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The Seismic Response of Precast Segmental Bridge Superstructures with Bonded Tendons

The Seismic Response of Precast Segmental Bridge Superstructures with Bonded Tendons
Author: Marc John Veletzos
Publisher:
Total Pages: 344
Release: 2007
Genre: Bridges
ISBN:

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Precast segmental construction of bridges can accelerate construction and minimize the cost of bridges in highly congested urban environments, environmentally sensitive regions, difficult to access ravines, and wide river crossings where medium to long repetitive spans are needed. Despite their proven benefits, the use of precast segmental bridges in seismic regions of the United States remains very limited. A main obstacle to their use is concern regarding the seismic response of segment joints. Recent research has shown that segment joints can undergo very large rotations that open up gaps in the superstructure, while maintaining its load carrying capacity, and with little, if any, damage. This dissertation investigates the seismic response of precast segmental bridges using detailed 2D non-linear time-history analyses and focuses on the behavior of segment-to-segment joints constructed using the balanced cantilever method. The joint model was calibrated using results available from experimental work on large scale sub-assemblages. Analytical models of full scale precast segmental bridges with geometries and characteristics, similar to the Otay River Bridge and the San Francisco-Oakland Bay Bridge Skyway in California, were also used in this study. A suite of twenty near field earthquake records was used to determine the median joint response as well as to quantify the effect of vertical motion on the joint response. The earthquake records were scaled using two different scaling methods and the effect on the structure response was studied. Four different pre-earthquake stress conditions were studied to determine if the effects of creep, shrinkage and temperature impact the seismic response of segment joints. In addition, a preliminary investigation into the possibility of removing a portion of the superstructure longitudinal post-tensioning and allowing non-linear elastic response of the segment joints during a significant seismic event was performed. Results indicated that vertical earthquake motions and the pre-earthquake stress-state can alter the response of segment joints. The results also showed that the method of record scaling does not significantly alter the median response, but may effect the variation in response. Furthermore, reducing the longitudinal post-tensioning near the piers may be possible provided that service load cases do not govern the design.


Seismic Testing of Precast Segmental Bridges, Phase III

Seismic Testing of Precast Segmental Bridges, Phase III
Author:
Publisher:
Total Pages: 0
Release: 2005
Genre: Concrete bridges
ISBN:

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This report discusses the main findings of a test examining the seismic behavior of a precast, post-tensioned, segmental bridge superstructure with a cast-in-pl ace, hollow, rectangular column. The half-scale specimen modeled a prototype bri dge from midspan to midspan and down to midheight of the column. The bridge was built using the balanced cantilever method and the tendon layout of the specimen was designed to most closely match that of the prototype segment joints nearest to the column. The test was completed in two stages; the first stage prestressi ng level was designed to avoid any joint openings. This was a validation of exis ting bridge design procedures in which damage is limited to the column, and the superstructure remains elastic. The second stage involved removing some of the t endons to enable inelastic deformations of the joints in the superstructure and to impose on the joints nearest the column a more severe loading condition. The second stage of the test was done as an introductory examination of the performa nce of a bridge when damage is not limited to the column and inelastic motion is allowed in the superstructure. The primary objectives of the test were to inves tigate the response of the opening of the superstructure joints, column-superstr ucture interaction, and plastic hinge formation in the column, and the anticipat ed system failure mechanism. Extensive Instrumentation was used in the column as well as the joints of the superstructure to record the damage and performance o f those bridge components.


Seismic Design and Retrofit of Bridges

Seismic Design and Retrofit of Bridges
Author: M. J. N. Priestley
Publisher: John Wiley & Sons
Total Pages: 704
Release: 1996-04-12
Genre: Technology & Engineering
ISBN: 9780471579984

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Because of their structural simplicity, bridges tend to beparticularly vulnerable to damage and even collapse when subjectedto earthquakes or other forms of seismic activity. Recentearthquakes, such as the ones in Kobe, Japan, and Oakland,California, have led to a heightened awareness of seismic risk andhave revolutionized bridge design and retrofit philosophies. In Seismic Design and Retrofit of Bridges, three of the world's topauthorities on the subject have collaborated to produce the mostexhaustive reference on seismic bridge design currently available.Following a detailed examination of the seismic effects of actualearthquakes on local area bridges, the authors demonstrate designstrategies that will make these and similar structures optimallyresistant to the damaging effects of future seismicdisturbances. Relying heavily on worldwide research associated with recentquakes, Seismic Design and Retrofit of Bridges begins with anin-depth treatment of seismic design philosophy as it applies tobridges. The authors then describe the various geotechnicalconsiderations specific to bridge design, such as soil-structureinteraction and traveling wave effects. Subsequent chapters coverconceptual and actual design of various bridge superstructures, andmodeling and analysis of these structures. As the basis for their design strategies, the authors' focus is onthe widely accepted capacity design approach, in which particularlyvulnerable locations of potentially inelastic flexural deformationare identified and strengthened to accommodate a greater degree ofstress. The text illustrates how accurate application of thecapacity design philosophy to the design of new bridges results instructures that can be expected to survive most earthquakes withonly minor, repairable damage. Because the majority of today's bridges were built before thecapacity design approach was understood, the authors also devoteseveral chapters to the seismic assessment of existing bridges,with the aim of designing and implementing retrofit measures toprotect them against the damaging effects of future earthquakes.These retrofitting techniques, though not considered appropriate inthe design of new bridges, are given considerable emphasis, sincethey currently offer the best solution for the preservation ofthese vital and often historically valued thoroughfares. Practical and applications-oriented, Seismic Design and Retrofit ofBridges is enhanced with over 300 photos and line drawings toillustrate key concepts and detailed design procedures. As the onlytext currently available on the vital topic of seismic bridgedesign, it provides an indispensable reference for civil,structural, and geotechnical engineers, as well as students inrelated engineering courses. A state-of-the-art text on earthquake-proof design and retrofit ofbridges Seismic Design and Retrofit of Bridges fills the urgent need for acomprehensive and up-to-date text on seismic-ally resistant bridgedesign. The authors, all recognized leaders in the field,systematically cover all aspects of bridge design related toseismic resistance for both new and existing bridges. * A complete overview of current design philosophy for bridges,with related seismic and geotechnical considerations * Coverage of conceptual design constraints and their relationshipto current design alternatives * Modeling and analysis of bridge structures * An exhaustive look at common building materials and theirresponse to seismic activity * A hands-on approach to the capacity design process * Use of isolation and dissipation devices in bridge design * Important coverage of seismic assessment and retrofit design ofexisting bridges