Time Planning and Control. Precedence Diagram

Transcription

1 Tme Plannng and ontrol Precedence agram

2 Precedence agrammng S ctvty I LS T L n mportant extenson to the orgnal actvty-on-node concept appeared around 14. The sole relatonshp used n PRT/PM network s fnsh to start type of dependency, wth s =. Precedence dagrammng ncludes precedence relatonshps among the actvtes. In ddton, one may specfy a lag tme assocated wth any of the precedence relatonshps, whch can be used to account for overlappng tmes among actvtes. The computaton of actvty tmes (publshed n 173) s more complex than ON.

3 Lag / Lead Tmes In many cases, there s a delay between the completon of one actvty and the start of another followng or there s a need to show that one actvty wll overlap another n some fashon. successor "lags" a predecessor, but a predecessor "leads" a successor. Lag tme can be desgnated on a dependency lne wth a postve, negatve, or zero value. Lmtatons and sadvantages of Lag: Lag would complcate the schedulng process. Lags are not extensvely used except where the tme effects are substantal for specal proect type. S ctvty I LS T L

4 Precedence agrammng Relatonshps Types and constrant 1. Start-to-Start (SS ) [() cannot start tll () starts] SS IJ SS s equal to the mnmum number of tme unts that must be completed on the precedng actvty () pror to the start of the successor (). Lag s always appled to SS relaton. 2. nsh-to-nsh ( ) [() cannot fnsh tll () fnshes] IJ s equal to the mnmum number of tme unts that must reman to be completed on the successor () after the completon of the predecessor ().

5 Precedence agrammng Relatonshps Types and constrant 3. nsh-to-start (S ) [() cannot start tll () fnshes] S IJ S s equal to the mnmum number of tme unts that must transpre from the completon of the predecessor () pror to the start of the successor (). 4. Start-to-nsh (S ) [() cannot fnsh tll () starts (rare)] S IJ ' S s equal to the mnmum number of tme unts that must transpre from the start of the predecessor () to the completon of the successor (). S IJ ''

6 Precedence agrammng Relatonshps Types and constrant. Start-to-Start and nsh-to-nsh (ZZ ): ZZ s a combnaton of two constrants,.e., a start-to-start and fnsh-to-fnsh relatonshp. It s wrtten wth the SS tme unts frst, followed by the tme unts. S uraton ctvty () LS Total loat L Types of constrants wth lag/lead uratons SS S S ZZ SS ( ) S uraton ctvty () LS Total loat L

7 Precedence agram omputaton S ctvty I LS T L orward Pass omputatons Intal Tme + S [1] S = Max. all S + SS + S + S - [2] = S +

8 Precedence agram omputaton S ctvty I LS T L ackward Pass omputatons Termnal Tme LS - S [3] L = Mn. all L - LS - SS + L - S + [4] LS = L

9 Precedence agrammng alculatons XMPL or the gven precedence dagram, complete the forward and backward pass calculatons. ssume the proect starts at T=, and no splttng on actvtes s allowed. lso assume that the proect latest allowable completon tme (proect duraton) s scheduled for 3 workng days. evelop system spec. (=) SS 3 4 Wrte comp. program (=12) S SS Test & debug program (=) S 12 ecument program (=12) ollect system data (=4) S Run program (=)

10 Precedence agrammng alculatons ON dagram evelop system spec. (=) SS 3 4 Wrte comp. program (=12) S SS Test & debug program (=) ollect system data (=4) S 12 S ecument program (=12) Run program (=) N 4

11 Precedence agrammng alculatons xample omputaton ctvty ctvty S S Intal S Max S ( Tme ) S 3 12 Intal 1 SS Tme orward Pass omputatons [1] S [ 2 ] Max ( all S Intal Tme S ) S SS S S ctvty S Max ( ) S Intal SS Tme 3 S SS 3 S 4 SS 4 S 12 S N

12 Precedence agrammng alculatons xample omputaton ctvty ctvty S S Max() S S Intal T S 1 21 me Intal Tme S Max (, ) OR, S 27 orward Pass omputatons [1] S [ 2 ] Max ( all S Intal Tme S ) S SS S S ctvty S Max S ( SS 3 S 4 SS ) S OR, S Intal S 27 Tme S 12 S N

13 Precedence agrammng alculatons xample omputaton L Termnal Tm ctvty LS L ctvty ctvty L LS L LS Mn L Termnal L (, ) L e Tm 3 3 e Termnal LS S OR 24 1 S 3 24 Tm e ackward Pass omputatons [3] L [ 4 ] LS Mn ( all L Termnal Tm e LS S ) L LS SS L S SS 3 S 4 SS S 12 S N 3 3 3

14 Precedence agrammng alculatons xample omputaton ctvty ctvty L LS Termnal LS S Mn ( ) Or LS S L LS L Tm e Termnal Tm e 3 LS S 1 1 L Mn ( ), OR LS SS ackward Pass omputatons [3] L [ 4 ] LS Mn ( all L Termnal Tm e LS S ) L LS SS L S ctvty L Mn ( ) LS LS L 11 3 SS 3 S 4 SS 3 1 Termnal Tm e 3 L SS S 12 S N 3 3 3

15 Precedence agrammng alculatons omputng Slack Tme (loat Tme) arlest arlest Latest Latest On Start nsh Start nsh Slack rtcal ctvty S LS L LS S Path No No 14 1 No No No No

16 xample 2 S ctvty I LS T L Gven the precedence network for a small engneerng proect wth actvty duratons n workng days, t s requred to compute the actvty tmes (S,, LS, and L) and total floats (T) and then ndcate the crtcal actvtes. 3 S 3 I SS 1 1 S 2 ZZ 3,2 J L S 3,4 S 4 SS 4 7 S H K

17 xample 2 alculate the arly actvty tmes (S and ). S ctvty I LS T L S 3 I SS S 2 ZZ 3,2 J L SS 4 22 S 3,4 7 1 S 4 S H K

18 xample 2 alculate the late actvty tmes (LS and L). S ctvty I LS T L S 3 I SS S 2 ZZ 3,2 J L S 3,4 S 4 SS S H K 22 1

19 xample 2 alculate Total loat for an actvty. S ctvty I LS T L S 3 I SS S 2 ZZ 3,2 J L S 3,4 S 4 SS S H K 22 1

20 xample 2 Indcate the crtcal actvtes. S ctvty I LS T L S 3 I SS S 2 ZZ 3,2 J L S 3,4 S 4 SS S H K 22 1

21 Notes on Schedule HMMOK TIVITY n actvty that extends from one actvty to another, but whch has no estmated duraton of ts own. It s tme-consumng and requres resources, but ts duraton s controlled, not by ts own nature, but by the two actvtes between whch t spans. Its S and LS tmes are determned by the actvty where t begns and ts and L tmes are dctated by the actvty at ts concluson. xamples: ewaterng, Haul road mantenance

22 Notes on Schedule MILSTONS Mlestones are ponts n tme that have been dentfed as beng mportant ntermedate reference ponts durng the accomplshment of the work. Mlestone events can nclude dates mposed by the customer for the fnshng of certan tasks as well as target dates set by the proect manager for the completon of certan segments of the work.

23 Notes on Schedule MILSTONS stnctve geometrc fgure s preferred to represent a mlestone (crcles, ovals, or other shapes) can be used. ny nformaton pertanng to a mlestone and consdered to be useful may be entered.

24 Notes on Schedule Reducng Proect uraton How can you shorten the schedule? Va Reducng scope (or qualty) ddng resources oncurrency (perform tasks n parallel) Substtuton of actvtes