Comparison and Renaissance of Classic Line-of-Balance and Linear Schedule Concepts for Construction Industry

Line-of-Balance (LOB) is a useful analytical tool for repetitive activities in construction projects, which allows showing which crew is assigned to what repetitive work unit of an activity. LOB is closely related to the linear scheduling method, but possesses some challenges: It must be clarified how it counts, as previous studies displayed an apparent measurement gap at the origin, implicitly representing that LOB starts at the first unit finish. Slopes in linear scheduling and LOB are different, even though both portray a measure of progress of an activity. This paper therefore tracks evolution and current use of LOB versus linear schedules. Its contribution to the body of knowledge is threefold: First, based on a literature review, LOB is found to be rooted in Activity-on-Arrow (AOA) diagrams, which makes it event-centered, not progress-centered. Differences in representing the start and productivity between LOB and linear scheduling are reviewed and explained both mathematically and graphically. Second, different LOB concepts are extracted and assessed to facilitate comparing LOB from its original use in manufacturing against the limited application of its objective chart in the construction industry. Third, a mathematical formulation based on singularity functions is developed, which can model staggering, continuity, and interruptability scenarios. Fourth, the repetitive nature of LOB and LSM enables resource-specific equations that model the level of detail of individual crews performing individual tasks

Comparison and Renaissance of Classic Line-of-balance and Linear Schedule Concepts for Construction Industry

AbstractLine-of-Balance (LOB) is a useful analytical tool for repetitive activities in construction projects, which allows showing which crew is assigned to what repetitive work unit of an activity. LOB is closely related to the linear scheduling method, but possesses some challenges: It must be clarified how it counts, as previous studies displayed an apparent measurement gap at the origin, implicitly representing that LOB starts at the first unit finish. Slopes in linear scheduling and LOB are different, even though both portray a measure of progress of an activity. This paper therefore tracks evolution and current use of LOB versus linear schedules. Its contribution to the body of knowledge is threefold: First, based on a literature review, LOB is found to be rooted in Activity-on-Arrow (AOA) diagrams, which makes it event-centered, not progress-centered. Differences in representing the start and productivity between LOB and linear scheduling are reviewed and explained both mathematically and graphically. Second, different LOB concepts are extracted and assessed to facilitate comparing LOB from its original use in manufacturing against the limited application of its objective chart in the construction industry. Third, a mathematical formulation based on singularity functions is developed, which can model staggering, continuity, and interruptability scenarios

Precedence permutation patterns creating criticality constellations: Exploring a conjecture on nonlinear activities with continuous links

The inaugural challenge of the 2016 Creative Construction Conference has posed two related questions on how many possible criticality constellations with different behaviors for delays and acceleration exist and how said constellations can occur for nonlinearly and monotonously progressing activities that have continuous relations. This paper systematically solves these questions by performing a thorough literature review, assembling theoretical foundations for link constellations, performing a computer simulation of all possible permutations, and providing a mathematical proof by contradiction. It is found that (for the initially assumed self-contained activities in a network schedule that exhibit only a linearly growing production), three newly hypothesized criticality constellations cannot exist. Nonlinear activity constellations with diverging or converging relative productivities are examined next. Lags in networks become buffers in linear schedules. It is found that a nonlinear curvature of the progress may induce middle-to-middle relations besides those between start and finish. If multiple curvatures are allowed, then partial segments can form relations, which increase the number of criticality constellations. This paper is extended from the 2017 Procedia Engineering conference version

Critical Duration Index: Anticipating Project Delays From Deterministic Schedule Information

[EN] Classical scheduling techniques are well-known to underestimate the average project duration, yet they remain widely used in practice due to their simplicity. In this paper, the new Critical Duration Index (CDI) is proposed. This index indirectly allows anticipation for the probability of a project ending late, as well as the average project duration extension compared with a deterministic project duration estimate. The accuracy of two simple regression expressions that use the CDI was tested on two representative data sets of 4,100 artificial and 108 empirical (real) projects. Results show that these regression expressions outperformed the only alternative index found in the literature. Besides allowing enhanced forecasting possibilities, calculating the CDI only requires basic scheduling information that is available at the planning stage. It can thus be easily adopted by project managers to improve their project duration estimates over prior deterministic techniques.This research is supported by the National Social Science Fund projects (No. 20BJY010); National Social Science Fund Post-Financing Projects (No. 19FJYB017); Sichuan-Tibet Railway Major Fundamental Science Problems Special Fund (No. 71942006); Qinghai Natural Science Foundation (No. 2020-JY-736); List of Key Science and Technology Projects in China's Transportation Industry in 2018-International Science and Technology Cooperation Project (Nos. 2018-GH-006 and 2019-MS5-100); Emerging Engineering Education Research and Practice Project of Ministry of Education of China (No. E-GKRWJC20202914); Shaanxi Province Higher Education Teaching Reform Project (No. 19BZ016); and Humanities and Social Sciences Research Project of the Ministry of Education (21XJA752003).González-Cruz, M.; Ballesteros-Pérez, P.; Lucko, G.; Zhang, J. (2022). Critical Duration Index: Anticipating Project Delays From Deterministic Schedule Information. Journal of Construction Engineering and Management. 148(11):1-12. https://doi.org/10.1061/(ASCE)CO.1943-7862.00023871121481

Financial Planning and Management Practices of Electrical Contractors

Contractors must carefully manage their cash outflows (e.g., for materials to enable their work) and inflows (after the work) to be profitable, particularly in an economy that is still recovering from the 2008–2012 recession that grew out of the mortgage crisis. Their importance for business success is undisputed, as bankruptcies due to insufficient cash flow underline. Therefore, this study investigated current business practices of electrical contracting companies of different sizes with respect to their financial planning and management. A detailed questionnaire was developed with best guidelines on survey studies and pilot testing. It was sent to members of the National Electrical Contractors Association. Respondent anonymity was ensured. The survey recorded demographics, business practices, operating conditions, and other important factors using 57 subquestions. Each section allowed feedback to clarify the numerical responses. Responses were well distributed across company sizes, so that the results are representative for the entire industry. The results indicated that contractors generally have a substantial amount of experience in financial decision making. Their approach is conservative and focuses on healthy growth. Yet, opportunities to fine-tune business practices are identified, e.g., immediate invoicing, considering discounts to accelerate payment receipts, attempting to negotiate and use favorable credit terms, reviewing payment performance, and performing frequent cash flow forecasts. Some of the differences in the responses can be attributed to different company sizes. To help especially smaller companies in planning their cash flow, a spreadsheet for implementation has been created

Financial Planning and Management Practices of Electrical Contractors

Contractors must carefully manage their cash outflows (e.g., for materials to enable their work) and inflows (after the work) to be profitable, particularly in an economy that is still recovering from the 2008–2012 recession that grew out of the mortgage crisis. Their importance for business success is undisputed, as bankruptcies due to insufficient cash flow underline. Therefore, this study investigated current business practices of electrical contracting companies of different sizes with respect to their financial planning and management. A detailed questionnaire was developed with best guidelines on survey studies and pilot testing. It was sent to members of the National Electrical Contractors Association. Respondent anonymity was ensured. The survey recorded demographics, business practices, operating conditions, and other important factors using 57 subquestions. Each section allowed feedback to clarify the numerical responses. Responses were well distributed across company sizes, so that the results are representative for the entire industry. The results indicated that contractors generally have a substantial amount of experience in financial decision making. Their approach is conservative and focuses on healthy growth. Yet, opportunities to fine-tune business practices are identified, e.g., immediate invoicing, considering discounts to accelerate payment receipts, attempting to negotiate and use favorable credit terms, reviewing payment performance, and performing frequent cash flow forecasts. Some of the differences in the responses can be attributed to different company sizes. To help especially smaller companies in planning their cash flow, a spreadsheet for implementation has been created

Modeling early payment discounts and late payment fees with singularity functions

Cash flow management is a vital concern of construction contractors. To break its vicious cycle of ‘pay as late as possible, get paid as early as possible’ in which the project participants may engage to their mutual detriment, potential incentives and disincentives that are used in financial transactions should be systematically investigated. Both are time-dependent functions that define a discount or surcharge based on whether a transaction is performed before or after a deadline. They can thus be expressed by so-called singularity functions, which are activated on said cutoff date. The new model expands prior research on cash flows by linking early (prompt) payment discounts – for which a practical nomograph is provided – directly with their counterpart of late payment fees. The values of both can be calculated from the individual financing interest of the participants to assess different scenarios based on their relative time value of money. They thus gain the ability to make financially informed decisions on offering a discount and imposing a fee appropriately, and accepting the discount or incurring a fee, respectively.Non UBCUnreviewedFacultyOthe

Temporal perspectives in construction simulation modeling

Temporal perspectives play a vital role in shaping narratives. Such perspectives include models of time that support the practice of construction management. Although formal representations of time are rarely noticed, they strongly influence the variables and relationships that can be encoded in process models. The objective of this paper is to illustrate the distinct ways in which the time can be formalized and how they impact the understanding of project performance and productivity. It explores existing and new temporal representations on how they contribute to improving reasoning capabilities in construction processes. Existing models differ by whether they use time points or intervals to represent activities (e.g. activity-on-node networks versus Gantt bar charts) and how clearly they communicate changes during execution. While traditional approaches exhibit shortcomings, singularity functions have significant potential for further development and could benefit from conceptual integration with situational simulation toward a powerful and integrated temporal modeling scheme