Structural Inspection Of Communication Steel Mast Tower

 

 

 

The inspection of communication steel mast towers is carried out in five modules: tower base and foundation, tower body main structure, connecting nodes, ancillary facilities, overall performance and bearing capacity.

(1) Tower foundation and foundation testing

Basic appearance and defect detection:

Check for cracks, looseness, missing corners, and exposed reinforcement in the concrete foundation, and inspect for cracks, slippage, and settlement in the anchor foundation of the cable tower;

 

Basic Geometry and Deformation Detection:

Using a level to detect the overall settlement and uneven settlement of the foundation, measuring the top elevation of the foundation, and calculating the settlement difference; Use a total station to detect the horizontal deviation of the foundation top surface and verify the coaxiality between the foundation center and the tower center.

 

Foundation bolt system inspection:

Check the specifications, quantity, and burial depth of the anchor bolts, verify the consistency with the design values, check the looseness, corrosion, and thread damage of the bolts, test the pull-out/shear performance of the bolts, and investigate the bonding failure and loosening of the bolts with the concrete foundation; Check the integrity of the protective cap and anti-corrosion coating of the anchor bolts.

Basic concrete strength testing

 

(2) Inspection of the main steel structure of the tower body

Appearance and damage detection of components:

Inspect the surface cracks (circumferential/longitudinal), dents, deformations, and scratches on the steel pipes/sections of the tower body, and use ultrasonic flaw detectors to detect the depth of the cracks;.

 

Corrosion and section loss detection of steel:

Check the integrity of the anti-corrosion coating: peeling, flaking, powdering, and bubbling range. Use a coating thickness gauge to measure the coating thickness

Use ultrasonic thickness gauge to detect the actual wall thickness/section size of the corroded area of the steel, and calculate the section loss rate;

 

Geometric dimensions and deformation detection of tower body:

Cable mast tower: detect the bending deformation of the mast and investigate local instability of the mast.

 

Steel grade review:

Use the Leeb hardness method/spectrometer to verify the steel grade (usually Q235B, Q355B), verify whether it meets the design requirements, and avoid material misuse.

 

(3) Connection node detection (core: weld quality, bolt torque, node stiffness)

Steel structure nodes are the key to force transmission, and communication steel mast tower nodes are mainly composed of welded nodes and high-strength bolt nodes. Cable tower additional cable connection node detection is added, and node detection is the top priority of steel mast tower detection:

 

Welding node detection:

Testing locations: tower body segment splicing welds, antenna support and tower body connection welds, truss node welds, ladder and tower body connection welds;

Appearance inspection:% of defects such as weld excess height, undercutting, incomplete welding, porosity, slag inclusion, etc;

Non destructive testing: Ultrasonic testing (UT) is used to detect internal defects in key welds under stress.

 

High strength bolt node detection:

Testing parts: truss node bolts, antenna bracket fixing bolts, tower body splicing flange bolts;

Torque detection: Use a fixed torque wrench to detect the tightening torque of bolts, and review whether it meets the design/specification requirements (Q355 steel connection torque is generally ≥ 300N · m, Q235 steel ≥ 200N · m). The proportion of loose bolts is ≤ 5%;

 

(4) Auxiliary facility testing

Antenna and feeder bracket inspection:

Check the specifications and layout of the bracket, and verify its compatibility with the design load;

Inspect the connection welds/bolts between the bracket and the tower body, check for looseness, deformation, rust, as well as bending and instability of the bracket itself;

Check the fixed state of the feeder card and investigate the excessive additional load on the bracket caused by the sagging of the feeder.

 

Lightning protection and grounding system testing:

Check the connection reliability of the lightning arrester (top cap, lightning rod) on the tower body, without looseness or corrosion;

Check the connection between the grounding down conductor and the tower body, and measure the grounding resistance value;

Check the equipotential connection between the lightning protection system and communication equipment, and ensure no poor contact.

Other attachments: Check the fixed status of tower identification and aviation obstruction lights, and investigate local tower vibrations caused by loose equipment.

 

(5) Overall performance and bearing capacity verification

Based on the actual component parameters, connection status, and material properties detected on site, combined with the current load, professional software (PKPM, MIDAS/GEN) is used for modeling and verification, which is the core of the overall safety assessment:

 

Load calculation:

Dead load: tower weight, antenna/feeder/support weight, ladder/platform weight;

Live load: wind load, snow load, maintenance live load;

Special loads: lightning strikes, earthquake loads, typhoon loads.

 

Core verification items:

The overall compressive and bending bearing capacity of the tower body shall be reviewed, and the stress ratio, foundation pull-out resistance, overturning resistance, and anti slip bearing capacity of each segment of the components shall be checked. The overall stability of the tower body shall be verified, and the risk of overall collapse caused by local component instability shall be investigated. The overall stability of the cable system shall be verified for the guyed mast tower, and the coordinated force between the cable tension and the mast shall be reviewed.