11

KING FAHAD UNIVERSITY OF PETROLEUM AND MINERALSCONSTRUCTION ENGINEERING & MANAGEMENT DEPARTMENT

CEM 510**********

CONSTRUCTION DELAY COMPUTATION CONSTRUCTION DELAY COMPUTATION METHODMETHOD

BY Jonathan Jingsheng Shi, Member , ASCE, S.O. Cheung and David Arditi, Member, ASCE

REF: JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT – JAN/FEB,2001 VOL. 127 NO.1

FEB28,2006

22

OBJECTIVE:OBJECTIVE:

This paper presents a method for computing activity delays and assessing their contribution to project delay. The method consists of a set of equations, which can be easily coded into a computer program that allows speedy access to project delay information and activity contributions.

BACKGROUND:BACKGROUND: Most problem in construction is delay Construction contract = contract duration ( specified period of time) =

contractor must comply to achieve substantial completion within this time For unexpected reasons contractor fails to complete the project within the

contract period Owner will claim liquidated damages and obtain contractual release extension

of time Delay analysis based on responsibilities : delay excusable (compensable &

noncompensable ) and inexcusable Project delay result from computing activity delay Delay computation related to as-planned schedule contrasts as-built schedule Traditional delay analysis method based always on CPM analysis on other words

any delay on critical path delay the project completion This method is not based on CPM and no need for updating CPM Criticality of individual activities change from day to day due to delays &

accelerations which means if delay happen then extra effort from manager to up date the as-planned schedule with daily as-built information

DELAY OF ACTIVITY

FULLY EFFECT ON PROJECT DELAY

PARTIALLY EFFECT ON PROJECT DELAY

NO EFFECT

33

APPROACH APPROACH AS:AS:

1. Examine the occurrence of delay

2. Method for computing activity delays

3. Method for computing the contribution of activity delays to project delay

4. example

44

Occurrence of Construction delay

Activity completion delay to reasons:Activity completion delay to reasons:• Delay in the start of the activity

Delay in the precedence activities Delay in the start of the activity itself for

some reason

• Extend the duration of the activity

Activity delay

Delay start

Extended activity duration

No resources

Bad weather

Less resources

Change scope

ChangeSite

condition

Mang. decision

Late design

information

Delaydeliveries

Delay precedence

Project delayed

Project Not

delayedSucceed-

ingdelayed

SucceedingNot

delayed

55

Activity VariationActivity Variation VS=actual start time – planned start time …………………....….1

VF=actual finish time – planned finish time…………………....…2

VD=actual duration – planned duration ……........................3

From CPM network following relationshipFrom CPM network following relationship

Actual finish time=actual start time +actual duration …….…..4 Planned finish time=planned start time +planned duration….5

By subtract 4-5 then Eq 2 can be written as:By subtract 4-5 then Eq 2 can be written as:

VF = VS + VD ……………………………………………………….…..…6

VSP= could start time – planned start time ………………….. 7

VSS= actual start time – could start time …………………….. 8

VS = VSP + VSS ……………………………………….…… 9

By applying the 9 into 6 then:By applying the 9 into 6 then:

VF = VSP + VSS + VD ………. 10 Accelerate VA=VSS+VD extra time

66

Contribution of Activity Variation to Project delay VP = actual completion time - planned completion time (+ ve 0r – VP = actual completion time - planned completion time (+ ve 0r –

ve )ve )

Two factors:Two factors: PDAC =MEASURING THE PROJECT DELAY DUE TO PDAC =MEASURING THE PROJECT DELAY DUE TO

ACCUMULATED ACTIVITY VARIATIONS CONTRIBUTED BY THIS ACCUMULATED ACTIVITY VARIATIONS CONTRIBUTED BY THIS AND ALL ITS PRECEDING ACTIVITIESAND ALL ITS PRECEDING ACTIVITIES

PDA = PDA = MEASURING THE PROJECT DELAY CONTRIBUTED ONLY BY THIS ACTIVITY

Project delay is realized on the terminal activities ……..mechanism start from terminals and continue backward through intermediate activities

Terminal activities : are the last activities that do not have succeedings Variation in the completion time of the terminals may

contribute to project delay PDAC= actual finish time of the terminals - planned project finish

time PDA = min ( VA , PDAC ) Intermediate activities : those succeeding the terminals

DELAY OF ACTIVITY

FULLY EFFECT ON PROJECT

DELAY

PARTIALLY EFFECT ON

PROJECT DELAY

NO EFFECT

ji

7

Example Discussion

88

ConclusionConclusion This paper presents a method for computing activity delays and assessing

their contribution to project delay. The method consists of a set of equations, which can be easily coded into a computer program that allows speedy access to project delay information and activity contributions.

This method applicable to any intermediate construction stage for evaluating in-progress project delay

Traditional delay analysis method based always on CPM analysis require frequent updates of the as-built and as-planned schedules in order to keep track of the critical paths that may change daily. Such updating will require tremendous effort for site management. This method depend on as-planned schedule as basis of comparison for evaluating the variation in the project duration does not need to be updated.

This method is based on the finish-to-start relationship which is most common but not applicable to start-to-start or finish-to-finish relationships in current form , but equations can be expanded to these relationship as necessary.