Quantifying the Impact of Change Orders on Construction Labor Productivity Using System Dynamics
Quantifying the Impact of Change Orders on Construction Labor Productivity Using System Dynamics

Author: Sasan Golnaraghi

Publisher:

Published: 2021

Total Pages: 0

ISBN-13:

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Researchers and industry practitioners agree that changes are unavoidable in construction projects and may become troublesome if poorly managed. One of the root causes of sub-optimal productivity in construction projects is the number and impact of changes introduced to the initial scope of work during the course of project execution. In labor-intensive construction projects, labor costs represent a substantial percentage of the total project budget. Understanding labor productivity is essential to project success. If productivity is impacted by any reasons such as extensive changes or poor managerial policies, labor costs will increase over and above planned cost. The true challenge of change management is having a comprehensive understanding of change impacts and how these impacts can be reduced or prevented before they cascade forming serious problems. This thesis proposes a change management framework that project teams can use to quantify labor productivity losses due to change orders and managerial policies across all phases of construction projects. The proposed framework has three models; fuzzy risk-based change management, AI baseline-productivity estimating, and system dynamics to illustrate cause-impact relationships. These models were developed in five stages. In the first stage, the fuzzy risk-based change management (FRCM) model was developed to prioritize change orders in a way that only essential change orders can be targeted. In this stage, Fuzzy Analytic Hierarchy Process (F-AHP) and Hierarchical Fuzzy Inference System are utilized to calculate relative weights of the factors considered and generate a score for each contemplated change. In the second stage, baseline productivity model was developed considering a set of environmental and operational variables. In this step, various techniques were used including Stepwise, Best Subset, Evolutionary Polynomial Regression (EPR), General Regression Neural Network (GRNN), Artificial Neural Network (ANN), Radial Basis Function Neural Network (RBFNN), and Adaptive Neuro Fuzzy Inference System (ANFIS) in order to compare results and choose the best method for producing that estimate. The selected method was then used in the development of a novel AI model for estimating labor productivity. The developed AI model is based on Radial Basis Function Neural Network (RBFNN) after enhancing it by raw dataset preprocessing and Particle Swarm Optimization (PSO) to extract significant dataset features for better generalization. The model, named PSO-RBFNN, was selected over other techniques based on its statistical performance and was used to estimate the baseline productivity values used as the initial value in the developed system dynamics (SD) model. In the fourth stage, a novel SD model was developed to examine the impact of change orders and different managerial decisions in response to imposed change orders on the expected productivity during the lifecycle of a project. In other words, the SD model is used to quantify the impact of change orders and related managerial decisions on excepted productivity. The SD model boundary was defined by clustering key variables into three categories: exogenous, endogenous, and excluded. The relationships among these key variables were extracted from the literature and experts in this domain. A holistic causal loop diagram was then developed to illustrate the interaction among various variables. In the final stage, the developed computational framework and its models were verified and validated through a real case study and the results show that the developed SD model addresses various consequences derived from a change in combination with the major environmental and operational variables of the project. It allows for the identification and quantification of the cumulative impact of change orders on labor productivity in a timely manner to facilitate the decision-making process. The developed framework can be used during the development and execution phases of a project. The findings are expected to enhance the assessment of change orders, facilitate the quantification of productivity losses in construction projects, and help to perform critical analysis of the impact of various scope change internal and external variables on project time and cost.

Using System Dynamics to Study the Effect of Change Orders on Labor Productivity
Using System Dynamics to Study the Effect of Change Orders on Labor Productivity

Author: Shrouk Gharib

Publisher:

Published: 2021

Total Pages: 0

ISBN-13:

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Abstract: Change orders in construction projects lead to numerous negative impacts, including loss of labor productivity, delays, and cost overruns. Owners and contractors are usually in disagreement when it comes to allocating the extent of responsibilities with respect to the resulting overruns. Each party tries to hold the other party fully responsible for such overruns through a series of claims and disputes. Several delay analysis techniques have been developed to aid in settling such disputes, however, they do not fully grasp the rippled impacts of change orders and do not assist parties in reaching consensus when it comes to finding the isolated rippled impacts of each change order. This research aims to develop a framework that supports delay analysis based on dynamic modeling with a focus on the impacts of change orders. System dynamics is utilized as the base modeling methodology due to its capability of capturing rippled impacts and complex interrelations. A novel calibration methodology is also developed to enable using this framework in any construction project. After development and verification, the framework was tested on a sample construction project that faced delays due to change orders. The developed model was able to quantitatively link the productivity losses and delays to each change order, which helped in clearly allocating the responsible parties for the delays. In addition, several what-if-scenarios were conducted to enhance the understanding of how such impacts could have been avoided. This research is envisaged to support owners and contractors in quickly reaching consensus regarding the impacts of change orders; thus, minimizing the corresponding disputes and fostering a healthier contracting environment.

Modeling Productivity Losses Due to Change Orders
Modeling Productivity Losses Due to Change Orders

Author: Ali Emamifar

Publisher:

Published: 2019

Total Pages:

ISBN-13:

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Change orders are an integral part of construction projects regardless of project size or complexity. Changes may cause interruption to the unchanged scope of work and working conditions and, if poorly managed, may be detrimental to project success. Many studies have been carried out to quantify the impact of change orders on construction labour productivity, with varying degrees of accuracy and variables considered. These studies reveal that quantifying loss of productivity due to change orders is not an easy task and requires a comprehensive and holistic method. There are several methods for quantifying loss of productivity, such as measured mile analysis (MMA) and the total cost method (TCM). Although measured mile analysis (MMA) is a well-known and widely accepted method for quantifying the cumulative impact of change orders on labour productivity, it is not readily applicable to many cases. In this research two models were developed to quantify losses arising from change orders. The first model does not account for the timing of change orders, but the second model considers the timing of change orders on labour productivity. Two models were developed and tested utilizing artificial neural networks and two sets of data collected by others in that field. The two datasets were statistically analyzed and preprocessed in order to transfer the data to normal distribution form and eliminate insignificant variables considered in their development. Using best subset regression, a total of seventeen variables were reduced to nine variables accordingly. Also, the study datasets were categorized into three types of timing periods; early change, normal change and late change to create the timing model. This was implemented to enable a comparison with models developed by others. Three types of artificial neural network techniques were experimented with and evaluated for possible use in the developed models. These three types are Feed Forward Neural Network, Cascade Neural Network, and Generalized Regression Neural Network. Candidate techniques were evaluated and analyzed by neural network parameters and analysis of variance (ANOVA) to select the most efficient type of neural networks, and subsequently using it to develop two models; one considers timing and the second does not. The analysis performed led to the selection of the cascade neural network for the development of the two models productivity losses due to change orders. The developed models were tested and validated utilizing several actual cases reported by others. The models were applied to a number of cases and the results were compared to those generated by frequently cited models to demonstrate their accuracy. The comparison outcome showed that the developed models can generate more accurate and satisfactory results than those of reported in previous studies.

Modeling the Cumulative Impact of Change Orders
Modeling the Cumulative Impact of Change Orders

Author: Karim Ashraf Sabry Iskandar

Publisher:

Published: 2016

Total Pages: 0

ISBN-13:

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Change orders occur in almost every construction project and regularly cause variations to the contractors' anticipated working conditions, resources, and manner of work completion. Change orders are major source of additional congestion, change in sequence, and loss of momentum in the construction jobsite. They frequently cause unforeseen labor productivity loss, which forces contractors to extend their stays on projects. Contractors encounter a lot of resistance from owners when proving productivity loss attributable to change orders, which may lead to unresolved disputes and lengthy litigations. Previous researchers attempted to set standards and methods in order to quantify the cumulative impact of changes on labor productivity. Some of the previous studies were based on case studies of two or three projects, others included a larger number of projects and more reliable analysis. Generally, it is very difficult to conclusively determine the exact amount of productivity loss attributable to change orders. As a result, there is a continuous need to enhance and enrich the cumulative impact research field. This current research is based on a database of one hundred and forty-five mechanical and electrical projects, encompassing two project groups: projects impacted by changes, and projects unimpacted by changes. Using two-sample t-tests and Chi-squared tests, a series of numerical and categorical variables were found to be significant in distinguishing between impacted and unimpacted projects, thus revealing the underlying causes of productivity loss associated with change orders. Furthermore, sixty-eight impacted projects were used in order to quantify the cumulative impact of changes using linear regression analysis. A series of statistical model selection criteria were applied in order to carefully identify the best predictive models. Candidate models were statistically diagnosed and thoroughly tested to check their validity. Statistical tests and measures were used in order to check whether there are outlying or influential observations in the models. In addition to that, new projects were collected to verify the future predictive ability of the candidate models. The analysis identified the following six factors as best cumulative impact predictors: percent owner initiated change orders, overmanning, turnover, absenteeism, percent time spent by project manager on project, and productivity tracking. The models developed in this research provide the construction industry with means that could be used during dispute resolutions to support the contractors' calculations and assertions for cumulative impact claims. Finally, this study incorporates a significant statistical component that highlights the most common challenges that analysts face when building linear regression models, such as multicollinearity and the presence of hidden extrapolations. The models developed in this research were extensively analyzed in full details through various statistical tests and measures in order to avoid misleading and deceptive results.

Proceedings of the 21st International Symposium on Advancement of Construction Management and Real Estate
Proceedings of the 21st International Symposium on Advancement of Construction Management and Real Estate

Author: K. W. Chau

Publisher: Springer

Published: 2017-12-18

Total Pages: 1500

ISBN-13: 9811061904

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This book presents the proceedings of CRIOCM_2016, 21st International Conference on Advancement of Construction Management and Real Estate, sharing the latest developments in real estate and construction management around the globe. The conference was organized by the Chinese Research Institute of Construction Management (CRIOCM) working in close collaboration with the University of Hong Kong. Written by international academics and professionals, the proceedings discuss the latest achievements, research findings and advances in frontier disciplines in the field of construction management and real estate. Covering a wide range of topics, including building information modelling, big data, geographic information systems, housing policies, management of infrastructure projects, occupational health and safety, real estate finance and economics, urban planning, and sustainability, the discussions provide valuable insights into the implementation of advanced construction project management and the real estate market in China and abroad. The book is an outstanding reference resource for academics and professionals alike.

Estimating Productivity Losses Due to Change Orders
Estimating Productivity Losses Due to Change Orders

Author: Ihab Assem

Publisher:

Published: 2000

Total Pages: 0

ISBN-13:

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This thesis presents a computer model for quantifying the adverse impact of change orders on construction productivity. In order to provide an in-depth analysis of change orders and develop a reliable model, a comprehensive field study was carried out. The field study was conducted at a Montreal based firm, specialized in project management and construction claims. A total of 117 actual projects, constructed in Canada and the USA between 1990 and 1998, were initially analyzed for possible use in the developments made in this thesis. Only 33 work-packages from these projects were utilized in the development of the present model. These work packages have an original total value of more than $110M, planned direct hours of 1,023,583 for the original scope of work and a total of change orders direct hours of 166,002. Additional cases, obtained from the literature, were used to supplement the collected data in order to improve the reliability of the developed model. The analyzed cases are used to model the timing effect of change orders as well as the work type on productivity losses. The data collected was used in the development of ten neural network models for predicting percent productivity loss. (Abstract shortened by UMI.).

Applying Earned Value Management to Design-Bid-Build Projects to Assess Productivity Disruption
Applying Earned Value Management to Design-Bid-Build Projects to Assess Productivity Disruption

Author: Stephen P. Warhoe

Publisher: Universal-Publishers

Published: 2013

Total Pages: 392

ISBN-13: 1612334164

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One of the most important jobs of a project manager is to manage a project's budget and schedule. These tasks can easily be very difficult to accomplish on projects that are complex, especially since successful project execution relies heavily on people who are expected to perform their roles individually and as a team. One of the most difficult aspects of managing projects is estimating how fast and effectively humans will perform a task; that is, determining how productive workers collectively will be each day, each week, or within any time period during the life of a project. Because projects are unique and are typically one-off endeavors, there is usually little previous empirical data to rely upon for the project manager to forecast productivity before or during the project's execution. The crux of the problem lies with adequately identifying not only the labor work flow process, but also the influences that affect the work flow process. When scope changes are introduced into the work flow of a project, the types and number of influences and their cause and effect relationships can significantly increase in numbers. This phenomenon often turns complicated projects into extremely complex ones and the final outcome can be greater than the sum of the individual inputs. For project managers who are unable to get their arms around this very real situation, forecasting the outcome of a project often becomes out of control, especially for projects that are large and heavily labor intensive. This study takes a post-positivist approach to design and builds a system dynamic model with which construction projects that are delivered using the design-bid-build methodology can be simulated to show generically how the influences that affect construction projects can affect worker productivity. No other studies are known to exist that design or build such a model for construction projects that use the design-bid-build delivery method. The model that was designed in the study is based on the works of several academics' works as well as the input of several experts in the construction field, including this study's author. As opposed to attempting to create a simulation model based on the uniqueness of a single project, a "mosaic" approach was used in creating the model in that elements of the model were identified and taken from studies found through the literature review as well as interviews with construction industry experts. The stock and flow structure of the study's model is intended to be a composite of many construction projects and can be used for any project delivered using the design-bid-build methodology. From the research, the model was created and tested using good modeling practice in that the model testing phase followed the process created by one of the pre-eminent system dynamic modelers in the world (refer to Sterman, 2000). The result is a model that simulates the work flow of labor hours in a design-bid-build construction project which can be affected by an immeasurable number of influences that can and do occur on construction projects.