Modelling Building Construction Durations in Nigeria

Modelling Building Construction Durations in Nigeria.

ABSTRACT

Following widespread acceptance by researchers that the effects of qualitative/managerial construction time-influencing factors need to be considered in project scope-based construction time predicting models, several multivariate models combining project scope and qualitative/managerial factors have been developed.

However, it has been shown in literature that the applicability of these models is clearly limited to the regions/countries where they were developed. This study was therefore aimed at developing a multivariate construction time predicting model that will be applicable to the Nigeria construction industry.

A self-administered questionnaire survey was used to source information on the quantitative (project scope) factors considered in the study as well as to assess the extent of influence of the qualitative factors on construction time.

Principal component regression was used for the data analysis and model development, using SPSS 16.0 for windows.

Following a non-normal distribution of errors and a low R2 value obtained when multiple linear regression analysis was first conducted, the study’s data set was double log transformed and then partitioned/reclassified to account for public and private sector projects.

Three models were developed following the multiple linear regression analysis repeated after transforming and partitioning/reclassifying the study’s data set.

Two of these models (the public sector model and the private sector model) had high R2 values and were found after testing and validation, to be suitable for predicting construction time, while one of the models (the all projects model) had a low R2 value and was consequently found to be unsuitable for predicting construction time.

The models with high R2 values serve as a useful tool to project managers and contractors for predicting construction time, thereby facilitating effective planning.

PROCEED NOW TO DOWNLOAD PAGE

TABLE OF CONTENTS

DECLARATION ……………. i
CERTIFICATION ……………………………. ii
DEDICATION ………………………. iii
ACKNOWLEDGEMENT …………….. iv
ABSTRACT …………………… v
TABLE OF CONTENTS …………………. vi
LIST OF FIGURES ………………. ix
LIST OF TABLES …………………………… x
1.0 INTRODUCTION ………………. 1
1.1 Background to the study …………… 1
1.2 Statement of the problem ………………. 3
1.3 Aim and Objectives ……………………………. 4
1.3.1 Aim of the research…………………… 4
1.3.2 Objectives ……………………………………… 4
1.4 Justification for the Study ……………… 5
1.5 Scope and Limitations ……………………….. 5
1.5.1 Scope of the study …………… 5
1.5.2 Limitations …………………………… 6
2.0 LITERATURE REVIEW …………. 7
2.1 Construction Time Estimating Methods in Practice ……………….. 7
2.2 Modelling Construction Time ………….. 8
2.2.1 The Bromilow (1969) time-cost model …………………… 8
2.2.2 Attempts to validate the Bromilow (1969) time-cost model ………… 10
2.2.3 Attempts to modify the Bromilow’s time-cost model …. 15
2.3 Modelling construction time in Nigeria …………………….. 25
2.4 Summary ………………….. 29
3.0 RESEARCH METHODS ……. 31
3.1 Research Approach ……………. 31
3.2 The Quantitative Research Approach …….. 31
3.3 The Self-administered Questionnaire Survey .. 32
3.3.3 Structure of the questionnaire ……………… 35
3.4 Statistical Methods/Approach used for Model Development … 37
3.4.1 Principal Component Analysis of the qualitative factors ………. 39
3.4.2 Multiple linear regression analysis to determine the nature and strength of the relationship between duration and a combination of the quantitative factors and the principal components of the qualitative factors.. 41
3.5 Approach used for model testing and validation ……………… 45
4.0 DATA PRESENTATION, ANALYSIS AND DISCUSSION …….. 46
4.1 Data Received from the Survey …………………….. 46
4.2 Data Reliability ………… 47
4.3 Characteristics of the Projects Surveyed ….. 48
4.4 Potential Predictor Variables ………………………. 49
4.5 Multivariate Model Development ……… 50
4.5.1 Principal component analysis of the qualitative factors ……… 50
4.5.2 Multiple linear regression analysis to determine the nature of the relationship between construction time and construction time influencing factor 57
4.5.3 Developing the Models ………………… 75
4.5.3.1 Transforming back and interpreting coefficient…. 76
4.6 Model testing and validation ……………………… 81
4.6.1 Checking for the assumptions of linearity …….. 81
4.6.2 Comparing the planner’s estimates and the model’s predictions …………. 82
5.0 SUMMARY, CONCLUSION AND RECOMMENDATION ……. 87
5.1 Summary of findings …………. 87
5.2 Conclusions ……………….. 90
5.3 Recommendations …… 90
REFERENCES ………………….. 91

PROCEED NOW TO DOWNLOAD PAGE

INTRODUCTION

1.1 Background to the study

The importance of ensuring accuracy and reliability of construction time estimates at the tendering stage cannot be overemphasized. Accurate early estimates of construction time typically provides clients and contractors with a basis for evaluating the success of a project and the efficiency of the project organisation (Nkado, 1995).

They also provide them with a basis for ascertaining logistical and cash flow implications for feasibility, budgeting, planning, monitoring and even litigation purposes (Skitmore and Ng, 2003).

Furthermore, they serve as a criteria in determining the best combination when performing time-cost optimization (Que, 2002). It is therefore clear that construction  time has become a vital tool used by clients and contractors to ensure the success of construction projects.

This success will however, only be achieved when construction time is accurately predicted.Construction time/periods are often calculated on the basis of the planner’s own previous experience on similar projects (Choudhury and Phatak, 2004).

However, as pointed out by Skitmore and Ng (2003), the need to reduce the problem of subjectivity associated with the planner’s experience and judgement to correctly interpret project and site information and make the best possible decisions, has long resulted in the development of construction time predicting models.

The development of construction time predicting models commenced with the use of project scope factors. Project scope is a measure of project size, which can be described as construction cost, project duration, gross floor area, number of storey, building type and procurement method (Walker, 1995).

PROCEED NOW TO DOWNLOAD PAGE

REFERENCES

Ameyaw, C., Mensah, S. and Arthur, Y.D. (2012). Applicability of Bromilow’s time- cost model on building projects in Ghana. In: Laryea, S., Agyepong, S.A., Leiringer, R. and Hughes, W. (Eds) Proceedings of the 4th West Africa Built Environment Research (WABER) Conference, 24-26 July 2012, Abuja, Nigeria, 881-888.
Bromilow, F.J. (1969). Contract time performance-expectations and the reality. Building Forum, 1(3), 70-80.
Bromilow, F.J., Hinds, M.F. and Moody, N.F. (1980). AIQS survey of building contract time performance. Building Economist, 19(2), 79-82.
Chan, A.P.C. (1999). Modelling building durations in Hong Kong. Construction Management and Economics, 17(2), 189–96.
Chan, A.P.C. and Chan, D.W.M. (2002). Benchmarking project construction time performance: the case of Hong Kong. Project Management-Impresario of the construction industry symposium.