Float Consumption Impact on Cost and Schedule in the Construction Industry

Quantifying and minimizing the risks associated with delays in the construction industry are the main challenges for all parties involved. Float loss impact in noncritical activities is one of the complicated delays to assess on a project’s duration and cost. This is due to the fact that the deterministic critical path method cannot cope with such delays unless they exceed the total float values. Further, stochastic analysis, which is used in this research to assess the impact of such delays, is perceived by many planners to be complicated and time consuming. This paper presents a method to control the risks associated with float loss in construction projects. The method uses a recently developed multiple simulation analysis technique that combines the results of cost range estimates and stochastic scheduling, using Monte Carlo simulation. The proposed method quantifies the float loss impact on project duration and cost. Least-squares nonlinear regression is used to convert the stochastic results into a polynomial function that quantifies the float loss impact by relating directly the float loss value to project duration and cost at a specified confidence level.     

Using Weibull Analysis for Evaluation of Cost and Schedule Performance

Large amounts of money are lost each year in the construction industry because of poor schedule and cost control. Few contractors specify and follow systematic schedule monitoring practices. Traditionally, the earned value method (EVM) is used to control and monitor schedule performance using the schedule and cost performance indices which compare the budgeted cost of work performed to what was originally scheduled or what is actually expended. This paper presents a statistical approach, namely Weibull analysis, to evaluate stochastically the schedule performance of construction or design projects. The approach can be used in conjunction with the EVM to enhance the evaluation and control of schedule performance. Weibull analysis is a common method for failure analysis and reliability engineering used in a wide range of applications. In this paper, the applicability of Weibull analysis for evaluating and comparing the reliability of the schedule performance of multiple projects is presented. The various steps in the analysis are discussed along with an example in which two projects are analyzed and compared. The authors conclude that Weibull analysis has several advantages and provides a relatively robust and effective method for construction managers to better control and monitor their projects.     

Reasons for Cost and Schedule Increase for Engineering Design Projects

Cost and schedule increases are common in engineering design projects. Some research has studied factors associated with better design performance, but the reasons for cost and schedule increases are not formally investigated. This paper identifies the reasons bottom up from four case project documents and further quantifies their contributions to cost and schedule increases. These reasons are complete and can be used to analyze the cause-effect relationship, trace responsibility, and improve performance for engineering design projects.     

Construction Project Network Evaluation with Correlated Schedule Risk Analysis Model

Schedules are the means of determining project duration accurately, controlling project progress, and allocating resources efficiently in managing construction projects. It is not sufficient in today’s conditions to evaluate the construction schedules that are affected widely by risks, uncertainties, unexpected situations, deviations, and surprises with well-known deterministic or probabilistic methods such as the critical path method, bar chart (Gantt chart), line of balance, or program evaluation and review technique. In this regard, this paper presents a new simulation-based model—the correlated schedule risk analysis model (CSRAM)—to evaluate construction activity networks under uncertainty when activity durations and risk factors are correlated. An example of a CSRAM application to a single-story house project is presented in the paper. The findings of this application show that CSRAM operates well and produces realistic results in capturing correlation indirectly between activity durations and risk factors regarding the extent of uncertainty inherent in the schedule.     

Decision Tool for Selecting the Optimal Techniques for Cost and Schedule Reduction in Capital Projects

Projects must meet budget, schedule, safety, and quality goals to be regarded as a success. Many factors come into play, and many decisions are made that influence a project’s outcome. Today, owners are often faced with deciding between an execution strategy that emphasizes either project cost or project schedule. Such a decision may be made not once, but throughout the life of the project. Project teams, when required by the owner to make a cost-schedule trade-off, generate common sense ideas, best practices, and other means of achieving the desired trade-off through brainstorming sessions. This paper offers a tool for systematically identifying the techniques which are most effective in achieving the trade-off goal. Project teams can then use these techniques in a timely fashion to increase the likelihood of project success.     

Cost and Schedule Monitoring of Industrial Building Projects: Case Study

Performance measurement is a helpful tool for taking corrective actions and controlling a project as far as this enables accurate time and cost forecasts during the first stages of the construction effort when the management team still has opportunities to make adjustments. This paper overcomes the dilemma of practicability and predictability of traditional estimates at completion based on early progress measurement by presenting the empirical results from the construction project of an industrial facility. The case may be a reference practice for assessing time and cost performance measurement of any building, whose layout can be reasonably partitioned into repeatable portions. In such circumstances, an effectively-managed traditional earned value method and appropriate metrics for computing performance provide project managers with accurate forecasts as useful tools for successful project management and control.     

Cost Information Model for Managing Multiple Projects

Construction companies must deal with several projects at once, but a system to manage multiple projects is not fully developed yet. The first step towards developing such system is to design an information model that is suitable for managing multiple projects. This paper presents the cost-based project modeling (CBPM) method in contrast to the traditional activity-based project modeling methods. The CBPM uses cost as a core of the model along with other project information organized around it. The CBPM serves as a platform for integrating project information from multiple projects. Various types of construction costs are hierarchically modeled to generate corporate-wide information such as project performances, cash flows, and other predictive indicators. Based on the information model, an object-oriented database was developed to contain cost data across several projects. In the model, a module that connects to external systems is built into the model to enhance interactivity with the legacy systems and the industry standards. A prototype system was developed and tested with actual project data to validate the information processing capabilities of the model. The findings from the test indicate construction cost can be an excellent medium that can organize various types of information of multiple projects.     

Integrated Schedule and Cost Model for Repetitive Construction Process

Several efforts have been made by many researchers to develop a model for schedule and cost integration in construction projects, but it is difficult to integrate and manage schedule and cost in an actual construction site using such a model. The integrated schedule and cost model developed in this study (1) enables the planning and control of repetitive construction processes and (2) can be used by a project manager in an actual construction site. Furthermore, an integrated schedule and cost model for the core wall construction, which is an important repetitive process in the recently booming high-rise building construction in terms of scheduling, was developed using the integration model developed in this study. It is expected that the integrated schedule and cost model developed can allow project managers to integrate the schedule and cost of repetitive construction processes more effectively and support the project managers’ decision-making.     

Analytical and Approximate Variance of Total Project Cost

The statistical variance of total project cost is usually estimated by means of Monte Carlo simulation on the assumption that exact analytic approaches are too difficult. This paper tests that assumption and shows that, contrary to expectations, the analytic solution is relatively straightforward. It is also shown that the coefficient of variation is unaffected by the size (floor area) of the project when using standardized component costs. A case study is provided in which actual component costs are analyzed to obtain the required total cost variance. The results confirm previous work in showing that the approximation of the second moment (variance) under the assumption of independence considerably underestimates the exact value. The analysis then continues to examine the effects of professional judgment, and, with the simulated data used, the approximation is shown to be reasonably accurate—the professional judgment absorbing most of the intercorrelations involved. An example is also given in which the component unit quantities are priced by their average unit costs and which again shows the approximation to be close to the true value. Finally, this is extended to show how the exact total project cost variances may be obtained for each project.     

Evaluating Risk in Construction–Schedule Model (ERIC–S): Construction Schedule Risk Model

Research was undertaken to develop a method to assist in the determination of the lower and upper activity duration values for schedule risk analysis by program evaluation and review technique analysis or Monte Carlo simulation. A belief network was the modeling environment used for this purpose, and the resulting model was named Evaluating Risk in Construction–Schedule Model. The development of the belief network model consisted of four steps. First, construction schedule risks were identified through a literature review, an expert review, and a group review by a team of experts. Second, cause effect relationships among these risks were identified through an expert survey. This led to the development of the structure of belief network model. Third, probabilities for various combinations of parents for each risk variable were obtained through an expert interview survey and incorporated into the model. Finally, sensitivity analysis was performed. The model was tested using 17 case studies with very good results.     

Automating Schedule Review for Expressway Construction

An expressway project is often divided into subprojects with different tendering packages, and carried out by several general contractors that apply different scheduling practices. Each schedule may contain hundreds of activities, each of which is associated with multiple pay items that determine its earned monetary value. With such huge amount of information, the reviewer can only check a sample piece of information, and the quality of review highly depends on the reviewer’s experience and devotion. Automated schedule review provides a solution to reduce such problems encountered in the industry. This paper presents a module-based schedule generation and review model, which includes a predefined set of network modules, network builder assistant computer system that helps schedulers manage and reuse the modules to build a new schedule, and another computer system network review assistant (NRA) that helps reviewers review schedules. The NRA uses generalized rule forms to represent the schedule critique knowledge collected from the industry. When potential errors are found, the NRA adopts case-based reasoning to suggest possible correction based on similar cases. The evaluation conducted by the practitioners using real projects indicates that NRA reduces review time, and provides more accurate review on finding activities and related pay items not conforming to standards, and reminding users of important but often omitted activities.     

Schedule Analysis under the Effect of Resource Allocation

The construction industry has employed various schedule analysis techniques to support delay claims. Paradoxically, resource-related issues are frequently ignored even though they can affect project completion time, too. The research presented here shows that delay analysis without resource allocation practice substantially affects results of schedule analysis. Some delay can cause unrealistic resource allocation in downstream work, which in turn may further delay the project. The effect of resource allocation can either add to or reduce the severity of some delaying event. Apportionment of delay responsibility may be inaccurate unless resource allocation practice is considered in the analysis. Practical and necessary steps are proposed to enhance the existing window analysis technique. A case study is presented to compare the enhanced window analysis with the existing window analysis. This research enables practitioners to make delay analyses and claims more practical and reliable. Further studies are needed to improve the usability, credibility, and acceptability of schedule analysis considering resource allocation.     

Removal of Redundant Relationships in an AON Project Network for Evaluating Schedule Complexity

Since redundant relationships in an activity-on-node (AON) project network indicate that the schedule is more complex than it actually is, they should not be considered when evaluating the schedule complexity. However, identifying the relationships that can be removed while maintaining the project logic is not an easy task. For this purpose, this paper proposes a methodology, adapted from interpretive structural modeling, that basically transforms an AON project network into a network called minimum-edge diagraph which contains no redundant relationships. The methodology steps are explained through a demonstrative example of a simple hypothetical project. The application of the methodology to the AON network of a real construction project shows that it is easy to use yet effective in removing redundant relationships.     

Critical Factors Affecting Schedule Performance: Evidence from Indian Construction Projects

Over 40% of Indian construction projects are facing time overrun ranging from 1 to 252 months; the reasons for which are being studied by researchers to suggest possible remedial measures. This paper identifies 55 attributes responsible for impacting performance of the projects. These attributes were then presented to Indian construction professionals in the form of a questionnaire. Statistical analysis of responses on the attributes segregated them into distinct sets of success attributes and failure attributes. Factor analysis of sets of success attributes and failure attributes separately grouped them into six critical success factors and seven critical failure factors. In order to understand the extent of contribution these factors have on the outcome of a construction project, a second stage questionnaire survey was also undertaken. The analyses of responses of the second stage questionnaire led us to conclude that two success factors and one failure factor: commitment of project participants; owner’s competence; and conflict among project participants contribute significantly in enhancement of current performance level of the project. The extent of their contribution has, however, been observed to vary for a given level of project performance. The analyses results are expected to help project professionals to focus on a few factors and get the optimum results rather than giving attention to all the factors and not getting the proportionate results.     

Float Allocation Using the Total Risk Approach

Float ownership is one of the controversial issues in the litigation of delay claims. As float time does not always affect the overall project completion time, many believe that this time can be used by any of the project parties and that it does not belong to a particular party. This study introduces the “total risk approach” for float allocation, a new approach that integrates several current approaches to allocate float among project parties. The approach is based on the basic concept that the party who has the greatest risk in a project should be entitled to float ownership and deserves compensation from other project parties who increase the risk associated with the project by consuming the float. This new approach takes into consideration the changes in float that may occur as a result of actions that delay or accelerate the project’s schedule.     

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.     

Modeling Microtunneling Projects using Computer Simulation

Tunnels projects are constructed to facilitate the execution of underground works with minor disturbance on surface structures and traffic. This is deemed important especially in downtown cities where disturbances should be minimized to assure flowability on surface and underground infrastructures. Microtunneling involves the use of a remotely controlled, guided pipe-jacking process in order to support excavation face. Microtunneling aids in avoiding the need of open trench for pipe laying, which causes extreme disruption to the surrounding. This paper presents a tool for planning microtunnels projects using computer simulation. The proposed tool aids contractors in planning microtunneling by estimating their associated time and cost of construction. There are six models that are coded in the proposed tool in order to capture the construction of microtunnels and shafts. The tool breaks down microtunnels projects into microtunnels segments and shafts which constitute several construction zones. An application example is presented to demonstrate the features of the proposed tool.     

Critical Path Method with Multiple Calendars

This paper presents the critical path method forward and backward passes with multiple calendars. Multiple calendars are required in many construction projects to effectively represent various project conditions such as work properties, resource availabilities, weather conditions, etc. For this reason, major project management software packages such as P3 and MS-Project provide functions to handle multiple calendars. However, the background theory of handling multiple calendars has not been disclosed, so users of those software packages simply assume without clear knowledge that the time data generated by them are correct. This paper provides how multiple calendars should be handled in scheduling. Applying the theory presented herein, it has been noticed that the P3 operations with two calendars may generate a wrong answer for a start-to-finish with zero lag and inconsistent results in all negative lags when nonworking days are involved. The theory covers all four relationships in the precedence diagramming method with lags of zero, positive, and negative values. This study should be of considerable benefit to the construction industry and academics because it details and advances the theory for scheduling with multiple calendars, which is real scheduling in practice.     

Automated Statistical Analysis in Stochastic Project Scheduling Simulation

This paper describes a stochastic simulation-based scheduling system (S3) that: (1) integrates the deterministic critical path method (CPM), the probabilistic program evaluation and review technique (PERT), and the stochastic discrete event simulation (DES) approaches into a single system and lets the scheduler make an informed decision as to which method is better suited to the company’s risk-taking culture; (2) automatically determines the minimum number of simulation runs in DES mode and therefore optimizes the simulation process; and (3) provides a terminal method that tests the statistical significance of the differences between simulations, hence eliminating outliers and therefore increasing the accuracy of the DES process. The system is based on an earlier version of the system called stochastic project scheduling simulation and makes use of all the capabilities of this system. The study is of value to practitioners because S3 produces a realistic prediction of the probability of completing a project in a specified time. The study is also of relevance to researchers in that it allows researchers to compare the outcome of CPM, PERT, and DES under different conditions such as different variability or skewness in the activity duration data, the configuration of the network, or the distribution of the activity durations.     

Computerizing ICBF Method for Schedule Delay Analysis

Schedule delay is a common construction dispute. For analyzing schedule delays, a previous study had proposed an academic analysis method, the “isolated collapsed but-for” (ICBF) method. However, because many construction projects involve numerous complex activities, the procedure of using the ICBF method for schedule delay analysis is time-consuming. Therefore, this study used Microsoft Visual Basic for Applications (VBA) language and spreadsheet techniques to develop an Excel-based program for rapid delay analysis rather than manual calculation. A case study confirmed that the program automatically produces analytical results with only common delay documents (as-planned and as-built schedules and identified delay events). Compared with previous studies, schedule analysts can obtain analysis results quickly and correctly. Research results provide not only a convenient tool for schedule delay analysis but also a guide to computerize various academic delay analysis methods in the future.