1,720,963 research outputs found
Anchorage of Epoxy-Coated Rebar Using Chemical Adhesives
Full text linkPost-installed reinforcement is used to connect a new concrete member to an existing concrete structure. Typically, uncoated rebar post-installed with a chemical adhesive is used in these applications, which may lead to corrosion. Departments of Transportation and local bridge owners have used and continue to use epoxy-coated rebar in post-installed applications due to its inherent corrosion resistance. Unfortunately, chemical adhesive manufacturers provide tensile strengths of their products for use with uncoated rebar and not epoxy-coated rebar. This work examined what effects the epoxy coating had on the tensile pullout strength and compared the results for epoxy-coated and uncoated rebar. Two slabs were constructed. One slab contained epoxy-coated rebar post-installed using four different chemical adhesive products and the other slab contained uncoated rebar post-installed using the same four different chemical adhesive products. Results indicated that the epoxy coating slightly reduced the tensile pullout strength of the post-installed rebar. The ratio of the tensile pullout strength of the epoxy-coated reinforcing bars to the tensile pullout strength of the uncoated reinforcing bars ranged from 0.94 to 1.05 and varied based on the chemical adhesive manufacturer. Results from t-test analyses indicated that differences in the tensile pullout strength for epoxy-coated rebar compared to uncoated rebar were statistically different when using three of the four chemical adhesives during installation. Recommendations were made to include a modification factor when calculating bond strength for an epoxy-coated reinforcing bar post-installed using chemical adhesives and to raise the MnDOT-specified uncracked bond stress (τuncr) of 1,000 psi or use the manufacturer published values for τuncr.Mills, Connor; Dymond, Benjamin Z.. (2019). Anchorage of Epoxy-Coated Rebar Using Chemical Adhesives. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/203915
Deterioration of Mixed Rebar and Fiber-Reinforced Concrete Bridge Decks
No full textBetween 1973 and 1989, approximately 600 bridge decks were constructed in Minnesota with a top layer of epoxy-coated rebar and a
bottom layer of uncoated rebar (i.e., mixed rebar deck) to potentially reduce corrosion in the top layer of rebar. In the last five years, at
least 20 bridge decks were constructed with polypropylene fibers in the concrete mix to reduce the width and amount of cracking. This
project investigated how mixed rebar or polypropylene fibers affected the rate of deterioration in bridge decks (e.g., spalling of underside
of deck concrete or unsound concrete on the top wearing surface) compared to control structure decks of approximately the same age.
Visual inspections were conducted on certain bridges to compare the visual degradation of the mixed rebar and fiber-reinforced decks with
their control structure decks. The results were subdivided to indicate how the superstructure type, average daily traffic, route type, and
wearing surface crack density affected the condition ratings and rate of deterioration. The mixed rebar decks reached worse condition
states than the control structures when comparing the condition of the underside of the deck; steel superstructures had the largest
negative affect on the deterioration. Recommendations included: create an inspection rating element for mixed rebar decks that quantifies
the underside of deck crack density, use a robust crack sealing method on mixed rebar decks when they have been at NBE Element #12 CS2
for approximately 7 years, and continue comparing fiber-reinforced decks to control structure decks to analyze the deterioration over time.Treat, Corin; Dymond, Benjamin Z.. (2019). Deterioration of Mixed Rebar and Fiber-Reinforced Concrete Bridge Decks. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/203695
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Understanding Causes of Concrete Culvert Pipe Joint Separation
No full textJoint separations affect approximately 20% of the Minnesota concrete pipe inventory (Taylor and Marr 2012). The goals of this research are to determine the factors that contribute to joint separation and recommend practices to mitigate this problem. Research efforts follow a three-pronged approach: (1) Examination of TAMS HydInfra database; (2) field survey of concrete culverts; and (3) computational modeling of soil-culvert systems. Database investigations were conducted using a Random Forest model along with individual feature analysis to determine factors that correlate with joint separations. Geographic features such as the county and route number of the culvert are more important for predicting joint separation than geometric features such as culvert size or cover depth. Field surveys reveal that separations typically occurred at the ends of pipes, or in the first untied joint from the end of the pipe if only some joints were tied. Joint separation was often observed alongside other distress such as infiltration or inslope voids. Computational modeling results show that embankment self-weight and traffic loading concentrate their highest demands under the center of the road, which did not match with field inspections. Soil freezing or changes of water-table level impose greater demands than traffic, and these maximum demands are located at the pipe ends, and thus these mechanisms are more likely to result in joint separation. Recommendations include tying all joints on installation, properly compacting the backfill, and limiting freezing expansion of the embankment materials, particularly if a cohesive soil cap is used.Hedegaard, Brock; Carranza-Torres, Carlos; Dymond, Benjamin; Faeli, Mehdi. (2026). Understanding Causes of Concrete Culvert Pipe Joint Separation. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278973
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Load Rating Assessment of Three Slab-Span Bridges Over Shingle Creek
No full textThree slab-span bridges crossing Shingle Creek in Brooklyn Center, Minnesota, have poor American Association of State Highway and Transportation Officials (AASHTO) load rating factors for certain truck configurations. Characterization of load distribution is useful for determining the load rating of bridges, but results in the literature have shown that the AASHTO code results in conservative load rating factors. The focus of this study was to determine if the load rating of the three concrete slab-span bridges was conservative and could be improved using results from live load testing and finite element analysis. Field testing used a suite of instrumentation that included displacement transducers, strain gauges, accelerometers, and tiltmeters. A three-dimensional solid-element finite element model was used to determine an expected range of behaviors and corroborate the field data regarding how load distributed when placed near and away from a barrier. In addition, a method for developing a simple plate model of slab span bridges was developed considering in-situ material properties and effects of secondary elements such as barriers. Results indicated that the AASHTO load rating was conservative, and an improved rating factor could be obtained considering the field test data and computational modeling results.Hill, Kendall A.; Dymond, Benjamin Z.; Hedegaard, Brock D.; Linderman, Lauren E.. (2022). Load Rating Assessment of Three Slab-Span Bridges Over Shingle Creek. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/243009
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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