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Full-Text Articles in Engineering
Thin Conductive Concrete Overlay For Bridge Deck Deicing And Anti-Icing, Sherif Yehia, Christopher Tuan
Thin Conductive Concrete Overlay For Bridge Deck Deicing And Anti-Icing, Sherif Yehia, Christopher Tuan
Christopher Y. Tuan
Concrete bridge decks are prone to ice accumulation. Bridge decks freeze before the roads approaching them freeze, making wintry highway travel treacherous. Road salts and deicing chemicals are effective for ice removal but cause damage to concrete and corrosion of reinforcing steel in concrete bridge decks. The resulting rapid degradation of existing concrete pavements and bridge decks is a major concern to transportation and public-works officials. The use of insulation materials for ice control and electric or thermal heating for deicing have been attempted, with unsatisfactory results. Conductive concrete is a cementitious admixture containing electrically conductive components to attain high …
Flexural Behavior Of Concrete-Filled Circular Steel Tubes Under High-Strain Rate Impact Loading, Yaohua Deng, Christopher Tuan
Flexural Behavior Of Concrete-Filled Circular Steel Tubes Under High-Strain Rate Impact Loading, Yaohua Deng, Christopher Tuan
Christopher Y. Tuan
Nine simply supported circular steel concrete-filled tubes (CFTs), two circular steel posttensioned concrete-filled tubes (PTCFTs), and one circular steel fiber–reinforced concrete-filled tube (FRCFT) have been tested in an instrumented drop-weight impact facility. The weight and the height of the drop-weight were varied to cause failure in some test specimens. The failure modes and local damages in those specimens have been investigated extensively. Failure in the steel tubes was commonly tensile facture or rupture along the circumference. Concrete core in the impact area commonly crushed under compression and cracked under tension. The use of prestressing strands and steel fibers significantly restrained …
Conductive-Concrete Overlays - An Innovative Solution For Bridge Deck Deicing, Sherif Yehia, Christopher Tuan
Conductive-Concrete Overlays - An Innovative Solution For Bridge Deck Deicing, Sherif Yehia, Christopher Tuan
Christopher Y. Tuan
Bridge decks are prone to ice accumulation, making winter travel treacherous. Road salts and some other deicing chemicals are cost effective, but may cause surface scaling, reinforcing-steel corrosion, or both. Another alternative is a thin, conductive-concrete overlay that, when connected to a power source, can generate enough heat through electrical resistance to prevent ice formation on the deck or melt ice after it forms. Using a conductive concrete overlay provides an environment-friendly deicing method that would prolong bridge service life by significantly reducing the use of road salt and deicing chemicals. When used on pedestrian bridges, sidewalks, and driveways, it …
Evaluation Of Use Of Lithium Nitrate In Controlling Alkali-Silica Reactivity In Existing Concrete Pavement, Christopher Tuan, Hoasu Sun
Evaluation Of Use Of Lithium Nitrate In Controlling Alkali-Silica Reactivity In Existing Concrete Pavement, Christopher Tuan, Hoasu Sun
Christopher Y. Tuan
This study presents the findings from a 2-year field trial in which lithium nitrate was applied at a rate of 0.006 gal/ft2 twice a year on an existing concrete pavement in Norfolk, Nebraska, in an attempt to arrest ongoing alkali-silica reaction (ASR) distress. Various destructive and nondestructive means were used to measure the effectiveness of the treatments. Concrete cylinders were cored for petrographic examination and split tension testing. Powder samples were taken to determine the lithium content. Nondestructive evaluations used crack mapping, a Schmidt hammer, a velocity meter, and an impact echo apparatus. The amount of lithium that penetrated into …
Electrical Resistance Heating Of Conductive Concrete Containing Steel Fibers And Shavings, Christopher Tuan
Electrical Resistance Heating Of Conductive Concrete Containing Steel Fibers And Shavings, Christopher Tuan
Christopher Y. Tuan
Conductive concrete is a category of concrete containing electrically conductive components to attain stable and high electrical conductivity. Due to its electrical resistance and impedance, a thin conductive concrete overlay can generate enough heat to prevent ice formation on a bridge deck when connected to a power source. Steel fibers and steel shavings were used for the conductive materials in this study. A conventional concrete slab, 1.2 x 3.6 m (4 x 12 ft), has been constructed with a 9 cm (3.5 in.) conductive concrete overlay for conducting deicing experiments in the natural environment. The conductive concrete mixture was developed …
Sources Of End Zone Cracking Of Pretensioned Concrete Girders, Christie J. Hasenkamp, Sameh S. Badie, Christopher Y. Tuan, Maher K. Tadros
Sources Of End Zone Cracking Of Pretensioned Concrete Girders, Christie J. Hasenkamp, Sameh S. Badie, Christopher Y. Tuan, Maher K. Tadros
Christopher Y. Tuan
Recent developments of high performance concrete, increasing amounts of prestressing, and increasing use of deep girders have resulted in increasing popularity of precast pretensioned concrete girders in bridge construction. These developments have increasingly contributed to end zone cracking. This paper summarizes the interim results of an ongoing research sponsored by the National Cooperative Highway Research Program (NCHRP) Project 18-14. The objectives of the research are: (1) to establish procedures for the acceptance, repair, or rejection of precast/prestressed concrete girders with longitudinal web cracking, and (2) to prepare a user's manual for the application of these procedures. The results from a …
End Zone Reinforcement For Pretensioned Concrete Girders, Christopher Y. Tuan, Sherif A. Yehia, Nipon Jongpitaksseel, Maher K. Tadros
End Zone Reinforcement For Pretensioned Concrete Girders, Christopher Y. Tuan, Sherif A. Yehia, Nipon Jongpitaksseel, Maher K. Tadros
Christopher Y. Tuan
In this study, a literature review was conducted to establish the background of current specifications and to evaluate the applicability of various theories and methods for design of end zone reinforcement. Analytical methods reviewed in this paper include finite element analysis, strut-and-tie modeling, and the Gergely-Sozen equivalent beam method. Previous experimental work combined with work conducted as part of this study was used to correlate between various theoretical and experimental results. This paper illustrates that no single theoretical method adequately represents the complex behavior at the end of a pretensioned concrete member. A general semi-empirical design procedure is proposed here. …
Curved, Precast, Pretensioned Concrete I-Girder Bridges, Wilast Amorn, Christopher Y. Tuan, Maher K. Tadros
Curved, Precast, Pretensioned Concrete I-Girder Bridges, Wilast Amorn, Christopher Y. Tuan, Maher K. Tadros
Christopher Y. Tuan
Modern highway construction frequently requires bridges with horizontally curved alignments. Such bridges can be created by superimposing a curved deck slab onto straight girders or by splicing segmental straight girders on the chords of a curved roadway. Of these two methods, a curved superstructure usually results in simpler construction and better appearance.
Bond Strength And Transfer Length Of Pre-Tensioned Bridge Girders Cast With Self-Consolidating Concrete, Amgad Girgis, Christopher Tuan
Bond Strength And Transfer Length Of Pre-Tensioned Bridge Girders Cast With Self-Consolidating Concrete, Amgad Girgis, Christopher Tuan
Christopher Y. Tuan
Self-consolidating concrete (SCC) is becoming increasingly popular in the precast/prestressed concrete industry in the United States. However, there have been concerns regarding the bond strength, transfer length, and development length of prestressing strands and mild steel reinforcement with SCC. Further, there are no design guidelines for using SCC. In this study, a literature survey on the bond strength of SCC was conducted. Moustafa pullout tests were performed to determine the bond strength of 0.6 in. (15.2 mm) pretensioning strands with sec. The transfer lengths of three pretensioned concrete bridge girders were measured using Demec points. Pullout tests were also performed …