In construction projects,
variability affects production rates, labor productivity, schedule control,
cost control, etc. Although the detrimental effects of variability in
construction are well known (Ballard, 1993; Tommelein et al, 1999), the
traditional construction planning process does not explicitly consider
variability, since projects are incorrectly assumed to be static, leading to
poor management decisions (Tommelein et al., 1999). Construction
industry has been criticized for being concerned with managing only tasks and
neglecting workflow (Koskela, 1992).
Ballard
and Howell (1998) through their research on public and private construction
projects reported that most of the projects suffered from low levels of
workflow reliability, resulting from ineffective planning and high percentage
of nonproductive time. They also reveal a poor level of planning resource
assignments, not involving operational level staffs in planning, lack of tools
and equipment, and failure to complete previous work were other reasons of low
workflow reliability. Thus, workflow reliability in the construction field has
been constantly measured at the level ranging from 30% to 60% (Ballard 1999).
On
the other hand, outsourcing work packages to subcontractors and other specialist
has been an integral part of construction system. Commitment, planning must be
agreed between these parties and in reality the relationship between them is
often opposing and non-collaborative, contractors always struggle to obtain
reliable commitments from the subcontractors (Maturana et al, 2007). Also, many
contractors contract work to subcontractors based on their personal relation
and on the bid amount which in the future has resulted in unreliable
commitments (Bustamante, 2007; Sacks and Harel, 2006). This is a prevalent
pattern in planning and decision making in construction (Laufer et al, 1994),
which may reduce planning reliability at the operational level.
Thus
there is a real need of a planning tool which will ensure the smooth workflow
at the construction site. Taking the activities from the master plan and
collaborating these activities with the weekly work plan of the subcontractors
and of the foremen for better reliable workflow and commitment.
Lookahead planning is tool of a Last
Planner System (LPS). LPS is a production planning and control system which is
mostly used to overcome the above-mentioned problems by providing a predictable
working environment, increasing workflow variability, and creating reliable
work plans to maximize project benefits. LPS also helps to change fragile
relationship between contractors and subcontractors to a more collaborative
environment, which has beneficial impacts on all parties (Alarcon et al., 2005;
Ballard 2000). The primary condition in the LPS is that activities should only
be committed if they can be performed i.e., all construction preconditions must
be available, converting what should be done into what can be done, helping to
promote a production environment based on commitment and trust among contractors
and subcontractors and among other stakeholders in the process planning.
Sajen Pradhan made a study
aimed to:
1. identify the
critical individual factors and the group, interrupting the workflow
2. implement and examine how the Lookahead planning of LPS helps to
improve workflow
3. provide recommendation and suggestion
Conclusions
1. Critical factors
affecting the workflow
The first objective of the study was to find the critical
factors affecting the workflow. Extensive and comprehensive literature review
from various sources was carried out to know the factors affecting workflow. Fifty
(50) factors were short listed and these factors were screen out into 8
different main categories of prerequisite works, design and information, labor,
materials, tools and equipment, working space, management, and external
condition. Before conducting survey expert verification was carried out and the
factors were reduced to 47.
The assessment of the factors
affecting workflow in high rise building of Nepal was done through survey from
30 respondents of project managers and engineer. The analysis of the survey
revealed critical top 10 factors which were 1) coordination between different
traders, 2) materials to be arrived at the site, 3) difficulty in coordinating
the work space, 4) quality of documents, 5) previous work not completed, 6)
lack of skill and experience to perform the assigned task, 7) rework required
to the previous work due to poor quality 8) change in scope of work, 9) Unviability
of budget for the work and 10) Turnaround time by the
engineers when there is a question with a drawing.
As the literature suggests making reliable/ predictable workflow
is much more important than doing more work so this study will surely help
project managers and project engineers to know in advance what are the factors
that they have to focus more so to have better smooth workflow. The spearman’s
correlation test among these factors also revealed moderate correlation where
significant level from 0.05 to 0.01.
Then the most critical group/category hindering workflow was also
analyzed. This analysis is believed to assist in development of the whole
project management system as the finding of the result highlighted the weak
part of the organization and directed the project heads in the specific
direction where the improvement is needed. The outcome of the study revealed
that management and supervision was the most critical group hindering the
workflow as per survey, followed by prerequisite works and drawings, and
materials group were also very critical.
2. Improvement of
workflow though Lookahead planning
The second objective of the
study was to implement and examine how the lookahead planning
of LPS helps to improve workflow. This objective is the major objective of the research and
for this two case studies were carried out in high rise buildings that were
under construction in Nepal. The criteria, tool, and the check list that were
used for the assessment of workflow was based on the finding from the
literature reviews on lookahead planning and on its components. The procedure
was verified by the 3 experts. The experiment was scheduled for 4 week, and both
the case study nature of data collected was qualitative. Then after the data
collection, data analysis was carried out to check the improvement in PPC and
in LU in the project after the introduction of the lookahead planning tool. It
was seen that both PPC and LU increased in the 2 case studies satisfying the
objective of the research.
Apart from the improving the
reliability of the plan, lookahead planning also had many benefits like
enhancing teamwork, developing the knowledge of lower level staff to make
decision, better communication, utilization of resources, and minimizing time
wastage. But there was still room for improvement in terms of PPC level which
was till moderate, thus the reasons for failing the work as planned were
investigated and it was found that issues related with management, drawing and
materials were the main reasons. This analysis was important to prevent the
same type of failures from recurring. All these reasons can be eliminated
through lookahead planning with its tools of collaborative meeting,
collaborative planning, and early constraint analysis, making work ready
against definition, soundness, sequencing, and size.
The findings of this research
can help project managers and consulting companies. The results can help
project managers better understand the relationship between work flow variation
and productivity and improve productivity by reducing work flow variation.
Workflow variation is significantly correlated with labor productivity
performance. This helps the company to pin point the weakness in the project
management system. But it has to be noted here that making reliable depends
upon type of project and management practice of the Project heads as well. Thus
workflow should be taken as a continuous improvement process where there should
be analysis of plan failures, finding root causes and suggesting improvement
strategies that prevent the same type of failure from recurring.
The thesis abstract is copied
below.
Architecture,
Engineering, and Construction (AEC) activities are naturally full of variables
and uncertainty and consist of many tasks which are to be performed in a
sequence. Variation in timely completion of these tasks can be high and can
have significantly negatively affect impact on project performance index and results in waste, inefficiency,
and productivity loss. To execute an elementary construction
task most efficiently, at least seven preconditions must be fulfilled. But due
to construction peculiarities, these preconditions may not be satisfied, and
thus the probability of missing one or many of these preconditions is greatly
high and which results in failure of the project in terms of schedule overrun,
cost overrun and disputes and claims. Thus improving the reliability of planning is the first
step to have stable construction workflow, and as affect their will be high
productivity and improved quality.
Studies have shown that to keep the workflow activity stable
the use of collaborative and flexible planning method is the key. Thus,
lookahead planning of Last Planner System (LPS) has been used for the research
case study. Lookahead planning is a mid-level planning which take the
activities from the overall project master schedules and aligns it with the
short term crew-level commitments. Lookahead planning filters out scheduled
activities that “should” be done but cannot be done and improves the success rate
of completing the tasks assigned in weekly and daily plans. It achieves the
above mentioned goals through:
1. Breaking down tasks into workable packages under the
collaboration of Project head with those who execute the work
2. Identifying and removing constraints to make task ready
for execution and
3. Designing operations through first run studies
Keywords:
Architecture, Engineering, Construction, Variables, Lookahead Planning, Last
Planner System, Workflow
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