Planning Particles -Part 3 (Plan to Execute, Execute to Plan)

3.1 Introduction

?Planning? is? a? general? term that? sets? a? clear? road? map? that? should? be? followed? to? reach? a destination. The term, therefore, has been used at different levels to mean different things. Planning involves the breakdown of the project into definable, measurable, and identifiable tasks/activities, and then establishes the logical interdependences among them. Generally, planning answers three main questions:

?-?? ?What is to be done?

-?? ?How to do it?

-?? ?Who does it?

?In construction, for example, plans may exist at several levels: corporate strategic plans, pre- tender plans, pre-contract plans, short-term construction plans, and long-term construction plans. These plans are different from each other; however, all these plans involve four main steps:

?-?? ?Performing breakdown of work items involved in the project into activities.

-?? ?Identifying the proper sequence by which the activities should be executed.

-?? ?Activities representation.

-?? ?Estimating the resources, time, and cost of individual activities.

?Detailed planning for tendering purposes and the preparation of construction needs to be conducted through brainstorming sessions among the planning team. The inputs and outputs of the planning process are shown in Figure 3.1.

3.2 Project Planning Steps

?The following steps may be used as a guideline, or checklist to develop a project plan:

1.?? Define the scope of work, method statement, and sequence of work.

2.?? Generate the work breakdown structure (WBS) to produce a complete list of activities.

3.?? Develop the organization breakdown structure (OBS) and link it with work breakdown structure o identify responsibilities.

4.?? Determine the relationship between activities.

5.?? Estimate activities time duration, cost expenditure, and resource requirement.

6.?? Develop the project network.

?3.2.1??? Work breakdown structure (WBS)

?The WBS is described as a hierarchical structure which is designed to logically sub-divide all the work-elements of the project into a graphical presentation. The full scope of work for the project is placed at the top of the diagram, and then sub-divided smaller elements of work at each lower level of the breakdown. At the lowest level of the WBS the elements of work is called a work package. A list of project’s activities is developed from the work packages.

?Effective use of the WBS will outline the scope of the project and the responsibility for each work package. There is not necessarily a right or wrong structure because what may be an excellent fit for one discipline may be an awkward burden for another.

?To visualize the WBS, consider Figure 3.2 which shows a house construction project.

As shown in Figure 3.2, level 1 represents the full scope of work for the house. In level 2, the project is sub-divided into its three main trades, and in level 3 each trade is sub-divided to specific work packages.

Figure 3.3 shows another example for more detailed WBS, in which the project WBS is divided into five levels:

Level 1: The entire project.

Level 2: Independent areas.

Level 3: Physically identifiable sections fully contained in a level 2 area, reflect construction strategy.

Level 4: Disciplines set up schedule.

Level 5: Master schedule activities, quantity, duration.

Example 3.1:

?The WBS for a warehouse is as follow:

?Foe more details, another two levels (third and fourth levels) can be added as shown below:

WBS and organizational breakdown structure (OBS)

?The WBS elements at various levels can be related to the contractor’s organizational breakdown structure (OBS), which defines the different responsibility levels and their appropriate reporting needs as shown in Figure 3.5. The figure, also, shows that work packages are tied to the company unified code of accounts. The unified code of accounts allows cataloging, sorting, and summarizing of all information. As such, the activity of installing columns formwork of area 2, for example, which is the responsibility of the general contractor’s formwork foreman, has a unique code that represents all its data.

?WBS coding

?A project code system provides the framework for project planning and control in which each work package in a WBS is given a unique code that is used in project planning and control. The coding system provides a comprehensive checklist of all items of work that can be found in a specific type of construction. Also, it provides uniformity, transfer & comparison of information among projects. An example of this coding system is the MasterFormat (Figure 3.6) which was developed? through? a? joint? effort? of? 8? industry? &? professional? associations? including: Construction ?Specifications ?Institute ?(CSI); ?and ?Construction ?Specifications ?Canada ?(CSC).

Figure ?3.7 ?shows ?an ?example ?of ?the ?coding ?system ?using ?a ?standardize ?system ?as ?the

MasterFormat. The Master format is divided into 16 divisions as follows:

?1)? ?General Requirements.

2)? ?Site work.

3)? ?Concrete.

4)? ?Masonry.

5)? ?Metals.

6)? ?Woods & Plastics.

7)? ?Thermal & Moisture Protection.

8)? ?Doors & Windows.

9)? ?Finishes.

10) Specialties.

11) Equipment

12) Furnishings.

13) Special Construction.

14) Conveying Systems.

15) Mechanical.

16) Electrical.

CSI – Masterformat (Building Construction):

Project activities

?The building block (the smallest unit) of a WBS is the activity, which is a unique unit of the project that has a specified duration. An activity is defined as any function or decision in the project that: consumes time, resources, and cost. Activities are classified to three typs:

?Production activities: activities that involve the use of resources such as labor, equipment, material, or subcontractor. This type of activities can be easily identified by reading the project’s drawings and specifications. Examples are: excavation, formwork, reinforcement, concreting, etc. each production activity can have a certain quantity of work, resource needs, costs, and duration.

?Procurement activities: activities that specify the time for procuring materials or equipment that are needed for a production activity. Examples are: brick procurement, boiler manufacturing and delivery, etc.

?Management? activities:? activities that? are? related? to? management? decisions? such? as approvals, vacations, etc.

?An activity can be as small as “steel fixing of first floor columns” or as large as “construct first floor columns”. This level of details depends on the purpose of preparing the project plan. In the pre construction stages, less detailed activities can be utilized, however, in the construction stages, detailed activities are required. Accordingly, level of details depends on: planning stage, size of the project, complexity of the work, management expertise.

A list of the double-span bridge activities is shown in Table 3.1

3.2.2??? Activities relationships

?In order to identify the relationships among activities, the planning team needs to answer the following questions for each activity in the project:

?-?? ?Which activities must be finished before the current one can start?

-?? ?What activity(ies) may be constructed concurrently with the current one?

Example 3.3:

?

Suppose that a site preparation and concrete slab foundation construction project consists of nine different activities:

A. Site clearing (of brush and minor debris), B. Removal of trees,

C. General excavation, D. Grading general area,

E. Excavation for utility trenches,

F. Placing formwork and reinforcement for concrete, G. Installing sewer lines,

H. Installing other utilities, I. Pouring concrete.

?Activities A (site clearing) and B (tree removal) do not have preceding activities since they depend on none of the other activities. We assume that activities C (general excavation) and D (general grading) are preceded by activity A (site clearing). It might also be the case that the planner wished to delay any excavation until trees were removed, so that B (tree removal) would be a precedent activity to C (general excavation) and D (general grading). Activities E (trench excavation) and F (concrete preparation) cannot begin until the completion of general excavation and grading, since they involve subsequent excavation and trench preparation. Activities G (install lines) and H (install utilities) represent installation in the utility trenches and cannot be attempted until the trenches are prepared, so that activity E (trench excavation) is a preceding activity. We also assume that the utilities should not be installed until grading is completed to avoid equipment conflicts, so activity D (general grading) is also preceding activities G (install sewers) and H (install utilities). Finally, activity I (pour concrete) cannot begin until the sewer line is installed and formwork and reinforcement are ready, so activities F and G are preceding. Other utilities may be routed over the slab foundation, so activity H (install utilities) is not necessarily a preceding activity for activity I (pour concrete). The result of our planning is the immediate precedence shown in Table 3.2.

Types of activities relationships

?Four types of relationships among activities can be defined as described and illustrated below

(Figure 3.12). Typically, relationships are defined from the predecessor to the successor activity.

?a) Finish to start (FS). The successor activity can begin only when the current activity completes.

b) Finish to finish (FF). The finish of the successor activity depends on the finish of the current activity.

c) Start to start (SS). The start of the successor activity depends on the start of the current activity.

d) Start to finish (SF). The successor activity cannot finish until the current activity starts.

3.2.3??? Drawing the project network

?A network is a graphical representation of the project activities and their relationships. ?A project network is a set of arrows and nodes. Before drawing the network, it is necessary to ensure that the project has a unified starting and ending point. The need for this start activity arises when there is more than one activity in the project that has no predecessors and the end activity is needed when there is more than one activity that has no successors. Also, networks should be continuous (i.e., each activity except the first and the last has both preceding and succeeding activities).

?There are two ways that are commonly used to draw a network diagram for a project:

?1.?? Activity on Arrow (AOA) representation.

2.?? Activity on Node (AON) representation

?3.2.3.1 Activity on arrow network (AOA)

?In this method, the arrows represent activities while the nodes represent the start and the end of an activity (usually named as events) (Figure 3.13). The length of the arrow connecting the nodes

The following are some rules that need to be followed when constructing an AOA network diagram:

-???? Each activity must have a unique i – j numbers, where i (the number at the tail of the arrow) is smaller than j (the number at the head of the arrow).

-???? It is recommended to have a gap between numbers (i.e., 5, 10, 15, etc.). This will allow for accommodation of missed activities.

-?? ?Avoid back arrows.

?In some situations, when more than one arrow leave the same node and arrive at another node, dummy activities must be used. The dummy activity is an activity with zero duration, consumes no resources, drawn as dashed lines, and used to adjust the network diagram. A dummy activity is? also? used when? one? activity? depends? upon two? preceding? activities? and? another? activity depends only upon one of these two preceding activities as shown in Figure 3.14.

?3.2.3.2 Activity on node network (AON)

?This method is also called the precedence diagram method. In this method, the nodes represent activities and the arrows represent logical relationships among the activities. If the arrow starts from the end side of an activity (activity A) and ends at the start side of another activity (activity

Comparison between AOA and AON

?While both networks can be used to represent a project network, there are some differences between them:

-?? ?There is no need for the use of dummy activities in AON representation.

-?? ?AON are more easily to draw and to read.

-?? ?In AOA, an activity can only start when all its predecessors have finished.

-?? ?AON allows for overlap/lag representation.

-???? AON allows for the representation of the four types of relationships while AOA allows only for the finish to start relationship.

?Example 3.9:

?What is the duration in days to install 6000 square feet of walls shuttering if:

?Solution

a.? ?Crew of 2 carpenters is used with output of 200 square feet/day

b.?? Productivity is measured as 0.008 man-hour/square feet. Number of carpenters=3, and number of working hours/day = 8 hours

?a.? ?Duration = 6000 / 200 = 3 days

b.?? Total man-hours needed = 6000 x 0.008 = 48 man-hours (if one man used) Duration = 48 / 8 = 6 days (if one man used)

Duration using 3 men = 6 / 3 = 2 days

?Example 3.10: (use of several resources)

?The construction of a reinforced concrete wall involves placing 660 m3 concrete, fixing 50 tone of steel, and 790 m2 of formwork. The following information belongs to the jobs involved in this activity:

- A 6 man concrete crew can place 16 m3 of concrete/day.

- A steel-fixer and assistant can fix 0.5 ton of reinforcement/day.

- A carpenter and assistant can fix and remove 16 m2 of shuttering/day. Calculate the duration of the activity considering the steel-fixer as the critical resource.

?Solution

?-?? ?using one steel-fixer: duration = 50 / 0.5 = 100 days

-?? ?using one carpenter: duration = 790 / 16 = 49.4 days

-?? ?using one concreting crew: duration = 660 / 16 = 41.25 days.

?Then, for a balanced mix of resources, use 2 steel-fixer crews, one carpenter crew, and cone concreting crew. Accordingly, the activity duration = 50 / 0.5 x 2 = 50 days.