An official website of the United States government
The development of offshore wind technology has become a feasible solution to meet the increasing demands for clean and renewable energy. The United States has a total of 4250GW offshore wind energy potential; however, 65% of it is in deep water zones (Lopez et al., 2022) where wind turbines with fixed foundations typically are economically and technically unfeasible. In those situations, floating turbines supported by subsea anchors are a more competitive solution. Based on previous studies, ring anchors can be more material-efficient than piles and caissons because they require less material. Ring anchors also perform better than drag anchors due to their greater embedment depth. To further understand the behavior of ring anchors in saturated sand, a series of centrifuge load tests were performed at the University of California Davis Center for Geotechnical Modeling (CGM) at an acceleration of 70g. This test series investigated the effect of the anchor embedment depth and loading angle on the monotonic loading behavior. The ring anchor models were embedded in dense saturated sand, and then connected to an actuator using taut steel wire ropes. Sensors were used to measure the line tension, displacement, and inclination. The results indicate that the ring anchors mobilize greater capacities as their embedment depth is increased and when they are loaded at angles close to the horizontal direction, while vertical loading leads to the smallest capacity. The anchor displacement during the tests deviated slightly from the loading direction, showing a horizontal deviation at the earlier stages of the tests and a vertical one after the peak load. Furthermore, soil disturbance induced by the anchor installation was found to have a strong effect on the vertical capacity of the ring anchors. Overall, this study provides valuable information regarding the monotonic loading behavior of ring anchors which can aid in their future field deployment.
more »
« less
Assessment of analysis techniques for multi-plate anchors in sand
This work focuses on the numerical simulation of multi-plate anchor systems (e.g., helical anchors) in sand subjected to vertical loading. In assessing the stiffness and capacity of these multi-plate anchor systems, full awareness of the abilities and limitations of the various analysis methods must be understood. This work first summarizes studies completed by others and then goes on to assess the failure mechanisms of multi-plate anchors in sand and the influence of (1) plate width-to-depth ratio, (2) number of plates, and (3) relative positioning of plates. The analysis makes use of (1) conventional limit analysis, (2) so-called modified limit analysis that employs reduced strength parameters to account for the influence of soil dilatancy, and (3) the displacement-based finite element method, which considers elastic as well as plastic deformation leading to failure. The work critically reflects on limitations in the current analysis methods for helical ground anchors.
more »
« less
- Award ID(s):
- 1846817
- PAR ID:
- 10161620
- Date Published:
- Journal Name:
- Proceedings of the 44th Annual Conference on Deep Foundations
- Page Range / eLocation ID:
- 341-350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Structures with deployable and compliant mechanisms are new to the domain of underground geotechnical systems. An anchor with rotationally deploying compliant thin-wall elements has been developed. This paper presents variations of this anchor that are targeted to increase the surface area associated with the anchor. This increased surface area correlates to higher skin friction to better resist tensile forces. The number and sizing of the deployable components, called awns, are investigated. The work presented here includes methods to change the deployment behavior of the awns by changing the shape of the awns and by using functionally graded materials for increased resistance when the anchor is subjected to uplift forces. Test members were fabricated from a combination of flexible and rigid polymers via additive manufacturing. Experimental testing included anchor deployment tests and awn tension tests. For deployment tests, torque was applied to an anchor placed in clear sand. Awn tension tests provided additional information about the deformation of functionally graded awns through isolated testing of the awns. The presented design and experimental methodologies give insights into the behavior of small-scale deployable anchors.more » « less
-
There is little research or understanding of curricular differences between two- and four-year programs, career development of engineering technology (ET) students, and professional preparation for ET early career professionals [1]. Yet, ET credentials (including certificates, two-, and four-year degrees) represent over half of all engineering credentials awarded in the U.S [2]. ET professionals are important hands-on members of engineering teams who have specialized knowledge of components and engineering systems. This research study focuses on how career orientations affect engineering formation of ET students educated at two-year colleges. The theoretical framework guiding this study is Social Cognitive Career Theory (SCCT). SCCT is a theory which situates attitudes, interests, and experiences and links self-efficacy beliefs, outcome expectations, and personal goals to educational and career decisions and outcomes [3]. Student knowledge of attitudes toward and motivation to pursue STEM and engineering education can impact academic performance and indicate future career interest and participation in the STEM workforce [4]. This knowledge may be measured through career orientations or career anchors. A career anchor is a combination of self-concept characteristics which includes talents, skills, abilities, motives, needs, attitudes, and values. Career anchors can develop over time and aid in shaping personal and career identity [6]. The purpose of this quantitative research study is to identify dimensions of career orientations and anchors at various educational stages to map to ET career pathways. The research question this study aims to answer is: For students educated in two-year college ET programs, how do the different dimensions of career orientations, at various phases of professional preparation, impact experiences and development of professional profiles and pathways? The participants (n=308) in this study represent three different groups: (1) students in engineering technology related programs from a medium rural-serving technical college (n=136), (2) students in engineering technology related programs from a large urban-serving technical college (n=52), and (3) engineering students at a medium Research 1 university who have transferred from a two-year college (n=120). All participants completed Schein’s Career Anchor Inventory [5]. This instrument contains 40 six-point Likert-scale items with eight subscales which correlate to the eight different career anchors. Additional demographic questions were also included. The data analysis includes graphical displays for data visualization and exploration, descriptive statistics for summarizing trends in the sample data, and then inferential statistics for determining statistical significance. This analysis examines career anchor results across groups by institution, major, demographics, types of educational experiences, types of work experiences, and career influences. This cross-group analysis aids in the development of profiles of values, talents, abilities, and motives to support customized career development tailored specifically for ET students. These findings contribute research to a gap in ET and two-year college engineering education research. Practical implications include use of findings to create career pathways mapped to career anchors, integration of career development tools into two-year college curricula and programs, greater support for career counselors, and creation of alternate and more diverse pathways into engineering. Words: 489 References [1] National Academy of Engineering. (2016). Engineering technology education in the United States. Washington, DC: The National Academies Press. [2] The Integrated Postsecondary Education Data System, (IPEDS). (2014). Data on engineering technology degrees. [3] Lent, R.W., & Brown, S.B. (1996). Social cognitive approach to career development: An overivew. Career Development Quarterly, 44, 310-321. [4] Unfried, A., Faber, M., Stanhope, D.S., Wiebe, E. (2015). The development and validation of a measure of student attitudes toward science, technology, engineeirng, and math (S-STEM). Journal of Psychoeducational Assessment, 33(7), 622-639. [5] Schein, E. (1996). Career anchors revisited: Implications for career development in the 21st century. Academy of Management Executive, 10(4), 80-88. [6] Schein, E.H., & Van Maanen, J. (2013). Career Anchors, 4th ed. San Francisco: Wiley.more » « less
-
Abstract A significant number of investigations have been performed to develop and optimize cold plates for direct-to-chip cooling of processor packages. Many investigations have reported computational simulations using commercially available computational fluid dynamic tools that are compared to experimental data. Generally, the simulations and experimental data are in qualitative agreement but often not in quantitative agreement. Frequently, the experimental characterizations have high experimental uncertainty. In this study, extensive experimental evaluations are used to demonstrate the errors in experimental thermal measurements and the experimental artifacts during testing that lead to unacceptable inconsistency and uncertainty in the reported thermal resistance. By comparing experimental thermal data, such as the temperature at multiple positions on the processor lid, and using that data to extract a meaningful measure of thermal resistance, it is shown that the data uncertainty and inconsistency are primarily due to three factors: (1) inconsistency in the thermal boundary condition supplied by the thermal test vehicle (TTV) to the cold plate, (2) errors in the measurement and interpretation of the surface temperature of a solid surface, such as the heated lid surface, and (3) errors introduced by improper contact between cold plate and TTV. A standard thermal test vehicle (STTV) was engineered and used to provide reproducible thermal boundary conditions to the cold plate. An uncertainty analysis was performed in order to discriminate between the sources of inconsistencies in the reporting of thermal resistance, including parameters such as mechanical load distribution, methods for measuring the cold plate base, and TTV surface temperatures. A critical analysis of the classical thermal resistance definition was performed to emphasize its shortcomings for evaluating the performance of a cold plate. It is shown that the thermal resistance of cold plates based on heat exchanger theory better captures the physics of the heat transfer process when cold plates operate at high thermodynamic effectiveness.more » « less
-
Abstract Rovers designed for polar exploration primarily operate in flat and arid central plateau of the Antarctic and are unsuitable for multi-terrain operation such as slushy slow, wet soil, open ice and open ocean. The Multi-terrain Amphibious ARCtic explOrer or MAARCO rover is a design concept that employs a pair of helical drives in order to traverse the diverse landscape of the Arctic for autonomous research missions. A small-scale prototype (3:10 scale) of the MAARCO rover was developed to test terrestrial motion. The prototype is a screw-propelled vehicle that has two helical drives (similar to Archimedes’ screw) actuated by two independent motors to employ a differential steering system. The prototype performed several different maneuvers on a dry and wet sand — moving in a straight line, turning left, and turning right, and moving sideways by controlling the rotational speeds of the two drives. The sensors on the prototype collect data on angular orientation, linear acceleration and motor rotations. Through the tests the rover provided critical insight into the dynamics of the MAARCO rover, particularly, the effect of substrate failure or non-failure on the linear displacement of the rover. Further testing on different substrates and of the rover design on inclines surfaces will provide the MAARCO team valuable insight into designing a full-scale rover design.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
