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Lean construction and building information modeling (BIM) are quite different initiatives, but both are having profound impacts on the construction industry. A rigorous analysis of the myriad specific interactions between them indicates that a synergy exists which, if properly understood in theoretical terms, can be exploited to improve construction processes beyond the degree to which it might be improved by application of either of these paradigms independently. Using a matrix that juxtaposes BIM functionalities with prescriptive lean construction principles, 56 interactions have been identified, all but four of which represent constructive interaction. Although evidence for the majority of these has been found, the matrix is not considered complete but rather a framework for research to explore the degree of validity of the interactions. Construction executives, managers, designers, and developers of information technology systems for construction can also benefit from the framework as an aid to recognizing the potential synergies when planning their lean and BIM adoption strategies. DOI: 10.1061/(ASCE)CO.1943-7862.0000203 CE Database subject headings: Computer aided design; Construction management; Information technology (IT); Lean construction. Author keywords: Computer aided design; Construction management; Information technology; Lean construction.

Rework has been identified as a major contributor to cost and schedule overrun in construction projects. Previous studies that have examined rework are based on a limited data sets and thus eschew generalizations being made about the key determinants. Using data from 260 completed building (n = 147) and civil engineering (n = 113) projects, path analysis is used to develop a structural model of the most significant causes of rework. The model revealed that the paths of client-directed changes, site management and subcontractors, and project communication were statistically significant contributors to rework costs. The analysis confirmed that the lack of attention to quality management resulted in higher rework costs being incurred in the projects sampled. The analysis also revealed that there were no significant differences between building and civil engineering projects in terms of the direct and indirect cost of rework experienced, and the effectiveness of the project management practices implemented. Considering the findings, it is suggested that generic strategies for reducing the incidence rework in construction and civil engineering projects can be developed. DOI: 10.1061/(ASCE)CF.1943-5509.0000054 CE Database subject headings: Buildings; Construction costs; Construction management; Quality control.

This paper examines the national approach to the stimulation of innovation in construction. Based on a qualitative systems thinking approach, a model of the National System of Innovation (NSI) is structured with five main NSI actors: local contractors; suppliers: national research institutions: government: and foreign contractors. This model, established by the assumption that local contractors' key motivation for innovation is based on profit maximization, highlights two main driving forces of construction innovation within the NSI: profit incentives and the social desirability of higher construction productivity and quality. The research findings indicate that high profit levels provide a higher number of growth momentums compared to the social desirability of innovation. Additionally, although social desirability of construction innovation is associated with a number of obstacles, high profit levels do not impose any significant hindrances. Based on the research findings, it is concluded that innovation policies should be focused on sustaining higher profit levels of contractors. The social desirability of innovation can be more efficiently utilized by regular reviews of national policies as the industry develops. DOI: 10.1061/(ASCE)0733-9364(2006)132:10(1069) CE Database subject headings: Construction management: Innovation: Simulation; Singapore.

This paper presents a regression model that relates job site productivity to process improvement initiatives (PIIs) executed both before and during construction. Applied during early project stages, this model helps industry practitioners to predict the expected value of labor productivity based on certain inputs related to preconstruction planning and construction execution. The model demonstrates the strong relationship of project performance to a variety of PIIs including design completeness, definition of a project vision statement, testing oversight, and project manager experience and dedication. The correlational research methodology targeted 75 projects representing approximately $274.53 million in civil construction. The data collection effort considered 45 PIIs (independent variables) using quantitative and qualitative measures. The modeling technique involved the use of multiple linear regression, a method that exploits available data from multiple, independent sources to focus on specific outcomes. The model was developed directly from contractor specific information and subjected to rigorous statistical analysis. The model provides project managers as front line industry practitioners with a deliberate yet practical approach to project management and productivity enhancement. The modeling results include verification analysis and a discussion of the model's usefulness and limitations. DOI: 10.1061/(ASCE)0733-9364(2006) 132:2(189) CE Database subject headings: Construction management; Process control; Productivity; Quality control; Contractors.

The practices implemented by owners that were associated with better project safety performances were described in a companion paper. This paper will expand on those research findings and present a model that evaluates the impact of different owner practices on project safety performance. Four indices were established which quantitatively describe the project characteristics, the selection of safe contractors, the contractual safety requirements, and the owner's participation in safety management. Analysis of variance and linear regression were conducted to evaluate the combined effects of different owner practices on project safety performance as measured by the total recordable injury rate (TRIR). Results show that project safety performances were closely associated with all the indices except the index to describe the selection of safe contractors. The linear regression model explained 42.6% of the total variance of the TRIR. A scorecard to evaluate the owner's involvement in construction safety was developed to serve as a practical means of conducting an assessment and predicting project safety performance. The owner's involvement can favorably influence project safety performance by setting safety objectives, selecting safe contractors, and participating in safety management during construction. DOI: 10.1061/(ASCE)0733-9364(2006)132:2(174) CE Database subject headings: Accident prevention; Construction industry; Contracts; Occupational safety; Owners.

Construction is a process-based industry. In such an industry it is important to have a clear understanding of the process. One way to achieve this is by the use of a process model. In a European Community funded research project the business process of a small U.K. construction company was modeled and analyzed. Both visual modeling and enactable modeling techniques were used in this exercise. This paper aims to show how process understanding can be better achieved by a combination of visual models and enactable models. This is supported by examples from the construction company process studied. The tools and techniques used in this exercise are those developed by the collaborators of the project. The visual modeling is done using ProcessWise WorkBench and Role Activity Diagrams. The view of the business process given by the ProcessWise WorkBench models is predominantly process based, whereas Role Activity Diagrams provide a role based view of the process. The enactable modeling is done using RolEnact, a modeling tool that enacts formal specifications of processes.

A novel yield criterion that includes different strengths along each material axis is presented. The criterion includes two different fracture energies in tension and two different fracture energies in compression. The ability of the model to represent the inelastic behavior of orthotropic materials is shown, and a set of experimental tests to characterize the constitutive behavior of masonry is proposed. The capability of the model to reproduce the strength behavior of different masonry types is demonstrated through a comparison with available experimental data in masonry panels subjected to uniform biaxial loading conditions. Finally, the model is validated against experimental results on masonry shear walls and good agreement is found. A clear understanding of the behavior of masonry shear walls, and the nonlinear phenomena involved in its collapse, is presented with the help of a detailed comparison between numerical and experimental results.

Since the early 1960s many techniques have been developed to plan and schedule linear construction projects. However, one, the critical path method (CPM), overshadowed the others. As a result, CPM developed into the powerful and effective tool that it is today. However, research has indicated that CPM is ineffective for linear construction. Linear construction projects are typified by activities that must be repeated in different locations such as highways, pipelines, and tunnels. Recently, there has been renewed interest in linear scheduling. Much of this interest has involved a technique called the linear scheduling method (LSM). Only recently has there been the ability to calculate the controlling activities of a linear schedule, independent of network analysis. Additional research needs to be done to develop some of the techniques available in CPM into comparable ones for linear scheduling. One of these techniques is resource leveling. This paper uses the vehicle of a highway construction project to present an integer linear programming formulation to level the resources of linear projects.

Time-cost trade-off analysis is one of the most important aspects of construction project planning and control. There are trade-offs between time and cost to complete the activities of a project; in general, the less expensive the resources used, the longer it takes to complete an activity. Using critical path method (CPM), the overall project cost can be reduced by using less expensive resources for noncritical activities without impacting the project duration. Existing methods for time-cost trade-off analysis focus on using heuristics or mathematical programming. These methods, however, are not efficient enough to solve large-scale CPM networks (hundreds of activities or more). Analogous to natural selection and genetics in reproduction, genetic algorithms (GAs) have been successfully adopted to solve many science and engineering problems and have proven to be an efficient means for searching optimal solutions in a large problem domain. This paper presents: (1) an algorithm based on the principles of GAs for construction time-cost trade-off optimization; and (2) a computer program that can execute the algorithm efficiently.

This paper presents a new application of process simulation to construction activities to assess the operational and economic impacts of technological innovations. The first construction model developed is structural steel erection, and this model is used to identify the potential benefits and costs of eight specific erection innovations, and any changes that may be required in material, equipment, or process to use them. The model includes the process flow diagram of detailed tasks which is matched to specific design elements, production rates, operating conditions, and resources to calculate activity durations, taking into account the capacity of the resources, worker safety, structural stability, and other constraints. The results from the simulation model incorporating the erection innovations indicates that structural steel erection could be significantly improved by the use of some technical innovations. In addition, the use of simulation for the evaluation of construction methods offers great promise. Index Terms - Construction industry, process simulation, structural steel erection, technological innovation, technology assessment, worker safety.

The application of simulation in the construction industry has always been hindered by the complexities involved in constructing simulation models and the resultant time requirement. This paper presents a modeling method for construction simulation - resource-based modeling (RBM), in which operating processes of active resources are defined as atomic models (basic and unique description of a particular process) and are stored in a model library. These atomic models can be modified to form project-specific atomic models according to user-specified project information. Through defined linking structures, they can be assembled into a working simulation model for the project. Therefore, the user can construct a simulation model for a project by simply specifying required resources and project site conditions. The modeler does not have to be proficient with simulation theory and the selected simulation language. Our experience with implementing simulation in the construction industry shows that this is an effective approach. A sample application is used to illustrate the RBM concepts and its advantages.

Modeling construction is a critical step for understanding it and improving its performance. The thrust of this research paper is the need for the development of valid credible models as a logical precursor to automation. This article reviews the key models used to represent construction. Through this examination, it makes an important distinction between process and system modeling concepts. This distinction is the basis for concluding that no single tool, by itself, is accurately capable of fully modeling both construction system and construction work processes. Thus an integrated approach to modeling is required. Accordingly, the research conducted by the writers utilized a new integrated modeling approach that combines a set of descriptive tools to allow the development of various perspectives of construction. This article presents one of these tools as a new system modeling concept that overcomes deficiencies in current system modeling approaches. The power of this new model is illustrated in a detailed comparison among key current system modeling concepts.

This paper presents a performance modeling methodology for application to individual projects. The model combines experience captured from experts with assessments from the project team. The methodology consists of a conceptual, qualitative-model structure and a mathematical-model structure. The conceptual-model structure, called the general performance model (GPM), is a simplified model of the variables and interaction that influence project performance. The mathematical model uses concepts of cross-impact analysis and probabilistic inference to capture the uncertainties and interactions among project variables. The GPM allows management to test different combinations of project-execution options and predict expected cost, schedule, and other performance impacts. The methodology provides a systematic and structured process for a project-team discussion on relevant planning issues in a project. Researchers should benefit from the exploratory and analytical capabilities of the methodology, as well as the flexible knowledge structure to update models and data. Computer implementation is also attractive as a means to disseminating research results.

Design-build contracting is becoming an increasingly viable alternative to traditional contracting techniques in the public sector. This interest has led to dialogue among public sector agencies for establishing greater understanding of the design-build process and its implementation. The present paper discusses results of recent research conducted to develop a formalized model for public sector design-build. The model includes identifying (1) Sequential, concurrent, and hierarchical management activities; (2) management decisions required throughout the process; and (3) relationships between activities and decisions required to plan the project. The five phases of design-build planning presented in the model include identifying facilities for design-build, performing project coordination, developing the request for proposal, performing proposal evaluation, and conducting contract administration. Though the scope of the research is primarily design-build contracting for the U.S. Army Corps of Engineers Military Construction Army program, it can be generalized to other public sector agencies.

This paper presents a model for selecting an approach to implement constructability. Constructability can be implemented using an informal or formal approach. Based upon this research, three approaches, one informal and two formal, have been identified and labeled as follows: (1) Informal approach; (2) formal project level; and (3) comprehensive tracking. The model consists of a hierarchy of decision levels. Within these levels, there exist three steps: (1) Individual assessment of owner and project characteristics resulting in a conclusion of informal or formal; (2) combining owner and project characteristics into a single conclusion of informal or formal; and (3) if formal is concluded, a decision as to whether it is formal project-level or comprehensive tracking. To assess owner and project characteristics, a framework of variables described by parameters has been developed. The characteristics of an owner consist of four variables: (1) Owner type; (2) objectives; (3) in-house expertise; and (4) constructability resources. The characteristics of a project are described by six variables: (1) Construction type; (2) contracting strategy; (3) project size; (4) technical difficulty; (5) location; and (6) peculiarities. The model was tested by six owners on seven different projects. The results were consistent with the constructability approach selected by the owner. The model can assist owners in efficiently determining the appropriate means by which to incorporate construction knowledge and experience into the designs of their projects.

In modeling for simulation, the proper representation of crucial real-world variables is of prime importance. This paper describes the creation of a model that allows simulation of the construction process to be conducted in a simple fashion, in the field, and in a way that is oriented to the attributes of the specific resources available for the process. The developed model uses resources and their attributes as variables. This allows for consideration of resources of different sizes for the same work task, calculation of running task durations during simulation, rule-based release of resources from queues, and maintenance of detailed statistics on each type and size of resource used in the system. Experimentation with established equipment mixes and conditions as shown in published handbooks for earthwork processes has verified the capability of the system to predict production rates for differing equipment mixes and site conditions.

The Nationals Park stadium in Washington D.C. was constructed in just under two years due to the use of the building information modeling (BIM) process. The BIM process incorporates 3-D modeling of the structure's components which is linked parametrically to almost all aspects of the project. This process is discussed in detail in the context of the National Park's construction.

This paper develops a probabilistic construction load process model for multistory reinforced-concrete building construction. This model considers loads causing peak structural actions on floor slabs for two widely used shoring procedures and includes probability distributions and temporal characteristics of slab self-weight, sustained construction live loads, 'material stacking' loads, and 'move-in' loads. Construction load statistics derived from Monte Carlo simulation show that the mean of maximum construction loads exceeds nominal (design) service (occupancy) loads whenever the nominal live-to-dead load ratio is less than approximately 1.0. A Type I extreme value distribution provided the best fit to the inferred distributions of construction live loads.

In this paper a number of serviceability issues related mainly to excessive deflections of structural floor elements (beams and slabs) are discussed. Field data of serviceability damage caused by excessive deflections of structural floor elements have been collected from various sources and probabilistic models are developed. Current serviceability specifications for allowable deflection limits in Australian, U.S., and other concrete structure codes have been compared against these probabilistic distributions of damaging deflections. Preliminary results confirm that allowable deflection limits in these design codes represent realistic lower-bound values of damaging deflections.

Research in monocular building extraction from aerial imagery has neglected performance evaluation in three areas: unbiased metrics for quantifying detection and delineation performance, an evaluation methodology for applying these metrics to a representative body of test imagery, and an approach for understanding the impact of image and scene content on building extraction algorithms. This paper addresses these areas with an end-to-end performance evaluation of four existing monocular building extraction systems, using image space and object space-based metrics on 83 test images of 18 sites. This analysis is supplemented by an examination of the effects of image obliquity and object complexity on system performance, as well as a case study on the effects Of edge fragmentation. This widely applicable performance evaluation approach highlights the consequences of various traditional assumptions about camera geometry, image content, and scene structure, and demonstrates the utility of rigorous photogrammetric object space modeling and primitive-based representations for building extraction. Index Terms - Monocular building extraction, performance evaluation, object detection, feature delineation, photogrammetry, computer vision, metrics.