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Mix Masters: At a UW lab, students are testing ways to give concrete a solid future.

Nestled in a former airplane hangar in the sprawling former Navy base at Magnuson Park, construction and engineering students from the University of Washington stress-test recipes for concrete—one of the world’s most used substances. Made with a combination of cement, water and aggregates, some type of concrete has been produced by every civilization since the Babylonians. Now, university students are joining in the centuries-long quest to refine and perfect this essential material at the University of Washington Center for Education and Research in Construction (CERC).

Dr. Fred Aguayo, who joined the faculty of the College of Built Environments in 2021, is the director of the Construction Methods and Concrete Materials Laboratory (which Aguayo has dubbed CM2L), as well as an assistant professor with the Department of Construction Management and an adjunct assistant professor with the Department of Civil and Environmental Engineering. You could say he enjoys watching cement “dry”—but of course he’s heard that one before. Since joining the UW, it’s his expertise in the field that has allowed more of a focus into concrete and its potential.

Read the full feature at UW Magazine

CM Welcomes Dr. Amos Darko

In pursuit of our vision for a more just and beautiful world, the College of Built Environments continues to implement an important part of our strategic framework: growing our capacity for collaborative interdisciplinary work with the goal of advancing climate solutions.

Dr. Amos Darko

We are excited to announce that Dr. Amos Darko has joined the Construction Management faculty as part of our interdisciplinary faculty cohort. Dr. Darko brings with him a wealth of expertise and experience in sustainability, sustainable built environment, sustainable construction, green building, modular construction, project management, and digital technologies including building information modeling and artificial intelligence.

Dr. Darko earned his Ph.D. degree from The Hong Kong Polytechnic University (PolyU) in 2019, and his BSc degree (First Class Honors) from Kwame Nkrumah University of Science and Technology (KNUST) in 2014. Before joining the University of Washington, Dr. Darko was a Research Assistant Professor at PolyU.

Dr. Darko has published numerous papers in leading international peer-reviewed journals, conferences, and books. His papers have been rated as highly cited and hot papers by the Web of Science. His paper is the most cited paper of all time in the International Journal of Construction Management. He has also been ranked among the world’s top 2% most cited scientists by Elsevier BV and Stanford University. Dr. Darko has received several awards for his outstanding work, including the Green Talents Award from the German Federal Ministry of Education and Research in 2020, the Global Top Peer Reviewer Award from the Web of Science Group in 2019, the Outstanding Overseas Young Scholars Award from Central South University in 2019, and the Best Construction Technology and Management Student Award from KNUST in 2014.

Dr. Darko’s work has been supported by the Research Grants Council of Hong Kong, Chief Secretary for Administration’s Office of Hong Kong, and several internal grants.

Dr. Darko is an Associate Editor of Green Building and Construction Economics, an Associate Editor of Humanities and Social Sciences Communications, and an Academic Editor of Advances in Civil Engineering.

“I am excited to collaborate with colleagues from diverse disciplines to tackle the pressing challenges of sustainability and climate change, and to contribute to shaping a more just and beautiful world,” said Dr. Darko.

Emergent Subcontracting Models in the US Construction Industry


Prime contracting models for engineering and construction projects are described extensively in the literature, but models between prime contractors and subcontractors are less well known. This study examined the established and evolving subcontracting models in the US construction industry to not only document their utilization but also investigate their advantages and disadvantages when employed. There search followed a two-phase/two-step approach. During Phase 1, the authors completed a regionally based study to identify subcontracting practices in the Pacific Northwest. As part of Phase 2, the study was expanded across the United States to gain a greater understanding of each of the identified subcontracting models, including advantages, disadvantages, and variations. Both phases were organized into two steps:(1) an online survey instrument was sent to professionals with either general or specialty contracting firms, and (2) follow-up semi-structured interviews were conducted with selected survey respondents to better evaluate each subcontracting model. The authors found that five sub-contracting models address the most common scenarios and the characteristics of each are familiar to the nationwide participant sample. There are subtle variations to the main five models that are being employed to varying degrees across the country. The impetus for these variations appears to be founded on the need to find better contractual arrangements and that subcontracting practices are dynamic by nature. Although most of the participants were from western and central divisions of the US Census Bureau geographical classification, participants from all geographic areas participated in the study. Increasing knowledge on how project delivery systems may affect disputes and claims or conflicts and legal issues of procurement systems, this article uniquely contributes to defining a taxonomy of subcontracting models while giving insights into the current and emerging trends in subcontracting practices, including how subcontractors are integrated into a projectteam.DOI:10.1061/(ASCE)LA.1943-4170.0000568.© 2022 American Society of Civil Engineers

Read Full Paper HERE`

ACT2: Time–Cost Tradeoffs from Alternative Contracting Methods

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ACT2: Time–Cost Tradeoffs from Alternative Contracting Methods

Incentive/disincentive (I/D) and cost-plus-time (A+B) are two of the most widely used alternative contracting methods (ACMs) for accelerating the construction of highway infrastructure improvement projects. However, little is known about the effects of trade-offs in terms of project schedule and cost performance. This study addresses this problem by creating and testing a stochastic decision support model called accelerated alternative contracting cost-time trade-off (ACT2). This model was developed by a second-order polynomial regression analysis and validated by the predicted error sum of square statistic and paired comparison tests. The results of a descriptive trend analysis based on a rich set of high-confidence project data show that I/D is effective at reducing project duration but results in higher cost compared to pure A+B and conventional methods. This cost-time trade-off effect was confirmed by the ACT2model, which determines the level of cost-time trade-off for different ACMs. This study will help state transportation agencies promote more effective application of ACMs by providing data-driven performance benchmarking results when evaluating competing acceleration strategies and techniques.

Technical Paper: Structural Equation Modeling …

Structural Equation Modeling for the Determinants of International Infrastructure Investment: Evidence from Chinese Contractors

International infrastructure investment can effectively accelerate infrastructure development in developing countries and thus support their social and economic progress. However, little is known of the factors that may determine the flow of international infrastructure investment to those countries. This study aims to bridge that knowledge gap, first by identifying the determinants of international infrastructure investment, and then by developing a structural equation model to reveal their underlying interrelationships. The structural equation model is applied to country-level data regarding international infrastructure investment with Chinese contractors in 141 countries worldwide over the 9-year period from 2009 to 2017. The results show that three determinants, namely infrastructure quality, labor supply, and investment interdependency, have a positive relationship with a country’s international infrastructure investment inflow. However, another determinant, institutional environment, has a significantly negative impact, which suggests that when making foreign infrastructure investment, Chinese contractors enter countries with a comparatively poor institutional environment with substantial political risks. The results also highlight how much a robust infrastructure development plan can help developing countries avoid the poor-infrastructure trap, a situation in which poor infrastructure quality discourages international infrastructure investment. These research findings may assist international infrastructure investment firms to make informed decisions with regard to financing and managing projects and help policymakers who focus on attracting foreign investment in infrastructure.

“Structural..” was based on a collaboration with Professor Chris Lee and Yunhong Wang, a Ph.D. student from Tsinghua Univ who visited UW last year via the VISIT program.

Safety is a marathon, not a sprint!

Using Four-Wheel Carts in The Roofing Trade

This animation is based on the real-life story of a roofing apprentice who left the industry after getting injured while overcoming a poorly-setup ramp with a material cart.  Three scientific, evidence-based solutions are provided to inform supervisors how a similar incident can be prevented through ergonomic workplace layout and task pre-planning.  The moral of the Tortoise and the Hare is embedded in the animation to encourage supervisors to become thoughtful leaders, creating a safer and caring environment for others.

Slow and steady wins the safety race!

This animation recreates the real-life story of a roofer who ruptured his Achilles tendon while maneuvering a heavily loaded cart.  Three solutions are recommended with embedded scientific evidence showing that even a simple solution like team pulling could have prevented this injury.  The moral of the Tortoise and the Hare is embedded in the animation to remind audiences to pay attention to the danger of ergonomic hazards.

Dynamic production scheduling model under due date uncertainty in precast concrete construction.

Journal of Cleaner Production 257, 120527

Abstract: Precast concrete structures (PCs) are widely used in the construction industry to reduce project delivery times and improve quality. On-time delivery of PCs is critical for successful project completion because the processes involving precast concrete are the critical paths in most cases. However, existing models for scheduling PC production are not adequate for use in dynamic environments where construction projects have uncertain construction schedules because of various reasons such as poor labor productivity, inadequate equipment, and poor weather. This research proposes a dynamic model for PC production scheduling by adopting a discrete-time simulation method to respond to due date changes in real time and by using a new dispatching rule that considers the uncertainty of the due dates to minimize tardiness.

Authored by:  Taehoon Kim, Yong-Woo Kim, and Hunhee Cho

Impact of Empowering Front-Line Managers on Planning Reliability & Project Schedule Performance

Journal of Management in Engineering 36 (3), 04020004

Abstract: This study applies empowerment theory to production planning at the level of frontline managers in a construction project. Using structural equation modeling, we investigate how empowering frontline managers impacts their planning performance. In contrast to prior studies, we find that although psychological empowerment of frontline managers has no direct effect on their production planning reliability or scheduling performance, it has an indirect effect on planning reliability and scheduling performance, as long as the organization supports empowerment structurally during production planning. This implies that a project manager should provide frontline managers at the operational level with proper formal and informal authority over workflow development, shielding, and resource allocation when planning production in order to enhance job performance through psychological empowerment.

Authored by:  Yong-Woo Kim and Byong-Duk Rhee