Ihab Saad – Developing the schedule

Hello. Today, we're going to learn about building the schedule. What

do we mean by building the schedule, and how to break down a

big project into smaller components, along which lines and

how many activities should a project have, and so on and so

forth. So basically, what we're going to discuss is how to

identify the activities in a project, how to determine the

activity durations and the relationships among the activities

and linking them and so on. This is going to be a review of what we

learned before about the different types of relationships and so on.

But we're going to talk primarily about the first task in schedule

development, which is activity definition, how to break down the

project into activities.

So construction planning can be either cost oriented or schedule

oriented. And to give an example on that, the cost oriented is

going to look at the direct costs and the indirect costs. The direct

costs are basically costs involved directly in the construction

operation on site, whereas indirect costs are going to be

costs needed to be spent on the project, but not necessarily

related to any particular activity. So for example, if you

have

a central purchasing department at the headquarters of the company.

This purchasing department is working on all projects or any

scheduling department, or any Central Department, the legal

department, for example, you cannot pinpoint and say they work

that long on this particular project or that project. So it's

going to be a general overhead for the head office, whereas direct

costs are going to be the cost of the people assigned to the

construction site, field engineers, Superintendent, project

manager, etc. When we look at the time aspect of the project, the

schedule oriented idea, we have time oriented, which is going to

be developing the critical path of the project and resource oriented

which is going to be, what kind of resources do we need? When are we

going to need them in what amount, and so on and so forth.

This resource oriented planning is going to be sort of joint between

the schedule oriented planning and the cost oriented planning,

because, again, every resource has its own cost, so we need to

calculate the cost of these resources as well.

Before starting our scheduling effort, we have to read the

specifications and the plans, because, for example, the general

conditions of the contract are going to have an effect on the

selection of the activity and the sequencing of the activities and

the responsibilities and so on and so forth. The staffing of the

project, of course, is going to be also contingent upon, upon these

plans and specs, choosing the appropriate technology, what kind

of technology is going to be available in the project, location

and affordable to the company that's going to be undertaking

that project, identifying and listing activities. How are we

going to break down a huge elephant like the project into

more manageable tasks or activities the size of an ant

compared to that elephant, and then calculating the activity

durations based on the resources that are going to be identified

for each activity and the resource availability, whether it's whether

it's money or materials, equipment, subcontractors, etc,

and labor, identifying the relationships between activities.

So which activity comes first, what's going to be the predecessor

to what, what's going to be a successor to what, which two

activities can be done at the same time, and what kinds of lags and

overlaps, what's what kinds of constraints are going to govern

the relationship between activities? All of that has to be

involved. And then, once we identify the relationships, after

breaking down the project into activities. We have to link these

activities, and once we have linked them, now we're going to

add the durations that we have already calculated to calculate

the activity times and the project duration based on the algorithm of

the critical path that we have already learned about, early

start, early finish, late start, late finish, total and free float,

which are going to be calculated from the forward pass, the

backward pass and determining the critical path of the project.

When we talk about the choice of technology, it's the choices of

appropriate of appropriate technology and methods for

construction which sometimes are often ill structured yet critical

ingredients in the success of the project. So if we do not have a

clear structuring of when are we going to need this piece of

equipment, we might end up acquiring it too early, which is

going to result in additional cost, or too late, which might

result.

In a delay to the project. Same thing applies to the materials. If

there's a shortage of that material, we have to order it in

advance. It might be a long lead item that needs a long time to

manufacture or to get ready for delivery to the construction site.

So we have to plan for the cost of storage and storage conditions and

so on and so forth. Or are we going to the to rely on just in

time delivery to the construction site at the time when the activity

is going to be performed, therefore not needing any storage.

Of course, the danger with just in time planning is that if you need

it right now and it's not delivered right now, that means

that you're going to have a delay. We need to consider the

constraints of the site and the influence of selected technology

on schedule and cost. So again, constraints of the site could be

either logistical constraints like access to the site, for example,

it could be political constraints. It could be other

other constraints that might affect the site. So weather

constraints, for example, maybe there are some activities that

have to be done in a dry environment. So if it rains, we

cannot perform them. The tower train should not be working when

the wind speed exceeds a certain speed, and things like that. So

we're going to look at the meteorological reports from

previous years to try to identify what are the constraints that are

going to be imposed on our construction activities,

to identify the list activities. Activities represent the necessary

framework to permit scheduling, along with estimating the

resources required by the individual activities. So we

again, that's why we need to have clear distinction. What is this

activity, what amount of work is going to be associated with that

activity? What kind of resources are going to be needed in what

amount and what's the cost of these resources, what's the

production rate of these resources? All of these details

are got to be required for each activity that's gone. That's why

we might end up having having something like a an activity form

that shows the name of the activity, its location, who's

responsible for it, what kind of resources are going to be

involved? What are the rates of application, or rates or for

performance of these resources? And that leads, at the end to the

duration of the activity and the cost of the activity.

The set of activities defined for a project should be comprehensive,

but not too refined, because, again, there's a very high

likelihood that we might end up adding activities or consolidating

some other activities. So basically, we're going to think

creatively based on our experience. How did we do it in

the past? And we're gonna develop a set of activities. But again,

have an open mind for the possibility of adding additional

activities if, for example, the activity duration exceeds, let's

say, a couple of weeks, maybe we need to break it down into two. Or

if the duration of the activity is less than one day. Maybe we need

to consolidate it with another activity to be more meaningful.

Construction plans can easily range between less than 100

activities to several 1000 defined tasks. And again, we are usually

going to start with a very summarized schedule, or collapsed

schedule, that's going to have the main milestones. When do I need to

start work, the notice to proceed. When do I need to finish the

underground work? When do I need to finish the skeleton, the

topping off of a steel structure, or the completion of the concrete

structure, for example? When do I need to have enclosed the building

to start the dry work inside the building and so on and so forth?

When is going to be my substantial completion? When it's going to be

my final completion? So we are identifying major milestones in

the project, and that's going to be my main initial schedule. And

then I'm going to fill in the blanks, so this is like a

skeleton, and then I'm going to add the flesh and the skin and all

the other details to that schedule.

Typically, each design element in the plant facility will have one

or more associated project activities. So the foundations are

going to have probably more than one activity. The walls are going

to have more than one activity. The HVAC AC system is going to

have more than one activity, and so on and so forth. Those

activities will involve different resources, or those activities

that do not require continuous the two types, two major types here,

activities that involve different resources, like any production

activity, for example, or any procurement activity, and those

activities that do not require any continuous performance, like

submittals, one of the activities is to submit a sample to the

Arctic engineer for review and approval or reviews. We're going

to have a review of a certain document, or we're going to have

an inspection.

Or something like that.

Building Element Classification can be used as a guidance to list

group major building activities. So we're going to have

foundations, superstructure, mechanical system, electrical

system, etc. These could be major classifications under which I'm

going to break them down into smaller entities until I reach the

level of activities. So here, for example, is one of the formats.

It's called the Uniformat, and it's sometimes used in estimating

and embedding as well as in scheduling. So here, for example,

we have the structure, the substructure, the shell interiors,

services, etc, and each one of them shows

little bit more level of detail. So the substructure is going to

have foundations and basement construction. It could also

include any infrastructure, utilities, pipes, cables, etc. And

then we can break it down even further into standard Foundation,

special foundations, slab on grade, basement excavation,

basement walls and so on. Each one of these can be further broken

down so standard foundations we're going to have basically maybe form

work, rebar,

concrete, and then back filling and

beams connecting these different foundations, or pile caps for

piles and things like that. All of these are going to be different

details for each one of these activities.

Another method, which most of you are probably more familiar with is

the master format. The Master format used to be known as 16

divisions in the past, that is what most contractors are familiar

with. And then the construction specifications Institute, or the

CSI, which is the body that developed both the Uniformat and

the master format, came up with a newer format in 2004

instead of the 16 divisions. Now it's anywhere between 48 and 49

divisions. So they broke down these divisions into more details,

and there are some divisions that are still blank, reserved for

further addition, like 3637 3839

there is nothing in there, but something can be added in the

future to this set of specification,

our vehicle to convert the big project into the major tasks until

we reach the level of details, is called the work breakdown

structure, or WBS. This is a very important tool to dissect the

project until we reach the level of work packages, which can be

broken down later on into activities. So a project work

breakdown structure is a deliverable or product oriented

grouping of project work elements showing shown in graphical display

to organize and subdivide the total work scope of the project.

So basically, what we're saying here is that the work breakdown

structure is a graphical translation of the scope of work

of the project. It can be used as a planning tool and as a control

tool as well, to make sure that we did not skip anything or forget

anything in our planning for the project. It is not an activity

listing. It stops one step short, or maybe two steps short of

activity listing. So we stop at what's called a work package,

which later on, can be broken down into activities. And it usually

follows what's called the 15555,

model, which means each entity is going to be broken down into five

sub entities, and each one of these five, in turn, is going to

be broken down in five. And which one of these is going to be broken

down in five until we reach a comfortable level of detail.

Again, it's not yet the activity level of detail one step higher,

which we call the work package.

So the decomposition of the total project work identifies the

deliverables and the related work, and it follows a structure and

organization, which is the WBS decomposes the dub the upper WBS

levels into lower level, detailed components. One becomes five,

developing and assigning identification codes to the WBS

components because we're going to use these for scheduling later on,

or with some modification, we can use them as cost accounts for our

cost accounting for the project. In this case, instead of being

called WBS, it's going to be called CBS, or the cost breakdown

structure similar to that as well. If you can imagine something like

an organization chart that shows at the top the president of the

CEO and the vice presidents, and then the directors and going going

down until you reach the field personnel. This is called an

organizational breakdown structure, or OBS. So these three,

the WBS, the CBS and the OBS.

Us break down one big idea into smaller levels that are even more

manageable and controllable, verifying that the degree of the

composition is

necessary and sufficient. So again, this is a tool for review

and for control, to make sure that everything in the scope of work

has been adequately covered in that work breakdown structure.

The work breakdown structure includes 100% of the work defined

by the project scope and captures all deliverables. It focuses on

deliverables, not activities, as we just mentioned, that's why it

stops at a work package activities can be created based on these work

packages or based on these deliverables.

To show you the flow of that work breakdown structure, we started

with level one house. That's the project that I want to build. I

broke down that house into a following layer. Again, we call it

15555,

but that's not carved in stone. It could be 14736,

and so on, but it's not going to be 120,

100 so it's going to be a gradual transition from one level to

another layer to a third layer, etc. So we have here the site

preparation, footings and foundations, land design, etc.

Framing the footings and foundations going to include

framing, roofing, utilities, etc. So again, you can break down each

one of these levels into further details until we reach a work

package level.

Now we can see here, for example, coding system,

Acme motors expansion. The name is am Acme motors, and then the

automated system is am 01 conveyor system, am 02 office building, am

03 and then you can break that down, design on engineering of the

office building. So it's going to be am o3 1am, o3 four, and so on.

Each one of these can be broken down, so it's going to be am 03401

and so on.

That's another example of how a work breakdown structure is going

to look like.

And we're going to finish here at the end, at the work tasks, which

can be broken down into activities that usually do not show on the

work breakdown structure.

Now from these works, work packages, we're going to break

that them down into activities. And each activity is going to be

represented by a verb and a noun,

installed carpet, paint wall, place or pour concrete and so on.

So there are three typical types of activities, either a

procurement activity, which is purchasing or contracting to get

steel or to get mechanical equipment or to get elevators or

electrical supplies or concrete production, which is the heart of

the construction schedule, placing that concrete and management so

the required submittals, owner or engineer approval, testing and

delays, which are not production or procurement activities, but

they still form major milestones and flags and constraints in the

project, therefore, we need to reflect them on the schedule. We

also have something called milestones, which we mentioned

initially. The project start is a major milestone. The project

completion is a major milestone. The building encloses a milestone.

Substantial completion is a milestone. And so on. These are

zero duration activities. It just shows that this is the separation

between the previous phase and the following phase

flags. We have something called the flag, which is half of a

milestone, start flag or finish flag. So if you look at the

milestone, it can be split to two halves. There's going to be start

Task, start flag, like, for example, the notice to proceed.

Notice to proceed, is going to act as a milestone or as a start flag

for the rest of the project and

completion of submittals. This is going to be a finished flag. There

could be a start flag for the submittals and a completion flag

for the submittals and so on.

Activities should include action related words, as we just said,

words announced, procurement is going to include words like,

fabricate, order, deliver. Production is going to include

install, place, erect, paint, clean, demolish. Management is

going to be submit, approve, Review.

Apply for a payment or for a request for inspection or things

like that.

In addition to descriptions, activities usually have activity

identifications or IDs, as we're going to see in the automated or

the computerized schedule, we're gonna have an activity ID and an

activity description separate from that ID. The IDs can show

locations, trades and work types, etc, etc, if you're if we go back

a couple of slides here, this is an activity ID, am 03, it could

something like that. Basically, this is not an activity, but it

can start. It can be the beginning of an activity. So if we go three

levels below that, it's going to be AM, 0301,

1225,

for example, that could be an activity.

And here's an example, the first four digits are going to be a

serial number for a project and

for example here, this is going to be a

a master format, CSI code, heavyweight, structural concrete.

And then 21 is the placement. And then it could be location

responsibility, and then column number 34 at the end. So each one

of these numbers represents something meaningful, and we're

going to have sort of a dictionary for these activity IDs so that

anyone who doesn't really know can follow the explanation and the

description in that dictionary to understand what this activity

stands for.

Here's another example.

So now that we have broken down the project into activities and

identified each activity, we need to start thinking about the

activity duration. The activity duration one more time is going to

be obtained from our famous equation Q over P. So in practice,

work test duration are determined by one or more of the following

methods. Past experience. Either we have done this activity so many

times in the past, so we can expect how long is it going to

take? Estimates based on Q over P. Order, you have to finish this

activity in five days, or something like that, or use of

predictive models. If we do this activity this way, it's going to

take that many days. If we do it that way, it's going to take that

many days again. It's based on both past experience and

estimates,

and the activity duration can either be deterministic or

probabilistic. Deterministic, which means there's only one

duration for the activity obtained again from the equation Q over p,

but probabilistic is there is some probability that we're not going

to finish in that duration based on the conditions, based on the

performance of the resources based on the availability of resources.

So if we're looking at historical data, we may say we've done this

activity 100 times in the past. 20% of the time it took extremely

long. It took 10 days. 20% of the time it was really done in short

time. It took only four days, but most of the time, in 80% or in 60%

of the previous 100 times that we've done this activity, it took

seven days. So now we have three different durations for the

activity, four, which is the shortest, 10, which is the

longest, and six or seven, which is the most repetitive from past

experience. Which one are we gonna use to schedule the project? Now

remember, this applies to every activity. If you have just 200

activities in the schedule, and you keep adding these different

probabilities, you're gonna end up with the lowest estimate, which is

two months, and the longest estimate, which is 18 months. You

definitely cannot go to the owner and say, Mr. Or Mrs. Owner, we're

gonna finish your project in two months, or maybe in 18 that

definitely is not gonna work. Therefore, we need to factor all

of these probabilities to come up with something meaningful with a

certain level of certainty. And this is basically what we're gonna

discuss in a future lecture called probabilistic scheduling. And

we're going to learn about the technique that we can apply to get

one duration out of these three different durations for each

activity

with the deterministic task duration, the activity may have a

fixed duration or a resource entity is to be captured for a

specific time. So I'm gonna have this excavator available for only

three days. Therefore I need to use it for a certain number of

hours each day to finish that task. I have a fixed amount of

work, and I know the production per hour. So how many hours per

day? How many days? That's how I'm going to estimate.

It the deterministic duration, the activity duration may be subject

to small variations about the specific mean value, so that from

any useful time scale, the work test duration is constant. The

duration, again, is equal to quantity divided by production

rate, Q over P that we have discussed so many times, so fast,

so far. Now when we talk about probabilistic duration

distributions, we're going to talk about this in more details, but

you're going to find that we have something called the mean or the

most likely duration, and we're going to have something called the

optimistic duration, which is the shortest possible, and the

pessimistic duration which is the longest possible. We're going to

see an equation based on statistics. How can we factor all

of these three into one duration for the activity? Basically,

basically converting determine probabilistic into as much

deterministic as possible?

We're going to use something called production table, or

product productivity tables. You can find some of these in the

means book, for example, or in the walker book for estimating. And

definitely, I will always suggest that each company builds its own

production tables, or productivity tables based on its own resources,

whether it subcontractors or equipment or labor or materials,

etc. So the productivity table is going to show you, for example,

that if the masonry unit size is eight inch blocks, with no

conditions, then you can produce up to 400 units per day per Mason.

So knowing what's the total number of units that we need to place, we

can divide it by the number of masons and get the number of days

that's going to be needed and so on. So you can see different

conditions. And if the wall is long, then definitely we're going

to have more production, because you're going to have minimum

interruptions. So we can achieve 430 units per day per Mason. If

the wall is not long, if it's a short wall with corners and a lot

of interruptions and so on, that's going to reduce our production

rate to 370, units per day, per meter. So based on these

productivity tables, we can estimate the duration of the

activity.

This is a quick review of the durations between activity, the

relationships between activities we discussed before the finish to

start, which is the most common relationship, also known as

traditional relationship. And we may add here between the two

activities a positive number that's going to be a lag, or a

negative number that's going to be an overlap. We also have the start

to start relationship where and again, here we can add a lag

between the two activities. It can be with or without lag the finish

to finish. Same thing connects the finishes or the ends of the

activity. It can either have lag or without lag. And the fourth

one, which is the start to finish, as we discussed before, very rare

in its use, and usually it might have either legs or no legs, that

it can go either way

between the activities. Again, we talked about legs and overlap, so

the legs going to be a positive number, whereas the overlap is

going to be a negative number.

So basically, this is a quick introduction about how to build a

schedule. So we're going to see some exercises that we're going to

be working on taking a project, how are we going to break it down

into activities or work packages, and then develop an activity list

based on that, to start our activity list and then add the

sequencing of the activities, add the durations of the activities,

and then calculate our schedule based on the algorithms of the

critical path method. I will see you in the next lecture. You.