COURSE: INDUSTRIAL ENGINEERING LESSON: CRASHING
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CRASHING OR TIME COST Main aim of crashing is to minimise cost. It is an extension of critical path model that considers the compromise between the time required to complete an activity and cost associated for its completion. The aim is always to strike a balance between the cost and time and to obtain an optimum project schedule. The total cost of any project consist of direct and indirect cost involved for its execution Crash Psint So s Crash time is the minimum activity duration to which an activity can be compressed by increasing the resources and hence by increasing direct cost. prox Nosmel Point Cost The slope of line gives the increasing in direct per unit time for crashing the activity Actun This is called cost slope Tn Dssation
CRASHING OR TIME COST The point where total cost is minimum correspond to time known as optimum project duration (To) and the cost optimum cost (Co).The objective of crashing a network is to determine the optimum project duration and optimum cost. Steps for crashing are I. Select the critical activity that has got the least cost slope 2. Reduce the duration of this activity in time units. Revise the network by adjusting time and cost of the crashed activity and again calculate critical path If the optimum project duration is achieved then stop, otherwise go back to step 1. 3. 4.
QUESTION The analysis of a network in relation to time and cost are given below. Crash the network and find the optimum cost when indirect cost is Rs 900 per day Jobs Normal Crash AC/AT Time (days) Cost (Rs) Time (Days) Cost (Rs) I-2 1-3 500 750 1400 1000 1150 800 1000 1500 2600 1800 1450 800 2400 500 750 600 400 300 2-4 2-5 7 4-5 700
SOLUTION Te 7-5 2. 5 1 6 2. 3 L-12 Total Costs) D. c.t1DC.
SOLUTION Nous, C-sasin the minimiun cost 3lape ac tvitonieat Past Hexe i fs activita 2-4 Crashing tt by 2 day 1 TLo2 L-6 2
SOLUTION Foom (2.5) o(S), (12) o (4,5) because the pat, hes to 3o ram ome of Seleet s pisn because cost is uem. by lay each TEsa oplion s best.
SOLUTION Ophn Soe 9 lo 12
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