Structural simulation erected storage tank with jacking system

Common tank erection usually from bottom to top structure but sometimes in certain location its impossible to apply, for example at tank farm live plant which is hot work not allowed in certain elevation so other erection method should be developed in this condition such as application of water curtain, welding habitat etc.

An alternative method is building it from top to bottom by using jacking equipment, in this posting I'm not going to discuss about the erection method since there are so many article and video in youtube with clear explanation, I’d like to share my previous experience how to decide required  qty of jacking tools base on structural simulation.

PRELIMINARY DATA:
Tank Spec:

• Roof type : Dome Roof
• Diameter : 34747 mtrs
• Total Shell Height : 23200 mtrs

Jacking tools spec:

• Each Jack capacity = 12 Ton
• Max space between jack = 3.5mtrs (from manufacturer)
• Max. actual safe wind load at lifting = 15 m/s

Other Data:

• Max Height allowed for hot work = 14 m
• Wind speed at site = 35 m/s per year

SIMULATION DATA:
Simulation model build in STAAD-PRO software with sequence as below:

Jacking device layout inside of tank structure with qty = 34 divided equally at circumference

Shell Plate thickness arrangement:

Dead load of roof with all of appurtenance generate by manual calculate = 119546.5 kg, then additional weight of shell plate will generated by software.
First erected structure by jack as per picture below:

DESIGN LOAD:

• Dead Load (DL)

Roof Load = Roof weight / Top angle Lenght

= 119456.5/(3.14 x 34747) =1092 kg/m = 10706.42 N/m

• Roof Life Load (Lr)

Roof life load as per API 650 

= 122.1 kg/sq. mtr (apply in top angle)

Roof life  load = 122 x roof area / top angle length

=122 x 1042.97 / 109.5 = 1163 kg/m = 11404.97 N/m

• Wind Load

    Wind pressure Refer to ASCE, use below equation for height variation                                                                           
    qz    =    0.613 Kz Kzt Kd V2      (ASCE 7-10 Para. 27.3.2)               
                                                                               
    P    =    q G Cp - qi (G Cpi)       (ASCE 7-10 Para. 27.4.1)                
Result as per below table :

With simplification in applying load as hidrostatc load, vary lineary as per height function
Load Model:

   

• Combination Load:

Shell ring plate analysed with load combination for Allowable Stress Design as per ASCE 7-10 para. 2.4

1. DL
2. DL + Lr
3. DL + 0.6 W
4. DL + 0.75(0.6W) + 0.75Lr

Design criteria to be applied with max. Von misses equivalent stress compare with yield strength of plate material
Result for plate stress distribution by STAAD PRO for each combination load :

ANALYSIS RESULT:

• Max. Plate Stress :

Max Stress caused by Load Combination no.6 DL + LR with result find
11.8 Mpa < 205/2 Mpa (Plate Yield Strength/Safety Factor) ==> OK

• Reaction Force

Max. Reaction Force caused in last lifting stage 8 with result find

Max. vertical force that carry by jack device = 11.95 ≤ 12 Ton ==> OK
(below max. jack capacity)

SUMMARY:

1. Plate stress in elastic region for every combination load, no indication shell plate will deform in plasticity since von misses equivalent stress result still below yield stress material
2. Generated Max. reaction force smaller than max. capacity of jacking device
3. Number of jacking device = 34 ea are sufficient to support stability and integrity of structure with considering structure weight and additional wind load