Analyzing the Relationship Between Production Constraints and Construction Work Flow Reliability: An SEM Approach (original) (raw)

Factors Affecting Work Flow Reliability - A Case Study

2009

Low work flow reliability is a major contributor to the construction industry’s dismal productivity record. The purposes of this paper are to identify the factors affecting work flow reliability, learn from failures of completing work plans, and recommend strategies to improve work flow reliability in order to improve productivity for construction projects. We collected production data of 592 working days in 12 working areas from a pipe installation project which implemented the Last Planner System. The data included the number of daily planned tasks, daily planned tasks completed, daily tasks completed non-planned, daily tasks uncompleted, daily planned man-days and completed man-days. Root causes of uncompleted tasks were also documented. Based on the data collected, correlation analysis was conducted to study the factors affecting work flow reliability. We found that commitment plan, prerequisite work, material and weather are the top four factors affecting work flow reliability....

Investigating the relationship between planning reliability and project performance: A case study

… of the International Group for Lean …, 2007

Variability is an endemic problem in construction projects, which leads to the general deterioration of their performance. During the last decade the Last Planner System (LPS™) has been increasingly applied in construction projects to improve planning reliability as a strategy to increase the project performance. LPS™ promotes a series of actions and methods to increase planning reliability, monitoring the Percentage of Plan Completed (PPC) in a short term planning period. Nevertheless, there is limited evidence studying properly the relationship between planning reliability and project performance. In this paper, the authors developed a detailed research in a home building project analyzing this relationship at activity and project level, in order to understand how changes of planning reliability levels impact over project performance during construction phase. For doing so, two indexes are proposed: A planning reliability index activity-based called Process Reliability Index (PRI), and an aggregated labour productivity index project-based called Project Productivity Index (PPI). At activity level, activity performance indicators are compared with PRI. At project level, PPI is compared with PPC as a project planning reliability index. Statistical analyses for both levels were conducted showing positive and robust trends to improve performance when planning reliability is increased.

Investigating the relationship between planning reliability and project performance

Production Planning & Control, 2008

Understanding the Relationship Between Planning Reliability and Schedule Performance: A Case Study

Proc., 17th Annual Conf. of the Int. …, 2009

The earned-value method (EVA) monitors the progress of the project using dollar value or man hours as the metric by comparing the amount of work completed against the work planned to be complete and indicate if the project is on or behind schedule by means of the Schedule Performance Index (SPI). The Last Planner System (LPS™) increase planning reliability by reducing workflow variability, through analyzing and removing activity restrictions, analyzing causes for not fulfilled plans and monitoring its improvements by means of Percentage of Plan Completed (PPC).

CONSTRAINT REMOVAL AND WORK PLAN RELIABILITY: A BRIDGE PROJECT CASE STUDY

Effective removal of constraints is critical in the Last Planner System (LPS ®)to improve work plan reliability. While removing constraints is important, it remains unclear to project managers about which types of constraint have the highest level of uncertainty and to what extent the constraint removal discussions are efficient for improving work plan reliability. This research uses a bridge project as an example to answer these research questions. The authors collected planning meeting minutes, look ahead plans, and production dataof11 weeks to analyze constraint removal discussions in weekly plan meetings and the associated Percent Plan Complete (PPC).Information theory method was used to calculate the amount of information gain and the information transmission efficiency for PPC improvement. Results show that " Prerequisite Readiness " is the most important constraint to discuss and contributes to 24% of the total information gain for PPC improvement. This constraint also has the highest information transmission efficiency of 36%, almost twice the average information transmission efficiency of the other constraints. The method proposed in this paper can be used repetitively on other projects and will help project managers to improve their meeting effectiveness in order to achieve higher work plan reliability.

The Relationship Between the Make-Ready Process and Project Schedule Performance

2008

This research investigates the importance of the make-ready process in last planner implementation. The make-ready process has the potential to improve workflow predictability and reliability in construction projects. The construction industry has recognized that timely constraint removal is an important and distinctive requirement of successful projects. Percentage of constraint removal (PCR) was used as a performance metric for the make-ready process. The authors tested the relationship between PCR and Percent Planned-work Completed (PPC), and hypothesize that PPC depends on the effectiveness of the make-ready process. Correlation and regression analyses were used to investigate how the effectiveness of the make-ready process (as measured by PCR) affects PPC. The results of the correlation coefficients for the relationship between PPC and PCR are significant (p<0.05). The regression analysis revealed that PPC positively related with PCR (p<0.1). Workflow reliability differed...

Comparing process improvement initiatives based on percent plan complete and labour utilization factors

11th Conference of the International Group for Lean Construction, 2003

The Last Planner System ® is a process-based system developed to enable production planning and control under a lean construction paradigm. The Percent Plan Complete (PPC) is a metric that reflects the effectiveness of production planning and the reliability of workflow from one trade to another. Process improvement initiatives are identified when 100% PPC is not achieved. In contrast to this system, conventional construction management derives its production process improvement initiatives from productivity improvement studies that use metrics of non-utilization such as non-productive time or Labor Utilization Factors (LUF) as the metric of superior production performance. This paper investigates the differences, if any, in process improvement initiatives predicated on PPC compared to those predicated on LUFs. This was accomplished by conducting a study in a Manufactured Housing plant where workers' utilization at 10 production stations were measured using productivity ratings while also measuring PPC at the same stations. The average LUF for the 10 stations was 52% and the average PPC for the same was 78%. Attempts to improve PPC through constraint analysis techniques revealed more fundamental problems than those revealed by trying to improve LUF. In addition, the PPC metric exposed the 'hidden-factory' despite that the production goals were being met. The study confirms that PPC is a global measure of production system planning efficiency while LUF is a measure of local production activation. A linear regression analysis was also performed revealing that PPC and LUF are not strongly correlated (r = 0.4, p-value = 0.3) in non-lean production systems. Thus, the only viable way to increase workflow reliability in production systems is to increase PPC.

Construction flow index: a metric of production flow quality in construction

Construction Management and Economics

A new, process-oriented approach is needed in construction management. Lean construction emphasizes the concept of flow as a way to understand production in construction, yet there is still no accepted metric for measurement of flow quality. This has hampered research and practice. The proposed construction flow index (CFI) is a composite measure that reflects the quality of production flow in repetitive construction projects. It incorporates measures of work continuity for crews, processing continuity for locations, production rate variation, amounts of work in progress, interference and operation sequence logic. Expert knowledge was acquired to establish weights for the CFI parameters, and its use was tested in evaluating the planned and actual production flows for a number of projects. Project managers can use the CFI to evaluate the quality of their construction plans and to measure and communicate production flow quality status to trade crews, enabling management and improvement of production flow. The CFI is also a valuable tool for construction research. The CFI challenges traditional construction management by measuring flow, where standard practice only measures transformation (earned value). It challenges lean construction practice using the Last Planner System, suggesting that the percent plan complete measure of plan reliability is insufficient.

Improving planning reliability and project performance using the reliable commitment model

Journal of …, 2010

Commitment planning reliability at an operational level is a key factor for improving project performance. In the last 15 years, the Last Planner System, a production planning and control system based on lean production principles, has improved commitment planning reliability in the construction industry. However, many construction decision makers continue to rely on their experience and intuition when planning their commitments, which hinders their reliability. The reliable commitment model ͑RCM͒ is proposed to improve commitment planning reliability at the operational level by using statistical models. RCM is an operational decision-making tool based on lean principles that supports short-term forecasting commitment planning using common-site information such as workers, buffers, and plans. RCM was tested in several case studies, demonstrating its production forecasting capabilities and its ability to help increase commitment planning reliability and improve project performance. RCM also supports workload and labor capacity matching decisions. RCM has the potential of becoming a useful production decision-making tool.

Rational commitment model: improving Planning reliability and project Performance

ANNUAL …, 2009

Reliability of planning commitments at operational level is one of the key factors to improve project performance. The Last Planner System (LPS TM ) is a tool designed to improve planning reliability in construction industry, however, the improvements in planning reliability are often limited due to the fact that the decision-making processes in construction, including those related to planning commitments, are mainly based on experience and intuition. The Rational Commitment Model (RCM) presented in this paper is a tool that helps to overcome this situation by introducing decision-making aids based on analysis of field data, which allows developing more reliable planning commitments using statistical models. RCM allows forecasting planning commitments for short term-periods using field production data such as labor available, buffer size, and planned progress. Several case studies have demonstrated the RCM forecasting capabilities and its practical use to improve reliability of planning commitments and project performance. The RCM also contributes to solve the well-known workloadcapacity problem and provides useful insight into lean production performance issues.

Analyzing the Relationship Between Production Constraints and Construction Work Flow Reliability: An SEM Approach (original) (raw)

Related papers