lift (skew & cog shift) methods

LIFT STEPSSTEPS TO PERFORM LIFT ANALYSIS USING SKEW & COG SHIFT PHENOMENON

SIMPLE LIFT

SLING

60 (min)

SIDE ELEVATIONPLAN

COG SHIFT : In COG shift we consider 1m shift of COG in every direction.

PLANWe will locate joints as shown below. Two joints will be added at same point, as show in the below fig.

ISOMETRIC VIEW

How to model slings

(111000)

(110000)

(111000)(111000)

(111000)(111000)

Model the slings as NOLD (no load) gap element, wih "0" density & the member classification as "9".

We will run the model file using "searun" we will get the self weight(dry), this weight will be the dry lift weight.

Now we will be calculating the moments shifting the COG = (total load*X)/(2*Y)Similarly calculate for each COG shift, the value of forces to be applied on P001, P002, P003, P004. create 4 load conditions and apply these loads under that load cases

Now create the skew load conditions1.) LOADCN NS0050% LOAD ON 9902

2.) LOADCN NS25LOAD CONDITION FOR NO SHIFT IN COG CASE 25% LOAD ON 9902WITH 50%, 25%, & 75% LOADS ON ONE SLING

3.) LOADCN NS7575% LOAD ON 9902

SIMILARLY WE CAN CREATE LOAD OCNDITIONS FOR EACH AND EVERY ONE OF COG SHIFT4.) LOADCN P10050% LOAD ON 9902

5.) LOADCN P125LOAD CONDITION FOR COG SHIFT TOWARDS P001 25% LOAD ON 9902

6.) LOADCN P17575% LOAD ON 9902


8.) LOADCN P225LOAD CONDITION FOR COG SHIFT TOWARDS P00225% LOAD ON 9922








SO THESE WILL BE OUR APPLIED LOADS IN +Z DIRECTIONSLOAD COMBINATIONs (COG & SKEW)COG = 1 X DEAD + 1 X NGDLCO00 = COG X 1 + NS00 X 1CO01 = COG X 1 + NS75 X 1CO02 = COG X 1 + NS25 X 1C100 = COG X 1 + P1 X 1 + P100 X 1C101 = COG X 1 + P1 X 1 + P175 X 1C102 = COG X 1 + P1 X 1 + P125 X 1SIMILARLY WE WILL HAVE THE FOLLOWING COMBINATIONSC200 = COG X 1 + P2 X 1 + P100 X 1C201 = COG X 1 + P2 X 1 + P175 X 1C202 = COG X 1 + P2 X 1 + P125 X 1C300 = COG X 1 + P3 X 1 + P100 X 1C301 = COG X 1 + P3 X 1 + P175 X 1C302 = COG X 1 + P3 X 1 + P125 X 1C400 = COG X 1 + P4 X 1 + P100 X 1C401 = COG X 1 + P4 X 1 + P175 X 1C402 = COG X 1 + P4 X 1 + P125 X 1INPUT FILE FINISHEDGAPINP FILEGAPOPTALL GAP ELEMENT DEFINED IN THE MODELYESUNITSMNMAX NUMBER OF ITRATIONS 600CONVERGENCE TOLERANCE0.01LCGAP C000 INC NL GRP SLI SL2 SL3 SL4LOAD COMBINCLUDESNO LOADGROUPSIMILARLY DO IT FOR C001, C002, C100, C101, C102, C200, C201, C202, C300, C301, C302, C400, C401, C402

COGCOGCOG1m

1m

1m

1m

COG9901,99029931,99329941,99429921,99229911,9912COG99019902P001P002P003P004P002-9902P001-9901P003-9903P004-9904COGYX

COG SHIFT LOADTotal Lift Weight=3672.88KNCalculationsThis excel sheet will help us calculating the moments to be applied in order to shift the centre of gravity

CASE 1C.O.G. Shift towards P001P1P001=-258.64P002=-258.64Force on point P001=-517.64KNP003=258.645.02mForce on point P002=0.37KNP004=258.64Force on point P003=517.64KN0.7060.709Force on point P004=-0.37KNP001=-259.00P002mmP003P002=259.00P003=259.00P004=-259.00

CASE 2C.O.G. Shift towards P002P2P001=-258.2722390438P002=-258.27223904380.707m0.706m5.02mForce on point P001=0.37KNP003=258.27223904380.708m0.706mForce on point P002=-516.91KNP004=258.2722390438Force on point P003=-0.37KNForce on point P004=516.91KNP001=258.638063745xP002=-258.638063745P003=-258.638063745P004=258.638063745P001P004yCASE 3C.O.G. Shift towards P003P3P001=259.370.7070.71P002=259.37mmForce on point P001=517.64KNP003=-259.37Force on point P002=1.10KNP004=-259.37P1Force on point P003=-517.64KNP2Force on point P004=-1.10KNP001=258.27P3P002=-258.27P4P003=-258.27P004=258.27How to use?CASE 4C.O.G. Shift towards P004P4P001=259.74just input the values in the yellow boxes as per the modelP002=259.74Enter the value of total lift weight in KN in C1Force on point P001=1.46KNP003=-259.74Force on point P002=518.01KNP004=-259.74Force on point P003=-1.46KNForce on point P004=-518.01KNP001=-258.27P002=258.27P003=258.27P004=-258.27

lift (skew & cog shift) methods

Documents