397 research outputs found
A Stellar Conversation with Dr. Bill Sheehan
No full textIncludes descriptive metadata provided by producer in MP3 file: "Rick Chappell, director of Dyer Observatory, talks with Bill Sheehan on
the anniversary of what would have been E.E. Barnard's 150th birthday.
Dr. Sheehan is the author of 'The Immortal Fire Within,' the definitive
biography on Barnard who is one of the world's most famous astronomers.
Dr. Sheehan examines Barnard's life--his humble beginnings, his historic
discoveries, his time at Vanderbilt and his famous photographs of the
Milky Way.
Running and Being: The Total Experience
No full textWritten by the late, beloved Dr. George Sheehan, Running & Being tells of the author\u27s midlife return to the world of exercise, play, and competition, in which he found a world beyond sweat that proved to be a source of great revelation and personal growth. But Running & Being focuses more on life than it does, specifically, on running. It provides an outline for a lifetime program of fitness and joy, showing how the body helps determine our mental and spiritual energies.https://openprairie.sdstate.edu/prairiestriders_pubs/1041/thumbnail.jp
Flexural Behaviour of Geopolymer Concrete T-beams Reinforced with FRP or Hybrid FRP/Steel bars
No full textSteel bar corrosion is the most severe failure mode of RC structures in corrosive environments. Deterioration has raised conservation and maintenance costs, which is a cause for concern for the construction industry. FRP bars are replaced for steel reinforcing bars in severe environments to prevent corrosion. Each tonne of OPCC produces an extra tonne of CO2. The OPCC must be replaced with binders that emit less CO2. Geopolymer binder is an alternative to Portland cement that does not emit CO2 during manufacture. GPC reinforced with any material should provide a building system that is durable, economical, and ecologically friendly. The main aim of this study is to examine the flexural behaviour of geopolymer concrete T-beams reinforced with GFRP or Hybrid GFRP/Steel bars. To achieve this aim, twelve geopolymer concrete flanged beams reinforced with various combinations with steel and GFRP bars were experimentally tested, and comprehensive computational finite element simulations and analytical studies were also carried out.
For the first group, six full-scale simply supported T-beams were cast and tested; one control specimen was made with OPCC, while the other five beams were made of GPC. For second group, six full-scale T-Beams were cast including one using OPCC as the control beam. The main characteristics examined were the two types of reinforcement, GFRP and steel, reinforcement ratio, the type of concrete and concrete compressive strength. Based on the results of the experiments, the ultimate strain of GPC is not the same as that of OPCC, which affects the mode of failure
Behaviour of continuous concrete deep beams reinforced with GFRP bars
No full textThis 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 (/ℎ), size
effect and web reinforcement ratio. Two /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 /ℎ ratios of 1.0 and
1.7, respectively. For specimens with web reinforcement, the increase of /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 /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 /ℎ ratio reduces
Behaviour of continuous concrete T-beams reinforced with hybrid FRP/Steel bars
No full textThis work aims to investigate the flexural behaviour of continuous hybrid
reinforced concrete T-beams (HRCT). The investigations consist of three parts;
the computational part, the experimental part and the finite element analysis. The
computational part included two parts, the first one is developing an analytical
programme using MATLAB software to investigate the moment-curvature
behaviour of HRCT-beams and to design the experimental specimens. This was
followed by the experimental part, where six full-scale reinforced concrete
continuous T beams were prepared and tested. One beam was reinforced with
glass fibre reinforced polymer (GFRP) bars while the other five beams were
reinforced with a different combination of GFRP and steel bars. The ratio of GFRP
to steel reinforcement at both mid-span and middle-support sections was the
main parameter investigated. The results showed that adding steel reinforcement
to GFRP reinforced concrete T-beams improves the axial stiffness, ductility and
serviceability in terms of crack width and deflection control. However, the moment
redistribution at failure was limited because of the early yielding of steel
reinforcement at the beam section that did not reach its moment capacity and
could still carry more loads due to the presence of FRP reinforcement.
The second part of the computational part included the comparison between the
experimental results with the ultimate moment prediction of ACI 440.2R-17, and
with the existing theoretical equations for moment capacity, load capacity, and
deflection prediction. It was found that the ACI 440.2R-17 design code equations
reasonably estimated the moment capacity of both mid-span and middle-support
sections and consequently predicted the load capacity of the HRCT-beams
based on fully ductile behaviour. However, Qu's and Safan's equations
underestimated the predicted moment and load-capacity of HRCT-beams. Also,
Bischoff's and Yoon's models underestimated the deflection at all stages of the
load for both GFRP and HRCT- beams.
For the numerical part, a three-dimensional finite element model has been
developed using ABAQUS software to examine the behaviour of HRCT-beams.
The experimental results were used to validate the accuracy of the FEM, where
an acceptable agreement between the simulated and experimental results was
observed. Accordingly, the model was used to predict the structural behaviour of
continuous HRCT-beams by testing different parameters
Violence and Restraint: An Interview with Aaron Sheehan-Dean
No full textToday we are speaking with Aaron Sheehan-Dean, Fred C. Frey Professor of Southern Studies at Louisiana State University and the Chair of LSU’s History Department. He teaches courses on nineteenth-century U.S. history, the Civil War and Reconstruction, and southern History. He is the author of Why Confederates Fought: Family and Nation in Civil War Virginia (UNC Press, 2007), Concise Historical Atlas of the U.S. Civil War (Oxford University Press, 2008), and is the editor of several other volumes. His most recent book, The Calculus of Violence: How Americans Fought the Civil War, was released by Harvard University Press in Fall, 2018. [excerpt
Drying shrinkage of self-compacting concrete incorporating fly ash
No full textThe present research is conducted to investigate long term (more than two years) free and confined drying shrinkage magnitude and behaviour of self-compacting concrete (SCC) and compare with normal concrete (NC). For all SCCs mixes, Portland cement was replaced with 0-60% of fly ash (FA), fine and coarse aggregates were kept constant at 890 kg/m3 and 780 kg/m3, respectively. Two different water binder ratios of 0.44 and 0.33 were examined for both SCCs and NCs. Fresh properties of SCCs such as filling ability, passing ability, viscosity and resistance to segregation and hardened properties such as compressive and flexural strengths, water absorption and density of SCCs and NCs were also determined. Experimental results of free drying shrinkage obtained from this study together with collected comprehensive database from different sources available in the literature were compared to five existing models, namely the ACI 209R-92 model, BSEN-92 model, ACI 209R-92 (Huo) model, B3 model, and GL2000 model. To assess the quality of predictive models, the influence of various parameters (compressive strength, cement content, water content and relative humidity) on the drying shrinkage strain are studied. An artificial neural network models (ANNM) for prediction of drying shrinkage strains of SCC was developed using the same data used in the existing models. Two ANNM sets namely ANNM1 and ANNM2 with different numbers of hidden layer neurones were constructed. Comparison between the results given by the ANNM1 model and the results obtained by the five existing predicted models were presented.
The results showed that, using up to 60% of FA as cement replacement can produce SCC with a compressive strength as high as 30 MPa and low drying shrinkage strain. SCCs long-term drying shrinkage from 356 to 1000 days was higher than NCs. Concrete filled elliptical tubes (CFET) with self-compacting concrete containing FA up to 60% are recommended for use in construction in order to prevent confined drying strain.
ACI 209R-92 model provided a better prediction of drying shrinkage compared with the other four models. However, a very high predictability with high accuracy was achieved with the ANNM1 model with a mean of 1.004. Moreover, by using ANNM models, it is easy to insert any of factors effecting drying shrinkage to the input parameters to predict drying shrinkage strain of SCC.Ministry of Higher Education, Liby
Evidence from near-death experience for the existence of consciousness outside the brain
No full textThis paper discusses near-death experience in terms of evidence for consciousness existing outside the brain. The number of near-death experiences has significantly increased over the past few decades due to the advances in defibrillation and CPR techniques. This has made it possible to do Prospective studies in hospitals in an attempt to correlate psychological, physiological and pharmacological causes for near-death experience. Four arguments for evidence of consciousness outside the brain are reviewed and examples from Retrospective studies are given. They are the consistency, reality, paranormal and transformation elements. Retrospective studies provide evidence that near-death experiences have similar elements regardless of demographic data, but the details of the events are not verifiable. Prospective studies carried out in hospitals in Great Britain, America and the Netherlands can confirm through medical records and witnesses that cardiac arrest survivors have conscious experiences during unconsciousness when their brain is dysfunctional. Examples from these studies provide evidence that consciousness exits outside the brain. However, the dying brain hypothesis and the hallucination hypothesis are also looked at as an explanation for these experiences.M.A.L.S.Includes bibliographical referencesby Marianne S Sheeha
Behaviour of buried pipes adjacent to ground voids under dynamic loading
No full textProtection of buried pipes is a serious issue that concerns countries around the world. Therefore, there is a need for new soil improvement techniques such as geosynthetic materials installation to protect these pipes from damage. This study used large-scale laboratory tests to study the behaviour of buried pipes. A total of 22 large-scale tests were performed to study the behaviour of buried flexible HDPE pipes with and without void presence under the protection of the geogrid reinforcing layers subjected to incrementally increasing cyclic loading.
The presence of voids located at the spring-line of the flexible buried pipes, led to a considerable increase in the soil surface settlement, pressure recorded at the pipe crown, spring-line and invert, pipe deformation and strain recorded in the pipe wall. Increasing the pipe burial depth contributed to significant reductions in the soil surface settlement, pressure recorded at the pipe crown and invert, pipe deformation and strain recorded in the pipe wall. However, the void presence limited the contribution of increasing the pipe burial depth. The inclusion of a geogrid reinforcing layer contributed to a considerable reduction in the soil surface settlement, pressure recorded at the pipe crown, spring-line and invert, pipe deformation and strain recorded in the pipe wall. The use of a combination of geogrid reinforcing layers and increasing the pipe burial depth contributed in diminishing the ground void presence effect, where better pressure distribution inside the system was achieved. Consequently, more protection was provided to the buried pipe
Dynamic soil-structure interaction of reinforced concrete buried structures under the effect of dynamic loads using soil reinforcement new technologies. Soil-structure interaction of buried rigid and flexible pipes under geogrid-reinforced soil subjected to cyclic loads
No full textRecent developments in constructions have heightened the need for protecting existing buried infrastructure. New roads and buildings may be constructed over already existing buried infrastructures e.g. buried utility pipes, leading to excessive loads threatening their stability and longevity. Additionally applied loads over water mains led to catastrophic damage, which result in severe damage to the infrastructure surrounding these mains. Therefore, providing protection to these existing buried infrastructure against increased loads due to new constructions is important and necessary.
In this research, a solution was proposed and assessed, where the protection concept would be achieved through the inclusion process of geogrid-reinforcing layers in the soil cover above the buried infrastructure. The controlling parameters for the inclusion of geogrid-reinforcing layers was assessed experimentally and numerically. Twenty-three laboratory tests were conducted on buried flexible and rigid pipes under unreinforced and geogrid-reinforced sand beds. All the investigated systems were subjected to incrementally increasing cyclic loading, where the contribution of varying the burial depth of the pipe and the number of the geogrid-reinforcing layers on the overall behaviour of the systems was investigated. To further investigate the contribution of the controlling parameters in the pipe-soil systems performance, thirty-five numerical models were performed using Abaqus software. The contribution of increasing the amplitude of the applied cyclic loading, the number of the geogrid-reinforcing layers, the burial depth of the pipe and the unit-weight of the backfill soil was investigated numerically.
The inclusion of the geogrid-reinforcing layers in the investigated pipe-soil systems had a significant influence on decreasing the transferred pressure to the crown of the pipe, generated strains along its crown, invert and spring-line, and its deformation, where reinforcing-layers sustained tensile strains. Concerning rigid pipes, the inclusion of the reinforcing-layers controlled the rebound that occurred in their invert deformation. With respect to the numerical investigation, increasing the number of the reinforcing-layers, the burial depth of the pipe and the unit-weight of the backfill soil had positive effect in decreasing the generated deformations, stresses and strains in the system, until reaching an optimum value for each parameter. Increasing the amplitude of the applied loading profile resulted in remarkable increase in the deformations, stresses and strains generated in the system. Moreover, the location of the maximum tensile strain generated in the soil was varied, as well as the reinforcing-layer, which suffered the maximum tensile strain.Government of Egyp
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