Overview of construction simulation approaches to model construction processes
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paper_title: Project-Network Analysis Using Fuzzy Sets Theory

paper_content:

Estimating the durations of construction activities requires experts knowledge. Statements used by these experts usually contain some sort of imprecision. Previous studies have demonstrated the use of fuzzy set theory for quantifying the imprecision associated with the durations or project activities. These studies, however, did not address the processing of this information for generating a complete schedule. This paper presents a new network scheduling method based on fuzzy sets theory. The proposed method incorporates a number of new techniques that facilitate: (1) the representation of imprecise activity durations; (2) the calculation of scheduling parameters; and (3) the interpretation of the fuzzy results generated. Two network examples are worked out to illustrate the use of the proposed method, and to compare its capabilities with Monte Carlo simulation. The results indicate that the proposed method is capable of providing schedules that can appropriately account for the nature as well as the type of uncertainties normally encountered in construction projects. The results are in close agreement with those obtained using Monte Carlo simulation. The calculations are, however, more simple, requiring less computational effort than that needed in Monte Carlo simulation. The proposed method is practical and can be easily computerized.
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paper_title: A hybrid simulation approach to model and improve construction labor productivity

paper_content:

This research presents an integrated fuzzy System Dynamics (SD) approach for modeling and improving of labor productivity. The complex inter-related structure of different factors affecting labor productivity is modeled using SD approach. Owing to the imprecise and uncertain nature of many factors affecting the labor productivity, fuzzy logic is integrated into system dynamics to account for the existing uncertainties. The values of different uncertain factors affecting the labor productivity are determined by fuzzy numbers based on the opinions of different experts involved in the project. Using the proposed fuzzy-SD approach, the value of labor productivity is determined as a fuzzy number considering the effects of all the influencing factors. Different alternative solutions are then defined to improve the labor productivity. The impact of the alternative solutions on project performance is simulated using the proposed fuzzy-SD model prior to their actual implementation. Using the proposed integrated fuzzy-SD approach, the project manager may decide on the most appropriate alternative solution to improve the labor productivity.
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paper_title: Subjective and interactive duration estimation

paper_content:

Scheduling of construction projects with an uncertainty content requires that the scheduler's subjective knowledge of various factors that might influence the duration of the activities comprising the project is incorporated. Depending on the participating factors and their significance, a different duration outcome is often observed for each activity. To include this uncertainty in the schedule, a statistical distribution is frequently used. This paper presents a system based on the premise that part of the information available, when duration distribution is being estimated, exists in a subjective form. We present an automated system that requires the modeler to specify the activity's minimum and maximum times and a set of linguistic descriptors of the external factors that are suspect of influencing the duration. The lower and upper end point estimates are often available from familiarity with the technology used, physical and logical constraints, or a combination of these situations. The subjective in...
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paper_title: Predicting Industrial Construction Labor Productivity using Fuzzy Expert Systems

paper_content:

The objective of this technical note is to illustrate the application of fuzzy expert systems to the modeling of a practical problem—that of predicting the labor productivity of two common industrial construction activities: rigging pipe and welding pipe. This note illustrates how to develop and test such a model, given the realistic constraints of subjective assessments, multiple contributing factors, and limitations on data sets. The factors that affect the productivity of each activity are identified, and fuzzy membership functions and expert rules are developed. The models are validated using data collected from an actual construction project. The resulting models are found to have high linguistic prediction accuracies. This note is of relevance to researchers by demonstrating how a fuzzy expert system can be developed and tested. It is of relevance to industry practitioners by illustrating how fuzzy logic and expert systems modeling can be exploited to help them solve real world problems.
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paper_title: Statistical Properties of Construction Duration Data

paper_content:

Simulators of construction operations often must approximate the underlying distribution of a random process using a standard statistical distribution (e.g., lognormal, normal, and beta). In many of these cases, the underlying distribution of the random process remains unknown to the modeler and its properties have to be inferred from the available sample of data or from experience with similar processes. This paper summarizes the findings of research aimed at investigating the statistical properties of construction duration data. Seventy-one samples of durations of construction activities are analyzed by: (1) Plotting the sample’s coefficient of skewness and kurtosis on a β\N\d1-β\N\d2 plane, and (2) constructing histograms for each sample and comparing them with the shapes of known probability density functions. The results of the research indicate that flexible distributions (e.g., the beta distribution and Pearson system) are required to ensure proper modeling for the diversified characteristics of construction duration data.
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paper_title: Methodology for synchronizing Discrete Event Simulation and System Dynamics models

paper_content:

Integrating Discrete Event Simulation (DES) and System Dynamics (SD) simulation methods require synchronization of their simulation clocks to ensure that actions are executed in an orderly manner. This paper presents a synchronization methodology for integrating DES and SD models. A hybrid simulation-based method consisting of SD components at the higher decision level and DES components at the lower decision level is expected to benefit from the developed method. The proposed methodology integrates DES and SD models on a single platform, which enhances the simulation of construction operations. It consists of three elements: (1) advancing mechanism, (2) DES advancing algorithm, and (3) messages sequence mechanism. The paper provides a description of the three elements of the synchronization method. An illustrative preliminary experiment that utilizes DES and SD engines is presented to demonstrate the use of the developed synchronization method and to illustrate its capabilities.
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paper_title: Agent-based modeling and simulation in construction

paper_content:

Agent-based modeling and simulation (ABMS) is a relatively new development that has found extensive use in areas such as social sciences, economics, biology, ecology etc. Can ABMS be effectively used in finding answers to complex construction systems? Our focus is to provide some answers to this question. Initial experimentation is conducted to understand the advantages of using ABMS either in isolation or in combination with traditional simulation methodologies. We provide a summary of this experimentation, conclusions and sets the agenda for future research in this area.
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paper_title: Using Agent-Based Modeling to Study Construction Labor Productivity as an Emergent Property of Individual and Crew Interactions

paper_content:

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.
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paper_title: System dynamics: A soft and hard approach to modelling

paper_content:

System Dynamics (SD) can be employed for qualitative and quantitative modelling. There are important tools and methods within SD that can be easily accommodated within qualitative modeling, also known as Soft Operational Research or problem structuring method. While traditional stocks and flows are the basic components of quantitative SD modeling, quantitative SD modeling shares many commonalities, e.g. empirically driven, thorough testing, and critical focused to outputs, with traditional simulation methods and quantitative Operations Research tools. This tutorial informs novice modelers on the aspects to consider when they want to use SD as a qualitative and quantitative modeling method. In any approach employed, the use of SD modeling needs to be grounded in relevant literature from the perspective employed, qualitative or quantitative.
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paper_title: Application of agent-based modeling and simulation to understanding complex management problems in CEM research

paper_content:

AbstractAs construction projects have become larger and more complex, they develop different features than smaller or traditional projects, which characterize them as complex systems. Still, Construction Engineering and Management (CEM) researchers have mostly relied on traditional approaches to investigate complex management problems, which might produce misleading results. This paper introduces Agent-Based Modeling and Simulation (ABMS) as a research method, and addresses how it could be applied to CEM research. With an illustrative example of the application of ABMS to CEM research, the theoretical background as well as the design, development, and test processes of ABMS are presented. We then made a recommendation on the promising research subjects in CEM area to which ABMS could be suitably applied.
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paper_title: Modelling construction project productivity using systems dynamics approach

paper_content:

Purpose - Improvement in productivity will not be achieved without bearing in mind that there is an enormous number of factors affecting productivity and that there is a necessity to locate the most influential ones among them. Doing so will enable researchers as well as practitioners to pinpoint the areas where efforts are to be directed in order to reach the optimum productivity of the studied project. The work described in this paper is based on data collected from the construction industry in the UK. In collecting the information, there are three initial aims: to determine what factors affected productivity at site level, to determine how these factors interacted and to determine the significance of the factors. Design/methodology/approach - The research method undertaken is to model productivity in construction using system dynamics. In particular, it concentrates on the use of system dynamics and project level productivity. The literature identifies 34 factors affecting productivity but based on a survey of professionals, five of these are recognised as important. They form the basis of a systems model whose development is described. Findings - The results of testing the developed model have suggested that investments in planning and control have most benefits on project productivity and that investments in safety, motivation and reduction of disruptions are beneficial. Originality/value - The use of system dynamics to model productivity represents untraditional and novel approach in research in construction. The developed model is valuable in that it can be used to evaluate management strategies and their effects on project productivity.
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paper_title: Understanding the complexity of project team member selection through agent-based modeling

paper_content:

Abstract Previous research has recognized the significance of a team's work capacity and suggested the selection of team members based on individual skills and performance in alignment with task characteristics. However, work teams are complex systems with interdependence between workers and the social environment, and exhibit surprising, nonlinear behavior. This study utilizes Agent-Based Modeling (ABM) to understand the complexity of project team member selection and to examine how the functional diversity of teams and worker interdependence affect team performance in different economic conditions. Data for model validation was collected from 116 construction projects for the period from 2009 to 2011. The results show that teams with higher functional diversity can enhance the overall firm performance when the economy is in a downturn. This study suggests managers using knowledge of worker interdependence to protect higher-performing workers by minimizing disruption of interdependence in team member selection for improving firm performance.
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paper_title: Strategic-Operational Construction Management: Hybrid System Dynamics and Discrete Event Approach

paper_content:

A significant number of large-scale civil infrastructure projects experience cost overruns and schedule delays. To minimize these disastrous consequences, management actions need to be carefully examined at both the strategic and operational levels, as their effectiveness is mainly dependent on how well strategic perspectives and operational details of a project are balanced. However, current construction project management approaches have treated the strategic and operational issues separately, and consequently introduced a potential conflict between strategic and operational analyses. To address this issue, a hybrid simulation model is presented in this paper. This hybrid model combines system dynamics and discrete event simulation which have mainly been utilized to analyze the strategic and operational issues in isolation, respectively. As an application example, a nontypical repetitive earthmoving process is selected and simulated. The simulation results demonstrate that a systematic integration of strategic perspective and operational details is helpful to enhance the process performance by enabling construction managers to identify potential process improvement areas that traditional approaches may miss. Based on the simulation results, it is concluded that the proposed hybrid simulation model has great potential to support both the strategic and operational aspects of construction project management and to ultimately help increase project performance.
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paper_title: Hybrid simulation studies and Hybrid Simulation systems: Definitions, challenges, and benefits

paper_content:

Hybrid Simulation (HS) is not new. However there is contention in academic discourse as to what qualifies as HS? Is there a distinction between multi-method, multi-paradigm and HS? How do we integrate methods from disciplines like OR and computer science that contribute to the success of a M&S study? How do we validate a hybrid model when the whole (the combined model) is greater than the sum of its parts (the individual models)? Most dynamic simulations have a notion of time, how do we realize a unified representation of simulation time across methodologies, techniques and packages, and how do we prevent causality during inter-model message exchange? These are but some of the questions which we found to be asking ourselves frequently, and this panel paper provided a good opportunity to stimulate a discussion along these lines and to open it up to the M&S community.
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paper_title: A hybrid simulation framework for modelling construction projects using agent-based modelling and system dynamics: an application to model construction workers' safety behavior

paper_content:

ABSTRACTThe integration of system dynamics (SD) with ideas from agent-based modelling (ABM) offers potential to combine the strengths of the two methodologies. By investigation of the previous research works, it is revealed that there is a lack of a simple and applicable framework to develop a hybrid SD–ABM simulation approach. This research proposes a hybrid SD–ABM simulation framework for modelling construction projects. The dynamics of project environment arising from the complex interrelated structure of various influencing continuous factors are taken into account using SD. The complexity of the system emerges from the interactions between different agents is also accounted by ABM. The SD and ABM simulation paradigms are finally combined. To evaluate the performance of the proposed hybrid simulation framework, it is implemented in a real construction project. The safety behaviour of different working groups involved in the project is modelled using the proposed hybrid simulation framework. The influe...
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paper_title: Modeling Framework and Architecture of Hybrid System Dynamics and Discrete Event Simulation for Construction

paper_content:

: Construction system modeling aims to improve construction work performance by tracking the dynamic behaviors of construction systems. More accurate system modeling can be achieved by considering the mutual effects of construction operations on the context level of the system. Hybrid models of discrete event simulation (DES) and system dynamics aim to capture these mutual effects to provide model developers with more precise system analysis. Although system dynamics models are used to capture the behavior of the system at the context level, DES models are utilized to capture construction operations. The potential benefits of utilizing hybrid models for complex systems have been argued and established, but there are still limited studies that have utilized this modeling approach for real construction systems. In this research, we have attempted to identify the challenging issues that have caused this problem and to confront this problem by proposing a hybrid framework and architecture, which address these challenges. To verify the effectiveness of the new model, the performance of the proposed hybrid modeling framework and architecture has been tested by applying the proposed model in a real-scale construction-related system.
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paper_title: A hybrid simulation approach to model and improve construction labor productivity

paper_content:

This research presents an integrated fuzzy System Dynamics (SD) approach for modeling and improving of labor productivity. The complex inter-related structure of different factors affecting labor productivity is modeled using SD approach. Owing to the imprecise and uncertain nature of many factors affecting the labor productivity, fuzzy logic is integrated into system dynamics to account for the existing uncertainties. The values of different uncertain factors affecting the labor productivity are determined by fuzzy numbers based on the opinions of different experts involved in the project. Using the proposed fuzzy-SD approach, the value of labor productivity is determined as a fuzzy number considering the effects of all the influencing factors. Different alternative solutions are then defined to improve the labor productivity. The impact of the alternative solutions on project performance is simulated using the proposed fuzzy-SD model prior to their actual implementation. Using the proposed integrated fuzzy-SD approach, the project manager may decide on the most appropriate alternative solution to improve the labor productivity.
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paper_title: Towards a theory of multi-method M&S approach: part I

paper_content:

The current level of theoretical, methodological, and pragmatic knowledge related to a multi-method modeling and simulation (M&S) approach is limited as there are no clearly identified theoretical principles that guide the use of multi-method M&S approach. Theoretical advances are vital to enhance methodological developments, which in turn empower scientists to address a broader range of scientific inquiries and improve research quality. In order to develop theoretical principles of multi-method M&S approach, the theory of falsification is used in an M&S context to provide a meta-theoretical basis for analysis. Moreover, triangulation and commensurability are characterized and investigated as additional relevant concepts. This paper proposes four theoretical principles for justification of the use of a multi-method M&S approach, which will be analyzed and used to implement methodological guidelines in a subsequent work. A final discussion offers initial implications of the proposed theoretical view.
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paper_title: Multi-method modeling

paper_content:

Frequently, the problem cannot completely conform to one of the three existing modeling paradigms (discrete event, system dynamics, or agent based modeling). Thinking in terms of a single-method modeling language, the modeler inevitably either starts using workarounds (unnatural and cumbersome constructs), or just leaves part of the problem outside the scope of the model (treats it as exogenous). If our goal is to capture business, economic, and social systems in their interaction, this becomes a serious limitation. In this paper we offer an overview of most used multi-method (or multi-paradigm) model architectures, discuss the technical aspects of linking different methods within one model, and consider examples of multi-method models. The modeling language of AnyLogic is used throughout the paper.
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paper_title: An Overview of Hybrid Simulation Phenomena and Their Support by Simulation Packages

paper_content:

Hybrid systems combine continuous behavior evolution speci fied by differential equations with discontinuous changes specified by discrete event switching logic. Numerical simulation of continuous behavior and of discrete behavior is well understood. However, to facilitate simulation of mixed continuous/discrete systems a number of specific hybrid simulation issues must be addressed. This paper presents an overview of phenomena that emerge in simulation of hybrid systems, reported in previously published literature. They can be classified as (i) event handling, (ii) run-time equation processing, (iii) discontinuous state changes, (iv) event iteration, (v) comparing Dirac pulses, and (vi) chattering. Based on these phenomena, numerical simulation requires the implementation of specific hybrid simulation features. An evaluation of existing simulation packages with respect to these features is presented.
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paper_title: Role of Simulation in Construction Engineering and Management

paper_content:

Construction simulation is the science of developing and experimenting with computer-based representations of construction systems to understand their underlying behavior. This branch of operations research applications in construction management has experienced significant academic growth over the past two decades. In this paper, the author summarizes his views on this topic as per his Peurifoy address, given in October 2008. The paper provides an overview of advancements in construction simulation theory as reported in literature. It then summarizes the key factors that contribute to successful deployment of simulation in the construction industry, and the key attributes of problems that make them more amenable for simulation modeling as opposed to other tools. The paper then provides an overview of long-term simulation initiatives leading to the next generation of computer modeling systems for construction, where simulation plays an integral role in a futuristic vision of automated project planning and control.
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paper_title: Multi-method modeling

paper_content:

Frequently, the problem cannot completely conform to one of the three existing modeling paradigms (discrete event, system dynamics, or agent based modeling). Thinking in terms of a single-method modeling language, the modeler inevitably either starts using workarounds (unnatural and cumbersome constructs), or just leaves part of the problem outside the scope of the model (treats it as exogenous). If our goal is to capture business, economic, and social systems in their interaction, this becomes a serious limitation. In this paper we offer an overview of most used multi-method (or multi-paradigm) model architectures, discuss the technical aspects of linking different methods within one model, and consider examples of multi-method models. The modeling language of AnyLogic is used throughout the paper.
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paper_title: Integrating Fuzzy Logic and agent-based modeling for assessing construction crew behavior

paper_content:

Construction crew worker behavior emerges from interaction with fellow crew members, social influence, interaction with the environment, and personal characteristics (e.g., self-efficacy, goal commitment). Agent-based modeling is a good solution for handling complex systems of interacting agents and therefore is suitable for modeling construction crew behavior. Agent-based modeling can handle system complexities that arise from interactions of the system components; however, many systems—especially those comprising human behavior and social relationships—also include subjective uncertainties, which are not accounted for in agent-based modeling. Fuzzy logic, on the other hand, is able to deal with subjective uncertainty; therefore, for modeling behavioral and social systems such as construction crew behavior, integrating these two techniques is advantageous. In this paper, we present the concept of agent-based modeling, then we introduce the concept of integrating fuzzy logic and agent-based modeling. Finally, we present the development of a fuzzy agent-based model of construction crew behavior that will allow us to predict construction crew performance. The contribution of this paper is in introducing the integration of fuzzy logic and agent-based modeling in construction modeling and developing a fuzzy agent-based model of construction crew behavior.
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paper_title: Project-Network Analysis Using Fuzzy Sets Theory

paper_content:

Estimating the durations of construction activities requires experts knowledge. Statements used by these experts usually contain some sort of imprecision. Previous studies have demonstrated the use of fuzzy set theory for quantifying the imprecision associated with the durations or project activities. These studies, however, did not address the processing of this information for generating a complete schedule. This paper presents a new network scheduling method based on fuzzy sets theory. The proposed method incorporates a number of new techniques that facilitate: (1) the representation of imprecise activity durations; (2) the calculation of scheduling parameters; and (3) the interpretation of the fuzzy results generated. Two network examples are worked out to illustrate the use of the proposed method, and to compare its capabilities with Monte Carlo simulation. The results indicate that the proposed method is capable of providing schedules that can appropriately account for the nature as well as the type of uncertainties normally encountered in construction projects. The results are in close agreement with those obtained using Monte Carlo simulation. The calculations are, however, more simple, requiring less computational effort than that needed in Monte Carlo simulation. The proposed method is practical and can be easily computerized.
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paper_title: Fuzzy sets versus probability

paper_content:

One of the aims of the theory of fuzzy sets is the development of a methodology for the formulation and solution of problems which are too complex or ill-defined to be susceptible to analysis by conventional techniques. Because of its unorthodoxy, it has been and will continue to be controversial for some time. Eventually, though, the theory of fuzzy sets is likely to be recognized as a natural development in the evolution of scientific thinking. In retrospect, the skepticism about its usefulness will be viewed as a manifestation of the human attachment to tradition andre sistance to innovation.
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paper_title: Methodology for integrating fuzzy expert systems and discrete event simulation in construction engineering

paper_content:

This paper demonstrates how fuzzy expert systems can be integrated within discrete event simulation models to enhance their modeling and predictive capabilities for construction engineering applications. A proposed methodology is presented for extracting the information from experts to develop the fuzzy expert system rules. The developed fuzzy expert system is integrated within a discrete event simulation model to enhance its modeling capability by explicitly accounting for the different factors affecting some of the simulation activities. A tunneling case study is used to illustrate the features of the integrated system. The outputs generated from the integrated system are very comparable to those from the original probabilistic simulation model. The integrated system represents a more realistic modeling scenario, since it thoroughly accounts for the different factors affecting the tunnel boring machine (TBM) advance rate. This paper is relevant to researchers because it provides an advance in combining ...
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paper_title: A hybrid simulation approach to model and improve construction labor productivity

paper_content:

This research presents an integrated fuzzy System Dynamics (SD) approach for modeling and improving of labor productivity. The complex inter-related structure of different factors affecting labor productivity is modeled using SD approach. Owing to the imprecise and uncertain nature of many factors affecting the labor productivity, fuzzy logic is integrated into system dynamics to account for the existing uncertainties. The values of different uncertain factors affecting the labor productivity are determined by fuzzy numbers based on the opinions of different experts involved in the project. Using the proposed fuzzy-SD approach, the value of labor productivity is determined as a fuzzy number considering the effects of all the influencing factors. Different alternative solutions are then defined to improve the labor productivity. The impact of the alternative solutions on project performance is simulated using the proposed fuzzy-SD model prior to their actual implementation. Using the proposed integrated fuzzy-SD approach, the project manager may decide on the most appropriate alternative solution to improve the labor productivity.
---
paper_title: Subjective and interactive duration estimation

paper_content:

Scheduling of construction projects with an uncertainty content requires that the scheduler's subjective knowledge of various factors that might influence the duration of the activities comprising the project is incorporated. Depending on the participating factors and their significance, a different duration outcome is often observed for each activity. To include this uncertainty in the schedule, a statistical distribution is frequently used. This paper presents a system based on the premise that part of the information available, when duration distribution is being estimated, exists in a subjective form. We present an automated system that requires the modeler to specify the activity's minimum and maximum times and a set of linguistic descriptors of the external factors that are suspect of influencing the duration. The lower and upper end point estimates are often available from familiarity with the technology used, physical and logical constraints, or a combination of these situations. The subjective in...
---
paper_title: Predicting Industrial Construction Labor Productivity using Fuzzy Expert Systems

paper_content:

The objective of this technical note is to illustrate the application of fuzzy expert systems to the modeling of a practical problem—that of predicting the labor productivity of two common industrial construction activities: rigging pipe and welding pipe. This note illustrates how to develop and test such a model, given the realistic constraints of subjective assessments, multiple contributing factors, and limitations on data sets. The factors that affect the productivity of each activity are identified, and fuzzy membership functions and expert rules are developed. The models are validated using data collected from an actual construction project. The resulting models are found to have high linguistic prediction accuracies. This note is of relevance to researchers by demonstrating how a fuzzy expert system can be developed and tested. It is of relevance to industry practitioners by illustrating how fuzzy logic and expert systems modeling can be exploited to help them solve real world problems.
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paper_title: Overview of fuzzy simulation techniques in construction engineering and management

paper_content:

Simulation has long been used in the construction domain to model construction systems. Simulation techniques (e.g., discrete event simulation, system dynamics, and agent-based modeling) are well-equipped to handle complex systems; however, they fail to account for the subjective uncertainties present in many construction systems. Fuzzy logic, on the other hand, is a powerful tool for dealing with subjective uncertainty; therefore, integrating these two techniques is advantageous in modeling construction systems. In this paper, we present an overview of simulation techniques in construction. Then, we introduce the advancements that have been made by incorporating fuzzy logic with simulation techniques, and we propose methodologies for developing fuzzy simulation models. Finally, we discuss the process of choosing a suitable simulation technique for construction modeling. In addition to providing an overview of simulation techniques accessible to the construction domain, the main contribution of this paper is in introducing methods for integrating fuzzy logic with simulation techniques.
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paper_title: Project Scheduling Using Fuzzy Set Concepts

paper_content:

Probabilistic methods are being used increasingly in construction engineering. However, when a parameter is expressed in linguistic rather than mathematical terms, classical probability theory fails to incorporate the information. The linguistic variables can be translated into mathematical measures using fuzzy set and system theory. A construction management problem, i.e., estimation of the duration of an activity, is solved using this theory. In order to implement the proposed technique, various membership functions need to be estimated using judgment or with the assistance of experts. The proposed technique is not sensitive to small variations in the membership values. This is a very desirable property. However, the method is sensitive to the choice of the fuzzy relations. The uncertainty in the fuzzy relations can be modeled along with other sources of uncertainty. The mean and variance of the parameters involved in the problem under consideration are estimated here using a new method. The method maxi...
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paper_title: Using fuzzy logic to implement decision policies in system dynamics models

paper_content:

A fuzzy logic-system dynamics methodology is proposed to enhance learning within virtual worlds.Theoretical discussion on the motivation and advantages of the integration.Case study applying the FL-SD methodology to a virtual world model of a Dynamic Balanced Scorecard. This paper aims to show how the use of fuzzy systems can enhance the application of system dynamics (SD), with the construction of virtual worlds, for organizational learning. By doing so, the main contribution is to propose a fuzzy-SD integrated methodology that allows a natural language modeling of decision policies. At first it will be revised the recent literature with practical and theoretical fuzzy-SD integration showing that the motivation and purpose of this article have not been explored yet. Following, it will be scrutinized the origin of system dynamics to theoretically justify the proposed fuzzy-SD integration for organizational learning. Finally, it will be presented a hypothetical case study based on the balance scorecard model to illustrate the methodology in action.
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paper_title: Modeling uncertain activity duration by fuzzy number and discrete-event simulation

paper_content:

This paper introduces how to incorporate fuzzy set theory and a fuzzy ranking measure with discrete-event simulation in order to model uncertain activity duration in simulating a real-world system, especially when insufficient or no sample data are available. Fuzzy numbers are used to describe uncertain activity durations, reflecting vagueness, imprecision and subjectivity in the estimation of them. A fuzzy ranking measure is merged with an activity scanning simulation algorithm for performing fuzzy simulation time advancement and event selection for simulation experimentation. The uses of the fuzzy activity duration and the probability distribution-modeled duration are compared through a series of simulation experiments. It is observed that the fuzzy simulation outputs are arrived at through only one cycle of fuzzy discrete-event simulation, still they contain all the statistical information that are produced through multiple cycles of simulation experiments when the probability distribution approach is adopted.
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paper_title: Integrating system dynamics and fuzzy logic modeling to determine concession period in BOT projects

paper_content:

Abstract The concession period is one of the most important decision variables in arranging a BOT-type contract which should be determined considering the existing risks and uncertainties. This research presents an integrated fuzzy-system dynamics (SD) approach for determination of concession period. The complex inter-related structure of different factors affecting a BOT project is modeled using the system dynamics approach. Owing to the imprecise and uncertain nature of different factors affecting the concession period, fuzzy logic is integrated into the system dynamics modeling structure. The values of different factors affecting the concession period are determined by fuzzy numbers based on the opinions of different experts involved in the project. The application of Zadeh's extension principle and interval arithmetic is proposed for the system dynamics to enable the system outcomes to be presented considering uncertainties in the input variables. To evaluate the performance of the proposed method, it has been employed in a highway project.
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paper_title: Modeling Framework and Architecture of Hybrid System Dynamics and Discrete Event Simulation for Construction

paper_content:

: Construction system modeling aims to improve construction work performance by tracking the dynamic behaviors of construction systems. More accurate system modeling can be achieved by considering the mutual effects of construction operations on the context level of the system. Hybrid models of discrete event simulation (DES) and system dynamics aim to capture these mutual effects to provide model developers with more precise system analysis. Although system dynamics models are used to capture the behavior of the system at the context level, DES models are utilized to capture construction operations. The potential benefits of utilizing hybrid models for complex systems have been argued and established, but there are still limited studies that have utilized this modeling approach for real construction systems. In this research, we have attempted to identify the challenging issues that have caused this problem and to confront this problem by proposing a hybrid framework and architecture, which address these challenges. To verify the effectiveness of the new model, the performance of the proposed hybrid modeling framework and architecture has been tested by applying the proposed model in a real-scale construction-related system.
---
paper_title: Multi-method modeling

paper_content:

Frequently, the problem cannot completely conform to one of the three existing modeling paradigms (discrete event, system dynamics, or agent based modeling). Thinking in terms of a single-method modeling language, the modeler inevitably either starts using workarounds (unnatural and cumbersome constructs), or just leaves part of the problem outside the scope of the model (treats it as exogenous). If our goal is to capture business, economic, and social systems in their interaction, this becomes a serious limitation. In this paper we offer an overview of most used multi-method (or multi-paradigm) model architectures, discuss the technical aspects of linking different methods within one model, and consider examples of multi-method models. The modeling language of AnyLogic is used throughout the paper.
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paper_title: An introductory tutorial on verification and validation of simulation models

paper_content:

Model verification and validation are defined, and why model verification and validation are important is discussed. A graphical paradigm that shows how verification and validation are related to the model development process and a flowchart that shows how verification and validation is part of the model development process are presented and discussed. The three approaches to deciding model validity are described. Comments are made on the importance of model accuracy and documentation. An overview of conducting verification and validation is presented and a recommended procedure for verification and validation is given.
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paper_title: Crew Allocation System for the Masonry Industry

paper_content:

Masonry construction is labor-intensive. Processes require a large number of crews made up of masons with diverse skills, capabilities, and personalities. Often crews are reassembled and the superintendent in the site is responsible for allocating crews to balance between the complexity of the job and the need for quality and high production rates. However, the masonry industry still faces increased time and low productivity rates that result from inefficiencies in crew allocation. This article presents a system for efficient crew allocation in the masonry industry formulated as a mixed-integer program. The system takes into consideration characteristics of masons and site conditions and how to relate these to determine the right crew for the right wall to increase productivity. With the system, superintendents are not only able to identify working patterns for each of the masons but also optimal crew formation, completion times, and labor costs. To validate the model, data from a real project in the United States is used to compare the crew allocation completed by the superintendent onsite with the one proposed by the system. The results showed that relating characteristics of workers with site conditions had a substantial impact on reducing the completion time to build the walls, maximizing the utilization of masons, and outlining opportunities for concurrent work.
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paper_title: Construction Baseline Productivity: Theory and Practice

paper_content:

In this paper, the theoretical basis for construction labor productivity measurement is presented. In particular, the theoretical basis for baseline productivity measurements is developed by examining a productivity database consisting of 23 projects involving masonry construction. An important hypothesis is presented showing that as the design becomes more complex, the baseline productivity worsens. It is also hypothesized that higher values of the coefficient of variation indicates a higher variability in management and craft skills and in the use of technology. Two measures are proposed to measure the performance of individual projects: the disruption index and the project management index. These two measures identify the best and worst performing projects. Cumulative probability distributions of the disruption index and the project management index were also developed to evaluate the 23-project database and compare it with other databases. The hypotheses developed from the 23-masonry project database were tested against an eight-project database of concrete formwork and a 12-project database of structural steel erection. Strong support for each hypothesis was found using the two additional databases.
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paper_title: Modeling Framework and Architecture of Hybrid System Dynamics and Discrete Event Simulation for Construction

paper_content:

: Construction system modeling aims to improve construction work performance by tracking the dynamic behaviors of construction systems. More accurate system modeling can be achieved by considering the mutual effects of construction operations on the context level of the system. Hybrid models of discrete event simulation (DES) and system dynamics aim to capture these mutual effects to provide model developers with more precise system analysis. Although system dynamics models are used to capture the behavior of the system at the context level, DES models are utilized to capture construction operations. The potential benefits of utilizing hybrid models for complex systems have been argued and established, but there are still limited studies that have utilized this modeling approach for real construction systems. In this research, we have attempted to identify the challenging issues that have caused this problem and to confront this problem by proposing a hybrid framework and architecture, which address these challenges. To verify the effectiveness of the new model, the performance of the proposed hybrid modeling framework and architecture has been tested by applying the proposed model in a real-scale construction-related system.
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paper_title: Methodology for synchronizing Discrete Event Simulation and System Dynamics models

paper_content:

Integrating Discrete Event Simulation (DES) and System Dynamics (SD) simulation methods require synchronization of their simulation clocks to ensure that actions are executed in an orderly manner. This paper presents a synchronization methodology for integrating DES and SD models. A hybrid simulation-based method consisting of SD components at the higher decision level and DES components at the lower decision level is expected to benefit from the developed method. The proposed methodology integrates DES and SD models on a single platform, which enhances the simulation of construction operations. It consists of three elements: (1) advancing mechanism, (2) DES advancing algorithm, and (3) messages sequence mechanism. The paper provides a description of the three elements of the synchronization method. An illustrative preliminary experiment that utilizes DES and SD engines is presented to demonstrate the use of the developed synchronization method and to illustrate its capabilities.
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paper_title: System dynamics: A soft and hard approach to modelling

paper_content:

System Dynamics (SD) can be employed for qualitative and quantitative modelling. There are important tools and methods within SD that can be easily accommodated within qualitative modeling, also known as Soft Operational Research or problem structuring method. While traditional stocks and flows are the basic components of quantitative SD modeling, quantitative SD modeling shares many commonalities, e.g. empirically driven, thorough testing, and critical focused to outputs, with traditional simulation methods and quantitative Operations Research tools. This tutorial informs novice modelers on the aspects to consider when they want to use SD as a qualitative and quantitative modeling method. In any approach employed, the use of SD modeling needs to be grounded in relevant literature from the perspective employed, qualitative or quantitative.
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paper_title: Crew Allocation System for the Masonry Industry

paper_content:

Masonry construction is labor-intensive. Processes require a large number of crews made up of masons with diverse skills, capabilities, and personalities. Often crews are reassembled and the superintendent in the site is responsible for allocating crews to balance between the complexity of the job and the need for quality and high production rates. However, the masonry industry still faces increased time and low productivity rates that result from inefficiencies in crew allocation. This article presents a system for efficient crew allocation in the masonry industry formulated as a mixed-integer program. The system takes into consideration characteristics of masons and site conditions and how to relate these to determine the right crew for the right wall to increase productivity. With the system, superintendents are not only able to identify working patterns for each of the masons but also optimal crew formation, completion times, and labor costs. To validate the model, data from a real project in the United States is used to compare the crew allocation completed by the superintendent onsite with the one proposed by the system. The results showed that relating characteristics of workers with site conditions had a substantial impact on reducing the completion time to build the walls, maximizing the utilization of masons, and outlining opportunities for concurrent work.
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paper_title: System dynamics: A soft and hard approach to modelling

paper_content:

System Dynamics (SD) can be employed for qualitative and quantitative modelling. There are important tools and methods within SD that can be easily accommodated within qualitative modeling, also known as Soft Operational Research or problem structuring method. While traditional stocks and flows are the basic components of quantitative SD modeling, quantitative SD modeling shares many commonalities, e.g. empirically driven, thorough testing, and critical focused to outputs, with traditional simulation methods and quantitative Operations Research tools. This tutorial informs novice modelers on the aspects to consider when they want to use SD as a qualitative and quantitative modeling method. In any approach employed, the use of SD modeling needs to be grounded in relevant literature from the perspective employed, qualitative or quantitative.
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Title: Overview of construction simulation approaches to model construction processes

Section 1: Introduction
Description 1: This section introduces the concept of simulation in construction processes and provides a brief overview of the paper's structure.

Section 2: Basic simulation methods
Description 2: This section describes the basic simulation methods, including Discrete-Event Simulation (DES), System Dynamics (SD), and Agent-Based Modeling (ABM).

Section 3: Hybrid simulation approaches
Description 3: This section details the hybrid simulation approaches that combine two or more basic simulation methods to leverage their advantages.

Section 4: Combinations of the basic simulation methods
Description 4: This section gives an example of combining all three basic simulation methods and discusses the benefits of such combinations.

Section 5: Use of FL
Description 5: This section explores how Fuzzy Logic (FL) can be combined with basic simulation methods to improve model accuracy.

Section 6: The structure of hybrid simulation models
Description 6: This section discusses the different structures that can be used to combine multiple simulation methods in a hybrid model.

Section 7: Interface variables in the hybrid simulation
Description 7: This section identifies and explains the interface variables that connect different components in a hybrid simulation model.

Section 8: Simulation framework
Description 8: This section presents a framework for modeling construction processes with simulation, outlining each step in the process.

Section 9: Application of the framework—an example
Description 9: This section demonstrates the application of the simulation framework using an example from masonry construction.

Section 10: Conclusion
Description 10: This section summarizes the benefits of construction simulation, discusses the potential of hybrid approaches, and suggests directions for future research.