Binary Resource Leveling Model: Activity Splitting Allowed

The resource leveling problem is common and has been studied numerous times. In these studies and the resulting solutions, there exists a common element, which is once an activity is started, it cannot be stopped and restarted again. That is, it cannot be split. In many instances in actual construction, there exist activities that can be stopped and restarted. However, not all activities have this characteristic. This paper presents a linear program binary variable model to level resources that permits selected activities to stop and restart. This splitting of activities results in improvement to the leveling solution that is traditionally achieved when splitting is not permitted. Examples are presented that illustrate the improvement in the solution obtained from the proposed model compared to models that do not allow splitting and compares the result to that obtained using commercially available software. The results are beneficial to construction professionals who may be unaware of the impacts of using activity splitting.     

Cost Optimization Model for the Multiresource Leveling Problem with Allowed Activity Splitting

Resource leveling aims at minimizing the resource usage fluctuations, which is accomplished by moving noncritical activities within their float. The project duration is fixed and is not affected by the leveling. Most of resource leveling techniques assumes that activities cannot be split. Although this assumption is valid for most construction activities, there are several activities that can be split to achieve better resource leveling. However, there is an added cost associated with splitting such as startup and restarting costs. This paper presents an optimization model for resource leveling that allows activity splitting and minimizes its associated costs. The objective is to level resources in a way that provides a tradeoff between the extra cost of acquiring and releasing resources versus the extra cost of activity splitting. The model can be used to determine at what values of the splitting cost, the preemption of an activity is recommended. One example problem is solved at the end of the paper in order to illustrate the proposed model.     

Constructing a Complex Precast Tilt-Up-Panel Structure Utilizing an Optimization Model, 3D CAD, and Animation

This paper presents the concept used to construct a complex residential tilt-up-panel structure utilizing three-dimensional (3D) modeling and animations. The residence comprises of 108 precast concrete panels of varying rectangular shapes with “dog legs” and window and door “cutouts” that look like an assembled jigsaw puzzle. The erection and installation procedure called for a maximum panel-to-panel joint tolerance of 1.27?cm (0.5?in.), often in 90° joints between panels. 3D animations were used to experiment with the construction process on the computer screen prior to construction in order to avoid potential costly on-site errors. In addition, the 3D animations were also used as a training tool for the contractors. This paper focuses on describing the methodology used to integrate a crane selection algorithm and optimization model with 3D modeling and animation for the selection, utilization, and location of cranes on construction sites. Analytical optimization processes were used to decrease the traveling time and distance of the selected crane, to improve the crane lifting sequence and to minimize the use of panel casting slabs.     

GPSLoc: Framework for Predicting Global Positioning System Quality of Service

While currently numerous existing engineering applications benefit from the global positioning system (GPS), it is anticipated that operation of many new, emerging applications (e.g., applications related to ubiquitous mobile computing) will rely on the information provided by this technology. Depending on the application requirement, GPS data may be collected and post-processed or collected and processed in real time. In either case, there are questions about availability, quality, and reliability of GPS data in engineering applications. To date, despite available techniques for realizing, and to some extent improving, a certain level of GPS accuracy, there is no integrated, coherent approach or technique that would provide users with solutions that combine GPS availability, quality, and reliability. To that end, we propose quality of service (QoS) assurance for GPS. With GPS QoS, users and applications would be provided with the means for predicting GPS solutions in advance meeting the requirements in a timely and cost-effective manner. We have developed a framework for the proposed GPS QoS called GPSLoc. In this paper, we discuss the requirements, methodologies, models, and algorithms for the GPSLoc framework and the experimentation with one of the GPS QoS parameters (visibility).     

Using Elitist Particle Swarm Optimization to Facilitate Bicriterion Time-Cost Trade-Off Analysis

The present study develops a new optimization algorithm to find the complete time-cost profile (Pareto front) over a set of feasible project durations, i.e., it solves the time-cost trade-off problem. To improve existing methods, the proposed algorithm aims to achieve three goals: (1) to obtain the entire Pareto front in a single run; (2) to be insensitive to the scales of time and cost; and (3) to treat all existing types of activity time-cost functions, such as linear, nonlinear, discrete, discontinuous, and a hybrid of the above. The proposed algorithm modifies a population-based search procedure, particle swarm optimization, by adopting an elite archiving scheme to store nondominated solutions and by aptly using members of the archive to direct further search. Through a fast food outlet example, the proposed algorithm is shown effective and efficient in conducting advanced bicriterion time-cost analysis. Future applications of the proposed algorithm are suggested in the conclusion.     

Business Strategy and Capital Allocation Optimization Model for Practitioners

Construction engineering companies usually provide a variety of services. To be competitive, companies have to organize their operations strategically based on market demands within the limitations of their own resources. Optimization of these resources is of vital importance for these companies. Historically, decisions on resource allocations to various construction market segments were made exclusively based on intuitive judgment. In previous literature, the proposed models on capital allocation place emphasis on formulating cash-flow forecasting and planning strategy on project level. However, existing technologies and established mathematical methods provide a sound base for quantitative analysis on company-level business strategy and capital allocation. This note proposes a linear programming model that can be conveniently applied by construction practitioners. The model incorporates the project cost structure and considers the business constraints such as bonding capacity and borrowing capital capacity. Its objective is to achieve maximum profit through improving project management efficiency and setting appropriate sales goals in various market segments based on market demands. It is a decision-making tool that provides “what-if” analysis. The solutions and alternatives of the model give the decision makers an excellent insight for making the best choice.     

Concept for Type-Local Instance–Global Instance Object Modeling and Application to Structural Design of Buildings

Rational data modeling is prerequisite to the computerization of design, and the use of design information in the subsequent work, in areas such as cost estimation and construction. In particular, the structural design of buildings consists of a long series of unit steps and is nonprocedural and data intensive compared with structural analysis problems that are procedural and computation intensive. Hence, there is a need to investigate the characteristics of the problem and to structure design information properly to effectively manage it in the structural design process. This paper discusses modeling concepts for managing design information efficiently and supporting the design process effectively. Type-local instance–global instance object modeling is the conceptual backbone of the model in this study and provides consistent modeling of structural components including not only primitive members such as beams and columns, but also composite elements such as floors, frames, and even whole buildings. This paper also provides core and extended object concepts for classifying structural design information into an overall design and for processing dependent temporary stages in the design. Foundational and application object concepts are introduced for extending the model to various types of structures. An integrated structural design system for buildings is developed based on these modeling concepts, and finally a brief discussion of the application of the object model throughout the entire structural design process in the integrated structural design system is given. It is expected that the modeling concepts proposed in this research can be applied to a range of other engineering applications.     

Version and Configuration Model for Structural Design Objects: Design and Implementation

This paper presents the design and implementation of a version and configuration model (VCM) for structural design objects. The VCM is developed to capture the incremental, evolutionary, multipath and iterative nature of the structural design process. Specifically, this model: (1) defines representational frameworks for representing the versions and configurations of design objects; (2) suggests sets of manipulation operations for creating and tracking the versions and configurations of design objects across the different representational frameworks; and (3) presents a prototype implementation scheme of a version manager, that is based on the representational frameworks and the manipulation operations of the proposed VCM. A case study of reinforced concrete T-beam is presented together with its prototype implementation using Object Pascal as a proof of concept. This is to describe the elements of the model, validate its effectiveness and demonstrate its viability. It is concluded that the VCM and its implementation is a valuable and necessary ingredient for developing a truly integrated structural engineering design system.     

Validation and Optimization of an Equilibrium Model of a Hot-Lime-Softening Treatment System

This paper describes the development and validation of an equilibrium model of an industrial hot-lime-softening boiler-water-treatment unit for a large-scale nickel processing facility in which approximately 6.6?ML per hour of water is processed. In the industrial process, multiple water sources of varying quality are combined before the softening treatment, which makes control and optimization of the softening unit complicated and has brought about the necessity of a robust numerical model of water treatment. In this paper, the numerical thermodynamic and adsorption relations describing the softening treatment process are presented. Lime, magnesia, and soda ash additions are modeled. Emphasis has been placed on calcium, magnesium, and silica treatments as these are of most relevance to the industry. Jar tests described in this paper are used to determine adsorption relations, estimate statistical uncertainties, validate the model performance, and optimize the model parameters. Parameter estimations for equilibrium constants are undertaken and provide insights into the range of model validity and interactions between additions and softened water quality. Further jar testing is utilized to evaluate the effectiveness of using the model to numerically derive optimal chemical additions.     

Virtual Reconstruction of Medieval Monastery Using Computer-Aided Design Model

A three-dimensional computer-aided design virtual reconstruction of the medieval monastery of Santa Maria de Salzedas (Portugal) is presented. This monastery is the second largest Cistercian monastery of Portugal. However, the majority of the monastery disappeared after the extinction of the religious orders in the Age of Enlightenment without letting any vestige, and with almost no existing documentation. In order to allow visitors to better understand the monument and to assist the current conservation works, a virtual reconstruction of the medieval monastery is presented. The adopted approach for reconstruction includes the identification of an ideal plan of the Cistercian Order, comparison with similar buildings of the same period and architectonic styles, a historic study and in situ survey to detect parts from the previous building, and definition of the modeling unit or proportion used by the builders.     

Simplified Performance Model of Gas Turbine Combined Cycle Systems

Conventional evaluation approaches for complex technologies, such as gas turbine systems, typically use process simulators for modeling, which are usually complicated and time-consuming. In order to facilitate policy analysis, a simplified desktop model for gas turbine systems based upon the air-standard Brayton cycle is developed in Microsoft EXCEL. The simplified model incorporates key process details and includes a comprehensive cost model. The model is calibrated based on a typical “Frame 7F” heavy duty gas turbine fired with natural gas and syngas. The model generally produces accurate and reasonable estimates for performance and cost comparable to reference data. The model responds appropriately to different syngas compositions, such as based on variation in moisture content and CO2 removal. Changes in syngas composition lead to different syngas heating values and thus affect gas turbine performance and cost. The effects of changes in inputs on key outputs are evaluated. Six key inputs are identified that are critical in order to obtain accurate estimates. The simplified model provides detailed technical information in a format that supports strategic planning and analysis.     

Stream Sockets versus Web Services for High-Performance and Secure Structural Analysis in Internet Environments

The increased growth of internet use in the last several years has opened up new possibilities for structural engineering analysis, moving from personal computer oriented software to client–server distributed software. In this paper two client–server applications for structural engineering based on stream sockets and on web services are presented. These two technologies have been chosen to compare, in terms of performance and complexity, new internet protocols with traditional ways of implementing client–server applications. Moreover, special care has been taken in the security aspects as the internet has become much more susceptible to breaches of security. Therefore, two new applications based on the same technologies have been created that guarantee a secure use of structural software. Also, two different client applications are presented to emphasize the versatility and power of internet distributed technology—one as a stand-alone application and the other as an integrated commercial computer-aided design program.     

CAD and Management of Construction Projects

The increasing interest in computer‐aided design (CAD) has prompted research that is aimed at identifying the opportunities for construction managers and building contractors. It has been found that the use of CAD systems in the U.K. is mainly confined to the production of detailed drawings. Indeed, most of the systems used are 2‐D drafting tools and incapable of supporting the integration of even modest amounts of nongraphical (construction) data. On the other hand, many 3‐D modeling systems have the potential to integrate construction data, although they appear to be almost ignored. The use of 3‐D modeling systems is considered to be the most suitable vehicle for successfully integrating these data. However, this is likely to necessitate the introduction of separate databases, preferably of the relational type. The use of 3‐D modeling systems in assessing the construction implications of outline designs also presents interesting possibilities and is discussed.     

Modified Harmony Search Algorithm and Neural Networks for Concrete Mix Proportion Design

This study proposes a new methodology with harmony search (HS) algorithm and neural networks (NNs) for concrete mix proportioning. The basic procedure for the methodology consists of four steps: (1) constructing a database of mix designs; (2) establishing appropriate models for strength and workability; (3) optimizing mix proportion using the modified HS algorithm; and (4) refining the mixture using NNs. The proposed methodology could be a useful decision-making tool for concrete mix design.     

Computer-Aided Site Layout Planning

This paper presents an interactive computer-aided site layout model to support site planning in a computer-aided design (CAD) environment and expands upon a model presented earlier by the writers. The developed model performs its task at two levels: Site representation, and site space analysis and allocation. The site representation is carried out using an open architecture supported by object-based concepts. The model offers three tiers of objects: (1) site objects, (2) construction objects, and (3) constraint objects. This structure facilitates the creation of new objects and reuse of domain knowledge, which allows for the gradual expansion and enrichment of the model’s knowledge base. At the space analysis and allocation level, the model introduces a geometric reasoning approach to analyze site space for finding an optimum or near-optimum location for facilities. This feature facilitates easy visualization of the site planning process and encourages user participation. The model is structured in three main modules: Database, Project Module, and Layout Control Module. The functionality of each module, along with their interconnectivity is described. The model is implemented using Visual Basic for Applications in AutoCAD environment and Microsoft Access. A numerical example of an actual site layout is presented to illustrate the functionality of the developed model.     

Automated Recognition of 3D CAD Objects in Site Laser Scans for Project 3D Status Visualization and Performance Control

This paper presents a new approach that allows automated recognition of three-dimensional (3D) computer-aided design (CAD) objects from 3D site laser scans. This approach provides a robust and efficient means to recognize objects in a scene by integrating planning technologies, such as multidimensional CAD modeling, and field technologies, such as 3D laser scanning. Using such an approach, it would be possible to visualize the 3D status of a project and automate some tasks related to project control. These tasks include 3D progress tracking, productivity tracking, and construction dimensional quality assessment and quality control. This paper provides an overview of the developed approach and demonstrates its performance in object recognition and project 3D status visualization, with data collected from a construction job site.     

Design of Tall Formworks by a Finite-Element Model

The design of formworks for holding fresh concrete possesses a difficult engineering challenge. Present standards assume fresh concrete to have a nonviscous fluid behavior when calculating the lateral pressure to which the formwork walls will be the subject. This paper describes a finite-element model to determine these pressures, taking into account the interaction between the fresh concrete and the formwork wall. The use of this numerical model shows that present standards may underestimate the lateral pressures that can be exerted particularly with respect to tall formworks. The paper also discusses the influence of different mechanical variables on the results returned by the proposed model. The proposed model may be of use to practicing engineers and of interest to researchers examining load distributions in formworks.     

Single- and Multievent Optimization in Combined Sewer Flow and Water Quality Model Calibration

Over the last three decades, storm-water quality modeling has been used increasingly commonly to describe the general system behavior and assess the pollution loads transferred in and spilled out of combined sewer systems. The calibration of quality models is, in most cases, based on conventionally obtained calibration data, e.g., by automated sampling. Long-term high-resolution online measurement data are available for the Graz West catchment (Graz, Austria), allowing an assessment of the full dynamics of discharge and pollution concentrations. This paper focuses on the application and comparison of single-event and two different multievent optimization schemes for sewer-water quality model calibration. While both single- and multievent optimization lead to satisfying results for the calibration events in discharge calibration, it is shown that validation events are better reproduced by using multievent calibration. Single- and multievent autocalibration of pollution concentration is based on the best dataset obtained from the discharge calibration. As for discharge, the pollutographs are reproduced satisfactorily, and multievent calibration is more stable. In all cases, the two multievent approaches performed equally well.     

Areas of Application for 3D and 4D Models on Construction Projects

In recent years more and more construction projects used three-dimensional/four-dimensional (3D/4D) models to support management tasks. However, project managers still struggle with evaluating how the 3D/4D model technology can be most efficiently applied on their specific project. One main reason for this struggle is that an account about how 3D/4D models have been used in the past is missing. This paper offers practitioners and researchers such an account of the application areas of 3D/4D model technologies including the purposes for which these technologies have been applied. The paper qualitatively aggregates the results of 26 case studies of 3D/4D model applications on construction projects to show researchers and practitioners how 3D/4D models have been applied to address project challenges. Using a “project challenge—3D/4D model application” matrix the paper explains each application area and describes why the application has been beneficial to the case study projects. The paper then analyzes the challenges that practitioners have faced with 3D/4D models on the test case projects. The main findings of this analysis are that practitioners on most of the test case projects have used the models for only one application area. The paper suggests that further research on the integration of 3D/4D model technologies into work and business processes of project teams is needed to address this opportunity for a more widespread use of 3D/4D models throughout the lifecycle of a project.     

Multiobjective Optimization of Earthmoving Operations

This paper presents a framework for optimizing earthmoving operations using computer simulation and genetic algorithms. It provides a multiobjective optimization tool geared towards selection of near-optimum fleet configurations. The optimization aims at minimizing time and cost of earthmoving operations. The proposed framework considers factors that influence earthmoving operations including equipment availability and project indirect cost. The simulation process, in the proposed methodology, utilizes discrete event simulation and object oriented modeling. The optimization process uses a recently developed genetic algorithm to search for a near-optimum fleet configuration employing Pareto optimality to account for multiobjective optimization. The algorithm considers a set of qualitative and quantitative variables that influence the production of earthmoving operations. The developed framework supports time–cost tradeoff analysis and can assist users in considering what if scenarios with respect to fleet configurations. A numerical example is presented to illustrate a number of practical features of the proposed framework and to demonstrate its capabilities in selecting near-optimum fleet configurations.