ACI Global Home Middle East Region Portal Western Europe Region Portal
Email Address is required Invalid Email Address
In today’s market, it is imperative to be knowledgeable and have an edge over the competition. ACI members have it…they are engaged, informed, and stay up to date by taking advantage of benefits that ACI membership provides them.
Read more about membership
Learn More
Become an ACI Member
Topics In Concrete
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
SP120-10
F. Wayne Klaiber, Kenneth F. Dunker and W. W. Sanders, Jr.
Approximately 40 percent of the bridges in the United States are classified as deficient and in need of rehabilitation or replacement. Of these bridges, many are classified as deficient because their load-carrying capacity is inadequate for today's increased traffic. This insufficient load-carrying capacity has resulted from poor maintenance, increase in legal load limits, deck overlays, changes in design specifications, and other factors. In response to the need for a simple, efficient procedure for strengthening existing bridges, the authors have been investigating the use of post-tensioning. They have investigated its use on simple span bridges as well as continuous span bridges. Various post-tensioning schemes have been tested on laboratory models and actual bridges. The paper briefly reviews the post-tensioning research that has been completed by the authors in the past few years. This work indicates that post-tensioning is a viable, economical technique for flexural strengthening of steel-beam composite-concrete deck bridges.
10.14359/3255
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
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
SP120-15
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
Results Per Page 5 10 15 20 25 50 100
Edit Module Settings to define Page Content Reviewer