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Flexural behavior of carbon/epoxy IsoTruss reinforced-concrete beam-columns /Ferrell, Monica Joy, January 2005 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2005. / Includes bibliographical references (p. 101-102).
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Investigation of Long-Term Prestress Losses in Pretensioned High Performance Concrete GirdersWaldron, Christopher Joseph 01 December 2004 (has links)
Effective determination of long-term prestress losses is important in the design of prestressed concrete bridges. Over-predicting prestress losses results in an overly conservative design for service load stresses, and under-predicting prestress losses, can result in cracking at service loads. Creep and shrinkage produce the most significant time-dependent effect on prestress losses, and research has shown that high performance and high strength concretes (HPC and HSC) exhibit less creep and shrinkage than conventional concrete. For this reason, the majority of traditional creep and shrinkage models and methods for estimating prestress losses, over-predict the prestress losses of HPC and HSC girders.
Nine HPC girders, with design compressive strengths ranging from 8,000 psi to 10,000 psi, and three 8,000 psi lightweight HPC (HPLWC) girders were instrumented to determine the changes in strain and prestress losses. Several creep and shrinkage models were used to model the instrumented girders. For the HPLWC, each model over-predicted the long-term strains, and the Shams and Kahn model was the best predictor of the measured strains. For the normal weight HPC, the models under-estimated the measured strains at early ages and over-estimated the measured strains at later ages, and the B3 model was the best-predictor of the measured strains. The PCI-BDM model was the most consistent model across all of the instrumented girders.
Several methods for estimating prestress losses were also investigated. The methods correlated to high strength concrete, the PCI-BDM and NCHRP 496 methods, predicted the total losses more accurately than the methods provided in the AASHTO Specifications. The newer methods over-predicted the total losses of the HPLWC girders by no more than 8 ksi, and although they under-predicted the total losses of the normal weight HPC girders, they did so by less than 5 ksi. / Ph. D.
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The behaviour of reinforced concrete cantilever columns under lateral impact loadLoedolff, Matthys Johannes 12 1900 (has links)
Microreproduction of original thesis. / Thesis (PhD)--Stellenbosch University, 1990. / Some digitised pages may appear illegible due to the condition of the original microfiche copy. / ENGLISH ABSTRACT: see item for full text / AFRIKAANSE OPSOMMING: sien item vir volteks.
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Time-dependent behaviour of concrete structures with special referenceto podium and frame structuresLiu, Chi-hong., 廖志航. January 2007 (has links)
published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy
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Flexural strengthening of reinforced concrete beams by bolted side platesSiu, Wing-ho., 蕭永皓. January 2009 (has links)
published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy
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Strength and Modulus of Recycled Aggregate Concrete Subjected to Wetting and Drying CyclesUnknown Date (has links)
The reuse of crushed aggregates for producing structural concrete is a major
concern especially when it comes to its strength and durability. This study evaluated
recycled aggregate concrete (RAC) for its strength and durability under simulated
environmental degradation in the form of wetting-drying (W-D) cycles. The study
consisted of two phases, each involving the determination of the compressive strength and
modulus of elasticity using the conventional method and also a nondestructive ultrasonic
pulse velocity method (Pundit Lab). Phase 1 involved 7-day curing followed by 30 W-D
cycles, while Phase 2 included 28-day cured samples subjected to 15 W-D cycles. It was
found that RAC specimens subjected to W-D cycles had minimal degradation in strength,
making the use of RAC in construction very promising. Results from Pundit Lab compared
reasonably well with conventional test results, showing promise as a nondestructive tool
for the evaluation of RAC properties. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
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Superplasticizers in concreteKapanpour, Mehrdad January 2010 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
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Stress intensity values for prenotched and precracked, plain concrete beamsFartash, Mojtaba January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
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Procedures for diagnosis and assessment of concrete buildingsHua, Wen-Gang. January 1993 (has links) (PDF)
Bibliography: leaves 213-234.
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Evaluation of water damage on asphalt concrete mixtures using the environmental conditioning systemAl-Joaib, Ali Abdulla 28 May 1993 (has links)
Asphalt concrete pavement is subjected to several damaging actions from traffic
loads, water (from precipitation and/or groundwater sources), and temperature. The
durability of the asphalt-aggregate mixture, its ability to withstand these damaging
actions for long periods, is a very important engineering property. While the durability
of the asphalt-aggregates mixture depends on several factors such as the mixture's
properties, construction methods, traffic loads and environmental conditions, they have
to be evaluated to predict their field performance. Based on mixture evaluations, the
mixtures that fail the test would have to be modified by additives or by changing the
materials.
The first objective of this thesis was to evaluate asphalt-aggregate mixtures for
water damage using the Environmental Conditioning System (ECS), and rank the
asphalt and aggregate types based on water sensitivity. The second objective was to
relate the ECS ranking of the asphalt and aggregate types to Oregon State University
(OSU) and University of Nottingham, UK (SWK/UN) wheel tracking test results, and
to Net Adsorption Test (NAT) results. The third objective was to evaluate open-graded
mixtures and rubber modified mixtures for water sensitivity using the ECS.
The ECS test results indicate that performance ranking of mixtures by asphalt
type or aggregate type alone cannot be made for the ECS test results due to the
significant interaction between asphalt and aggregate. Water sensitivity in the ECS is
significant for combinations of asphalt and aggregate. The ECS test results have shown that ECS performance ranking after one cycle is not statistically significant and does not correlate with ranking after three cycles. The results show that the ECS test program has similar aggregate rankings to those of the NAT and SWK/UN test program, while good agreement exists between SWK/UN wheel tracking results and the NAT test program results. However, poor agreement exists between the OSU wheel tracking results and those of the other two tests. Poor or very little agreement exists among the wheel tracking test results, ECS, and NAT test results in terms of asphalt type rankings.
When considering the comparisons of materials ranking by different test procedures, one must keep in mind that the mechanisms leading to varying "performance" are not the same. The testing reported herein was aimed at measuring water sensitivity, but all the tests do not do so directly. The NAT procedure addresses only the potential for stripping (adhesion) and is not capable of evaluating cohesion loss. The other tests (ECS, OSU and SWK/UN wheel tracking) included all the mechanisms simultaneously, and these provided a gross effect without clearly separating the cause of failure in each case.
Open-graded mixtures used by Oregon Department of Transportation (ODOT) performed well in the ECS in terms of water sensitivity. In the ECS evaluation, six mixtures passed the criteria of 75 % established for Indirect Retained Strength (IRS) test by ODOT, and one mixture was marginal. However, only one mixture passed the IRS evaluation, and another mixture was marginal. This confirms that the IRS test is a very severe test and is not suitable for water sensitivity evaluation of open-graded mixtures. Finally, the IRS test evaluation would suggest that these mixtures would fail prematurely after construction, but all of these mixtures have been used in projects which have been in service for more than three years with no visible signs of distress, or failures. / Graduation date: 1994
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