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Cive 421 > lecture21 > Flashcards

lecture21 Flashcards

1
Q

What we are after this lecture is when do we leave home and when to arrive to campus

A

We follow early path (early rising people)
Or
we follow just on time

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2
Q

We call those early start for the activity (earliest it can start earliest it can finish)
or
late finish activity

A

What drive late finsih is the successor.
For example what drives your walking to the campus to reach class, is the time of class.TO be just on time on class u just see when class will starts and u finish walking at just when class start so u will be there at time
SO ur current activity will finish just when ur next successor will start

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3
Q

Also if we take the project example, like the project takes 8 hours and u need to deliver at 8 am, so u start working on it at 12 am so u will be just on time

A

on the other hand early path , u start working on it before a day and get it done before and relax

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4
Q

The early path method have a leeway (float ) , meaning if i face something I will still have time to solve it

A

TRUE

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5
Q

What determines the early starts is finishing the predecssors (the prerequisetes) and the duration of the activity itself

A

true

What on the other hand determines late finish is when ur next successor will start

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6
Q

Consider the example in the slides ( you have eleven activities)
Activity K has 2 predessecors ( B and F)
Activity H and G have ( E and B)

A

The dotted lines just serve to show dependencies (What is the prerequisite of what)

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7
Q

How do we determine a schedule for this project

A

1st point;
We set a starting point ( you can start with day zero or day one , it will not matter; but u need to remember what day u started with so u wont mix)

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8
Q

Let us u started working in the morning of day one

A

What are the starting activities

A, B , and C (they dont have prerequisites)

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9
Q

What is the soonest activity A can finish

A

Morning of day 4 (night day of 3)

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10
Q

B finishes morning of day 3

A

true

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11
Q

C fiinishes morning of day 2

A

True

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12
Q

To do the schedule agree on starting point (Day 0 or Day 1)

Second we ddo forward path (u start from the starting point and u walk through the network)

A

Now we reached D;
D needs 4 days ;
When is it the soonest D can start ( D can start as soon as A finishes) So if A finishes at 4th day morning and D star ts, D will finish at morning of Day 8.
Same for E , starts when A is done

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13
Q

Similarly C and F

A

true

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14
Q

What about K

A

K can starts as soon as both B and F are done, which is the duration of the largest of them

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15
Q

The formula of the forward path for early start for an activitiy is

A

the early start of an activity is the maximum early finish of all of the predesscessor like in K above

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16
Q

Early finish=early start plus duration

A

true

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17
Q

For G 13

For H 11

A

true

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18
Q

For M 15

A

true

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19
Q

This is called forward path method

A

true

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20
Q

U can deduce project duration

A

14 days (U will finish at 15 but it take 14 days)

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21
Q

Second thing u can infer

A

U can infer the critical path which will drive the schedule
M, G , E , A
To get it exact u need to do the backword path

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22
Q

The forward path method is early start early finish

A

true

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23
Q

The backward path

A

We start from day finish and we walk backward

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24
Q

In backward path method

A

u say I took the forward path method and It took 14 days (finish at morning of day 15)
Morning of day 15 is soonest when I can finsih the project .
If he say 20 days in the given then u will start from day 20; else u use the forward path method to find the finishing day

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25
Q

Now u walk back from day finish

A 
Equation that governs , minimum
U start ending activities at 15 (anyone that doesnot have a successorL, K and M)
M 15-2=13
K 15-3 =12 
H Minimum of 13 and 14; 13-3=10
D has one successor L
14-4=10
We backword
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26
Q

Those activities were early start, late start, early finish and late finish are the same arer called critical

A

they cannot be delayed (Any delay will result in whole schedule delay)

27
Q

Rule of thumbs

A

U do forward path and backward path ,, u compute the float (amount of freedom on activities)
For example activity K can be delayed by 7 days without any delay in cshedule
U can do the that by make the difference delta
U must have the same difference delta whether in backward or o forward, else u did a mistake

28
Q

Rule of thumb

A

In both forward oath and backward u have to come back to where u started (If u started from 15 backward u must come back to day 1

29
Q

Activity F also have 7 days of float

A

true

30
Q

Also C have 7 days

A

true

31
Q

C, F, and K floats are dependednt

A

meaning If C get delayed by 4 , K can only get delayed by 3.
Then we say the entire path has 7 days of float
7 is total float

32
Q

How we determine delta

A

we lookk at difference late finish , early finish;

or late start , early start

33
Q

Floats are important to account for uncertainties (delays)

A

true

float help us absorb uncertainties

34
Q

Let us say say we look at path C,F, and K Which share a float of 7 days

A

Assume I have subcontractor C, subcontractor F , and subcontractor K.
I need to know how many days each subcontractor will get

35
Q

I can give them proportional flee days according to their duration

A

C 1 day
F 3 days
K 3 days

36
Q

I can give them also according to the uncertainties in their activities

A

Like if C more uncertain than F , I will put float to it.

Like procurement is more uncertain that pouring concrete.

37
Q

There is another type of float that is important, it is called free float

A

number of I can be delayed by without delaying any of the next activities (Not my entire projectbut any of my activities)

38
Q

To compute free float

A

Minimum early start of my successors minus my early finish

39
Q

Let us look at activity B for example

A

How many successors do I have : G, H and K

The minimum early start (8,8, 5) is 5 minus early finish (3) is 2 days

40
Q

Meaning B can take 2 more delays , if more than 2 days K will run into trouble (Not necessary the project)

A

true

It will delay the project if it is large enough to delay more than it is float

41
Q

Activity C has zero free float

A

true (2-2)

42
Q

by definisition activities with one predessecer has free float of zero

A

true

43
Q

Free float is always less than total float

A

true

44
Q

total float is the total time I have with delaying the entire project (I computed by difference between early start early finish, or late start late finish)

A

For k 7

for B 5

45
Q

Free float I am only looking at my successors (I dont want to delay them)

A

true

46
Q

for final activities free float = total float

A

no successors

true

47
Q

What happens when B uses all the days of free float

Like B delayed by 5 days (finishes morning of day 8

A

K will start late (morning of day 8), Now K wil have 4 daysof float
C and F are not affected (they will still share 7 days of float) but they are not sharing it with K

48
Q

B became critical

A

true

49
Q

How develop S curve

A

X-axis time

Y-axis let us say expenditures and income (clients payment)

50
Q

It just happened retainage is equal to profit

A

expenditure S curve (because expenditures low at begining then a lot of expenditures then low at the end )

51
Q

the way we drive S curve is the following

A 
we look at the schedule
Identify resources ( u do ot for labor , material ,equipment )
Day 1 then u look at resources (
how many days 14
which activities are taking place during first place A, B and C
second day A, B and F
3rd
A , F
4th
D,E,f
5ht
D,gK
6th
DEk
52
Q

Now what are the resources needed for the activities on daily basis

A 
like activity A 2 worker
B 1 worker
C 3 workers
D 4 worker
F 5
53
Q

Day 1 I have A , B and C

A

Implies I willl 6 worker
Second day 8 workers
3rd 7..
This is called resource tables

54
Q

Rule of thumb take any activity

A

it must show in the table as it shows in the duration;
like A rake 3 days implies it must show 3 times
Also they must be connected (they must show after each other because A is connected)

55
Q

last rule of thumb

If i add all the resources

A

total resources= mutiplication of the two columns

56
Q

If I create cumulative curve of all resource I will get the S curve

A

true

57
Q

Resource histogram

A

like number of workers needed over time
it will always be bell shaped
(need less at start and end)

58
Q

the peak is when u need them most

A

true

59
Q

curve will start when worker need

A

true

60
Q

I use to float sometimes to reduce peak in order to make them more near each other because of worker demand

A

true

this is called resource leveling

61
Q

If i generate S curve with late start

A

it will shift to the right

62
Q

When activity sip (delay)

A

S curve will lose slope

63
Q

For exam

A

redo exercises plus video
CDM schedule examples google
Bring different colors pen

Cive 421 (22 decks)

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