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Evaluation of healing in asphalt binders using dynamic shear rheometer and molecular modeling techniquesBommavaram, Ramamohan Reddy 15 May 2009 (has links)
A self-healing material has the inherent ability to partially reverse damage such as crack
formation that might have occurred during its service. Significant evidence exists in the
literature to indicate that asphalt binder is a self-healing material. It is also well known
that healing has a substantial affect on the performance of asphalt mixtures and
consequently on the serviceable life of asphalt pavements. For example, shift factors from
laboratory experimental data to field observed data show that laboratory data underpredict
field observations. There is a need to understand the mechanisms that are
responsible for healing in asphalt binders as well as to develop test methods that can be
used to determine properties related to these mechanisms. This thesis presents details
and findings from a two-part study that addresses each one of these two aspects. In the
first part of this study, a test method based on the use of a Dynamic Shear Rheometer
(DSR) was developed to determine the parameters of characteristic healing function of
asphalt binders. In the second part of this study, Molecular Modeling (MM) techniques
were used to determine the interrelationship between molecular structure, surface free
energy, self diffusivity, and other healing properties of asphalt binders.The healing characteristic equation parameter (Ro) which represents the
instantaneous healing nature of the asphalt binders is analogous to surface energy in
terms of effect on healing in asphalt binders. Ro values for three asphalt binders AAM,
AAD and ABD are calculated and compared with the surface energy values available
from the literature. It was observed that the Ro values are proportional to surface energy
values. Surface energy values for five asphalt binders AAM, AAD, AAB, AAG and AAF
are calculated using MM method based on SHRP representative molecules. These values
were observed to be proportional to the surface energy values from literature. Bulk and
surface diffusion coefficients of asphalt molecules are calculated using MM method.
Parametric analysis was done to determine the effect of chemical structure of asphalt on
its diffusion properties. It was observed that the higher percentage of saturates in the
chemical structure results into higher diffusion coefficients.
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Jesse Shera: A Bio-bibliographyRuderman, Laurie P. January 1968 (has links)
No description available.
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Til Ære for queer : Netflix-serien She-Ra og repræsentationen af queer / For the Honor of Queer : Netflix series She-Ra and the representation of queerNielsen, Ida January 2021 (has links)
This paper will examine, how queer is represented in the animated tv-serie She-Ra and the princesses of powerfrom 2018-2020. To understand this work, the paper will define representation, gender and queer, and examine the visual and narrative elements in the tv-serie. Through a visual analysis, the paper can understand if the serie represent queer values. Then the paper will look at some characters from the serie, to see if their visual design and the narrative structure reflects queer characteristics. This means the paper will define what are queer values and how is it shown in the characters of the show. It will be supplied with theory about queer and gender, for examples Raewyn Connell and Stuart Hall. The theory will supply characteristics, which have defined the social norms about genders through history. This paper concludes that the tv-serie reflects queer values through it’s visual and narrative structure. The characters have queer personalities. I need this paper with a discussion of the effects of queer representation and other ways to look at the serie from a perspective of gender.
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Behaviour of continuous concrete deep beams reinforced with GFRP barsShalookh, Othman H. Zinkaah January 2019 (has links)
This research aims to investigate the behaviour of glass fibre reinforced
polymer bars (GFRP) reinforced continuous concrete deep beams. For this
purpose, experimental, analytical and numerical studies were conducted.
Nine continuous concrete deep beams reinforced with GFRP bars and one
specimen reinforced with steel bars were experimentally tested to failure. The
investigated parameters included shear span-to-overall depth ratio (𝑎/ℎ), size
effect and web reinforcement ratio. Two 𝑎/ℎ ratios of 1.0 and 1.7 and three
section heights of 300 mm, 600 mm and 800 mm as well as two web
reinforcement ratios of 0% and 0.4% were used. The longitudinal
reinforcement, compressive strength and beam width were kept constant at
1.2%, ≈55 MPa and 175 mm, respectively. The web reinforcement ratio
achieved the minimum requirements of the CSA S806-12. The experimental
results highlighted that the web reinforcement ratio improved the load
capacities by about 10% and 18% for specimens having 𝑎/ℎ ratios of 1.0 and
1.7, respectively. For specimens with web reinforcement, the increase of 𝑎/ℎ
ratio from 1.0 to 1.7 led to reductions in the load carrying capacity by about
33% and 29% for beams with overall depths of 300 mm and 600 mm,
respectively. Additionally, a considerable reduction occurred in the shear
strength due to the increase of the section depth from 300 mm to 600 mm. The
experimental results confirmed the impacts of web reinforcement and size
effect that were not considered by the strut-and-tie method (STM) of the only
code provision, the Canadian S806-12, that addressed such elements.
In this study, the STM was illustrated and simplified to be adopted for GFRP
RC continuous deep beams, and then, the experimental results obtained from
this study were employed to assess the performance of the effectiveness
factors suggested by the STMs of the American (ACI 318-2014), European
(EC2-04) and Canadian (S806-12) codes as well as those factors
recommended by the previous studies to predict the load capacities. It was
found that these methods were unable to reflect the influences of member size
and/or web reinforcement reasonably, the impact of which has been confirmed
by the current experimental investigation. Therefore, a new effectiveness
factor was recommended to be used with the STM. Additionally, an upper bound analysis was developed to predict the load capacities of the tested specimens considering a reduced bond strength of GFRP bars after assessing
the old version recommended for steel RC continuous deep beams. A good
agreement between the predicted results and the measured ones was
obtained with the mean and coefficient of variation values for
experimental/calculated results of 1.02 and 5.9%, respectively, for the STM
and 1.03 and 8.6%, respectively, for the upper-bound analysis.
A 2D finite element analysis using ABAQUS/Explicit approach was carried out
to introduce a model able to estimate the response of GFRP RC continuous
deep beams. Based on the experimental results extracted from the pullout
tests, the interface between the longitudinal reinforcement and concrete
surface was modelled using a cohesive element (COH2D4) tool available in
ABAQUS. Furthermore, a perfect bond between the longitudinal reinforcement
and surrounding concrete was also modelled to evaluate the validity of this
assumption introduced by many previous FE studies. To achieve a reasonable
agreement with the test results, a sensitivity analysis was implemented to
select the proper mesh size and concrete model variables. The suitability and
capability of the developed FE model were demonstrated by comparing its
predictions with the test results of beams tested experimentally. Model
validation showed a reasonable agreement with the experiments in terms of
the failure mode, total failure load and the load-deflection responses. The
perfect bond model has overestimated the predicted results in terms of
stiffness behaviour and failure load, while the cohesive element model was
more suitable to reflect the behaviour of those specimens. The validated FE
model was then employed to implement a parametric study for the key
parameters that govern the behaviour of beams tested and to achieve an in depth understanding of such elements. The parametric study showed that the
higher the 𝑎/ℎ ratio the more pronounced the effect of web and the longitudinal
reinforcements and the lower the effect of concrete compressive strength; and
vice versa when 𝑎/ℎ ratio reduces.
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