Showing papers in "Journal of Construction Engineering and Management-asce in 2009"

Measuring the Impact of Rework on Construction Cost Performance

Abstract: Rework continues to affect both cost and schedule performance throughout the construction industry. The direct costs alone often tally to 5% of the total construction costs. Using the data obtained from 359 construction projects in the Construction Industry Institute database, this paper assesses the impacts of rework on construction cost performance for projects in various categories. In addition, it identifies the sources of this rework, permitting further analyses and the development of rework reduction initiatives. The results of this study establish that the impacts of rework differ according to project characteristics and that the sources of rework having the greatest impact are not significantly different among project categories. By recognizing the impacts of rework and its sources, the construction industry can reduce rework and ultimately improve project cost performance.

Research Trend of Public-Private Partnership in Construction Journals

Abstract: An impressive series of content analyses of Public-Private Partnership (PPP) publications between 1998 and 2003 from four internationally renowned construction journals (including the International Journal of Project Management, the Journal of Construction Engineering and Management, the Construction Management and Economics, and the Engineering Construction and Architectural Management) was reported. Their work inspired the writers of this paper to continue from where they left it. Based on a two-stage literature review, PPP articles from 1998 to 2008 were analyzed in terms of the annual number of PPP articles published, the writers’ contribution, and the research focus in their studies. From the analysis it was found that the number of PPP publications in these journals has been increasing. This finding might imply that PPPs are becoming more important to the construction industry at large. In addition, this study also found that the U.K. researchers have published the largest number of PPP articles, fo...

Empirical Comparison of Design/Build and Design/Bid/Build Project Delivery Methods

Abstract: This study compares the performance of design/bid/build and design/build to see if one project delivery method is superior in regards to time and cost. Similar military buildings were used to identify two samples of projects delivered with each of the two delivery methods. These projects provide a meaningful comparison because they include buildings of the same typology (i.e., U.S. Navy Bachelor Enlisted Quarters) delivered using similar design models. Project duration, project duration per bed, project time growth, cost growth and cost per bed were statistically compared. Upon completion of the analysis, the hypothesis that design/build projects are superior to design/bid/build projects in regards to time and cost was tested. Design/build projects were proven superior in performance in almost every measure. Other findings, including recommendations to practitioners and researchers, will be provided as well.

Measuring Safety Climate of a Construction Company

Abstract: Safety climate can benefit contractors, specialty contractors, and owners of industries by providing them with the knowledge of attitudes and perceptions that can help to consistently achieve better safety performance. The objective of this research was to determine safety climate that would enhance safety culture and positively impact perceived safety performance on construction projects. A safety climate questionnaire survey was conducted on the construction sites of a leading construction company and its subcontractors in Hong Kong. Approximately, 1,500 hard copy questionnaires were distributed and the response rate was excellent, resulting in 1,120 valid questionnaires being collected from 22 construction projects. By means of factor analysis, two underlying safety climate factors were extracted, accounting for 43.9% of the total variance. Multiple regression analysis confirmed that these climate factors, “management commitment and employee involvement” and “inappropriate safety procedure and work pra...

Construction Safety Risk Mitigation

Abstract: Construction safety and health management has improved significantly following the Occupational Safety and Health Act of 1970. In response to this legislation, contractors began implementing safety programs to reduce occupational safety and health hazards on construction sites. Researchers recently found that the current process of selecting specific elements for a safety program is informal. This paper describes the results of a recent study designed to determine the relative effectiveness of safety program elements by quantifying their individual ability to mitigate construction safety and health risks. In order to determine the effectiveness of individual safety program elements, the following research activities were performed: (1) an appropriate safety risk classification system was created using an aggregation of relevant literature; (2) highly effective safety program elements were identified in literature; and (3) the ability of each safety program element to mitigate a portion of each of the safety risk classes was quantified using the Delphi method. The results of the research indicate that the most effective safety program elements are upper management support and commitment and strategic subcontractor selection and management and the least effective elements are recordkeeping and accident analyses and emergency response planning. It is expected that the data presented in this paper can be used to strategically select elements for a safety program, target specific safety and health risks, and influence resource allocation when funds are limited.

Visualization of Work Flow to Support Lean Construction

Abstract: Implementation of advanced production management techniques, such as lean construction concepts like filtering of work packages to stabilize work flows, pull flow of teams and materials, and in-process quality control, demands effective and timely flows of information both to and from the workface. The key requirement—making the process state transparent to all participants—is more difficult to achieve in construction than in manufacturing, because work crews move continuously within a physical environment that is itself changing. Novel computer-aided visualization tools can fulfill the needs that simpler tools, such as Kanban cards, fulfill in manufacturing. Two prototypes with user interfaces designed to facilitate process flow have been devised and implemented within the context of building information modeling (BIM) software systems. They demonstrate aspects of the synergy between BIM and lean construction. Given the dynamic and dispersed physical environments and the fractured contracting arrangements typical of construction, BIM-based visualization interfaces are important tools for providing process transparency.

Construction Craft Workers’ Perceptions of the Factors Affecting Their Productivity

Abstract: In efforts to quantify craft workers’ perspective of construction productivity, a nationwide survey involving 1,996 craft workers was employed. The survey quantified the relative impact of 83 productivity factors, which had been identified through a series of focus group sessions involving craft workers conducted on construction jobsites located throughout the United States. The findings show that craft workers do have a good understanding of the factors affecting their daily productivity, and most of the adversarial factors affecting productivity can be addressed by site management teams. Factors involving tools and consumables, materials, engineering drawing management and construction equipment were identified as having the greatest impact on productivity from the craft workers’ perspective. A statistical comparative analysis was employed to distinguish the significant factors encountered by craft workers on projects with relatively low perceived productivity. The research further examined the differen...

Human Factors Analysis Classification System Relating to Human Error Awareness Taxonomy in Construction Safety

Abstract: In several studies it is widely accepted that human error is the main reason for up to 80% of all incidents and accidents in complex high-risk systems that exist in the aviation, petrochemical, healthcare, construction, mining, and nuclear power industries. The construction industry, greatly impacted by accidents, is accountable for more than 1,000 fatalities in each of the past 14 years. The human factors analysis classification system (HFACS) is a general human error framework originally developed and tested as a tool for investigating and analyzing the human causes of accidents with applications to rail, air, and offshore environments. This paper introduces the concept of HFACS along with the framework of human error awareness training (HEAT) and their potential contribution to the construction industry. Based on the HEAT approach, this paper proposes a new error analysis educational and classification tool for safety within the construction industry. The primary difference between HFACS and HEAT is found in the structure, content, and presentation of the information allowing for higher effectiveness in incident investigation and safety education and training in construction.

Defect Costs in Residential Construction

Abstract: The residential construction industry is an important contributor to the Australian economy; the industry employs a very large component of the national workforce, and yet the industry is plagued by defective work and poor quality. Previous research has revealed that defects and rework are endemic in the residential sector. In an attempt to quantify the degree of defects being experienced in new residential construction this paper provides an analysis of defects that were recorded by a government-owned housing insurance organization, the Housing Guarantee Fund. This research represents one of the most comprehensive research studies of building defects undertaken to date in Australia. The data used were not based on a sample like previous studies but instead represent all new houses constructed in Victoria, Australia between 1982 and 1997. An analysis of the data revealed that one house in eight reported defects, and that the cost of rectification was 4% of the construction contract value. The paper discusses the nature of the most important defects and investigates the impact of contractor type and building type.

Development of Lean Model for House Construction Using Value Stream Mapping

Abstract: Lean construction has recently attracted considerable attention in the home building industry. Lengthy delivery time and significant waste in the construction process have caused many home builders to seek a more effective production model that will increase process reliability, reduce total lead time, and improve quality. However, although housing construction provides the closest analogy to manufacturing, a high level of variability prevents the direct transplantation of lean paradigm and techniques. In collaboration with a local home builder, a systematic approach based on value stream mapping technique is developed in this research to analyze the current process and to formulate a lean production model. The model has four main features: synchronized first-in, first-out lane-based flow, production leveling at pacemaker, work restructuring, and improved operation reliability. A simulation template is built to verify the model and to assist in the development of interim implementation models. This paper presents data collection and value stream selection, current practice analysis, and specific changes proposed for the lean production model.

Activity-Based Safety Risk Quantification for Concrete Formwork Construction

Abstract: Most of safety risk research focuses on high-severity safety risks for large-scale construction processes. Such studies help firms identify the highest risk processes so they may be targeted for improvement. However, few studies quantify safety risk at the activity level or include low-severity, high-frequency risks that some literatures suggest contribute to a large proportion of total risk. This paper presents research that involved the holistic quantification of risks for the activities associated with the construction of concrete formwork. Three major research efforts are discussed: (1) identification of activities required to construct concrete formwork; (2) selection of an appropriate all-inclusive and mutually exclusive risk classification system; and (3) the quantification of the average frequency and severity levels for each risk classification associated with each activity. To identify formwork construction activities, 256 worker-hours of observation were conducted and the resulting activity descriptions were reviewed and validated by industry professionals. Risk classifications appropriate for this study were created by aggregating relevant literature. Finally, the Delphi method was implemented to individually quantify average frequency and severity using scales that define the entire spectrum of possible values. In total, 130 frequency ratings and 130 severity ratings were obtained over three rounds of Delphi surveys. Results indicate that there are 13 major activities required to construct concrete formwork and the highest risk activities are applying form oil, lifting and lowering form components, and accepting materials from a crane. The data presented in this paper can be used to target specific high-risk formwork construction activities for improvement.

Overview of the application of "fuzzy techniques" in construction management research

Abstract: During the last decade, “fuzzy techniques” have been increasingly applied to the research area of construction management discipline. To date, however, no paper has attempted to summarize and present a critique of the existing “fuzzy” literature. This paper, therefore, aims to comprehensively review the fuzzy literature that has been published in eight selected top quality journals from 1996 to 2005, these being Journal of Construction Engineering and Management, ASCE; Journal of Management in Engineering, ASCE; Construction Management and Economics; Engineering, Construction and Architectural Management; International Journal of Project Management; Building Research and Information; Building and Environment; and Benchmarking: An International Journal. It has been found that fuzzy research, as applied in construction management discipline in the past decade, can be divided into two broad fields, encompassing: (1) fuzzy set/fuzzy logic; and (2) hybrid fuzzy techniques, with the applications in four main ca...

Spatial and Temporal Exposure to Safety Hazards in Construction

Abstract: Given the dynamic nature of construction sites, analysis of construction activities and their related hazards is inadequate for reliable risk assessment if it does not explicitly account for the likelihood of exposure of potential victims to hazardous situations. In traditional risk level calculations for manufacturing industries, the number of victims is factored with the likelihood of an accident and the potential severity, but the victims are simply assumed to be those typically present at the accident location. In construction, exposure cannot be accounted for at a generic metaproject level: it must be assessed at the level of the activities and the physical context in which they are performed. Conceptually, accidents are "loss-of-control events" to which victims are exposed; without exposure, no accident is assumed to occur. A set of algorithms has been developed to demonstrate estimation of the likelihood of exposure of construction workers to loss-of-control events. The algorithms have been implemented in a prototype software application designed to predict fluctuating risk levels in construction projects. The software implements the "construction hazard assessment with spatial and temporal exposure" model for managing safety in construction, which empowers planners at all levels to adjust construction plans to mitigate high levels of risk or to undertake appropriate proactive measures to ensure safety when high risk levels are unavoidable.

Development and Initial Validation of Sustainable Construction Safety and Health Rating System

Abstract: This paper presents a study to develop and validate a sustainable construction safety and health (SCSH) rating system. The rating system provides an opportunity to rate projects based on the importance given to construction worker safety and health and the degree of implementation of safety and health elements. A Delphi survey using an expert panel of 12 experienced safety and health professionals representing different sectors of the construction industry was employed to develop the SCSH rating system. The study resulted in a rating system consisting of a total of 50 safety and health elements organized into 13 categories. Each category contains safety and health elements which carry credits based on their effectiveness in preventing construction worker injuries and illnesses. The rating system was initially validated based on data from 25 construction projects and found to accurately represent the safety performance of large projects. The SCSH rating system can be used as an effective tool to develop and plan construction safety and health programs and evaluate the potential safety performance of construction projects.

Organizational Culture and Knowledge Management Success at Project and Organizational Levels in Contracting Firms

Abstract: This research focuses on contracting firms within the construction sector. It characterizes and evaluates the composition of organizational culture using four culture types (clan, adhocracy, market, and hierarchy), the strategic approach for knowledge flow, and the success of knowledge management (KM) systems at different hierarchical levels of contracting organizations (project and parent organization level). Responses from managers of local or overseas contracting firms operating in Hong Kong were collected using a carefully constructed questionnaire survey that was distributed through electronic mail. The organizational value is analyzed in terms of the four cultural models. Clan culture is found to be the most popular at both project and organization levels, which means that the culture of contracting firms very much depends on honest communication, respect for people, trust, and cohesive relationships. On the other hand, hierarchy culture, which focuses on stability and continuity, and analysis and control, seems to be the least favored at both levels. Another significant finding was that the two main KM strategies for knowledge flow, codification and personalization, were employed at both project and organization levels in equal proportion. This indicates that successful KM efforts at both enterprise levels utilize a hybrid and balanced approach for their knowledge flow, and that they complement each other. The findings also revealed that knowledge management system success factors emphasize the support of the management level. The results show that KM is critical and beneficial as indicated by 64% at the project and 74% at the organization level. The expectation is higher for organizations as they are the organizational memories in which experiences of past projects are archived and connected. Understanding these factors and the relationships among them has been demonstrated to be critical in order to increase the chances of success or to help with making decisions when applying KM.

Framework for Measuring Corporate Safety Culture and Its Impact on Construction Safety Performance

Abstract: This paper presents the results of a structural equation model SEM that describes and quantifies the relationships between corporate culture and safety performance. The SEM is estimated using 196 individual questionnaire responses from three companies with better than average safety records. A multiattribute analysis of corporate safety culture characteristics resulted in a hierarchical description of corporate safety culture comprised of three major categories—people, process, and value. These three major categories were decom- posed into 54 measurable questions and used to develop a questionnaire to quantify corporate safety culture. The SEM identified five latent variables that describe corporate safety culture: 1 a company's safety commitment; 2 the safety incentives that are offered to field personal for safe performance; 3 the subcontractor involvement in the company culture; 4 the field safety accountability and dedica- tion; and 5 the disincentives for unsafe behaviors. These characteristics of company safety culture serve as indicators for a company's safety performance. Based on the findings from this limited sample of three companies, this paper proposes a list of practices that companies may consider to improve corporate safety culture and safety performance. A more comprehensive study based on a larger sample is recommended to corroborate the findings of this study.

Identification and Analysis of Factors Affecting Safety on Construction Sites with Tower Cranes

Abstract: Tower cranes are the centerpiece of production on today’s typical building construction sites. Tower cranes hoist and transport a variety of loads near and above people, working under crowded conditions, occasionally with overlapping work zones, and often under time, budget, and labor constraints. This work regime further increases the safety risk on sites that are inherently hazardous workplaces. This paper presents the results of a study that identified the major factors affecting safety in tower-crane environments and evaluated the degree to which each factor influences ongoing safety on site. Use of statistical data on accidents was ruled out as a source of information due to the countless number of incidents that go unreported, the common inability of statistics to provide root causes, and the questionability of statistics as a predictor of accidents. The research methodology was therefore based on comprehensive questioning of an expert team that included the safety managers and equipment managers of...

AHP-Based Weighting of Factors Affecting Safety on Construction Sites with Tower Cranes

Abstract: Aspiring to adopt a nonstatistical quantitative approach to safety assessment, this study implements a multiattribute decision-making tool to elicit knowledge from experts and formalize it into a set of weighted safety factors. The environment addressed is the construction site and the specific factors studied are those affecting safety due to the operation of tower cranes. Nineteen senior construction equipment and safety experts were interviewed and led through the analytic hierarchy process (AHP) to provide their assessments on the relative importance of safety factors obtained in an earlier study. The results accentuate the dominance of the crane operator and general superintendent on the site safety scene and play down the contribution of “classic” site hazards such as power lines. Quantitative measuring of safety, such as reflected in the weights obtained in this study, is important in communicating safety requirements and focusing the limited resources available for safety improvements. These facto...

Impact of Green Building Design and Construction on Worker Safety and Health

Abstract: Sustainable, or “green,” rating systems, such as the United States Green Building Council’s Leadership in Energy and Environmental Design (LEED), are leading to changes in the way owners, designers, and contractors approach the design, construction, and operation of buildings. The processes and features included in green design and construction may have positive and/or negative impacts on construction worker safety and health. This paper presents the findings of a research study of the impact of green building design and construction practices on construction worker safety and health. Occupational Safety and Health Administration (OSHA) recordable and lost time injury and illness data from green projects (as identified by LEED) and from nongreen projects was collected through a structured questionnaire survey. The data collected was analyzed to test for the presence of a difference in OSHA recordable incident rates (RIRs) and lost time case rates (LTCRs) between green and nongreen projects. It was found t...

Determination of Key Performance Indicators with Enterprise Resource Planning Systems in Engineering Construction Firms

Abstract: The study focuses on developing a unified approach to define information specificities for key performance indicators (KPIs). Borrowing from the time-system theory, the paper defines different types of KPI and identifies that a KPI has two dimensions—knowledge specificity and time specificity. Different approaches are presented to analyze knowledge and time sensitivities. This paper addresses a key question related to enterprise resource planning (ERP) systems applications in the engineering construction industry: what are the areas of business processes within the engineering construction industry where ERP cannot be used to collect KPIs related to business processes? The writers review empirical and specialized processes within the construction industry to identify business processes not covered by existing ERP systems. A survey focused on qualitative aspects of ERP systems implementation in engineering construction firms was conducted among ERP-enablers in the construction industry and provided a basis...

Using Agent-Based Modeling to Study Construction Labor Productivity as an Emergent Property of Individual and Crew Interactions

Abstract: Lean construction research has shown that managing work flow effectively and maintaining labor flow on site can improve construction labor performance. Related research also shows that congestion on construction sites often leads to lowered efficiency. Using these findings as a point of departure, we use the agent-based modeling method to represent the construction site as a system of complex interactions and explore whether labor efficiency can be treated as an emergent property resulting from individual and crew interactions in space. This allows us to use a "bottom-up" approach to analyzing labor efficiency, which supplements existing "top-down" approaches to modeling the impacts of space congestion on labor efficiency. A pilot implementation of the agent-based model, and preliminary results illustrating the relationships between congestion and labor efficiency are presented. The empirical studies exhibit system behavior that support published principles of work-force management. The primary contribution of this paper is that it provides a method that can be used to efficiently utilize construction space, and develop plans and schedules that account for congestion arising from crew interactions in space.

Drivers for Adopting Public Private Partnerships—Empirical Comparison between China and Hong Kong Special Administrative Region

Abstract: The private sector has long been involved in delivering public sector projects, whether its role has been as a partner or just as a contractor for the government. Over recent years the interest in adopting public private partnerships (PPPs) has increased internationally. Many research studies have presented positive reasons for the governments and the private sector to welcome this form of procurement, rather than continue adopting the traditional options. This paper aims to explore and compare the key drivers for adopting PPP in China and the Hong Kong Special Administrative Region (referred to as Hong Kong from here onwards). An empirical questionnaire survey was conducted in both of these administrative systems and survey respondents were invited to rate their perceptions on the importance of 15 different drivers identified. Eighty-seven completed survey questionnaires were returned for analysis. The findings indicated that respondents from China rated economy-related drivers higher, whereas Hong Kong ...

Latent Structures of the Factors Affecting Construction Labor Productivity

Abstract: At any moment in time, a multitude of factors simultaneously impact construction productivity. Utilizing the knowledge of thousands of construction craft workers, the writers quantitatively analyzed the underlying structure of the factors affecting construction productivity and identified which factors the craft workers consider to be more relatively important as well. This research identified 83 factors affecting construction labor productivity through 18 focus groups with craft workers and their immediate supervisors on nine jobsites throughout the U.S. Next, a nationwide survey was administered to 1,996 craft workers to assess the impact of these factors on construction labor productivity. Principal factor analyses identified 10 latent factors to represent the underlying structure of 83 productivity factors. In addition, the relative importance of the factors' impact on construction productivity was examined based on the crafts' union status, trade, and position (craft worker versus foreman). The writers also compared their results to similar previous efforts, and more importantly, identified significant differences that may impact future productivity improvement strategies. This research will help industry and the research community better understand the factors affecting construction labor productivity and more effectively direct future efforts to improve its performance.

Cognitive Approach to Construction Safety: Task Demand-Capability Model

Abstract: In the evolution of safety research, the literature identifies three paradigms: normative, error-based, and cognitive engineering. Traditionally, strategies to improve construction safety have been based on the normative paradigm—compliance with prescribed safety rules. However, the normative approach ignores how the characteristics of the production system and team processes influence the work behaviors and the possibility of errors and accidents. These factors are the focus of the cognitive engineering perspective. This study develops a cognitive model of construction safety, which conceptualizes safety as an emergent property of the production system. The model proposes that during a task, the task demands and the applied capabilities determine the potential for errors and accidents. It also proposes that the production practices and the teamwork processes of the crew shape the work situations that the workers face—that is, the task demands and the applied capability. Empirical evidence from recent cas...

Performance and Strategy of Chinese Contractors in the International Market

Abstract: The past decade has witnessed the steady growth of Chinese international contractors (CICs), who have become important and influential players in the international market. The enormous development demands worldwide, especially in developing countries, attract CICs to engage in the market. Similarly, the strong support from the Chinese government plays an important role for the expansion of Chinese contractors globally. Some leading CICs perform very well in certain fields and countries. This brings the competitiveness of CICs to the attention of the international community. The strengths, weaknesses, opportunities, and threats (SWOT) approach was adopted in order to analyze CICs’ strengths, weaknesses, opportunities and threats in international construction markets. Literature from various sources was reviewed in the first instance, which is followed by an interview survey with 42 CICs employees. A SWOT strategy matrix is used to establish a framework that can help CICs to select suitable business develop...

Developing ERP Systems Success Model for the Construction Industry

Abstract: Recently, a significant number of major construction companies embarked on the implementation of integrated information technology solutions such as enterprise resource planning ERP systems to better integrate various business functions. However, these integrated systems in the construction sector present a set of unique challenges, different from those in the manufacturing or other service sectors. There have been many cases of failure in implementing ERP systems in the past, so it is critical to identify and understand the factors that largely determine the success or failure of ERP implementation in the construction industry. This paper presents the process of developing an ERP systems success model to guide a successful ERP implementation project and to identify success factors for ERP systems implementation. The paper identifies factors associated with the success and failure of ERP systems, and develops a success model to analyze the relationships between key factors and the success of such systems. The proposed ERP systems success model adapts the technology acceptance model and DeLone and McLean's information systems success model and integrates those with key project management principles. The goal of the ERP systems success model is to better evaluate, plan, and implement ERP projects and help senior managers make better decisions when considering ERP systems in their organization.

Requirements and Incentives for Reducing Construction Vehicle Emissions and Comparison of Nonroad Diesel Engine Emissions Data Sources

Abstract: Nonroad construction vehicles and equipment powered by diesel engines contribute to mobile source air pollution. The engines of this equipment emit significant amounts of carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter. These pollutants pose serious problems for human health and the environment. Therefore, it is necessary to regulate and control the levels of these pollutants. Furthermore, there are emerging requirements and incentives for “greening” of construction vehicle fleets and operations. Currently, there are two types of standards that regulate air pollution for these types of vehicles: technological standards for engines and quality standards for air. It is also necessary to quantify the levels of emissions that nonroad construction vehicles and equipment produce. Quantification may be based on existing data sources (such as the EPA NONROAD model) or by collecting data directly from the vehicles as they work in the field. The purpose of this paper is to introduce the chall...

Chinese Contractors in Africa: Home Government Support, Coordination Mechanisms, and Market Entry Strategies

Abstract: Africa is a traditional overseas market for Chinese contractors. Since the launch of “going out’ national strategy in the new century, and with the support and control of the government and subordinate agencies, associations and banks, and innovative approach such as Angola Mode, Chinese contractors’ presence in the emerging African market continues to grow. Based on original empirical data collected through interview and questionnaire surveys, this paper analyzes the mechanisms the Chinese government has established to facilitate Chinese contractors’ entry into Africa and the perspectives of Chinese contractors about the African market in terms of opportunities and threats. Regression analysis based on existing datasets indicates that despite perceived opportunities and threats, Chinese contractors’ performance in Africa in terms of business revenue actually hinges upon the availability of construction capital. The study also reviews the market entry modes used by Chinese contractors, concluding that the...

Integrated Model for the Stressors and Stresses of Construction Project Managers in Hong Kong

Abstract: Construction projects involve multistakeholders e.g., architects, structural engineers, surveyors, contractors, suppliers, etc. completing a large number of unpredictable tasks in a complex process within a limited period of time. Construction project managers C-PMs are the key persons in achieving project success throughout the construction process, as they are responsible for planning the construction program, organizing human resources, controlling operations and the budget, and forecasting probable difficulties. Hence, C-PMs always encounter a great deal of stress in construction projects. Apart from the subjective feelings experienced by individual C-PMs, C-PMs may also feel objective stress due to the deviation between their actual abilities and their expected abilities on tasks or projects. To understand the integrated relationships between the various stressors and stresses of C-PMs, a survey was conducted of 108 C-PMs in Hong Kong. This paper attempts to investigate the causal relationships between stressors and stresses both subjective and objective. The study reveals seven stressors of C-PMs in the industry. Based on the results of a correlation coefficient, an optimized stressor-stress structural equation model is established. Four critical stressors were found to have significant impact on both the subjective and the objective stresses of C-PMs, including work overload, poor interpersonal relationships, poor work environment, and poor nonwork environment. A number of recommendations were made for both construction companies and individual C-PMs in their offices and at home in order to optimize their work performance in the real world.

Optimizing Resource Leveling in Construction Projects

Abstract: Construction schedules, generated by network scheduling techniques, often cause undesirable resource fluctuations that are impractical, inefficient, and costly to implement on construction sites. This paper presents the development of two innovative resource leveling metrics to directly measure and minimize the negative impact of resource fluctuations on construction productivity and cost. The first metric quantifies the total amount of resources that need to be temporarily released during low demand periods and rehired at a later stage during high demand periods. The second measures the total number of idle and nonproductive resource days that are caused by undesirable resource fluctuations. The two new metrics are incorporated in a robust and practical optimization model that is capable of generating optimal and practical schedules that maximize the efficiency of resource utilization. An application example is analyzed to illustrate the use of the model and demonstrate its capabilities. The results of this analysis show that the present model and metrics are capable of outperforming existing metrics and eliminating undesirable resource fluctuations and resource idle time.