Continued ...
💫Bolted or welded connection: design gusset plates, stiffeners, and welds. Provide stiffener plates where legs meet tank ring.
8) Corrosion, durability, and maintenance
Material selection: suitable structural steel grade (S235, S275 etc. or per Ethiopian code). Tank liner or stainless if required.
Protective coatings: primer + paint system or galvanizing for exposed members. Consider sacrificial anodes or cathodic protection if aggressive environment.
Drainage & cleaning access: design manholes, drain points.
Inspection access: ladders, platforms, fall protection, safety cages. Plan for periodic inspection of welds, bolts, and paint.
9) Service piping & hydraulic considerations
Inlet/outlet piping: internal piping routing and anchor points so pipe thrusts do not load the tower unnecessarily.
Valves & air vents: overflow, venting, anti-surge measures.
Water hammer: include air chambers or surge protection to avoid sudden loads.
10) Practical design recommendations / good practices
Use vertical main legs rather than slanted legs if possible; slanted legs create bending eccentricities.
Provide full cross-bracing in both directions; bolt connections to gusset plates.
Make the foundation wider than the tower footprint (reduce overturning).
Keep center of gravity low — place platform and tank as low as practical.
Use a stiff tank support ring so tanks don’t create unbalanced loads on legs.
Design for both full and empty tank conditions (empty can change dynamic and wind behavior).
Avoid slender, long members without intermediate bracing (tie beams at one or more levels).
Provide redundancy — if one member fails, the structure shouldn’t collapse catastrophically.
11) Typical analysis workflow (step-by-step)
i. Determine tank weight (full & empty) and CG location.
ii. Compute static vertical reactions if tank supported by ring to N legs.
iii. Calculate wind and seismic lateral loads and moments about foundation.
iv. Model tower in frame analysis software (SAP2000, STAAD, ETABS, or static hand-checks for simple towers). Use 3D frame model including tank mass at top.
v. Extract member axial, shear, and moment forces for critical load combinations.
vi. Size columns & braces by axial, buckling, and interaction checks.
vii. Design connections and gusset plates.
viii. Design foundation for combined vertical, shear, and moment (eccentricity method or footing with overturning check).
ix. Check serviceability (deflections, vibration).
x. Prepare detailed drawings, erection sequence, and inspection plan.
12) Checks and special considerations
Eccentric loads from slanted legs or offset tank support.
Resonance / vortex shedding for tall slender towers — check for dynamic amplification (tall slender towers may need dampers or periodic cross-bracing spacing to break up long unbraced lengths).
Local plate buckling under concentrated loads (use stiffeners).
Redundant load paths (avoid single-bolt critical connections).
Safety: fall protection, signage, lightning protection if tower is tall.
13) Documentation & commissioning
Structural calculations, drawings, load assumptions, material specs, welding procedures, NDT requirements.
Erection procedure and temporary bracing plan.
Testing: hydrostatic test of tank, proof load test of structure if required.
Maintenance & inspection schedule.
@etconp
💫Bolted or welded connection: design gusset plates, stiffeners, and welds. Provide stiffener plates where legs meet tank ring.
8) Corrosion, durability, and maintenance
Material selection: suitable structural steel grade (S235, S275 etc. or per Ethiopian code). Tank liner or stainless if required.
Protective coatings: primer + paint system or galvanizing for exposed members. Consider sacrificial anodes or cathodic protection if aggressive environment.
Drainage & cleaning access: design manholes, drain points.
Inspection access: ladders, platforms, fall protection, safety cages. Plan for periodic inspection of welds, bolts, and paint.
9) Service piping & hydraulic considerations
Inlet/outlet piping: internal piping routing and anchor points so pipe thrusts do not load the tower unnecessarily.
Valves & air vents: overflow, venting, anti-surge measures.
Water hammer: include air chambers or surge protection to avoid sudden loads.
10) Practical design recommendations / good practices
Use vertical main legs rather than slanted legs if possible; slanted legs create bending eccentricities.
Provide full cross-bracing in both directions; bolt connections to gusset plates.
Make the foundation wider than the tower footprint (reduce overturning).
Keep center of gravity low — place platform and tank as low as practical.
Use a stiff tank support ring so tanks don’t create unbalanced loads on legs.
Design for both full and empty tank conditions (empty can change dynamic and wind behavior).
Avoid slender, long members without intermediate bracing (tie beams at one or more levels).
Provide redundancy — if one member fails, the structure shouldn’t collapse catastrophically.
11) Typical analysis workflow (step-by-step)
i. Determine tank weight (full & empty) and CG location.
ii. Compute static vertical reactions if tank supported by ring to N legs.
iii. Calculate wind and seismic lateral loads and moments about foundation.
iv. Model tower in frame analysis software (SAP2000, STAAD, ETABS, or static hand-checks for simple towers). Use 3D frame model including tank mass at top.
v. Extract member axial, shear, and moment forces for critical load combinations.
vi. Size columns & braces by axial, buckling, and interaction checks.
vii. Design connections and gusset plates.
viii. Design foundation for combined vertical, shear, and moment (eccentricity method or footing with overturning check).
ix. Check serviceability (deflections, vibration).
x. Prepare detailed drawings, erection sequence, and inspection plan.
12) Checks and special considerations
Eccentric loads from slanted legs or offset tank support.
Resonance / vortex shedding for tall slender towers — check for dynamic amplification (tall slender towers may need dampers or periodic cross-bracing spacing to break up long unbraced lengths).
Local plate buckling under concentrated loads (use stiffeners).
Redundant load paths (avoid single-bolt critical connections).
Safety: fall protection, signage, lightning protection if tower is tall.
13) Documentation & commissioning
Structural calculations, drawings, load assumptions, material specs, welding procedures, NDT requirements.
Erection procedure and temporary bracing plan.
Testing: hydrostatic test of tank, proof load test of structure if required.
Maintenance & inspection schedule.
@etconp
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