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Difference between AOA & AON PMRE Practicals

Difference Btw AOA & AON

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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 /