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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 23 Abstracts search results
Document:
SP120-16
Date:
June 1, 1990
Author(s):
Antoine E. Naaman
Publication:
Symposium Papers
Volume:
120
Abstract:
A simple methodology for the solution of beams prestressed or partially prestressed with external or unbonded tendons in the linear elastic cracked and uncracked range of behavior is described. It leads to equations allowing the computation of stresses in the concrete section, the tensile reinforcing steel, the compression reinforcing steel, and the prestressing steel. In particular, it is shown that the stress in unbonded tendons is a function of the applied loading, the steel profile, and the ratio of the crack width (or crack band width) to the span. These factors can all be accounted for through the use of a strain reduction coefficient ê for the uncracked range of behavior and a similar coefficient êc for the cracked range of behavior. It is shown that, when the strain reduction coefficients ê and êc are taken equal to unity, the solutions developed here revert to the solutions developed earlier for partially prestressed beams with bonded tendons.
DOI:
10.14359/2765
SP120
Editors: Antoine Naaman and John Breen
SP120 External prestressing--that is, the use of unbonded prestressing tendons outside the concrete section of a structural concrete member--offers substantial economic savings and a dramatic increase in construction speed, making it an extremely attractive option for the construction of new concrete structures, particularly bridges. It is also a logical choice for the rehabilitation and strengthening of many existing structures. ACI's symposium volume, External prestressing in Bridges, provides the last word on this important technological development Based on experience in both the U.S. and Europe, the book addresses: *The state of the art, *Technologies for construction, *Applications in new construction and rehabilitation, *Testing and experimental observations, *Analysis and design considerations. Covering practical construction information as well as analysis and design, this is required reading for anyone involved in building bridges.
10.14359/14153
SP120-15
Robert J. F. Macgregor, Michael E. Kreger, and John E. Breen
An experimental investigation was conducted to examine the service and ultimate load behavior of segmentally precast box girder bridges with external post-tensioning tendons. A primary interest of this study was to examine the effect of joint type (dry versus epoxied joints) on the stiffness, strength, and ductility of the structure. A three-span reduced scale segmental box girder model was constructed, then tested in three stages. Flexural behavior was examined first, then shear tests were conducted on the damaged structure. Test results and observations are presented.
10.14359/3277
SP120-13
Christian Menn and Paul Gauvreau
A research project is currently underway at the Swiss Federal Institute of Technology, Zurich, to establish the feasibility of an alternative structural system for short-span highway bridges. Concerns over the long-term durability of structural systems currently used in the 25 to 40 m span range provided the primary motivation for the study. The proposed system consists of a solid concrete slab that is externally prestressed. The external tendons are deviated at the third points of each span using struts. A 1:3-scale model bridge has been constructed and is currently being tested to verify the behavior of the bridge under permanent, service, and ultimate static loads, as well as dynamic and fatigue loads. The favorable results obtained thus far have confirmed the feasibility of the proposed structural system, and will serve as a basis for extending the concept to spans greater than 40 m in length.
10.14359/3266
SP120-12
R. J. Beaupre, L. C. Powell, J. E. Breen, and M. E. Kreger
A laboratory investigation was performed to study deviation saddles, a type of tendon deviator used in externally post-tensioned precast segmental box girder bridges. Ten reduced-scale models of deviation saddles were fabricated and loaded to ultimate using a specially designed testing apparatus that applied load to each deviator just as would be applied to a deviator in a bridge. The objectives of the study were to: experimentally investigate the strength and ductility of deviators; evaluate deviator details in light of observed performance; define behavioral models for deviators; determine the effects of using epoxy-coated reinforcement; and establish design criteria. Data from the test series are presented, two analysis techniques are formulated, and design recommendations are made for design of tendon deviators.
10.14359/3261
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