4(d) Network Analysis

8/3/2019 4(d) Network Analysis

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NETWORKNETWORK

ANALYSISANALYSIS


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ProjectProject

A project is a series of activities directed to accomplishment of a desired objective.

Plan your work first..then work your plan


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Network analysis

Introduction

Network analysis is the ge ner al nam e give n to cert ain sp ec ific tech niqu es wh ich can b e used for the planning, manag e me nt an d co ntro l of p roject s.

One de fini t ion of a p roject:

A project is a temporary endeavour undertaken to create a "unique" product or service


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NETWORK Network: A network constitutes the heart of such a planning, scheduling and

monitoring system structurally; anetwork is a graphical model depicting the interrelationship between the various

elements of the Project Work System.

A network propagates the holistic

approach work together.


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V arious Types Activities Time Duration

of Network

CPM Network Deterministic Deterministic

PERT Network Deterministic Probabilistic Decision Network Probabilistic Deterministic

GERT Network Probabilistic Probabilistic

Ongoing Scheduling & Monitoring, Project Diary, Feedback information, Multi Level scheduling & Monitoring.


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Histor yHistor yDe ve loped in 1950sCPM by Du Pont for che mical plan t s

PERT by U.S. Navy f or Pola ris missil e

PERT was de ve loped by the US Navy for the planning an d co ntro l of

the Pola ris missil e pro gram an d the e mp hasis was on compl et ing thepro gram in the shorte st possibl e t ime . In a dd it ion PERT had theabili t y to co pe w ith un cert ain a ct ivit y compl et ion t ime s (e .g. f or apa rt icula r act ivit y the most like ly compl et ion t im e is 4 week s bu t itco uld be any where betwee n 3 week s an d 8 week s).

CPM was de ve loped by Du Pont an d the e mp hasis was on thetr ade-o ff b etwee n the co st o f the project an d it s over allco mpl et ion t im e (e .g. f or cert ain a ct ivit ie s it may b e possibl eto decre as e the ir co mpl et ion t ime s by sp e nding m ore mone y -how doe s th is aff ect the o ver all co mpl et ion t ime o f theproject? )


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CPM CPM -- Crit ical Pa th MethodCrit ical Pa th Method

De fini t ion: In CPM act ivit ie s a re show n as a n etwork ofprecede nce re la t ionships using a ct ivit y-on-node network co ns tr uct ion

Single e st ima te of a ct ivit y t ime Deter minis t ic act ivit y t ime s

USED IN : Prod uct ion manag e me nt - for the jo bs ofre pet it ive in na t ure where the act ivit y t ime e st ima te s canbe pred icted with co nsi der abl e cert ain t y due to the ex iste nce of pas t ex per ie nce .


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PERTPERT --

Project Evalua t ion & R e view Tech niqu e sProject Evalua t ion & R e view Tech niqu e s

De fini t ion: In PERT act ivit ie s a re show n as a n etwork ofprecede nce re la t ionships using a ct ivit y-on-arrow network co ns tr uct ion

Mult ipl e t ime e st ima te s Pro babilis t ic act ivit y t ime s

USED IN : P roject management - for non-re pet it ive jo bs(re se arch an d de ve lopm e nt work ), where the t ime an d co st e st ima te s te nd to be qui te un cert ain. T his tech niqu e use spro babilis t ic t ime e st ima te s.


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Originated by H.L.Gantt in 1918

Gan tt ch a rt

Advan t ag e s- Gan tt ch art s a re qui te co mm only us ed .The y p ro vide an e asy g rap hicalre pre se nt a t ion of whe n a ct ivit ie s (mig ht )t ake pla ce .

Limit a t ions

- Do not cle arly in dica te det ails re ga rd ingthe pro gre ss of a ct ivit ie s

- Do not give a cle ar indica t ion ofinterre la t ion s hip b etwee n the se pa ra te act ivit ie s


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CPM/P ERTCPM/P ERT

The se de ficie ncie s can b e e limina ted to a la rge exte nt byshow ing the interde pe nde nce of va rious a ct ivit ie s by m e ans ofco nn ect ing a rrow s call ed network tech niqu e .

Overt ime CPM an d PERT bec am e one tech niqu e

ADVANTAGES:

Precede nce re la t ionships la rge project s more e ffi cie nt


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The Project NetworkThe Project Network

Use of n ode s an d arrow s

Arrow s An a rrow le ads f ro m t ail to he ad d irect ionally Ind ica te ACTIVITY,a t ime co nsuming e ffort th a t is re qui red to per for m a pa rt of the work .

Node s A node is re pre sented by a c irc le- Ind ica te EVENT, a p oin t in t ime where one or more act ivit ie s s t a rt

an d/or finis h .


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Act ivit y on Node & Act ivit y on ArrowAct ivit y on Node & Act ivit y on Arrow

Act ivit y on Node

- A co mpl et ion of an a ct ivit yis re pre se nted by a n ode

Act ivit y on Arrow

- An a rrow re pre se nt s a t as k,wh ile a n ode is the co mpl et ion of a t as k

- Arrow s re pre se nt order ofe ve nt s


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Act ivit y Sla ckAct ivit y Sla ck

Each e ve nt has two imp ort an t t ime s ass oc ia ted with it :- Earlie st t ime , T e , wh ich is a cal e ndar t ime whe n a e ve nt can

occ ur whe n all the predece ssor e ve nt s co mpl eted a t the e arlie st

possibl e t ime s- Late st t ime , TL , wh ich is the la te st t ime the e ve nt can occ ur with

out de laying the subs e qu e nt e ve nt s an d co mpl et ion of p roject .

Differe nce betwee n the la te st t ime an d the e arlie st t ime of an e ve nt is the sla ck t ime for th a t e ve nt

Posit ive sla ck : Slack is the am oun t of t ime an e ve nt can b e de lay ed witho ut de laying the project co mpl et ion


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Crit ical Pa thCrit ical Pa th

Is th a t the se qu e nce of a ct ivit ie s an d e ve nt s where there is n o sla ck i. e .. Zero sla ck

Longe st pa th thro ugh a n etworkminimum p roject co mpl et ion t ime


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Be ne fit s of CPM/P ERTBe ne fit s of CPM/P ERT

Use ful a t many s t ag e s of p roject manag e me ntMathe ma t ically simpl e

Give cr it ical pa th an d sla ck t imePro vide project doc um e nt a t ionUse ful in m onitor ing co st s


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Q ue st ions Ans wered by C PM & PERTQ ue st ions Ans wered by C PM & PERT

Compl et ion date?On Sched ule?With in Budget?Crit ical Act ivit ie s?How can the project be finis hed e arly a t the le as t co st?


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ex ampl eex ampl e

Illus tr a t ion of n etwork analysis of a min or rede sign of a p rod uct an d it s ass oc ia ted pa ckaging.

The key question is: How long will it take to complete this project ?


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For c la r it y, th is lis t is ke pt to a minimum by sp ec ifying onlyimm ed ia te re la t ionships, th a t is re la t ionships inv olving a ct ivit ie s

th a t "occ ur ne a r to e ach other in t im e ".


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"Wha t act ivit ie s mus t be finis hed be fore th is a ct ivit y can s t a rt "

co uld we co mpl ete th is p roject in 30 week s?

co uld we co mpl ete th is p roject in 2 week s?

One ans wer co uld be , if we first do act ivit y 1, the n a ct ivit y 2, the n a ct ivit y 3,...., the n a ct ivit y 10, the n a ct ivit y 11 an d the project wo uld the n t ake the sumof the act ivit y co mpl et ion t im e s, 30 week s.

What is the minimum possible time in which we can complete this project ?

Be fore st a rt ing any of the ab ove act ivit y, the qu e st ionsas ked would be


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We shall s ee be low how the network analysis d iag ram / pict ure we co ns tr uct he lps us to ans wer th is qu e st ion.


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CRITICALPATH TAKES24 WEEKS FOR THE COMPLETION OF THE PROJECT


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Limit a t ions to CPM/P ERTLimit a t ions to CPM/P ERT

Cle arly de fin ed , in de pe nde nt an d st abl e act ivit ie sSpec ified precede nce re la t ionships

Over emp hasis on cr it ical pa th s


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PERT PERT (P

rojectEv

aluation &(P

rojectEv

aluation &R e v iew T echnique)R e v iew T echnique)


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11.. AA projectp roject consistsconsists of of 99 acti v itiesacti v ities whosewhosep recedencep recedence relationshi p srelationshi p s andand theirtheir estimatesestimates areare

shownshown asas followsfollows: :ACT IVITY T ime E stimates

Op timistic (a) Most L ikely (m) P essimistic (b)

1 -2 3 6 15

1 -6 2 5 142-3 6 12 302- 4 2 5 83- 5 5 11 17

4 -5 3 6 156- 7 3 9 2 75 -8 1 4 257 -8 4 1 9 22


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Exercise

Exercise

a) Find the duration and v ariance of each acti v ity .

b) D raw the p roject network .c) Find the critical path and

corres ponding e x pected p rojectcom p letion time .

d) What is the p robability of com p leting the p roject on orbefore 3 5 months?


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22 .. AA projectp roject consistsconsists of of 99 acti v itiesacti v ities whosewhose p recedencep recedencerelationshi p srelationshi p s andand theirtheir timetime estimatesestimates areare shownshown asas followfollow

ACT

IVITY Immediate

p redecessor(s)T ime E stimates

Op timistic (a) Most L ikely(m)

P essimistic (b)

A - 4 6 8B - 2 3 4

C - 5 5 5D A 8 10 1 2E A 4 5 6F B, E 5 6 7

GC

5 8 11H C 6 8 1 0I D 7 7 1 3J F, G 8 1 0 1 2K H 2 3 4L K 4 5 6


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Exercise

Exercise

a) Find the duration and v ariance of each acti v ity .

b) D raw the p roject network .c) Find the critical path and

corres ponding e x pected p rojectcom p letion time .

d) What is the p robability of com p leting the p roject on orbefore 30 weeks?


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GERTGERTGERT A proced ure for the for mula t ion an d e valua t ion of sys te ms using

a n etwork app ro ach . Pro bl e m s olving with the GERT (grap hicale valua t ion an d re view tech niqu e ) p roced ure ut iliz e s the followingste ps :

1. C onvert a quali t at ive de scr ip t ion of a sys te m or pro ble m to age ner aliz ed network simila r to the cr it ical pa th methodP ERT t ype

of n etwork .2. C ollect the d at a n ece ssa ry to de scr ibe the fun ct ions as cr ibed to the

bran che s of a n etwork .3. C ombin e the bran ch fun ct ions ( the network co mp onent s) in to an

e quival e nt fun ct ion or fun ct ions wh ich de scr ibe the network .

4. C onvert the e quival ent fun ct ion or fun ct ions in to per forman ceme asu re s for st udying the syste m or solving the pro ble m f or wh ichthe network w as cre ated . T he se mig ht include e ither the aver ag eor va rian ce o f the t ime or co st to co mpl ete the network .

5. Make inf ere nce s bas ed o n the per forman ce me asu re s de ve loped in

ste p 4.


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Both analy t ic an d simula t ion app ro ache s hav e bee n us ed to per for mste p 4 of the proced ure . GERTE was de ve loped to analy t ically

e valua te network mode ls of lin e ar syste ms thro ugh an a dap t a t ion ofsignal fl ow- grap h theor y. For nonlin e ar syste ms, inv olving co mpl exlogic an d qu e uing si t ua t ions, Q -GERT was de ve loped . In Q -GERT, asimula t ion of the network is p er for med in order to o bt ain s t at ist icale st ima te s of the per for man ce me asu re s of in tere st .

GERT network s have bee n de sign ed , de ve loped , an d used to analyz ethe following si t ua t ions : c laims p roce ssing in an insu ran ceco mpany, p rod uct ion lin e s, quali t y co ntro l in manufa ct uringsyste ms, ass e ssm e nt o f jo b p er for man ce ai ds, bu rgla ry re sis t an ce o fbuil dings, capa cit y of ai r ter minal cargo fa cilit ie s, judicial co urtsyste m oper a t ion, e quipm e nt all oc at ion in co ns tr uct ion planning,

re fue ling of mili t a ry ai rlif t force s, planning an d co ntro l ofma rket ing re se arch , planning f or co ntr act ne got ia t ions, risk analysisin pip e line co nstr uct ion, e ff ect s of fun ding an d adminis tr at ivestr ate gie s on nu cle ar fusi on p ower plan t de ve lopm e nt , re se arch an dde ve lopm e nt planning, an d syste m re liabili t y.

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4(d) Network Analysis