# Construction management



## Ambrug20 (Oct 7, 2010)

I am weak solving CMP problems. I can figure out Critical Path, but if the question is more advance, I am lost. Can somebody fine the easiest way to explain an earliest or latest start date. I also came across the problems such

The connection matrix shown represents a road transportation network between 6 locations.

node

1	2	3	4	5	6

node	1 0	1	0	0	1	1

2 1	0	1	0	0	1

3 0	1	0	1	1	0

4 0	0	1	0	1	0

5 1	0	−1	1	0	1

6 1	1	0	0	1	0

The total number of arcs in the network is

0

1

2

3 , where they asked to find arc links with specific direction assigned to it.

Solution: 

An arc is a link with a specific direction assigned to it. From the following graphical representation of the network, there is one arc.

In the connection matrix, a negative number indicates that the direction of travel from one node to another goes against the direction assigned to that arc. The answer is B

i wasn't able to post an arc, but i don't anderstand this problem


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## EnvEngineer (Oct 7, 2010)

I dont recall that the type of problem you are describing being included in the NCEES outline for the exam, and therefore will most likely not be on the exam. Maybe others feel differently

Early start and late finish are how one task is related to other tasks not on the same path. Picture two task taking place at the same time, sanding flooring and sanding window sills, if the flooring required 5 days and the sills only require 2 days but both need to be done prior to the finish work the sills can start later or finish earlier than the sanding of the floors. This allows you to move tasks (start and finish day) w/o changing the overall schedule to better use resources. PS there is also 3 days of float time there for the sill task.


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## pmblair (Oct 7, 2010)

Not sure about the arc lengths and stuff....

I think in the typical CPM problem you need to do a "forward pass" and then a "reverse pass". This will give you all the data needed to complete the CPM. The Cerm does a shitty job of explaining it.

A quick google search of cpm foward pass, and i got this.... http://www.dramatispersonae.org/DesignEcon...ToddHeadon).pdf

looks like a good reference with out really looking at it.


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## Ambrug20 (Oct 7, 2010)

pmblair said:


> Not sure about the arc lengths and stuff....
> I think in the typical CPM problem you need to do a "forward pass" and then a "reverse pass". This will give you all the data needed to complete the CPM. The Cerm does a shitty job of explaining it.
> 
> A quick google search of cpm foward pass, and i got this.... http://www.dramatispersonae.org/DesignEcon...ToddHeadon).pdf
> ...


thank you to all of you, sometimes the easiest task looks harder than we think :bann:


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## pmblair (Oct 7, 2010)

The Cerm does a bad job of explaining it. As my senior Russian Female Co-worker, pre democracy says, "that guy dont know that that well".



Lindberg doesn't know CPM's that well.


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## chess5329 (Oct 7, 2010)

pmblair said:


> The Cerm does a bad job of explaining it. As my senior Russian Female Co-worker, pre democracy says, "that guy dont know that that well".
> 
> 
> Lindberg doesn't know CPM's that well.


Hi pmblair,

Is there too much to ask if you can include in your previous example how to calculate FF and TF?.......... for those (including me) who still having doubts with this staff!

Thanks


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## pmblair (Oct 7, 2010)

TF is the amount of time an activity can be delayed before it delays the Whole Project... FF is the amount of time an activity can be delayed before it delays start of next activity.

I seen some really good examples in the civil engineering handbook.

NCEES has a really good example in the afternoon construction depth just make sure you look at the errata for the corrected answer. http://www.ncees.org/Documents/Public/pe_civil_errata.pdf

Its on page 3 #508.

The errata added those 1's for A and B because they should 0's. But whatever it can be 1. I start mine at 0.

So start at a A and do a forward pass all the way to G and H filling in all your ES and EF, early start and early finish.

Basically its 0 or 1 + number of days for the activity, duration. When one item like F has 2 precedents, like B and F you use the larger EF, this is your critical path. G has 2 precedents and D is the critical path. C to D is a Finish to Finish and has a 3 day lag. So when you do a lag you add the 3 days to USUALLY the ES but since it is finish to finish you add to EF and then since it is finish to finish subtract the duration to get your ES.

Once you get down to end G and H you use the largest EF as your Lf and then go backwards doing a reverse pass filling in all the LS and LF late start and Late finish.

Total Float is LF -EF

Free Float is ES-EF

I hope that all made sense i been drinking wine ;0 B)


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## chess5329 (Oct 7, 2010)

pmblair said:


> TF is the amount of time an activity can be delayed before it delays the Whole Project... FF is the amount of time an activity can be delayed before it delays start of next activity.
> I seen some really good examples in the civil engineering handbook.
> 
> NCEES has a really good example in the afternoon construction depth just make sure you look at the errata for the corrected answer. http://www.ncees.org/Documents/Public/pe_civil_errata.pdf
> ...


Well......this is what I got from your previous example.

CPM= Start-1-5-6-7-9-Finish

Act 1: TF=0 ; FF=8

Act 2: TF=6 : FF=21

Act 3: TF=3 : FF=16

Act 4: TF=2 : FF=4

Act 5: TF=0 : FF=1

Act 6: TF=0 : FF=8

Act 7: TF=0 : FF=16

Act 8: TF=3 : FF=17

Act 9: TF=0 : FF=2

I used formulas TF=LF-EF and FF= ESa-EFb.

I'm not drinking wine, but I had a long day at work...........so, this is for anybody that want to help, correct me if I did something wrong!

Thanks


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## pmblair (Oct 8, 2010)

I didnt work that one in the ..........http://www.dramatispersonae.org/DesignEconomics/cpmNotes(ToddHeadon).pdf.

But in the NCEES example..

ES,EF,FF,TF,LF,LS

A)0,3,0,0,3,0

B)0,4,1,1,5,1

C)3,5,0,0,5,3

D)6,8,0,2,0,8

E)5,6,2,4,10,9

F)5,9,0,0,9,5

G)8,10,2,2,12,10

H)9,12,0,0,12,9

Hope it helps.


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## chess5329 (Oct 8, 2010)

pmblair said:


> I didnt work that one in the ..........http://www.dramatispersonae.org/DesignEconomics/cpmNotes(ToddHeadon).pdf.
> But in the NCEES example..
> 
> ES,EF,FF,TF,LF,LS
> ...


It looks really well, now I know wwhat I did wrong in my previous post........sorry for that mistake.......like I said it was a long day!!!!!!!

m,


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## humner (Oct 9, 2010)

no, the long day will be on October 29th just before 5 pm, then you are going to wonder where the day went!


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