply and demand parties! : The products produced according to the drawings approved by the competent authorities at the level shall be inspected according to the requirements indicated on the thank paper. 7,70
19.5024.38
17.7022.1225.55
19.3021.3829.2534.1239.00
21.102r.383t.6536.9342.2d
24. t030. 6236. 742. 38
48.7558.50
Test section
Odd moment
5.551.2026715
6.45,1.30
Standard test bend
2025,30
7. 251. 50290 17
8. 05 1. 7 301|20
3035|40
9.752.0032325
4. 751. D
Table 2 Standard test bending moment of assembled tapered rod
Standard test bending range
297, 17↓202530
354045
Standard test bending reverse
40/45/50
3540455055370354045
455055363303540
45.50 5560
41745:50
7.251.5450,5060
45750607080
90100110490
90100120
350:35
Test bending moment
Standard test bending moment
4104555607080
61080100120150180210
9010011012052370809010011012013056380100130160190200603801001201501802109.752.048360
Note① When using the transmission test, the standard test bending moment is the bending moment at the support point section. ② For 350, 390, 43 and $470, it is [6.00+6.00]: the tip diameter of the upper rod section of the assembly rod. The numbers listed in the table refer to the standard test bending moment values ​​of the lower rod section. ?The allowable value of the pole bearing capacity test bending moment Mt-[Sur]Mk, [Su]-bearing capacity comprehensive test coefficient is 2.u. ④ With the agreement between the supply and demand parties, poles with other bearing capacity test bending moments can also be produced. Products produced according to the drawings approved by the superior supervisory department shall be inspected according to the requirements specified in the drawings. 4623
GB 4623- 94
Table 3 Standard test bending moment of equal diameter poles
1.5,6. 00+9.00
Note: {Monthly support test, standard test bending moment is the maximum equal moment at the two-point interval. ②The allowable value of the pole bearing capacity test bending moment M.-M[3
bearing capacity comprehensive test coefficient is 2.0. With the agreement between the supply and demand parties, poles with other bearing capacity test bending moments can also be produced. Products produced according to the drawings approved by the superior supervisory department shall be inspected according to the requirements specified in the drawings. 5 Technical requirements
5.1 Product dimensions
Should comply with the requirements of this standard, or be manufactured according to the design drawings. 5.2 Raw materials
5.2.1 Cement
It is advisable to use Portland cement, ordinary Portland cement, slag Portland cement, sulfate-resistant Portland cement, or rapid-hardening Portland cement with a strength of not less than 525, or not less than 425, and its performance should comply with the provisions of GR175, GB199, GB748 and GR1344 respectively. 5.2.2 Aggregates
Sand should be medium-coarse sand, and gravel or pebbles should be used. Their quality should comply with the provisions of GB/T14684 and GB/T14685 respectively. And it should comply with the provisions of (GBI204. 5.2.3 Water
Drinking water should be used for mixing concrete, and the water quality should comply with the provisions of JGJ63. 5.2.4 Admixtures
The properties of admixtures added to the mixture should comply with the provisions of GB8076. It is strictly forbidden to add ammonium salt admixtures. 5.2.5 Steel
5.2.5.1 Prestressed steel bars
It is advisable to use cold-drawn grade [, cold-drawn grade II, cold-drawn grade I, grade V (heat-treated) steel bars, grade A cold-drawn low-carbon steel wire, carbon steel wire, notched steel wire and steel wire, carbon structural steel. The properties of steel should comply with the provisions of GB1499.GB5223, GB5224 and GB4463 respectively, and grade A cold-drawn low-carbon steel wire should comply with the provisions of GBI204. 5.2.5.2 Non-prestressed steel bars
It is advisable to use Grade [, Grade 1, Grade 2 steel bars and Grade B cold-drawn low-carbon steel wire, and their performance should comply with the provisions of GB701 and GBJ204 respectively. 5.3 Concrete
The design strength grade of the centrifugal concrete for prestressed electric poles should not be lower than Grade C50. When prestressing is applied, it shall not be lower than 70% of the designed concrete strength grade, and shall not be lower than 80% of the designed concrete strength grade when leaving the factory. 5.4 Structural requirements
5.4.1 Protective layer thickness
When the diameter of the prestressed steel bar is 6mm or less, the protective layer thickness shall not be less than 12mm; when the diameter is 6mm or less, the protective layer thickness shall not be less than 15mm: There must be a concrete protective layer on the top of the main reinforcement head at the joint end of the steel plate ring. 5.4.2 Steel bar processing
shall comply with the requirements of Appendix A (supplementary work) of this standard. 5. 5 Technical requirements for prestressingbzxZ.net
GB 4623-94
5.5.1 In order to reduce the influence of prestressed steel bar sag, over-tensioning can be adopted. The tensioning process and stress control method shall comply with the provisions of GB201. 5.5.2 Prestressed steel bar shall not be broken.
5.6 Connections, embedded parts and reserved holes of electric poles
5.6.1 When electric poles are manufactured in sections, steel plate rings, flanges or other joint forms can be used for connection. 5.6.2 For the connection between the main screen and the connecting parts, the prestressed steel bar should be connected by the method of first inserting the steel bar and then inserting the joint. The bearing surface of the joint should be in the same plane. Non-prestressed steel bar should be connected by jointing. The quality of the joint should comply with the provisions of (3[204). 5.6.3 The strength of the pole joint shall not be less than 95% of the cross-sectional bearing capacity at the joint. 5.6. 4 Embedded parts, reserved holes and drainage holes shall be set in the design drawings and cleaned: 5.6.5 The outer metal parts of grounding screws, foot nails, wiring pots, etc. shall be clearly marked and cleaned. 5.7 Other requirements
5.7.1 Before the product leaves the factory, the ends shall be sealed with concrete or mortar. If there are special requirements, they shall be handled separately. 5.7.2 After demoulding or before leaving the factory, the prestressed steel bar heads at both ends of the pole must be removed and effective anti-corrosion measures shall be taken. 5.8 Appearance quality
shall comply with Table 4 Regulations.
Table 4 External quality requirements
And crack 1:
Edge joint
Steel drawing
[or flange]
Joint surface with sample body
Quiet porridge and root end
Jumping or grouting
Inner and outer plate surface
Inner surface collapse
Neck surface, sticky skin"
Neck hole around slight damage
Steel plate ring welding 11 separation
Superior products
Vertical and horizontal directions are not allowed
The degree is not more than 3 mm;
Each length is not more than 100mml
The length is not more than 5;
No overlap
The depth is not more than mm1
The circumferential length is not more than 1/6 of the circumference!
The longitudinal length is not more than 20mm
The longitudinal length is not more than 2m
Not allowed
Not allowed
The total area is not more than 1%
The depth of the grip is not more than 10snnt
The distance is greater than 1m
The vertical and horizontal average
Not allowed
The detection is not more than 5 +
#Director's wife in 200 mm:
Cumulative length not less than 8% of the rod length
No joint
Depth not more than 5mm:
Circumferential length not more than 1/5Circumference:
Longitudinal length not more than 3mm
Circumferential length not more than 15mm
Longitudinal length not more than 30mm
Total area not more than 3%
Depth not more than 8mm
That is, the distance is greater than 10mm
Note: 1 Surface cracks do not include cracks and water level. 2) The total area fraction of the account and the adhesive is the ratio of the total adhesive surface to the inner and outer surface area of ​​1m length. 5.9 The allowable deviation of each part shall comply with the provisions of Table 3. The vertical and horizontal deviations are not allowed. The depth is not more than the thickness of the upper protective layer. Each length shall not exceed 300 μm. The cumulative length shall not exceed 10% of the lower support length. The overlap length shall not exceed 10 mm. The lapping length shall not exceed 10 mm. The lapping length shall not exceed 10 mm. The lapping length shall not exceed 50 μm. The circumferential length shall not exceed 1/circumference. The circumferential length shall not exceed 50 μm. The lateral length shall not exceed 50 μm. The total area shall not exceed 5%. The depth shall not exceed 10 mm. The short distance shall not exceed 10 mm
End inclination
Embedded parts
Protective thickness"
GB 4623—94
Table 5 Allowable deviations of each part
Superior product
Complete rod
Assembled rod section!
Small tip diameter
Rod diameter or large diameter
Vertical error of rod center (screen type)
Spacing between two longitudinal holes
Reserved hole
Horizontal error
Fixed type
Buried type
Diameter
End cover
Difference between steel plate and flange axis and rod section axis Rod outer weight ≤,400
Rod outer weight ≥400
First-class product
No/1 G00
not less than/
qualified products
not less than 800
not less than L/1 rno not less than L/1 nmr not more than L/1 noo5
D,/100
Note: 1) If the user unit agrees, when the assembled rod support section is produced according to the designed length, the rod length deviation is the difference between the manufacturing length and the designed length. 2) The protective layer thickness deviation is the difference between the manufacturing length and the designed length: it is measured after the bearing capacity test and bending test. 3] [) Diameter of the pole at the buried pipe:
5.10 Primary performance
Mechanical properties include crack resistance, crack width, bearing capacity test bending moment and deflection test. The standard test bending moment listed in Table 1, Table 2 and Table 3 or the design drawings shall be used as the inspection report and shall meet the following requirements: 5.10.1 When the prestressed concrete pole is loaded to the standard test bending moment, no cracks shall appear. When the pole length of the conical pole is less than or equal to 12m, the top deflection shall not be greater than; when the pole length is greater than 12m, the pole top deflection shall not be greater than -70
GB 4623-94
5.10.2 When the partial prestressed concrete pole is loaded to 80% of the standard test bending moment, no cracks shall appear. When loaded to the standard test bending moment, the crack width shall not be greater than 0.1 mml: When the pole length of the conical pole is less than or equal to 12m, the top deflection shall not be greater than m, the pole top deflection should not exceed 1, the pole length is greater than L, + Ls
, equal diameter poles and tapered poles with special requirements for deflection and crack width, the deflection and crack width are 12 m, the pole top deflection should not exceed
degree shall be stipulated by the agreement between the supply and demand parties.
5.10.3 When loading to the bearing capacity test moment, none of the following situations shall occur: a.
The crack width in the tension zone reaches 1.5mm or the tension steel bar is broken; b. Concrete failure in the compression zone:
Deflection: According to the conical rod of the cantilever test: diameter greater than or equal to F400mm, cantilever test equal to the equal diameter rod of the joint support test: true diameter 300rm, deflection three Note: The pin diameter is S10mm or more. The assembled tank-shaped sections with a length of 8m or less are not subjected to the turbulence test: 6 Test method
6.1 Centrifugal concrete strength
It is determined by using centrifugal annular specimens with the same material, mix ratio, molding process and curing conditions as the product concrete. The test method is shown in Appendix B (Supplement).
6.2 Appearance and dimensions
6.2.1 The technical requirements of the measuring tools for appearance and dimensions are shown in Table 6. Table 6 Technical requirements of measuring tools
Test items
Curvature
End frequency
Protective depth
Crack width
Flange thickness
Tool name
Steel coil #
Standard
Steel ruler
Depth vernier caliper
Depth vernier caliper
20 Readings, microscope
Appearance and measurement are shown in Table 7,
>~-150 mm
0~-15c mm
o--:s
--200 mm
0~~20: mm
G~G nam
0--1:0
Appearance and specification size measurement
Fitting surface crack hoop
Joint chain slurry
Technical requirements for testing measuring tools
Accuracy indication value difference
Grade 1 ±5. 0 mmtn
Grade 2 ±1. 2 mm
Grade 3 1. 2 mm
Above 0.02 mml
-0. 02 mm
±. c2 mm
Measurement method
Observation, with 20) Reading microscope measurement
Observe, use 2m long steel tape measure
Division position
Bump or leakage (tip and root end)
Inner and outer surface reinforcement
Inner surface dry wall drop
Non-stick skin
Reserve my quotation
Damp plate mouth distance
Protection stop
Bending degree
End inclination
Cranial hole
Inner diameter of pot plate
Flange thickness
GB 4623—94
Continued Table 7
Measurement method
Present situation · Use 2m long steel ruler (or steel ruler) to measure and observe, use 2 1 long steel tape measure (or steel ruler) to measure the plate observation, month 2. m long steel coil (or steel ruler) to observe, use 2m long steel tape measure (or 15mm fine ruler) to observe. Depth is measured with depth vernier caliper, distance is measured with 150 mm steel ruler. Length is measured with 20 m long steel tape measure. Thickness is measured with 2m long steel coil (or 150mm long steel ruler). Thickness is measured with 2 long differential ruler. Depth vernier caliper is measured with 150 mm steel ruler. 90° angle ruler and 150 Lm steel ruler are used. 2 tn long steel differential ruler (or 130 mm Measure with a 2㎡ long steel tape measure (or inner diameter)
0~-t50
Measure with a vernier caliper
Measure the difference between the axis of the steel plate ring and the flange and the axis of the pole section 6.3 Mechanical properties of electric poles
Measure with a hanging hammer and a 15Vmt) steel ruler
6.3.1 Cantilever test method is used for dimensional poles. Simple support test method is used for equal diameter poles. Test equipment and procedures are shown in Appendix C (Supplement). 6.3.2
After the bearing capacity and bending moment test, measure the thickness of the protective layer at the following positions. Three points are measured on the dimensional pole: the first point is at the support (point B), the second point is 0.6m from the end, and the third point is between the first two points).
Equal diameter poles are measured at the middle and end supports. 7 Inspection rules
7.1 Inspection items
7.1.1 Inspection items
Include appearance quality, dimensional deviation, crack resistance test, crack width test, standard test deflection under bending moment and concrete strength test, etc.
7.1.2 For poles of the same type, same material, same process and same tip diameter (or point diameter), every 1,000 pieces is a batch. However, if the total number of poles produced within two months is less than 1,000 pieces or less than 30 pieces, it can also be regarded as an acceptance batch. 7.1.3 Inspection items
7.1.3.1 Appearance quality and dimensional deviation
10 poles are randomly selected from each batch for appearance quality and dimensional deviation inspection. 7.1.3.2 Mechanical properties
From the qualified products in appearance quality and size and deviation inspection, randomly select one pole for crack resistance inspection, crack width inspection and standard inspection 18:
deflection inspection under bending moment.
7.1.4 Provisions
7.7.4.1 Appearance quality and size deviation
GB 4623-94
If there are no more than 2 poles that do not meet a certain grade among the 10 inspected poles, the appearance quality and size deviation of the batch of products are judged to be of the same grade.
2 Mechanical properties
7. 1. 4.2
When the crack resistance inspection, crack width inspection and standard inspection deflection under bending moment all meet the requirements of Article 5.10 of this standard, it is judged to be acceptable. If any item does not meet the requirements of Article 5.10, 2 more poles are allowed to be sampled for re-inspection. If there is still one pole that does not meet the requirements of Article 5.10, the product is judged to be unqualified in terms of mechanical performance.
7.1.4.3 General definition
On the basis of the concrete strength and mechanical performance, if the appearance quality and dimensional deviation meet the requirements of a certain grade, the product is judged to be a product of the corresponding grade. However, products with qualified mechanical properties after re-inspection can only be judged as qualified products. 7.2 Type inspection
7.2.1 Inspection conditions
Type inspection should be carried out in any of the following circumstances: When the structure, material, or process undergoes major changes: a.
When the product is stopped for a long time and production is resumed; b.
When there is a big difference between the inspection results of two type inspections; c.
d. When the continuous production of a certain type of product is 3,000 pieces or the total production within 4 months is less than 300 pieces; when the national or local quality supervision and inspection agency proposes to conduct an inspection. e.
7.2.2 Inspection items
Include concrete strength, appearance quality, dimensional deviation, and small work performance. 7. 2.3 Sampling
7.2.3.1 Appearance quality and dimensional deviation
Same as 7.1.3.1.
7.2.3.2 Mechanical properties
Randomly select 3 poles from the poles that meet the requirements of appearance quality and dimensional deviation. 7.2.4 Determination
7.2.4.1 Appearance quality and dimensional deviation
Same as 7.1.4.1.
7.2.4.2 Mechanical properties
When the samples are tested for crack resistance, crack width, bearing capacity, bending moment and deflection, they all meet the requirements of 5.10 of this standard: the mechanical properties of this batch of products are considered qualified. If one of them fails, two more poles can be selected for re-testing. If there is still one that fails, the mechanical properties of this batch of products are considered unqualified.
7.2.4.3 Overall judgment
On the basis of qualified concrete strength and three mechanical properties, if the appearance quality and dimensional deviation meet the requirements of a certain grade, the batch of products is judged as products of the corresponding grade. Products with qualified mechanical properties after re-testing can only be judged as qualified products. 7.3 Repair
Products with appearance defects that are allowed to be repaired should be repaired intact and can be accepted as products of the corresponding grade after passing the inspection. 8 Marking and factory certificate
8.1 Marking
8.1.1 Permanent marking
GB 4623-94
Manufacturer's name or trademark. Mark on the surface of the positive pole. Its position: 3.5 m above the root end for poles with a tip diameter of 190 mm or more; 3.5 m from the root end for poles with a tip diameter of less than 91 mm. 8.1. 2 Temporary markings include pole type, tip diameter (or white diameter), pole length, standard test bending moment (or code) and manufacturing year, month and H. They are written on the pole surface with paint and are slightly lower than the permanent markings: The marking method is as follows;
Value diameter (or diameter) × pole length × standard test moment (or code)
(year, month and day)
Note! Tip diameter or diameter is expressed in mm, pole length is expressed in m, test bending moment is expressed in k, m is expressed in m. The quality of the concrete pole is expressed in \Y\, and the partial prestressed concrete pole is expressed in \3Y\. The fulcrum mark is indicated on the pole surface according to the position plate specified in Figure 3, indicating the symbol +, for example
8.2 Certificate of Compliance
Equal diameter cup, 300×9×45×Y yuan
1951 - 10 - 2
, 150x10XCXBY trademark
engraved support:
1901 +10 + 5
Out! The certificate of conformity shall include the following contents: a.
Certificate number:
Number of this standard:
Manufacturer's name and trademark;
Product specifications, quantity and year of manufacture; H:
Concrete performance test results;
Assembly rod main reinforcement upsetting strength test results: Appearance and dimensional deviation test results;
Mechanical performance test results!
Signed by the technical inspection department of the manufacturer.
9 Storage and transportation
9.1 Storage
9.1.1 The product stacking site should be flat.
9.1.2 Products should be stacked with two or three supports according to different pole lengths. For poles with a length of 12m or less, use two supports: pole length 12m. Use two supports. The position of the pole support is shown in Figure 32.15-
0.58 1. H4
Two-support point storage
G point also provides
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