Two‐stage profit optimization model for linear scheduling problems considering cash flow

Linear projects with repetitive activity in units are considered for investigation, and a two‐stage profit optimization model for linear scheduling problems using constraint programming (CP) is proposed. To maintain work continuity for repetitive activities, interruption time and crew availability are addressed, and the optimization process is presented as follows: (1) optimizing the primary objective (project profit); (2) minimizing total interruption time, given the optimized value of the primary objective. Repetitive activities incur batches of budget expenditure according to activity implementation time. Cash flow and financial elements are therefore integrated into the optimization model. Owing to flexible CP techniques, contractors’ requirements, such as credit limit and payment conditions, can be integrated simply into the model formulation for practical use. Lastly, a bridge example is adopted, with various constraints such as duration limitation, for scenario analysis. Consequently, the two‐stage optimization process optimizes project profit, and also maximizes work continuity for linear scheduling problems.     

A competency‐based performance model for construction project managers

The role of competency‐based performance management is growing in significance in many industries and sectors. Unlike functional competences, which measure performance against predetermined minimum occupational standards, competency‐based systems are founded on the key behavioural competencies that underlie superior levels of performance. In order to identify the key behaviours leading to performance excellence amongst construction project managers, in‐depth behavioural event interviews were used in which managers were asked to recount critical management incidents, decisions and actions from which their behavioural competencies could be identified. By delineating the sample according to their performance against a range of role‐based criteria, the competencies defining superior management performance were determined. Statistical techniques were then used to develop a model that can be used to predict likely employee performance, which was subsequently validated on a second criterion sample. The research identifies 12 core behavioural competencies that underpin effective project management performance, of which two – ‘composure’ and ‘team leadership’ – were the most predictive. The paper explores the potential role and application of the framework in the drive for performance excellence within the industry, such as in selection, management development, succession planning, performance management and team deployment. It is argued that it offers an innovative alternative to normative micro‐competence‐based approaches that do little to engender performance excellence amongst the industry's key managers and professionals.     

A non‐linear model of visual quality

The paper focuses on the debate that took place between the Royal Fine Art Commission and the electricity supply industry of England and Wales during the post‐war years in respect of the design, layout and location of power stations.     

A practical approach to project scheduling: considering the potential quality loss cost in the time–cost tradeoff problem

Crashing project activities is a typical way to shorten their completion times to meet project due dates, and previous research on quality in time–cost tradeoff problems focused on maximizing the individual activity quality of projects. However, implementing project scheduling that takes into account the potential quality loss cost (PQLC) in time–cost tradeoff problems is a practical approach, since individual activity quality is defined by conformance to project contractor requirements. We propose a mixed integer linear programming model that considers the PQLC for excessive crashing activities. This model will help project planners develop practical project schedules.     

Multi-mode resource-constrained discrete time–cost-resource optimization in project scheduling using non-dominated sorting genetic algorithm

Minimizing both project time and cost is an important matter in today's competitive environment. Therefore trade-off between project time and cost is necessary. In projects, each activity can be started at different time points, depending on its precedence relationship and resource availability. Also cost and duration of the activities could be changed depending on the allocated resources. In addition, another strategy that affects the project total time and cost is resource leveling, which is applied to reduce excessive fluctuations in the resource usage. In this paper multi-mode resource-constrained project scheduling problem (MRCPSP), discrete time–cost trade-off problem (DTCTP) and also resource allocation and resource leveling problem (RLP) are considered simultaneously. This paper presents the multi-mode resource-constrained discrete time–cost-resource optimization (MRC-DTCRO) model in order to select starting the time and the execution mode of each activity satisfying all the project constraints. To solve these problems, non-domination based genetic algorithm (NSGA-II) is employed to search for the non-dominated solutions considering total project time, cost, and resources moment deviation as three objectives. The results of MRC-DTCRO model presented in this paper show that adding the resource leveling capability to the previously developed multi-mode resource-constrained discrete time–cost trade-off problem (MRC-DTCTP) models provides more practical solutions in terms of resource allocation and leveling, which makes this research applicable to both construction industry and researchers.     

A model for smoothing time‐series data in construction

The understanding of the behaviour of time‐series data has been a matter of concern to researchers and practitioners in a variety of fields ranging from social science and economics to engineering. Also, the behaviour of many phenomena within fields relating and peripheral to construction is described as a time series. Typically, the time‐series analysis is carried out in order to forecast the future values of the series. These techniques, however, are also used to abstract the generalities within the series, hence facilitating the replication of the entire profile, reflecting only the main characteristics of the profile. There is a variety of techniques that can be applied to a set of time‐related data. The choice of the technique is, therefore, dependent on the nature of the problem and the characteristics of the data. The diversity of available techniques is, on the one hand an advantage for all analysts. However, this diversity is also an indication that there is no universal technique that is applicable to a diversity of time‐series data.

This work fundamentally addresses the issue of smoothing and curve‐fitting techniques rather than predicting and forecasting. A technique is offered which is tested against a set of criteria that are designed to focus on the accuracy of imitation and the practicality of operation: the ability to deal with a large number of time‐series sets of data in a consistent, replicable and automated way. The viability of the technique is demonstrated by its application to expenditure profiles of a large number of construction projects. The size of the sample and the diversity in the profiles of the expenditure patterns provided an appropriate testing ground for the universality of the model.

The results indicated that the model can effectively transform a jagged time series into a smooth pattern, while complying with a set of criteria many of which are common to several other research works relating to time‐series data analysis. The proposed technique sequences a number of basic smoothing methods and the process involves the treatment and incorporation of the residual values.     

A power‐based leadership approach to project management

The concept of leadership relates to power structuring whereby the project leader may lead and motivate through power disposition. Power, in its diverse guises, combines interpersonal and structural elements and can be enhanced through political manoeuvring. Power may also be distributed unevenly between individuals in the project team. In this article a power‐based model of project leadership is developed, underpinned by a behaviour‐performance‐outcome approach and an appropriate methodology is developed for testing the construction enterprises in China using structural equations modelling. The fitness indices show that the resulting model which postulates that the motivational function of good leadership operates through managing power gaps by means of power‐sharing and power‐amassing is acceptable. The effects (both predominant magnitudes and statistical significance) from the project managers' referent power to power‐sharing and power‐amassing show that the project manager's inherent personal traits and credentials are critical to his/her power exercising so as to motivate members to secure management effectiveness.     

An economic–probabilistic model for project selection and prioritization

This paper presents an economic–probabilistic model for project selection and prioritization that enables necessary investments and potential benefits and their inherent variability to be quantified, thus providing a stochastic analysis of expected returns for projects. The model was developed in three steps: definition of criteria; definition of the most appropriate method to be used; and model building. A practical test to evaluate the applicability and usefulness of the model comprising a portfolio of investment projects at a power distribution company was conducted. The results show three major contributions of the proposed model: i) a set of sufficiently complete criteria, ii) the combined use of economic and probabilistic approaches which qualifies the information available to decision makers, and iii) the use of financial language, which is more easily understood and has a concrete meaning for both management and technical staff.     

A construction project cash flow model—an idiographic approach

The paper introduces and supports the contention that an idiographic methodology is appropriate to the post- hoc study and interpretation of individual construction project cash flows. A cash flow model based on the logit transformation is proposed to be consistent with this methodology. The model is based on historical data, and yields two parameters to describe each individual project. The model is tested using two samples totalling 72 projects. Goodness of fit for the model, using a measure of standard deviation from 1.0% to 4.6%, with a median of 2.5%, is found for individual projects.

The experimental hypothesis (that there is substantial variation between projects) is supported by the graphical and statistical evidence of deviation, which is argued to be the result of the individual ontology of each project - systematic error - rather than random error from an ideal. The paper concludes that forecasts of individual cash flows are invalid when derived from analysis of grouped data.     

A taxonomy for construction terms in privatized‐infrastructure finance: supporting semantic exchange of project risk information

There is an increasing need for effective flow of information between the various participants in privatized infrastructure projects particularly between construction companies and financial institutions. A taxonomy is developed for relevant concepts in the domain of privatized‐infrastructure finance. The taxonomy is an attempt to create information interoperability between the construction and financial industries. The taxonomy models the concepts of a privatized‐infrastructure finance into six main domains: processes, products, projects, actors, resources and technical topics (technical details and basic concepts). The taxonomy was designed to be consistent with Open Financial Exchange (OFX). It was developed through the analysis of 10 case studies and involvement in project development and interaction with industry experts. The taxonomy was validated through interviews with domain experts, and through the analysis of two independent case studies. A prototypical semantic web‐based portal for communicating project risks was developed to in order to illustrate the use of the taxonomy. Project partners are able to post and view risk items and their status in this portal, observe who is handling them, be aware of what decisions have been made to manage them and what lessons learned are available to address these risks.     

How do project management competencies change within the project management career model in large Chinese construction companies?

Due to the increasing complexity and flexibility of business activities, project-based organizations have become common. In such organizations, project management competencies, which refer to a collection of knowledge, personal attitudes, skills, and relevant experience, are core assets that must be taken seriously. Formalized project management career paths have been widely implemented in the construction industry. However, most recent studies treat project management competencies as static constructs and fail to consider their dynamic changes as a career path advances. To fill this gap in the literature, this study conducted an empirical examination of project management competencies integrated with a career model for the construction industry. First, key project management competencies are identified through a literature review. Then, a project management career model for large Chinese construction companies is developed based on an empirical investigation of six large Chinese construction companies from various sectors. Moreover, a quantitative analysis is performed to explore how these competencies dynamically change as position levels rise in the career model. The research findings indicate that significant differences in project management competencies exist at different levels of the career model. However, the distribution remains steady at different project management position levels for conceptual and organizational competencies, human competencies, and technical competencies.     

Compaction-induced stress in geosynthetic-reinforced granular base course——A discrete element model

A discrete element method (DEM) model was used to simulate the development of compaction-induced stress in a granular base course, with and without geogrid reinforcement. The granular base course was modeled as a mixture of uniformly sized triangular particles. The geogrid was modeled as a series of equally spaced balls that interact with each other through long-range interaction contacts. The long-range interaction contact was also used to simulate a deformable subgrade. The compactor was modeled as a solid cylinder rolling at a constant speed. The DEM model shows that the geogrid-reinforced granular base course gains additional compaction-induced stress due to the residual tensile stress developed in the geogrid. The residual tensile stress in the geogrid increases with the number of compaction passes. Parametric analyses were also conducted to assess the effects of geogrid stiffness and subgrade modulus on the compaction-induced stress.     

The Ten‐Year Plan for the port of Antwerp (1956–1965): a linear city along the river

The Ten‐Year Plan for the port of Antwerp (1956–1965) funded the expansion of the port’s infrastructure over a 10‐year period. Strictly, a national government‐funded infrastructure programme for the construction of a set of canal docks, the programme laid the basis for a broader urbanization of the north‐eastern Antwerp metropolitan region. The importance of the operation lies primarily in its role as an instrument of urbanization rather than in the improvement of the transport and transshipment capacity of the port because it opened up a large territory to industrial settlement. The linear layout of the project along the Scheldt River led planners to conceive the further urbanization of the adjacent region on a linear city model, with satellite communities attached to the industrial and infrastructural strip. Compared with the contemporary Europoort plan for the port of Rotterdam, where several planning agencies implemented conflicting plans for functionally distinct infrastructures and the construction of a new town, the success of the Antwerp approach resides in the flexible and strategic implementation of the project as a co‐production between various authorities and private parties.     

Stochastic model for BOD and DO in streams when the velocity is random and distance‐dependent

The stochastic model studied in this paper is a random differential equation of the form X(t) = A(t) X(t) = Y(t), t ≥ 0, with initial conditions X₀ = X(0). X(t) is a vector with biochemical oxygen demand (BOD) and dissolved oxygen (DO) at a distance t downstream from the pollution source for components. The velocity of the stream is incorporated into the vector A(t) and is random and distance dependent. The inhomogeneous term Y(t) and the initial conditions are random vectors. Therefore, this model contains random initial conditions, random coefficients and random inhomogeneous terms. Simulated trajectories of the BOD and DO are computed.     

A novel hybrid cellular automata–linear programming approach for the optimal sizing of planar truss structures

This paper presents a novel hybrid cellular automata (CA) linear programming (LP) methodology for the size optimisation of planar truss structures. The method uses the nodal displacements and internal forces of the truss as the design variables of the optimisation problem. The objective function is the volume of the structure and the constraints of the original optimisation problem are recast in terms of the new decision variables in the two-phase step. Starting with an arbitrary set of nodal displacements and internal forces, these are updated in turn in an iterative two-phase process. In the first phase, the internal forces are kept fixed and the nodal displacements are found using a CA approach. In the second phase, a LP is used to find the set of internal forces of truss elements which minimises the total volume of the structure. The effectiveness and efficiency of the methodology is also examined with its application to some benchmark truss structures.     

Influence of process performance during the construction stage on achieving end‐project goals

Within a project environment, good process performance can be seen as indicative of eventual success of achieving end‐project goals. A model is proposed for identifying the links between process performance during construction and end‐project goals. The model is developed using process mapping technique to identify a number of process‐based key performance indicators (KPIs) designed for use in controlling process performance in the construction stage. These KPIs were then linked to generic project goals to measure the perceived degree of influence of process performance on the achievement of end‐project goals. The strength of these links within the model was established through a number of in‐depth interviews with respondents. Analysis of the results using methods of ranking and statistics has shown that some processes are perceived to have stronger relationships with the end‐project goals than others. The proposed process‐based KPIs hence offer an opportunity for control of the processes during the construction stage and eventually to influence the projects’ outcomes. In addition to the management of project time and cost, the model provides a broader focus of control that includes other multiple aspects such as the management of interactions between internal and external stakeholders as well as of information and quality management.     

A performance‐based bridge LCCA model using visual inspection inventory data

Since most bridge life cycle cost analysis (LCCA) depends heavily on the analyst's experience to determine the times and costs of remedial actions over a bridge's lifetime, the results are often subject to question because of their subjectivity. While some work has been done over the years to develop reliable deterioration models for determining such times and costs, the proposed models often require sophisticated inspection data, which is costly to obtain, and/or complex mathematical calculations. A simple linear deterioration model based on visual inspection inventory data concerning bridge components is introduced and integrated into the LCC analysis. The proposed model provides an alternative approach to bridge LCC analysis that can improve the objectivity of analysis and does not require input of sophisticated inspection, and thus facilitates application of bridge life cycle cost analysis. The LCCA method developed in this study is applied to a case study of alternative PCI (Pre‐stressed Concrete I‐girder) and a PCB (Pre‐stressed Concrete Box‐girder) bridges for the purpose of model validation.     

A user‐based method for rating street trees

Responses to questionnaires completed by 1,174 householders who rated characteristics of their street trees were subjected to factor analysis. The most important factors were general benefits, ground disturbance, disease, safety, seasonal marking, droppings and suckers, which became the basis for scales on which each species could be scored. These scales represent an economical and coherent method which can complement simulation and expert rating systems, for describing householder opinion towards street trees.