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Difference btw AOA & AON
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Difference between AOA & AON
PMRE Practicals
AOA network - activity on arrow AON network- activity on node
iEETi
j
LETj
TFLij FFLij
EETj
LETi
Aij
Dij
ESij
LSij
EFij
LFij
Activity name Duration
ES EF
LFLS
FFTF/
Comparison of AOA, AON
AOA
Activities depicted on arrow
Nodes are termed events- which have EET- early event times & LET- Late event times
AOA takes up on FS relationship and no lag can be depicted
It is a stepping stone to AON and is not used presently
AON
Activity depicted on node
Here arrows depict relationships such as FS- finish to start, SS-start to start, SF- Start to finish, FF- Finish to finish
The arrows may also show lag along with relationships for eg. FS2, FS0, SS1, etc.
Checking AOA & AON networks for correctness
AOA No two arrows to be present between two
events
2 dummies arrows can be drawn from one event and vice versa
No cyclic loops allowed
AON No dummy activities to be present except
start and finish
No cyclic arrows allowed , same as in AOA network
Formulas
AOA Network
EETj = EETi + Dij (during forward pass step)
LETi = LETj- Dij (during backward pass step)
TF= LSij- ESij or LFij- EFij
Freefloat= EEThead- EET tail - Dij
AON Network1. EFi= ESi + Duri (during forward pass)
2. LSi= LFi - Duri (during backward pass)
3. When relationship is FS(lag) Freefloat of i= ESj-FSlag-EFi
4. When relationship is SS(lag) Freefloat of i = ESj-SSlag-ESi
5. When relationship is SF(lag) Freefloat of i = EFj-SFlag-ESi
6. When relationship is FF(lag) Freefloat of i = EFj-FFlag-EFi
iEETi
jLETj
TFLij FFLij
EETj
LETi
Aij
Dij
ESij
LSij
EFij
LFij
Activity- i, Duri
ESi EFi
LFiLSi
FFiTFi/
FS(lag) Activity- j, Durj
ESj EFj
LFjLSj
FFjTFj /
Step to solve AOA & AON network
AOA Network
1. First step-- Forward pass to calculate- EET, ES, EF
2. Second step-- Backward pass-LET, LF LS
3. Third step-- Total float & Free float calculation
4. Final step- Find critical path (activity with both Total float & free float as zero)
AON Network1. First step-- Forward pass to calculate-ES, EF
(here no EET exists), and (when lag exists) lag should be added to ES of subsequent activities
2. Second step-- Backward pass- LF LS (here no LET exists), (when lag exists) lag should be subtracted to get LS or LF of preceding activity
3. Third step-- Total float & Free float calculation (for free float formula changes for each type of relationship FS, SS, SF, FF)
4. Final step- Find critical path (activity with both Total float & free float as zero)
iEETi
jLETj
TFLij FFLij
EETj
LETi
Aij
Dij
ESij
LSij
EFij
LFij
Activity- i, Duri
ESi EFi
LFiLSi
FFiTFi/
FS(lag) Activity- j, Durj
ESj EFj
LFjLSj
FFjTFj /