LATERAL RESISTANCE OF JACK SYSTEM (ANALYSIS BY STAAD Pro)

Hi,

Project: Jacking of  Gantry Crane Structure for Installation of Additional Leg.Crane Selfweight = 600 Tons

I end up modelling this kind of structure in STAAD Pro to determine if the whole system will be stable during jacking time and if the crane members can sustain the loadings imposed (selfweight + wind pressure) during jacking. Initially the crane is 45m high and will be jack up to 76m final height by making use of 8 jacks  and bolted parts of CHS each 2m  (see attached image). 

I know jack theoretically can provide vertical restrain (Fy) only but in reality since it will be subjected to immense vertical weight of 600Tons (each jack will carry = 75Tons) it cannot be easily move laterally and somehow there will be a lateral restrain (Fy & Fz).

Question: How can i determine this lateral resistance and have it model as spring support in STAAD? is it using (Fy/Fz = (coef of friction)* (Normal Force))? I need to quantify this as my cable support is highly tensioned without lateral resistance coming from the jack support. 

Thank you in advance for your advice,

Master Mac

  

Parents
  • I'm not sure I totally understand, but if your goal is to provide a spring support, with lateral resistance based on friction, then the process would be to assign a spring in the lateral directions with some large stiffness, run the analysis to establish the vertical reaction, then adjust the spring based on that vertical reaction and friction coefficients. It's not a perfect way to model friction since the spring will deflect linearly under any lateral load, where real friction supports don't deflect at all unless the force is enough to overcome the friction. To do that would require multi-linear spring analysis which does not seem worth the effort here.



    Answer Verified By: Master Mac 

  • Thanks Seth, i actually did not assign spring anymore and fully understand that modelling friction type support is way impractical as it behaves differently compared to spring supports. What i did is a very straight forward, run the analysis with only vertical supports (jack supports), take the minimum vertical reaction for all cases, calculate the lateral restraining force by multiplying this min. vertical reaction to coeff. of friction. Then run the analysis but this time with lateral restraints, identify the lateral forces and compared to the calculated limiting lateral force.

    Furthermore, this situation of considering friction type support is very rare and i really don't expect this feature to any structural software.

    Thank you once again,
    Master Mac
Reply
  • Thanks Seth, i actually did not assign spring anymore and fully understand that modelling friction type support is way impractical as it behaves differently compared to spring supports. What i did is a very straight forward, run the analysis with only vertical supports (jack supports), take the minimum vertical reaction for all cases, calculate the lateral restraining force by multiplying this min. vertical reaction to coeff. of friction. Then run the analysis but this time with lateral restraints, identify the lateral forces and compared to the calculated limiting lateral force.

    Furthermore, this situation of considering friction type support is very rare and i really don't expect this feature to any structural software.

    Thank you once again,
    Master Mac
Children
No Data