# Ihab Saad – Line of Balance

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## AI: Transcript ©

30s of that piece of equipment.

The formula for the distance in miles, again, this is from the

construction equipment

class time is equal to number of passes times distance divided by

speed times efficiency. So we have the number of passes for each one

of the activities, whether it's nine passes, six passes, etc, the

distance is going to be the same for all the activities because

we're doing it for the same segment of the highway. Speed has

been obtained from the previous slide, depending on the gear and

efficiency is, how many productive minutes do you get per hour from

that piece of equipment? No piece of equipment is going to work

continuously. 60 minutes an hour. It's going to be probably 50

minutes an hour, or 45 minutes an hour. So the efficiency is going

to be probably 75% 83% something like that.

So distance is going to be in miles, speed in miles per hour.

Resulting time is going to be in hours.

The efficiency factor for an average operator during daylight

hours, we would expect a 50 minute per hour efficiency or a 0.83

which is 50 divided by 60 efficiency factor.

So the time to ditch,

the number of passes is six, distance is four miles, speed is

2.3 miles per hour efficiency factor point eight three. So by

applying the equation, we get the duration for this activity is

going to be 12.6 hours.

To reshape same distance for miles, number of passes I did

increase a little bit, and the speed has also increased. So we do

it in 14 hours. And then for grading, it's going to be done in

only four point point three hours, because it's a lower number of

passes and a higher speed.

So the total duration for this process, if these activities were

done as finished to start back to back, is going to be 12.6 plus 14

hours, plus 4.3 hours.

Now how we know that we don't need to do one activity for all four

miles in order to be able to start the following activities? In this

case, they can start as a start to start with some lag. In this case,

the lag is going to be called our buffer that we talked about. So

the activity slope does not have to be constant, which means the

duration, the progress rate, or the production rate, which in this

case is the speed does not have to be constant.

So it can vary from one segment to another. You can start very slow,

and then build up speed and then slow down again towards the end.

So if we were to produce it graphically through a line of

balance, it's going to be appear something like this. Of course,

the lines are not going to be exactly parallel, because the

production rate, and therefore the speed of the activity, is going to

vary from one activity to another.

The curves in the previous example are usually placed by broken

straight line again, because the speed might not you may slow down

little bit, you may increase your speed a little bit, and so on.

So

if the activity is at one location, which means you're not

moving, you're spending time without moving. Then in this case,

you are it's represented by horizontal line, like here, for

example, again, horizontal line means that there's no there's time

passing with no progress being done.

On the other hand, this is another example three activities,

surveying, underground utilities and foundation. The underground

utilities can be a little bit slower than surveying and the

foundation. So if we do it this way, you're going to have an

interference or a clash, and we cannot accept that. So how are we

going to deal with that?

The buffer is going to be the linear schedule. The linear

schedule uses two types of buffers, the time buffer and the

location or space buffer. Time buffer is formed by a horizontal

offset from one activity to its follower, the gap between the

activities, what we call the lag, or the delay. Location buffer is

formed by a vertical offset from one activity to is follow.

So this, for example, here is a buffer that's introduced at the

end to make sure that the activity is not clash.

So this is the buffer,

horizontal buffer, or time buffer,

and then another example of a time buffer also.

And then here, this is a vertical buffer.

It shows the difference in location. So this is going to be

at a certain location, this is going to be at another location.

So.

The example. Don't worry about it, because the example at the end is

going to explain all of these things. The productivity rate of

an activity can vary. Therefore the line representing its progress

can be broken. So it's going to proceed at certain speed, chain

speed, accelerate it and then slow it down at the end, which is going

to be represented by a broken line. How are we going to update?

So this is a planning tool. How are we going to make it a control

tool as well? How are we going to update our project schedule,

updates reflecting actual performance information, include

time of occurrence, when did it actually happen, amount or

percentage of work completed and changes. In case of changes,

changes for to future work. An updated schedule is a revised

schedule reflecting project information at a given data date.

Same thing, the vertical line, as we did with the Gantt chart, is

going to represent the data date regarding completed activities, in

progress, activities and changes in logic, cost and resources

required and allocated at any activity level.

So the data date also known, if you remember, from updating, also

known as cutoff date as of date status date. All of these are

different names, the date as of which all progress on a project is

reported. It's not the current date or the time. Now this may be

two weeks ago when I made the update for my schedule.

So here, for example, this was the original schedule,

and then I introduced the data date to measure my actual

performance. And this green line for earth moving represented the

planned schedule. The red line, the dark red line, represents the

actual schedule. So this shows the delay in the activities.

In fact,

it shows that the activity the line is milder, therefore the

progress was slower, therefore we have a delay. We were supposed to

be here on this date after four days, but we are only here.

We are at the same point at after five five days, so we are one day

behind scale.

Let's look at an example, and this example, hopefully is going to

make things very clear.

A project consists of five activities. These

five activities are excavating a trench, laying a sub base of

gravel, laying a concrete pipe, back filling after you lay the

pipe and you connect them, of course, and then compacting to

flatten and to level the site so we have length of the pipe, which

is the same, 1000 feet, and then we have production rates that are

shown in the table. To excavate the trench is going to be done at

the pace of 100 linear feet per day. So it's going to take

basically 1000 feet divided by 100 linear feet per day, which is

going to take 10 days laying a sub base of gravel, is going to be

again, 125 linear feet per day. So to this whole activity is going to

take 1000 feet divided by 125

that's going to give eight days laying a concrete pipe, 75 linear

feet per day. We can calculate the duration back filling 200 linear

feet per day much faster. So it's going to take only five days, and

then compacting

150 linear feet per day, so it's going to be about maybe six and a

half days, which can be rounded up to seven days. So from this

production rate, we can basically calculate the durations,

just as we said on the previous slide, 1000 divided by 100 which

is a production date, gives 10 days, eight days, 30.335

6.67 days.

So if we were to plot these activities, how are we going to do

that?

This is the first one showing the speed. So

one segment is going to take that long, or one day is going to take

that amount, and then the following day, and so on. So the

first activity. Here's the first activity, and then I'm going to

introduce a two day buffer between activities, because, as you can

see from the previous from the previous table here,

this activity is faster. Laying a sub base of gravel takes only

eight days. So if I were to proceed at the same speed as the

first activity, we're gonna clash at a certain point. So what I did

is I waited. I calculated this from the end. I drew the graph

first, and based on that, I decided, when am I going to be

able to start the second activity? But I did it from the end. I

looked when is the last

excavation part is going to take place? And then I added two days

from the end, from the back. So if we start on day zero, for example.