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" Recommendations for Durability and Seismic Design of a Socket Connection in Steel Bridge Substructures "
Jayaprakash, Arjun
Balik, Charles
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1053467
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| Doc. No
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TL52584
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| Main Entry
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Jayaprakash, Arjun
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| Title & Author
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Recommendations for Durability and Seismic Design of a Socket Connection in Steel Bridge Substructures\ Jayaprakash, ArjunBalik, Charles
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| College
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North Carolina State University
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| Date
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2020
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| Degree
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Ph.D.
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| student score
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2020
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| Note
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330 p.
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| Abstract
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A substructure system consisting of driven consisting of driven steel piles that double as columns above ground is a prominent choice for structures such as marginal wharves, piers, and bridges. External socket connections, such as the grouted shear stud (GSS) connection, offer a simple and cost-efficient option for connecting these pile-columns to the cap-elements. The GSS connection is formed by a larger diameter pipe stub socket directly welded to the cap-element into which the columns can be inserted. The annular region thus formed can then be filled with high-strength grout to complete the connection. Welded shear studs inside the connection provide resistance to column pull out. Although the GSS connection has been shown to exhibit exceptional structural performance under laboratory conditions, there were a few issues that required consideration before widespread deployment of the connection in practice. The study discussed in this dissertation was undertaken to address the following issues. First was the issue of connection durability. Since the Alaska Department of Transportation and Public Facilities (AKDOT) is interested in using this connection in their bridges, there was a need to investigate its long-term durability in extreme cold climates. Second, to implement this connection in engineering practice, standard structural design guidelines were deemed necessary. And third, since the state of Alaska also happens to fall in an active seismic zone, the design guidelines also required to include recommendations for estimating non-linear structural response of bridge piers with the GSS connection. To determine the long-term durability of the GSS connection, it was sufficient to establish either that commonly available grouts are durable themselves, or that grout deterioration does not compromise the structural integrity of the connection. First, four commonly available commercial grouts were chosen to determine their vulnerability to freeze and thaw damage and their propensity to cracking under restrained shrinkage. Experiments suggested that some grouts are indeed vulnerable to freeze and thaw degradation while others show exceptional performance. Since material durability tests were inconclusive, the next step was to determine if grout deterioration would impair the structural capabilities of the GSS connection. Four large scale steel bridge pier specimens incorporating the GSS connection were structural tested. To determine the consequences of grout deterioration, the performance of specimens with deteriorated GSS connections was compared to that of a control specimen. Connection deterioration was achieved by mixing expanded polystyrene (EPS) aggregates in the grout, which reduced the compressive strength and elastic modulus of the grout. Direct comparison between the global structural behavior of the piers with deteriorated connections and the control specimen indicated that grout deterioration does not compromise the structural integrity of the GSS connection. To provide guidelines for optimum design, there was a need to better understand the force transfer mechanism within the connection. Large scale experimental data was subsequently used to investigate the force transfer mechanism. The embedment length of the column inside the connection was found to be the most important parameter for a successful design. Subsequently, a model was developed to calculate the lower bound capacity of the GSS connection. Seismic design procedure for bridges demands that the designer can estimate the total displacement of piers at important limit states. In the case of steel bridge piers with socket connections, estimation of limit state displacements is not trivial because of additional flexibility in the system attributable to cap-beam flexure and socket connection rotation. Using the data collected from the large-scale tests, finite element modeling, and parametric studies, a semi-empirical model was developed to establish essential limit state displacements and the rate of strength
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| Descriptor
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Civil engineering
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Balik, Charles
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North Carolina State University
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