Generic Process Mapping and Simulation Methodology for Integrating Site Layout and Operations Planning in Construction

The present research is intended to address dynamic construction-process simulation methods, with a focus on how to effectively model resource transit among various activity locations in the site system. Following a review of basic simulation paradigms and recent research developments, we propose a new process mapping and simulation methodology for modeling construction operations. The simulation algorithm is presented and the process mapping procedure is illustrated step by step using an earth-moving example featuring technology and resource constraints. It is straightforward to convert the resultant process mapping model describing workflows and resource flows over site locations into a simulation model. A STROBOSCOPE model is formed for the same problem definition to contrast and cross-validate our methodology with the established activity cycle diagram-based modeling approach. One additional case of modeling the concreting site operations by the hoist and barrow method is also given to demonstrate the application of the proposed methodology in practical settings.     

Simulation Approach to Evaluating Cost Efficiency of Selective Demolition Practices: Case of Hong Kong’s Kai Tak Airport Demolition

This research resorted to the use of construction operations simulation modeling to investigate the cost efficiency of waste-handling practices on the Kai Tak Airport demolition project in Hong Kong. By modeling the site operation of sieving and stockpiling broken concrete, the well-established construction simulation methodology of CYCLONE was contrasted with the newly developed simplified discrete event simulation approach (SDESA). Further, the SDESA model was readily extended to include (1) raw demolition waste collecting and sorting; (2) broken concrete sieving and stockpiling; (3) steel bar recycling; and (4) debris disposal at the landfill. The production rate derived from simulation was indicative of a close match between the simulation model and the actual site system. The resulting simulation model provided a basis for evaluating the cost efficiency of actual site operations and alternative resource provision scenarios being postulated. Through computer simulation, the actual site operation was found smooth and efficient with utilization rates for resources of different types ranging from 79 to 99%. In addition, the cost–time reduction ratios were calculated for four alternatives of resource provisions in comparison with the original base case. The research findings suggested that provided the project budget had satisfied the higher cash flow requirement, doubling the resource provision on site would potentially cut the project duration by half and not increase the total direct cost.     

Activity-Based Construction (ABC) Modeling and Simulation Method

This research presents the activity-based construction (ABC) modeling and simulation method. ABC modeling (ABC-Mod) uses one single element (e.g., activity) for modeling general construction processes instead of multiple elements as required by current simulation systems. ABC simulation (ABC-Sim) executes the ABC model by manipulating activities in three stages: (1) Select activity; (2) advance simulation; and (3) release simulation entities. ABC-Mod and ABC-Sim constitute a unique simulation method, generally addressed as ABC. In summary, ABC is a general-purpose modeling and simulation method with an emphasis on construction application. Compared with existing simulation systems, it has all of the major features required for modeling and simulating the dynamic and random behaviors of a construction process. It requires no more knowledge to use than the critical path method does. Therefore, ABC is a simulation method for construction engineers and it has a potentially wide range of application in the industry.     

Development of Lean Model for House Construction Using Value Stream Mapping

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.     

Integrating Construction Operation and Context in Large-Scale Construction Using Hybrid Computer Simulation

This research proposes a hybrid simulation approach based upon the principles of system dynamics (SD) and discrete event simulation (DES), which facilitates a better understanding of complex interactions among various processes in large-scale construction. The significance of the construction context that interacts with construction operations is highlighted, and a hybrid SD-DES approach is proposed as a means to capture the feedback between the two. In particular, this paper focuses on how to seamlessly integrate SD and DES within the framework of a modeling perspective. For the purpose of substantiating the discussion, a pipeline installation process is modeled using the proposed hybrid approach, with specific consideration given to how the approach can serve to address complex interactions between operation and context.     

RISim: Resource-Interacted Simulation Modeling in Construction

Discrete-event simulation is an effective approach to analyze construction operations. However, it is usually time-consuming and knowledge demanding to develop a practical simulation model, and thus not cost-effective due to the uniqueness and relatively short life of construction projects. The capability of discrete-event simulation modeling has not been popularly recognized by site managers until recently. A clear and explicit solution is to simplify and speed up the model development cycle, so as to enable users without much knowledge of simulation technology to easily generate a model in a relatively short period of time. In this paper, a resource-interacted simulation (RISim) modeling approach is presented, which adopts a resource oriented methodology to promote an intuitive feel to simulation modeling. In RISim, an operation is modeled in two abstraction levels—namely, the resource level and process level. An operation is viewed as a collection of resources and their interactions. Complex resources and simple resources are used to respectively represent resources with or without their own processes. The operation logic is mainly represented with internal complex resource flows, which are integrated by simple resource flows between complex resources. Resource flows can be easily conceived by site managers, enabling them to build up the logic naturally and simply. A resource library is used to implement resource reusability. Finally, an example in concrete delivery operation illustrates the methodology of resource-interacted simulation modeling and its potential for “plug-in and simulate.”     

Research status on modeling and simulation of iron ore sintering process

Iron ore sintering is a part of blast furnace ironmaking production. In order to upgrade the sintering automation and intelligent manufacturing, it is necessary to carry out sintering process modeling and simulation optimization. The research status of sintering process modeling and simulation was discussed. And three kinds of model, namely process mechanism and feature information characterization model, data- driven fusion model and field state analysis numerical simulation model, were summarized from the aspects of information modeling and intelligent optimization. The advantages and disadvantages of a series of model construction methods were analyzed by combining with automation requirement of sintering process, and the simulation models application trends were proposed. According to the requirement of sintering intelligent manufacturing that included in the ??Made in China 2025?? plan, the production practices of sintering process modeling and simulation optimization are crucial.     

中日城市建筑垃圾处置技术、政策对比研究

在对中日两国在建筑垃圾方面的相关政策、法律法规调研的基础上,聚焦于两国具有代表性的城市上海和东京,通过举例论证等方式详细介绍了两国各自在建筑垃圾处置方面的现状和工艺技术。我国在建筑垃圾的处置方面,以简单的人工分选、破碎、筛分为主,处置的废料来源主要以废弃混凝土和拆房垃圾为主。受制于处置费用,废料的品质向纯混凝土和混有约10%混凝土的砖混垃圾两极分化,后期的再生骨料应用市场也截然不同。日本在建筑垃圾治理方面,配套的法律政策、再生产品后期消纳途径、对应的再生产品应用标准都十分健全,治废企业可以实现较好的良性运转。在处置技术方面,日本工厂依赖多道人工进行精细分选,以提高后期再生产品的品质。同时,日本在治理前期的建筑垃圾和被污染的土壤方面,技术也更加成熟、先进。结合两国的调研结果,文末提出了我国对于建筑垃圾处置的管理政策、标准规范一些建议。     

Life-Cycle-based Solid Waste Management. I: Model Development

This paper describes an integrated solid waste management (ISWM) model to assist in identifying alternative SWM strategies that meet cost, energy, and environmental emissions objectives. An SWM system consisting of over 40 unit processes for collection, transfer, separation, treatment (e.g., combustion, composting), and disposal of waste as well as remanufacturing facilities for processing recycled material is defined. Waste is categorized into 48 items and their generation rates are defined for three types of sectors: single-family dwelling, multifamily dwelling, and commercial. The mass flow of each item through all possible combinations of unit processes is represented in a linear programming model using a unique modeling approach. Cost, energy consumption, and environmental emissions associated with waste processing at each unit process are computed in a set of specially implemented unit process models. A life-cycle approach is used to compute energy consumption and emissions of CO, fossil- and biomass-derived CO2,NOx,SOx, particulate matter, PM10 and greenhouse gases. The model is flexible to allow representation of site-specific issues, including waste diversion targets, mass flow restrictions and requirements, and targets for the values of cost, energy, and each emission. A companion paper describes the application of this model to examine several SWM scenarios for a hypothetical, but realistic, case study.     

Integrating Construction Process Documentation into Building Information Modeling

The research described in this paper extends the use of building information modeling (BIM) throughout the construction phase of the project life cycle. The owner is a military base that uses three-dimensional (3D) modeling for underground services and the footprints of the buildings. They were interested in determining the feasibility of capturing the construction process and related documents into a similar format. The research was conducted in parallel with traditional methods. The objectives of this project were to create a 3D as-built model, a four-dimensional as-built model, and attach the construction process information to the model for the owner to use after construction. A literature review indicates that BIM application stops at the preconstruction phase with a limited amount of research regarding data collection of the construction process. Significant contributions include practical 3D data collection methods and extending the BIM software products to accommodate construction process documentation. Results indicate that BIM software is not specifically prepared to accomplish these objectives and some modification to procedures as well as software were necessary for the BIM to capture the construction process documentation.     

Materials Handling System Simulation in Precast Viaduct Construction: Modeling, Analysis, and Implementation

The interactive, complicated system environment of a construction site renders conventional site layout planning and scheduling techniques to be inadequate in coping with materials handling system design in construction. In this paper, we present a university-industry joint endeavor for improving the effectiveness of the materials handling system on a precast viaduct construction project in Hong Kong by implementing the simplified discrete-event simulation approach (SDESA) along with its computer platform resulting from recent research. How to apply the simulation methodology of SDESA is elaborated step by step. Particular emphasis is placed on procedures of establishing a simulation model, validation of the simulation model, design of simulation experiments, and analysis of simulation results. With process flowchart, site layout plan, and process animation produced in a view-centric simulation environment, it is straightforward to establish, validate, and communicate the operations simulation. The research team convinced the project director, as well as field managers, of the functionality and effectiveness of operations simulation. The knowledge derived from simulation added to experiences of site managers in materials handling system design. With the aid of simulation, even junior engineers would be capable and confident to draw up an actionable construction plan that would lead to enhancement of cost effectiveness and productivity in the field.     

Process Model Perspectives on Management and Engineering Procedures in the Precast/Prestressed Concrete Industry

The preparation of detailed models of information and process flow by 14 member companies of the North American Precast Concrete Software Consortium has provided a unique window into the current management, engineering design, and production operations in this industry. The modeling was performed using the authors’ Georgia Tech Process for Product Modeling tool, within the framework of the consortium’s effort to develop a precast concrete product model and to specify new integrated three dimensional modeling software. The paper opens with a comparative economic review of precast construction internationally and in North America, which reveals that the market share of precast construction in North American is relatively low. The models are analyzed and aspects of the underlying management procedures that they reveal are discussed, such as types of contracting arrangements, cost estimating, design outsourcing, engineering design communication, mold design, product diversity, and quality control. The results highlight aspects of precast management processes that may be re-engineered through appropriate application of information technology.     

固体废物处理技术进展

系统地论述了我国固体废物目前的现状、产量，分析了医疗废物、生活垃圾焚烧厂飞灰、生活垃圾和工业固体废物处理过程中存在的主要问题和解决办法，提出了深入开展固体废物处理与资源化研究的方向，特别是有关生活垃圾深度分选技术研究和应用、危险废物的预处理技术等。     

Modeling Controlled Water Systems

The particular challenges of modeling controlled water systems are discussed. The high degree of freedom due to the control structures increases the risk of producing the right output for the wrong reasons. On the other hand, many controlled water systems are (partly) manually operated or at least supervised by an operational water manager. The decisions of these managers are not as rigid as a computer simulated control strategy. Therefore, getting a very close fit with a water-system control model is mostly not possible. A modeling framework is proposed that takes advantage of the vast availability of measurement data in controlled water systems. The water level and flow data at control structures allow for intensive validation and subsystem calibration to reduce the degree of modeling freedom and to model separately the natural rainfall-runoff and hydrodynamic processes. The framework is successfully applied to improve a simulation model of the controlled water system of Rijnland, The Netherlands. The yearly volume error was reduced from 11% to less than 1% and as a consequence, the short-term peak events were modeled more accurately as well. The resulting water-system control model is more reliable for both design studies and operational decision support. The framework will contribute to prepare more reliable simulation models of controlled water systems.     

Activity Object-Oriented Simulation Strategy for Modeling Construction Operations

The application of an object-oriented (OO) approach including the OO modeling concept and the OO programming mechanisms to develop an activity object-oriented (AOO) simulation strategy for modeling construction operations is introduced. After discussing simulation strategies generally used for construction simulation and analyzing the problems related to the simulation strategies, the AOO simulation strategy that guides modeling or controls simulation experiments for construction simulation is introduced. The AOO simulation strategy considers activities to be objects and is able to overcome some pitfalls that result from other general simulation strategies. In addition, the AOO graphical modeling interface associated with the AOO simulation strategy is described. Finally, comparisons of the graphical model or the simulation results of the AOO simulation system with other simulation tools are illustrated.     

Spatial System Dynamics: New Approach for Simulation of Water Resources Systems

A new approach called spatial system dynamics (SSD) is presented to model feedback based dynamic processes in time and space. This approach is grounded in control theory for distributed parameter systems. System dynamics and geographic information system (GIS) are coupled to develop this modeling approach. The SSD modeling approach offers a single modeling framework for developing conceptually different models. It also provides the much-needed capability to model feedback based complex dynamic processes in time and space while giving insight into the interactions among different components of the system. The proposed approach is superior to existing techniques for dynamic modeling such as cellular automata and GIS and addresses most of the limitations present in these approaches. The SSD approach can be used to model a variety of physical and natural processes where the main interest is the space–time interaction, e.g., environmental/water resources processes, natural resources management, climate change, and disaster management. The applicability of the proposed approach is demonstrated with an application to flood management in the Red River basin in Manitoba, Canada.     

Construction Process Reengineering by Integrating Lean Principles and Computer Simulation Techniques

A construction process reengineering framework and its corresponding methodologies have been developed by integrating lean principles and computer simulation techniques. Instead of classifying activities into value-adding and non-value-adding activities, or into conversion and flow activities as is common in lean production practices, this framework classifies activities into main and supportive activities and/or into normal and interactive activities. This classification makes it more effective in modeling the construction workflow and reengineering the construction process. It also avoids the confusion of the classification of activities into value-adding and non-value-adding activities encountered in the construction industry. In addition, computer simulation techniques are incorporated into the framework to virtually simulate and assess the efficiency and effectiveness of the reengineered construction process that is achieved based on lean principles. Simulation makes it easier to quantify and assess the effectiveness and efficiency of the reengineered construction process.     

Quantification of Spatial Temporal Congestion in Four-Dimensional Computer-Aided Design

This paper further develops the models proposed by prior research in the field of workspace conflict using four-dimensional computer-aided design. The approach developed here analyzes spatial demand and supply from the perspective of construction operators, and a modeling methodology based on spatiotemporal utilization is proposed. The utilization factor model is developed to show that the criticality of the operator’s spatiotemporal demand leads to worksite congestion and that congestion is a form of worksite conflict. The interference of other space entities increases the space demand, and this increment is quantified with a “dynamic space interference” index This indicator is developed to identify activity spaces which suffer congestion. A decision making tool, the “congestion penalty indicator,” is developed which obtains a schedule-level value for analysis, evaluation, and comparison. Finally, a case study on the refurbishment of an oil refinery column is used to demonstrate the application of the above concepts in successfully identifying a better schedule with respect to on-site congestion.     

Models Quantify the Total Maximum Daily Load Process

Mathematical models have been used for many years to assist in the management of water quality. The total maximum daily load (TMDL) process is no exception; models represent the means by which the assimilative capacity of a water body can be quantified and a waste load allocation can be determined such that the assimilative capacity is not exceeded. Unfortunately, in many TMDLs, the use of models has not always adhered to the best modeling practices that have been developed over the past half-century. This paper presents what are felt to be the most important principles of good modeling practice relative to all of the steps in developing and applying a model for computing a TMDL. These steps include: Problem definition and setting management objectives; data synthesis for use in modeling; model selection; model calibration and, if possible confirmation; model application; iterative modeling; and model postaudit. Since mathematical modeling of aquatic systems is not an exact science, it is essential that these steps be fully transparent to all TMDL stakeholders through comprehensive documentation of the entire process, including specification of all inputs and assumptions. The overriding consideration is that data richness and quality govern the level of model complexity that can be applied to a given system. The model should never be more complex than the data allow. Also, in applying a model, one should always attempt to quantify the uncertainty in predictions. In general, quantifying uncertainty is easier with simple models, which is another reason to begin with a simple framework.