MACROS: Multiobjective Automated Construction Resource Optimization System

This paper presents the development of a practical and automated system for optimizing the utilization of construction resources to simultaneously minimize project cost and duration while maximizing project quality. The system is named the Multiobjective Automated Construction Resource Optimization System (MACROS), and it incorporates four newly developed modules: (1) a multiobjective optimization module to quantify and optimize the impact of resource utilization decisions on construction duration, cost, and quality; (2) a relational database module to facilitate the storage and retrieval of construction scheduling and optimization data; (3) a middleware module to provide seamless integration between the internal modules in MACROS and external commercially available project management software; and (4) a user interface module to facilitate the input of project data and the visualization and ranking of the generated optimal construction plans. An example project of 180 activities is analyzed to illustrate the use of MACROS and demonstrate its unique and practical construction optimization capabilities.     

Estimating Work Zone Road User Cost for Alternative Contracting Methods in Highway Construction Projects

Highway construction often causes an additional road user cost (RUC) to motorists due to traffic flow interruption and congestion in work zones. Consequently, facility owners, such as the Florida Department of Transportation (FDOT), are often interested in using alternative contracting methods such as A+B contracting to expedite construction. Although many of these contracting methods rely on the RUC to determine incentives or disincentives, no standard method for RUC calculation is available to FDOT district engineers. In addition, existing methods are neither practical nor user-friendly for determining incentives or disincentives. This study intends to develop a RUC calculation procedure for the FDOT that focuses on using data that are easily accessible to FDOT district engineers, such as drawings and maintenance of traffic plans. The procedure is developed based on traffic analysis methods published in the Highway Capacity Manual, previous studies on user benefit analysis and work zones, and empirical data specific to Florida. Case studies are used to illustrate the procedure and to compare it with two other existing models, the Arizona model and the queue and user cost evaluation of work zone model, through correlation analysis, comparison of calculation assumptions, and data input analysis. This study shows that the suggested procedure produces consistent RUC estimates.     

SERC—A Model for Estimating Construction Inputs

One of the main problems in the process of design and management of construction projects is obtaining accurate information for preliminary estimates. This information is crucial for the development of integrated systems for construction management because of the relationship between construction input data and subjects such as estimating, cost control, scheduling, resource management, etc. Existing methods for estimating input that originated in industrial engineering are inadequate for the unique conditions of the construction industry. The model described in this paper applies statistical analysis of data from past projects, and enables the user to estimate the data needed for the construction of a new project. The model is based on the following components: Project items and their quantities; inputs needed to produce those items; and factors that affect inputs of a specific project. The model equation was calculated using multiple regression techniques. The paper concludes with a case study of a construction input configuration for a concrete structure.     

Integrated Simulation System for Construction Operation and Project Scheduling

Simulation modeling is important in predicting the productivity of construction operations and the performance of project schedules. It would be desirable if operation and project models are vertically integrated in practice. However, existing discrete event simulation systems do not allow integrating operation and project models. This paper introduces an integrated simulation system named “Construction Operation and Project Scheduling” (COPS). COPS analyzes the productivity of construction operations as well as the performance of a project schedule individually and jointly. It creates operation models, maintains these models in its operation model library, conducts sensitivity analysis with different resource combinations, finds the optimal resource combination that satisfies the user’s requirements relative to hourly production and hourly cost of the operation, feeds this information into a project schedule, and executes stochastic simulation-based scheduling. A case study is presented to demonstrate this integrated simulation system.     

Charging composition and structure optimisation in the sintering process (Part I)

In this paper, an optimisation system for charging composition and structure in the sintering process was established in order to reduce the sinter cost in the ironmaking process. The system comprised four modules: sinter metallurgical performance testing and analysis, sintering burdening design and optimisation, sintering matching calculation, and sinter component and property prediction. The data for the first module came from actual production values of a steelworks and from testing in the laboratory. Based on material balance theory, the second module used a linear programming method to optimise sinter cost, quality and quantity. The third module was built to predict the sintering production data. The fourth module can be used to predict some composition and properties of the sinter based on a Back-Propagation neural network. The system integrated all of these modules using Visual Basic and MATLAB. As the result, the optimum charging composition and structure of sinter which satisfies all constraint conditions can be obtained. Compared with traditional production testing and hand calculation in the sintering process the system can reduce the sinter cost and greatly decrease the production risk. Industrial application proves that the system is very useful and efficient in reducing sinter cost while ensuring output quantity and quality.     

Construction Congestion Cost (CO3) Basic Model

The Construction Congestion Cost System (CO3) is an integrated set of tools to estimate impact of traffic maintenance contract provisions on congestion, road user cost, and construction cost. CO3 produces realistic budgets and selects practical contracting methods that provide an acceptable balance between construction cost and congestion. This paper describes the underlying CO3 model of traffic demand, delay, and user cost, particularly the methods by which CO3 calculates traffic backup and delay, diverted and canceled trips, and road user cost. It provides examples that illustrate the CO3 model and methods. CO3 models the common characteristic of construction work zones by which road capacity can vary from hour to hour as lanes close and open and work conditions change. Traffic demand also varies with time of day, and drivers may divert to an alternate route or cancel trips because of delays caused by construction. CO3 estimates traffic delay due to traffic congestion as a function of demand and capacity, and it estimates traffic cancellations and diversions as functions of traffic delay.     

Construction Congestion Cost (CO3) Traffic Impact and Construction Cost

The Construction Congestion Cost System (CO3) is an integrated set of tools to estimate impact of traffic maintenance contract provisions on congestion, road user cost, and construction cost. Engineers use CO3 to produce realistic budgets and select practical contracting methods that provide an acceptable balance between construction cost and congestion. This paper demonstrates computation of impacts associated with alternative methods of maintaining traffic during construction. The Routes Sheet computes equivalent average vehicle routes for complex diversion routes. The Input Sheet provides for documentation of vehicle and route inputs and computes user cost for individual trips through the work zone, diversions, and cancellations. The Traffic Sheet computes daily traffic impacts and user costs for each construction method. The Construction Sheet computes impact of different construction methods on construction costs. The Impact Sheet summarizes daily impacts and computes total project traffic impacts, road user costs, and construction costs for all alternatives. These tools provide practical information with which engineers select construction methods whose impacts are acceptable.     

Siren: A Repetitive Construction Simulation Model

SIREN (SImulation of REpetitive Networks) is a computer model of repetitive construction such as the construction of multi‐story buildings, housing estates, linear projects, etc. The user interactively inputs a precedence diagram for the repetitive unit (e.g., one floor of a skyscraper) and additional “sub‐networks” that are not part of the repetitive sequence (e.g., first floor of skyscraper). From this information, the computer generates the whole network. Data is input via an IBM‐PC at which point extensive error checking is carried out. The model itself is coded in the GPSS language and runs on a remote mainframe computer. It simulates the various crews as they queue to carry out activities. A working schedule and cumulative cost curve are produced and statistics are gathered on crew and equipment utilization, all being output graphically. A Monte‐Carlo simulation is also included as probability distributions may be associated with the duration of each activity. This yields confidence intervals on cumulative costs throughout the project and on milestone attainment.     

D-SUB: Decision Support System for Subcontracting Construction Works

Letting work to subcontractors is a very common practice in construction industry. Subcontractors help contractors overcome problems including the need of special expertise, shortage in resources, and limitation in finances. The decision to subcontract involves designating work items to be subcontracted and making assignments to subcontractors. Generally, work assignments to subcontractors can be for the total quantity of a work item or a proportion thereof. This paper presents a decision support system that makes assignments to subcontractors of the work items designated for subcontracting. Moreover, the system calculates and plots the overdraft profile based on the financial terms of the contract and project schedule. The ultimate goal of the system is to make work assignments to subcontractors under constraints economical and predict the expected profit at the end of the project. The system encompasses four basic components including project data, linear programming module, sensitivity analysis module, and financial analysis module. The sensitivity analysis adds strength and flexibility to the system by allowing the user to experiment with different scenarios. Finally, the developed system that represents a structured method for making subcontracting decisions is demonstrated through an illustrative example project.     

Determination of Most Economical Scrapers Fleet

Scrapers are valuable construction equipment for large earthmoving operations. Their production rates vary widely as they depend on the equipment performance, operation’s travel time, and haul-road conditions. Determining the most economical selection of the size, model, and number of scrapers is a rather tedious process that involves repetitive calculations. A spreadsheet application was created in order to facilitate such calculations and select the most economical scraper from the list of available equipment for the job under consideration. The application is made of seven spreadsheets containing a scrapers’ database, performance charts, soil properties, and other supporting worksheets. The application provides a user interface to solicit all data entries specific to a project. Once the user enters the required data the system compares the production rate, time required for the job, determines the estimated unit cost for each scraper in the database, and recommends the most economical selection.     

Estimating Labor Production Rates for Industrial Construction Activities

This paper discusses an approach based on artificial neural networks that enables an estimator to produce accurate labor production rates (labor∕unit) for industrial construction tasks such as welding and pipe installation. The paper first reviews factors that were found to affect labor production rates on industrial construction tasks, current estimating practices and their limitations, and the process followed in collecting historical production rates. An artificial neural network model is then described. The model is composed of a two-stage artificial neural network, which is used to predict an efficiency multiplier (an index) based on input factors identified by the user. The multiplier is then used to adjust an average production rate given in man-hours∕unit for use on a specific project. Estimates of production rates from the new approach are compared to the existing estimating practices and conclusions are presented.     

Production System Loading–Cycle Time Relationship in Residential Construction

Production home building possesses characteristics similar to manufacturing processes, such as the construction of more or less similar houses repeatedly and a growing demand for mass customization of homes. As a result of these similarities, larger homebuilders often attempt to view their production system as an assembly line process. However, the management tools generally utilized by these home builders are those used in other sectors of the construction industry, such as critical path method scheduling, cost estimating, and earned value analysis. These management tools do not provide an explanation or control/prediction tools for many undesirable situations that arise during home building, such as increasing cycle time which slows delivery of product to consumers and increases project capital costs, and increasing amounts of work in process that increases capital investment and thereby decreases company financial performance. In order to bring better management tools to the residential construction industry, this study examines relationships between cycle time, work in process, system throughput, new construction starts, and the capacity of the production system using building permit data for new single family homes in Chandler, Ariz. The applicability of Little’s law, a basic equation used in factory production management models, to a residential production system is examined. This study shows a definite, predictable relationship between cycle time, work in process, and production system throughput. It provides a pathway for further study of production system characteristics that have historically not been included in construction management models, with the expectation of developing new construction management tools that will account for more of the characteristics of construction production systems that affect project performance and company financial performance.     

Computer Model for Life-Cycle Cost Analysis of Roadway Pavements

This paper describes the development of a computer model that performs life-cycle cost analysis (LCCA) of roadway pavements, analyzing the cost of both the agency and the user. Agency costs are a function of the type of rehabilitation, restoration, resurfacing, or reconstruction (i.e., 4R) treatment applicable to each pavement type, given its surface distress and structural condition. The cost of each treatment is calculated from the unit prices specified for the activities involved and the roadway geometry. User costs include vehicle operating and nonvehicle operating costs, which are a function of pavement roughness, as well as user delay costs, which are a function of lane closure practice. User benefits are calculated as savings in user costs due to reduction in pavement roughness from its current state to that of a new pavement. At the roadway network level, sections are flagged for analysis in decreasing benefit-cost order, whereby the cost of the most capital-intensive 4R treatment is considered. Sections flagged at the network level are carried forward to the project level analysis. The project level analysis allocates the available budget among the sections selected to maximize user benefits over the analysis period. The software package implementing this methodology, called pavement investment decisions (PID) is generic; that is, it allows customizing through a series of input screens to fit the pavement management database and practices of any state Department of Transportation (DOT).     

压覆资源开采经济参数敏感性分析

针对压覆矿产资源开采工程量大、程序复杂的特点,以财务评价为基本评价方法,建立了以最大收益为目标作为压覆资源开采经济评价的收益模型,并确定了压覆资源价值、开采成本及搬迁成本基本模型中各参数的基准参数值。以收益模型为基础,进行了模型参数变量扰动的敏感性分析,分析得出铝土矿价格是模型中的最重要的敏感因素,并对其他敏感因素进行了敏感性排序,可为工程评价提供一定的指导。     

Long‐Range Forecasting Highway Construction Costs

In the process of decision making for design and execution of highway construction projects, long‐range cost forecasting is one of the most significant and complicated problems. This paper describes the development of a model that enables the user to make long‐range cost projections, taking into consideration general characteristics of the highway construction industry, as well as pertinent local conditions. The model presented uses conventional statistical methods to represent the main categories of typical jobs in the highway construction industry. From these categories, a composite model is created by assigning different weights to the input elements costs and then choosing a series of indicators to predict price trends for each separate element of the composite model. Use of this model reveals that bid volume in a certain area is a factor that has significant influence upon cost forecasts. This paper is accompanied by a case study based on actual data from highway construction projects performed for the Florida Department of Transportation in the years 1968–1981.     

Simplified Spreadsheet Solutions.?I: Subcontractor Information System

This paper presents a subcontractor information system (SIS) to support the estimating and project control functions of subcontractors and small∕medium-size contractors. For the proposed SIS to be simple and practical, it was developed in a spreadsheet program designed to maintain information related to resources and projects and to generate important business reports. Resource data are stored in six worksheets for labor, equipment, crews, material, subcontractors, and alternative methods of construction for various tasks. In addition, a separate worksheet is designed for each project to be used for estimating and control purposes. The latter worksheet allows the user to specify the work breakdown structure and optional methods for construction. As such, it represents a transparent estimating model that allows for quick what-if analysis regarding time and cost. In addition, the reporting worksheet provides information related to time, cost, and resource use at the individual and the multiproject levels. In a companion paper, the use of the SIS as basis for overall schedule optimization is described.     

HKCONSIM: A Practical Simulation Solution to Planning Concrete Plant Operations in Hong Kong

Newly developed approaches for construction simulation have been used to model the one-plant-multisite ready mixed concrete (RMC) production system, validated by real-life operations data in Hong Kong. HKCONSIM—a computer system for simulation modeling and analysis of Hong Kong’s RMC production operations was developed in-house. The system is suitable for the resource provision planning and the production planning of a RMC plant, so as to meet given demands at a number of sites for concrete over a working day. The emphasis of the simulation modeling is on the interactions of multiple sites with the plant, and the objective is to improve the supply service levels and the utilization of plant resources. One significant improvement achieved via the research is that to simulate the RMC production operations with HKCONSIM does not require familiarity by the user with any software-specific terminology and modeling schematics, in contrast with existing simulation methods; the process of constructing a simulation model is reduced to specifying the attributes for each pour and site and providing the plant and truckmixer resources available on self-explanatory on-screen forms. Therefore, by experimenting on a HKCONSIM produced model the user, being a practitioner in the concreting industry, can readily study complicated relationships between the pattern of demand for concrete, the resources available to the system, and the service levels achieved together with the utilization levels achieved for the resources involved. Conclusions are given on the research and recommendations for future work made.     

Productivity Scheduling Method: Linear Schedule Analysis with Singularity Functions

This paper describes a new integrated method of linear schedule analysis using singularity functions. These functions have previously been used for structural analysis and are newly applied to scheduling. Linear schedules combine information on time and amount of work for each activity. A general model is presented with which activities and their buffers can be mathematically described in detail. The algorithm of the new method forms the body of the paper, including the steps of setting up initial equations, calculating pairwise differences between them, differentiating these to obtain the location of any minima, and deriving the final equations. The algorithm consolidates the linear schedule under consideration of all constraints and, thus, automatically generates the minimum overall project duration. The model distinguishes time and amount buffers, which bears implications for the definition and derivation of the critical path. Future research work will address float and resource analysis using the new model.     

厚料层烧结技术的经济学解释

烧结料层透气性的Voice公式与经济学中的"柯-道生产函数"具有相似性,它们都是用来说明投入与产出之间的技术关系。用经济学中"规模效用递减"的基本法则和"边际分析"方法,引入到烧结生产中料层高度和抽风负压对烧结矿产出的分析中;作出了烧结生产的等成本曲线、等产出曲线;获得厚料层烧结生产条件下数量型增长和效益型增长的理论模型;首次从经济学角度解释了中国厚料层烧结生产机理和扩张路径,给出了烧结生产经济区的定义和确定方法;最后,提出厚料层烧结技术的发展方向不是单一或多个投入要素的提高,而是需要向提高全要素生产率的方向发展。