| Author | Suwat Chritamara |
| Call Number | AIT Diss. no. ST-01-01 |
| Subject(s) | Construction industry--Management
|
| Note | A dissertation submitted in partial fulfillment ofrequirements for the degree of Doctor
of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ST-01-01 |
| Abstract | This study is concerned with the application of the system dynamics concept to construction
projects. A dynamic model has been developed for the specific case of design and build (D!B)
construction projects. System dynamics methodology was used because construction projects
comprises of complex systems with various variables, non-linear behaviors, uniqueness and
feedback structure.
An attempt has been made in this study to improve D!B project time and cost performance. A
generic system dynamics model is developed that incorporates major sub-systems and their
relationships inherent in D!B constructions projects. The model was validated and calibrated
for typical large D!B infrastructure projects using time and cost related problems experienced
in Thailand.
The research was started by undertaking a review of design and build construction literature.
The main variables and critical problems were identified at the initiating stage. Problems such
as unclear scope development at the beginning, information sharing between client and
contractor, design changes, communication and coordination lapses among parties and project
interface problems with the environment are commonplace in D!B procurement. Critical
variables such as insufficient owner information, ill-conceived scheme of employer
requirement, change of employer requirement, significant change of original design, delay of
design approval, client initiated changes during construction were included in the model to
investigate their effects on time and cost performance of a D!B project.
The D!B dynamic model is divided into seven sections: 1) Employer's information; 2) Design;
3) Man-power; 4) Material; 5) Equipment; 6) Construction; and 7) Financial sub-systems. The
model was validated and tested using data collected from D!B construction projects in
Bangkok.
By statistical analysis, the model's simulation output was shown to be quantitatively quite
close to the actual data collected. Qualitatively, the model has been validated by all necessary
tests including (1) test of model structure by comparison with existing literature and through
consultation with concerned field experts; (2) dimensional test of model equations; and (3)
behavioral tests to ensure that the model is sufficiently stable. Thus, the model validation and
calibration process has helped to confirm that the model is a good replication ofreality.
Through sensitivity analysis of the model, design and construction changes from the owner or
contractors are identified as the most sensitive parameters impacting project schedule and cost.
The model expands to significant policies for improving design and build construction system.
The experimentation of the model shows that different kinds of policies have different effects
on project performance measured in terms of cost and time optimization. For the overall
improvement in both time and cost, the combination of full overtime schedule, average
material ordering, and fast track construction with moderate crashing of design was found to be useful. Whereas for cost optimization alone, extending construction schedule, combined
with material ordering based on actual usage, and design and build with traditional
construction method is the most appropriate.
Fast track construction with moderate D/B integration seems to improve project's cost
performance because of overlapping although some additional costs are added due to increases
in design changes and errors to be corrected and construction changes and rework to be done,
together with communication times needed to transfer design information to the construction
fu nction. These costs can be reduced by decreasing D/B the overlap between D/B from high to
moderate.
From this study, it is found that crashing the project may not really be economical in some
circumstances. In the experimentation, the project time and cost increased after moderate
design schedule crashing (more than 20%). It is recommended that projects should not involve
crashing design schedule especially in projects where design changes and errors are likely to
be large and affect many other related sub-systems.
In addition, the owner will benefit by knowing what level of initial scope definition is most
beneficial to the project. Completing development of the scope of a project before engaging
the design-builder can make the project finish early. However, involving the contractor in the
scope development yields cost benefits. The simulation result shows that the client has to
provide substantial initial scope at the beginning (between 50-70%) for cost and time to be
optimized. |
| Year | 2000 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ST-01-01 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Ogunlana, Stephen 0.; |
| Examination Committee(s) | Chotchai Charoenngam;Nguyen Luong Bach;Nagendra N., Nagarur;Ndekugri, Issaka E.; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2000 |