Construction scheduling & Cost control

CONSTRUCTION SCHEDULING & COST CONTROL

By

PROF. LIAQAT ALI QURESHI

UET TAXILA

Planning & Scheduling

Planning:

Process of choosing the method and order of work

Scheduling:

Process of determining the interrelationship of associated timings of operations.

Steps in Construction Scheduling

Splitting of the project into work activities Determining logic relationships/interrelationships

between activities. Construction of Network Diagrams. Assigning durations to work activities. CPM Calculations resulting in start times, finish

times and float calculations of activities. Marking of critical Path Construction of Bar Charts / Time phased

diagrams.

Activity

An element of work performed during the course of a project. Or

An amount of work that can be identified so that we know what it involves and can recognize, when it starts and finishes.

An activity normally has an expected duration, an expected cost, and expected resource requirements

Network Diagrams

Any schematic display of the logical relationship of project activities.

Always drawn from left to right to reflect project chronology.

Usually a combination of arrows and nodes. Mainly of two types:

1. Arrow Diagram2. Node Diagram / Precedence Diagram

Arrow Diagrams

Activities shown by Arrows. Relationship between activities shown by nodes / events.

Length of arrows does not obey any scale. Start-to-finish relationships. Dummies. Numbering of nodes / events. Milestones

Use of Dummy Activity

Activity Durations

Activity duration is forecasted by any of the several means, including:(1) Check Past Records.(2) Check Standards and / or cost guides, if available.(3) Ask the workers, who will do it(4) make an educated guess

Any time units may be allotted to activity durations like days, hours, weeks, months, shifts, etc.

In CPM, a single duration is forecasted for an activity.

In PERT (Program Evaluation & Review Techniques), 3 durations are forecasted for an activity and mean taken by weighted average method. Then, Project’s Duration or any Event Completion Time is calculated by probability distribution.

CPM Calculations

Calculates the following for each activityEST = Earliest Starting TimeEFT = Earliest Finishing TimeLST = Latest Starting TimeLFT = Latest Finishing TimeTF = Total FloatFF = Free Float

Total Float is Maximum time for which an activity can be delayed without delaying the project.

Free Float is maximum time for which an activity cane be delayed without delaying the start of proceeding activity.

Total Float = Free Float + Interfering Float

Critical Path

The path (or paths) in the network diagram, from start to finish, on which all the activities have zero total and free floats, is called Critical Path.

It is the longest path (or paths) from start to finish in a net work diagram.

It gives minimum normal time to complete a project.

It is usually marked by double lined arrows in a network diagram.

SINGLE SPAN BRIDGE PROJECT (ACTIVITY DESCRIPTION)

Activity Code Operation Dependence Est. Dur.(Days)

ENA Earthworks, north abutment - 5

ESA Earthworks, south abutment ENA 4

CONN Construction, north abutment ENA 14

CONS Construction, south abutment ESA, CONN 12

COMN Compaction, north abutment CONN 2

CIMS Compaction, south abutment CONS, COMN 2

RNB Road, north of bridge COMN 2

RSB Road, south of bridge RNB,COMS 2

PB Prefabricate bridge deck - 18

TD Transport deck to site PB 2

EB Erect bridge deck TD, CONN, CONS, COMN

3

LBS Lay bridge surface EB, RNB, RSB 2

ICB Install crash barriers etc. EB 1

L Landscape RNB, RSB 1

Node Diagrams

Activities shown by Nodes, relationship between Activities shown by arrows or links.

Easier to construct. Generally no need of dummies. Instead

dummies used only to give single start or finish.

CPM Calculations similar to Arrow diagrams.

Bar Chart

Gives Pictorial Representation of Activities. Activities begin at EST and show their EFT, FF,

TF, Durations, etc. Arrows at the relative ends to show dependency. Status Line Concept Unable to show complete interdependency

between Activities. Time-scaled Network Diagrams show complete

interdependency between Activities.

COST MANAGEMENT

COST MANAGEMENT

Includes processes required to ensure that the project is completed within the approved budget.

Processes involved are:

1- Resource Planning

2- Cost Estimating

3- Cost Budgeting

4- Cost Control

1- Resource Planning

Involves determining what physical resources (people, equipment, materials etc) and what quantities of each should be used to perform project activities.

Inputs to Resource Planning

1. Work Breakdown Structure:

A deliverable-oriented grouping of project elements that organizes and defines the total scope of the project. It Identifies the project elements that will need resources.

2. Historical Information

3. Scope Statement:

Contains the project justification and the project objectives.

Inputs to Resource Planning

4. Resource Pool Description:

Knowledge of what resources are potentially available.

5. Organizational Policies:

The policies of the performing organization regarding staffing and the rental or

purchase of supplies and equipment.

Tools and Techniques to Resource Planning

1. Expert Judgment

2. Alternative identifications:

To adopt different approaches for the same problem.

Outputs from Resource Planning

1. Resource Requirements:

Description of what types of resources are required and in what quantities for each element of the work break down structure.

Cost Estimating

Developing an approximation (estimates) of the costs of the resources needed to complete project activities.

Includes identifying and considering various costing alternatives.

Cost Estimating and Pricing

Cost Estimating involves developing an assessment of the likely quantitative result-how much will it cost the performing organization to provide the product or service involved.

Pricing is a business decision-how much will the performing organization charge for the product or service

Inputs to Cost Estimating

Work Breakdown Structure Resource Requirement Resource Rates:

scheduled or non-scheduled Activity Duration Estimates Historical Information Chart of Accounts:

Describes the coding structure used by the performing organization to report financial information in its general ledger

Tools and Techniques for Cost Estimating

Analogous Estimating / Top-down Estimating:

Using the actual cost of a previous, similar project as the basis for estimating the cost of the current project. It is less costly but less accurate. (Rough-cost Estimate)

Parametric Modeling:

Using project characteristics (parameters) in a mathematical model to predict project

costs.

Tools and Techniques for Cost Estimating

Bottom-up Estimating:Estimating the cost of individual work

items, then summarizing or rolling up the individual estimates to get a project title. (Detailed Estimate)

Computerized Tools:Use of computerized tools such as

project management software and spreadsheets to assist with cost estimating.

Outputs from Cost Estimating

Cost Estimates Supporting Details like Scope of work,

Calculation sheet, Assumptions made, Possible range of results, etc.

Cost Management Plan describing how cost variances will be managed.

Cost Budgeting

Allocation of overall cost estimates to individual work items in order to establish a cost baseline for measuring project performances.

Inputs to Cost Budgeting

Cost Estimates Work Breakdown Structure Project Schedule

Tools and Techniques for Cost Budgeting

Tools and Techniques for developing project Cost Estimates are used to develop budgets for work items as well

Outputs from Cost Budgeting

Cost Baseline

A time-phased budget that will be used to measure and monitor cost performance

on the project. It is developed by summing estimated costs by period and is usually displayed in the form of an S-curve.

Cost Control

Cost Control is concerned with(a) Influencing the factors which create changes to the cost baseline to ensure that changes are beneficial.(b) Determining that the cost baseline has changed(c) Managing the actual changes when and as they occur

Cost Control

Cost Control includes: Monitoring cost performances to detect

variances from plan. Ensuring that all appropriate changes are

recorded accurately in the cost baseline Preventing incorrect, inappropriate, or

unauthorized changes from being included in the cost baseline.

Informing appropriate stakeholders of authorized changes.

Inputs to Cost Control

Cost Baseline Performance Reports

Provide information about cost performance such as which budgets have been met and which have not. It also alerts the project team to issues which may cause problems in the future.

Inputs to Cost Control

Change Requests

These may occur in many forms-oral or written, direct or indirect, externally or internally initiated, and legally mandated or optional. These may require increasing the budget or may allow decreasing it.

Tools and Techniques for Cost Control

Cost Change Control System

It defines the procedures by which the cost baseline may be changed. It includes the paperwork, tracking systems, and approval levels necessary for authorizing changes.

Performance Measurement

It helps to assess the magnitude of any variations which do occur.

Tools and Techniques for Cost Control

Additional Planning

Perspective changes may require new or revised cost estimates or analysis of

alternate approaches.

Computerized Tools

Outputs from Cost Control

Revised Cost Estimates Budget Updates Corrective Action Estimate at Completion

It is a forecast of total project costs based on project performance.

Lessons Learned

OBJECTS OF COST CONTROL

1 – To have a knowledge of the profit and loss of the project throughout the duration of the project.

PROJECT PROFITS1) Client payments.2) Sale of surplus or scrap material and plant3) Payments for plants or labor by others, where, this plant or labor is ,

from time to time not required for the project.PROJECT LOSSES1) Labor and site office costs2) Plant costs3) Site overheads i.e. site facilities, access roads and office etc4) Cost of tendering including bonds, insurance, etc.5) Material costs.6) Head office overheads proportioned over all current projects.

OBJECTS OF COST CONTROL

2 – To have a comparison between the actual project performance and that conceived in the original project plan.

Comparison is basically done according to the following bases:

1) According to units of production2) According to line items; e.g., labour, material,

equipment, overheads, ---

3 – Provides feedback data on actual project performance to future project planning

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