ETDs

This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.

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Endurance limit for HMA based on healing phenomenon using viscoelastic continuum damage analysis

Description

Perpetual Pavements, if properly designed and rehabilitated, it can last longer than 50 years without major structural rehabilitation. Fatigue endurance limit is a key parameter for designing perpetual pavements to mitigate bottom-up fatigue cracking. The endurance limit has not been implemented in the Mechanistic Empirical Pavement Design Guide software, currently…

Perpetual Pavements, if properly designed and rehabilitated, it can last longer than 50 years without major structural rehabilitation. Fatigue endurance limit is a key parameter for designing perpetual pavements to mitigate bottom-up fatigue cracking. The endurance limit has not been implemented in the Mechanistic Empirical Pavement Design Guide software, currently known as DARWin-ME. This study was conducted as part of the National Cooperative Highway Research Program (NCHRP) Project 9-44A to develop a framework and mathematical methodology to determine the fatigue endurance limit using the uniaxial fatigue test. In this procedure, the endurance limit is defined as the allowable tensile strains at which a balance takes place between the fatigue damage during loading, and the healing during the rest periods between loading pulses. The viscoelastic continuum damage model was used to isolate time dependent damage and healing in hot mix asphalt from that due to fatigue. This study also included the development of a uniaxial fatigue test method and the associated data acquisition computer programs to conduct the test with and without rest period. Five factors that affect the fatigue and healing behavior of asphalt mixtures were evaluated: asphalt content, air voids, temperature, rest period and tensile strain. Based on the test results, two Pseudo Stiffness Ratio (PSR) regression models were developed. In the first model, the PSR was a function of the five factors and the number of loading cycles. In the second model, air voids, asphalt content, and temperature were replaced by the initial stiffness of the mix. In both models, the endurance limit was defined when PSR is equal to 1.0 (net damage is equal to zero). The results of the first model were compared to the results of a stiffness ratio model developed based on a parallel study using beam fatigue test (part of the same NCHRP 9-44A). The endurance limit values determined from uniaxial and beam fatigue tests showed very good correlation. A methodology was described on how to incorporate the second PSR model into fatigue analysis and damage using the DARWin-ME software. This would provide an effective and efficient methodology to design perpetual flexible pavements.
ContributorsZeiada, Waleed (Author) / Kaloush, Kamil (Thesis advisor) / Witczak, Matthew W. (Thesis advisor) / Zapata, Claudia (Committee member) / Mamlouk, Michael (Committee member) / Arizona State University (Publisher)
Created2012
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Important factors in the design of assistive technology to avoid the stigmatization of users

Description
Some disabled users of assistive technologies (AT) have expressed concerns that their use of those AT devices brings particular attention to their disability and, in doing so, stigmatizes them in the eyes of their peers. This research studies how a wide range of design factors, influence how positively or negatively…

Some disabled users of assistive technologies (AT) have expressed concerns that their use of those AT devices brings particular attention to their disability and, in doing so, stigmatizes them in the eyes of their peers. This research studies how a wide range of design factors, influence how positively or negatively users of wearable technologies are perceived, by others. These factors are studied by asking survey respondents to estimate the degree to which they perceive disabilities in users of various products. The survey was given to 34 undergraduate Product Design students, and employed 40 pictures, each of which showed one person using a product. Some of these products were assistive technology devices, and some were not. Respondents used a five-bubble Likert scale to indicate the level of disability that they perceived in this person. Data analysis was done using SPSS software. The results showed that the gender of the respondent was not a significant factor in the respondent's estimation of the level of disability. However, the cultural background of the respondent was found to be significant in the respondent's estimates of disability for seven of the 40 pictures. The results also indicated that the size of AT, its familiarity to the mainstream population, its wearable location on the user's body, the perceived power of the user, the degree to which the AT device seemed to empower the user, the degree to which the AT device was seen as a vehicle for assertion of the user's individuality, and the successfulness of attempts to disguise the AT as some mainstream product reduced the perceived disability of the user. In contrast, symbols or stereotypes of disability, obstructing visibility of the face, an awkward complex design, a mismatch between the product's design and its context of use, and covering of the head were factors that focused attention on, and increased the perception of, the user's disability. These factors are summarized in a set of guidelines to help AT designers develop products that minimize the perceived disability and the resulting stigmatization of the user.
ContributorsValamanesh, Ronak (Author) / Velasquez, Joseph (Thesis advisor) / Black, John (Committee member) / Herring, Donald (Committee member) / Arizona State University (Publisher)
Created2014