Project-specific Constraints Research Articles

Diversity, equity, and inclusivity in observational ambulatory assessment: Recommendations from two decades of Electronically Activated Recorder (EAR) research.

Ambient audio sampling methods such as the Electronically Activated Recorder (EAR) have become increasingly prominent in clinical and social sciences research. These methods record snippets of naturalistically assessed audio from participants' daily lives, enabling novel observational research about the daily social interactions, identities, environments, behaviors, and speech of populations of interest. In practice, these scientific opportunities are equaled by methodological challenges: researchers' own cultural backgrounds and identities can easily and unknowingly permeate the collection, coding, analysis, and interpretation of social data from daily life. Ambient audio sampling poses unique and significant challenges to cultural humility, diversity, equity, and inclusivity (DEI) in scientific research that require systematized attention. Motivated by this observation, an international consortium of 21 researchers who have used ambient audio sampling methodologies created a workgroup with the aim of improving upon existing published guidelines. We pooled formally and informally documented challenges pertaining to DEI in ambient audio sampling from our collective experience on 40+ studies (most of which used the EAR app) in clinical and healthy populations ranging from children to older adults. This article presents our resultant recommendations and argues for the incorporation of community-engaged research methods in observational ambulatory assessment designs looking forward. We provide concrete recommendations across each stage typical of an ambient audio sampling study (recruiting and enrolling participants, developing coding systems, training coders, handling multi-linguistic participants, data analysis and interpretation, and dissemination of results) as well as guiding questions that can be used to adapt these recommendations to project-specific constraints and needs.

Formwork Engineering for Sustainable Concrete Construction

This study provides a comprehensive review of the engineering challenges of formwork in concrete construction. The paper investigates different formwork systems, their design based on form pressure, and the difficulties of form stripping. Alternative binders are gaining more and more interest by opening new opportunities for sustainable concrete materials and their impact on form pressure and concrete setting is also investigated in this paper. The discussion involves several engineering challenges such as sustainability, safety, and economy, while it also explores previous case studies, and discusses future trends in formwork design. The findings pinpoint that choosing an appropriate formwork system depends significantly on project-specific constraints and that the development of innovative materials and technologies presents significant benefits but also new challenges, including the need for training and regulation. Current trends in formwork design and use show promising possibilities for the integration of digital technologies and the development of sustainable and ‘smart’ formwork systems. Continued research within the field has the possibility to explore new formwork materials and technologies, which will contribute to the implementation of more effective and sustainable practices in concrete construction.

Loudness control in a small volume Recital Hall

Mississippi State University’s new music building features a 173-seat Lecture Hall that also serves as a recital hall. The limited volume presents an acoustical challenge to accommodate a variety of uses—most concerning are the louder and larger ensembles with up to 25 musicians and 50 singers sharing the stage. Due to project-specific constraints, the 24 foot stage-to-ceiling height and the 60,000 cubic foot volume are less than the early design-phase recommendations for the expected uses, which raises concerns about loudness buildup and inability to generate desired reverberation. Our goal is to implement variable loudness control systems that provide a useful reverberation range with good clarity across different settings. We identify and justify four loudness control strategies—maintain early, supportive reflections; shape the room to form patterns of sustained sound in areas with adjustable absorption; reduce high-frequency sustain in areas near audiences; avoid flutter echoes—and illustrate how those strategies were integrated into the architectural design through room shaping, fixed wall treatments, and deployable curtains and banners. We discuss subjective and instrumented observations about the loudness (measured in Sound Strength G), reverberation time (measured in T30), clarity (measured in Clarity Index C80), and overall character of the room response.

Integrated Offsite Logistics Scheduling Approach for High-Rise Modular Building Projects

By maximizing offsite work and minimizing onsite activities, modular construction has become increasingly popular in high-rise, high-density cities. For successfully delivering high-rise modular buildings, a key issue is the effective scheduling of offsite logistics, consisting of module manufacturing, transportation, and storage. This paper proposes an integrated offsite logistics scheduling approach for high-rise modular building projects that addresses project-specific constraints and uncertainties, based on the stochastic Petri net (SPN) method. The proposed approach supports multi-criteria decision-making, that considers completion time, total cost, storage capacity utilization, and production process stability under what-if scenarios. Its efficacy and novelty for offsite logistics scheduling were demonstrated through a real-life project case study. The results indicate the need to (1) strengthen suppliers’ demand responsiveness by shortening module production time; (2) enhance manufacturing flexibility by increasing factory storage utilization; (3) improve supply chain synchronization; and (4) capitalize on the government’s role in offsite logistics enhancement. The findings methodologically innovate offsite logistics scheduling, and practically support contractors and module suppliers in successfully delivering high-rise modular building projects in high-density cities.

Lifecycle Analysis of Recycled Asphalt Pavements: Case Study Scenario Analyses of an Urban Highway Section

Roads account for a major part of energy/resource consumption and emission of GHGs, such as CO2, PM, NOx, O3, etc., due to high demand for virgin materials, specifically in developing regions. The applicability of recycled materials, such as recycled asphalt pavement (RAP) and other alternative approaches for, e.g., warm-mix asphalt (WMA), in developed countries is hindered by project-specific constraints and lack of empirical studies in these regions. Lifecycle assessment studies on the usage of these road options from actual projects in the developing countries can aid decision makers choose sustainable material approaches by providing case study examples as guidelines. To that end, this study analyses environmental in/out-flows for a traditional approach and multiple green approaches (RAP and WMA) for a major highway section in Abu Dhabi through a 30-year (2015–2045) lifecycle approach. Roadworks were modelled in SimaPro according to real-world conditions, and the expected burden mitigation in each stage is calculated. Benefits of using optimum RAP-based options and a virgin-material-based WMA case against the baseline virgin material case were also investigated. Results showed benefits of WMA as higher than replacing virgin asphalt with recycled asphalt (25% RAP asphalt base, 15% RAP binder and wearing courses). Land use (19%) and energy consumption (16%) showed the highest reduction, followed by ozone depletion (14%), ionizing radiation (11%), PM (8%), acidification (7%) and global warming potential (6%) across all pavement lifecycle stages and environmental indicators. Similar results were obtained for other scenarios with lesser degrees of reduction, which show the significance of replacing HMA with WMA for real-world projects, specifically in mega road projects in Abu Dhabi and the Middle East towards cutting the significant carbon footprint of asphalt pavements.

BIM-Based Pavement Management Tool for Scheduling Urban Road Maintenance

The latest advancements in road asphalt materials and construction technologies have increased the difficulty for engineers to select the appropriate pavement design solution with consideration of proper timing for maintenance planning. On the other hand, Building Information Modeling (BIM) tools allow practitioners to efficiently store and manage large amounts of data, supporting decision making in road asphalt pavement design and management. The present work focused on the elaboration of a BIM-based maintenance analysis tool for the specific evaluation of several condition indicators and the selection of proper maintenance solutions designed to include alternative materials and advanced recycling technologies. A traditional BIM workflow was integrated with additional user-defined property sets to investigate the need for maintenance at the present date and predict the degradation curve of the condition indicators through the least square interpolation of time series of data. The analysis tool also provided the selection of available pavement alternatives from a library of designed solutions based on their compliance with project-specific constraints (maximum budget, minimum useful life, and availability of secondary raw materials and in-place recycling technologies). The proposed BIM tool aims to be a practical and dynamic way to integrate maintenance planning considerations into road pavement design, encouraging the use of digital tools in the road industry and ultimately supporting a pavement maintenance decision-making process oriented towards a circular economy.

The Effect of Size on Postrelease Survival of Head-Started Mojave Desert Tortoises

AbstractCaptive-rearing conservation programs focus primarily on maximizing postrelease survival. Survival increases with size in a variety of taxa, often leading to the use of enhanced size as a means to minimize postrelease losses. Head-starting is a specific captive-rearing approach used to accelerate growth in captivity prior to release in the wild. We explored the effect of size at release, among other potential factors, on postrelease survival in head-started Mojave desert tortoises Gopherus agassizii. Juvenile tortoises were reared for different durations of captivity (2–7 y) and under varying husbandry protocols, resulting in a wide range of juvenile sizes (68–145 mm midline carapace length) at release. We released all animals (n = 78) in the Mojave National Preserve, California, United States, on 25 September 2018. Release size and surface activity were the only significant predictors of fate during the first year postrelease. Larger sized head-starts had higher predicted survival rates when compared with smaller individuals. This trend was also observed in animals of the same age but reared under different protocols, suggesting that accelerating the growth of head-started tortoises may increase efficiency of head-starting programs without decreasing postrelease success. Excluding five missing animals, released head-starts had 82.2% survival in their first year postrelease (September 2018–September 2019), with all mortalities resulting from predation. No animals with >90-mm midline carapace length were predated by ravens. Our findings suggest the utility of head-starting may be substantially improved by incorporating indoor rearing to accelerate growth. Target release size for head-started chelonians will vary among head-start programs based on release site conditions and project-specific constraints.

Project-specific constraints influencing productivity of tradespeople in the Nigerian construction industry

PurposeThe purpose of this paper is to establish the perception of tradespeople about project-specific constraints (PSCs) influencing construction productivity in Nigeria.Design/methodology/approachUsing a qualitative descriptive survey comprising face-to-face semi-structured interviews and a purposive sampling method, views of eight groups of tradespeople and seven project managers on live construction projects in Nigeria were collected. The study used conventional content analysis with the aid of NVivo 12 pro computer software for the analysis.FindingsThe research evaluated the PSCs and their effect on construction productivity of tradespeople. The findings identified five key PSCs, namely: lack of promotions/reward system, unsafe/poor health condition of workers, delay in material availability, inadequate site amenities and an ageing workforce. These results support earlier research on constraints influencing labour productivity, however, the poor health condition of workers and material unavailability appear to be more unique when compared to other previous studies.Research limitations/implicationsThe study focussed on the Federal Capital Territory Abuja and the Lagos State of Nigeria. It provides insight into the PSCs influencing the productivity of tradespeople in the Nigerian construction industry. Further research to identify the PSCs in depth, in the Eastern part of Nigeria is necessary.Practical implicationsThe PSCs influencing tradespeople’s productivity was identified. The level of the relative impact of the PSCs is expected to guide the project team in addressing the PSCs in a method that is cost effective.Originality/valueThis study is original research that has underlined some areas of improvement in construction project performance.

Test case selection-prioritization approach based on memoization dynamic programming algorithm

In the software industry, selection and prioritization techniques become a necessity in the regression and validation testing phases because a lot of test cases are available for reuse, yet time and project specific constraints must be respected. In this paper we propose a dynamic programming approach in solving test case selection-prioritization problems. We focus on low memory consumption in pseudo-polynomial time complexity applicable in both selection and selection-prioritization problems over sets of test cases or test suites. In dynamic programming optimization solutions, huge amounts of memory are required and unfortunately the memory is limited. Therefore, lower memory consumption leads to a higher number of test cases to be involved in the selection process. Our approach is suited for medium to large projects where the required memory space is not higher than the order of tens of GBytes. We employed both objective methods as the dynamic programming algorithm and subjective and empiric human decision as defining the prioritization criteria. Furthermore, we propose a method of employing multiple project specific criteria in evaluating the importance of a test case in the project context. To evaluate the proposed solution relative to the classical dynamic programming knapsack solution, we developed a suite of comparative case studies based on 1000 generated scenarios as close as possible to real project scenarios. The results of the comparative study reported the proposed algorithm requires up to 400 times less memory in the best-case scenarios and about 40 times less memory in average. The solution delivers optimal results in pseudo-polynomial time complexity, is effective for amounts of test cases up to the order of millions and compared with the classical dynamic programming methods leads to higher number of test cases to be involved in the selection process due to reduced memory consumption.

Sludge digestion instead of aerobic stabilisation – a cost benefit analysis based on experiences in Germany

As a consequence of a worldwide increase of energy costs, the efficient use of sewage sludge as a renewable energy resource must be considered, even for smaller wastewater treatment plants (WWTPs) with design capacities between 10,000 and 50,000 population equivalent (PE). To find the lower limit for an economical conversion of an aerobic stabilisation plant into an anaerobic stabilisation plant, we derived cost functions for specific capital costs and operating cost savings. With these tools, it is possible to evaluate if it would be promising to further investigate refitting aerobic plants into plants that produce biogas. By comparing capital costs with operation cost savings, a break-even point for process conversion could be determined. The break-even point varies depending on project specific constraints and assumptions related to future energy and operation costs and variable interest rates. A 5% increase of energy and operation costs leads to a cost efficient conversion for plants above 7,500 PE. A conversion of WWTPs results in different positive effects on energy generation and plant operations: increased efficiency, energy savings, and on-site renewable power generation by digester gas which can be used in the plant. Also, the optimisation of energy efficiency results in a reduction of primary energy consumption.

Skewed Slab-on-Girder Steel Bridge Superstructures with Bidirectional-Ductile End Diaphragms

Specially designed ductile end diaphragms of steel bridge superstructures have previously proved, both theoretically and experimentally, to dissipate seismic input energy, protecting other substructure and superstructure members. Although ductile diaphragms have been introduced in the latest AASHTO guide specifications as a structural system that can be used to resist transverse earthquake effects, no guidance is provided on how to implement these ductile diaphragms in skewed bridges. To address this need and to resolve some shortcomings of the known end diaphragm systems (EDSs), two bidirectional end diaphragm configurations, namely, EDS-1 and EDS-2, with buckling restrained braces (BRBs) are proposed and numerically investigated. Bidirectional end diaphragm is a new concept, and can be implemented both in straight and skewed steel bridge superstructures to resist bidirectional earthquake effects. To assess the relative effectiveness of the proposed systems and to investigate how various parameters relate to seismic response, closed-form solutions are developed using nondimensional bridge geometric ratios. Numerical results indicate that skewness more severely affects end diaphragm behavior when φ≥30°. Also, comparisons reveal that although both end diaphragm systems can be used with confidence as ductile seismic fuses, each of the two systems considered have advantages that may favor its implementation, depending on project-specific constraints.

Implementation of the ASCE BOK-2: Some Thoughts

Faculty required credentials are discussed in Chapter 4 of the BOK-2, which states, in part, “A good guide of minimum relevant practical experience required is you must be able to both perform the engineering being taught as well as critique and judge the relative merits of alternative solutions in the context of project-specific constraints.” This is a significant step forward in raising the bar for the engineering education process. A systematic program should be established that will create adequate opportunities for faculty to develop the necessary practical and professional credentials. We also suggest that universities provide opportunities for this practical experience to occur. There are many ways to obtain experience. During the process of obtaining practical experience, many opportunities will occur for faculty to interact with industry. Research opportunities to solve many of the existing engineering and construction problems likely will occur. The paper “Importance of Practical and Professional Experience for Engineering Faculty” Kirschenman 2008 describes a few ways to obtain practical experience. In addition to experience, faculty should obtain adequate credentials in the nontechnical, professional, and leadership areas in order to teach these required areas. Faculty should lead this process of raising the bar. An important piece of the puzzle is establishment of a faculty reward system that encourages achievements in the areas of professional practice in order to reinforce that faculty development will be beneficial to implementing the BOK-2. Ways should be developed in the faculty reward system to encourage faculty achieving the appropriate expe

Construction Time-cost Trade-off Analysis Using Ant System

During the last decade, evolutionary methods such as genetic algorithms have been used extensively for solving time-cost trade-off (TCT) problems in construction projects. More recently, Ant systems (AS), which are evolutionary methods based on the foraging behavior of ants, have been successfully applied to a number of combinatorial optimization problems. In this article, a formulation is developed that enables AS to be used for the TCT analysis. With its robust optimization search, the AS model minimizes the total project cost as an objective function and accounts for project-specific constraints on time and cost. The findings of this study indicate that AS algorithms are an attractive alternative to meta-heuristic optimization algorithms in the construction engineering and management domain in terms of computational efficiency and their ability to find near-global optimal solutions.

Optimization of construction time-cost trade-off analysis using genetic algorithms

In the management of a construction project, the project duration can often be compressed by accelerating some of its activities at an additional expense. This is the so-called time-cost trade-off (TCT) problem, which has been studied extensively in the project management literature. TCT decisions, however, are complex and require planners to select appropriate resources for each project task, including crew size, equipment, methods, and technology. As combinatorial optimization problems, finding optimal decisions is difficult and time consuming considering the number of possible permutations involved. In this paper, a practical model for TCT optimization is developed using the principle of genetic algorithms (GAs). With its robust optimization search, the GAs model minimizes the total project cost as an objective function and accounts for project-specific constraints on time and cost. To maximize its benefits, the model has been implemented as a VBA macro program. This automates TCT analysis and combines it with standard resource-management procedures. Details of the proposed TCT model are described and several experiments conducted to demonstrate its benefits. The developments made in this paper provide guidelines for designing and implementing practical GA applications in the civil engineering domain.Key words: computer application, time-cost trade-off, construction management, genetic algorithms, and optimization.

Managing multiple construction robots with a computer

The Construction Robotic Equipment Management System (CREMS) prototype presented in this paper has been applied to the evaluation of performance of ten diverse construction robots. individual task characteristics along with the robot physical parameters have been analyzed in arriving at appropriate effectiveness and productivity parameters. The wall inspection, clean room inspection and concrete placement tasks were analyzed using a uniform analysis procedure. The number of erected units has been the primary focus of beam and column erection evaluation. Consistency and relative density were considered as parameters associated with productivity of a robotic excavation control system. Underground utilities encountered during excavation imposed limits on the speed of progress and interruptions along the delivery path of concrete distribution. These are regarded as major project-specific constraints for these tasks. An example application of CREMS to robotic excavation has been provided.