Communication tower design and manufacturing technical requirements.
1. Project overview and design scope:
1.1: Project Overview: Some base stations are planned to use the China Mobile Communication Base Station standard tower type, and the tower type is 40 meters single tube tower and 30 meters three tube tower (5 total).
1.2: Design Scope: The standardization design scope of China Mobile Communication Base Station Tower is the above-ground part of the common mobile tower for mobile communication in general wind pressure areas, including steel structure design and lightning protection grounding design, excluding microwave tower, roof tower, landscape tower, basic wind The area with a pressure of ≥0.6kN/m2, the foundation of the tower, and the design of the base station room. This standardized design is included in the type X of the tower, as shown in Table 1. This document provides a 40-meter single-tube tower with a wind pressure of 0.45kN/m2 and a standardized design drawing of a 30-meter three-tube tower. It does not cover the anchor bolt and foundation design, and only requires technical requirements for the grounding grid design.
2. Selection instructions:
2.1: Determine the basic wind pressure: According to the “Code for Loads of Building Structures”, “the 50-year wind pressure in all cities in Zhejiang”, the basic wind pressure (kN/m2) of the proposed tower area is 0.45, which is 0.45.
2.2: Special requirements of the tower:
2.2.1: Install the tower of LOGO: In order to install LOGO, the basic wind pressure is 0.35, 0.45 kN/m2. The tower with basic wind pressure of 0.45 kN/m2 0.55 kN/m2 can be selected, but the following conditions should be met: word count ≤ 6, the side length ≤ 1m, the total weight is not more than 200kg, the installation position shall not be higher than half of the tower height, the hollowing treatment and the hollowing rate shall not be less than 50%.
2.2.2: Installation of small microwave towers: All towers can be equipped with a small microwave with a diameter of less than 600mm and a dead weight of less than 30kg. Special microwave towers or sizes, when the weight is greater than the above requirements, require special design.
2.2.3: Iron towers located in mountainous areas: The iron towers located in the mountainous areas (mountain slopes, basin valleys, and valley mouths) shall be in accordance with the principle of wind load equivalent after considering the terrain correction in accordance with the provisions of Article 7.2.2 of the Code for Loads of Building Structures. Use after checking.
2.2.4: Tower A ground roughness areas located in Class A ground roughness areas refer to offshore seas and islands, coasts, lakeshores and desert areas. Such areas are rarely encountered. The construction of mobile communication towers is based on actual conditions. Case handling.
3. Structural design description:
3.1: Design principle: According to the opinions of the planning department of the group company, the basic principle of the standard design of the tower is determined as “safe, applicable, economic and beautiful”. Safety means that it can withstand various functions that may occur during normal construction and normal use; applicable means that it has good working performance in normal use, that is, it can meet normal communication requirements and is easy to maintain. Economy means that the cost of pursuing production and installation is low on the premise of meeting safety and applicable requirements. Aesthetics means pursuing smooth lines and harmony with the surrounding environment on the premise of meeting installation, application and economic requirements.
3.2: Design basis: China Mobile base station tower standard construction drawing design follows the following standards, norms and procedures: “Unified standard for building structure reliability design” GB50068-2001 “Building structure load specification” GB50009-2001 “Steel structure design specification” GB50017- 2003 "Code for Quality Acceptance of Steel Structure Engineering Construction" GB50205-2001 "Code for Seismic Design of Buildings" GB50135-2006 "Design Rules for Steel Tower Structures" GBJ1-84 "Technical Regulations for Welding of Building Steel Structures" JGJ81-2002 "Mobile Communication Engineering Steel" The design code of the tower structure is YD/T5131-2005 and the preliminary design documents and the spirit of the relevant meeting of the company's planning department
3.3: Structural safety level and design service life: The design design period of the structure is 50 years, the design service life is 50 years, the structural safety level is 2nd grade, and the seismic fortification category is C.
3.4: Calculation procedure and method adopted by the design: The angle steel tower adopts the “Tower Steel Structure Design Software MWT2.0 and MAST1.0 SPT1.0” compiled by Tongji University to carry out finite element calculation analysis according to the space truss.
3.5: Load value:
3.5.1 Permanent loads include structural main materials, bolts, gusset plates, lightning rods, platforms, antennas, feeders, ladders, etc.
3.5.2 Variable loads include wind loads, seismic loads, snow loads, ice-wrapping loads, platform live loads, and ladder overhaul loads.
188.8.131.52 Wind load Since the mobile communication tower is built in townships and urban suburbs, the ground roughness is classified as Class B. When the cross section of the tower is quadrangular, under the action of wind load or earthquake, two working conditions of horizontal working condition and 45 degree direction are considered.
184.108.40.206 Seismic action The seismic action is checked according to the basic seismic intensity of the earthquake in Zhejiang. The results show that the seismic action combination is a non-control combination.
220.127.116.11 The live load of the platform live load platform is considered as 2.0kN/m2; the horizontal load at the top of the platform bar is considered to be 1.0kN/m.
18.104.22.168 The ice load is considered to affect the gravity load and the increase of the wind shield area caused by the surface of the structural members, cables and antennas. According to the geographical division, Hangzhou is a light-wrapped ice area, and the basic ice thickness can be 5-10mm. Wrap-covered ice can also be affected by topography and local climate. Therefore, there may be heavy wraps or no wraps in individual locations in the light-wrapped ice zone. Similarly, light wraps or super-spots in individual locations may occur in the re-wrapped ice zone. Wrapped in ice. The check calculation indicates that the ice load combination is a non-control combination.
22.214.171.124 Snow load Since the platform load is generally greater than the snow load, the snow load is considered differently.
3.6: Component verification:
3.6.1 Control of the ultimate state of the bearing capacity The load-bearing effect of the component under basic combination conditions is lower than the design value of the component resistance. Control indicators include component strength-to-stress ratio, overall stability (strong, weak axis) stress ratio
3.6.2 Control conditions for the normal use limit state According to the "Mobile Communication Engineering Steel Tower Structure Design Specification", the horizontal displacement of any point of the iron tower structure calculated by the standard combination is not more than 1/75 of the height from the point.
3.6.3 Component length-to-fine ratio check Φ ≤ 150 cross-bar and slanting rod λ ≤ 150, when the internal force is less than 50% of the bearing capacity of the rod, λ ≤ 200 auxiliary rod, cross-bar λ ≤ 200 Pull rod λ≤350
3.7 Various tower types adopt the material specifications as shown in the drawing paper, and the wall thickness of all column materials has a negative tolerance of 0.00mm.
3.8 node connection
3.8.1 Uniform requirements: 1) The bolt hole is the bolt diameter plus 1.5mm, except for the bolt hole of the anchor bolt. 2) The bottom part of the bolt is made of anti-theft nut. 3) Q345B and Q345B welding materials are E50XX, Q345B and Q235 welding materials are E43XX. 4) In addition to the height of the weld, the following principles are used: double-sided welding, 0.7 times plate thickness (thinner parts); single-sided welding, 1.2 times plate thickness (thinner members); minimum not less than 4 mm.
3.8.2 Angle steel tower should meet: 1) All the angled steel should be shovel, and the angled steel should be shoveled. 2) The tower body diagram should be combined with the lightning rod and platform diagram to lay out the bolt holes. 3) Two maters and one gasket are used for the connection between the platform and the main material. 4) When the main material is connected to the joint, if the thickness difference of the main material is greater than 2 mm, the backing plate with the thickness equal to the difference of the thickness of the main material should be added.
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