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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 17 Abstracts search results
October 1, 2005
R. El-Hacha, T.I. Campbell and C.W. Dolan
This paper provides an overview of the ACI 440.4R-04 document on“Prestressing Concrete with FRP Tendons” reported by ACI Committee 440 on “Fiber-Reinforced Polymer Reinforcements”. The document is one of the Emerging TechnologySeries published by ACI. The paper outlines the content of the document and thephilosophy of applying FRP technology as opposed to conventional steel forprestressing. The document offers general information on the history and use of FRP forprestressing applications, and a description of the unique material properties of FRP. Italso focuses on the current state of design, development, and research needed tocharacterize and ensure the performance of FRP as prestressing tendons in concretestructures. The proposed guidelines are based on knowledge gained from worldwideexperimental research, analytical work, and field applications of FRPs used asprestressed tendon. Current developments in the document include a basicunderstanding of flexural and axial prestressed members with FRP tendons, FRP shearreinforcement, bond of FRP tendons, and unbonded or external FRP tendons forprestressing applications. The document concludes with a list of research needs.
Assuming the prestressing force remains constant with applied externalload, the analysis of beams prestressed with unbonded tendons under service loads,where the section is uncracked, is no different than the analysis of beams with bondedtendons. However, after cracking, significant differences emerge, the most importantof which is that the stress in the unbonded tendon is member dependent, that is, itdepends on the deformation of the member, while the stress in the bonded tendon issection dependent, that is, it depends on the curvature of the section. This causes thestress in unbonded tendons to be significantly smaller than that for bonded tendons,and that is particularly important at nominal bending resistance.This paper summarizes the analysis procedure for beams prestressed with unbondedtendons at service and ultimate limit states; it focuses in particular on three problems:1) how to analyze a beam in the elastic uncracked range of behavior; 2) how to analyzea beam in the elastic cracked range of behavior; and 3) how to analyze a beam atnominal bending resistance.
A survey of the first uses of precast, prestressed or post-tensioned foldedplates roofs show that this structural system start in the 1950’s and end in the 1970’s Ahistoric perspective of this structural system will be presented starting in the 1950’s andending in the 1970’s. While prestressed concrete was making a break-through in theUnited States with the Walnut Lane Bridge in Philadelphia, PA, Europe was usingprestressed concrete in various types of structural systems. One of these systems wasthe folded plate roof system. Approximately a decade later in the United States, theCloverleaf Lanes Bowling Alley in Dade County, Florida used the same application inwhich the corrugated slab spanned 120 feet and extending transversely 286 feet. In1962, this system of folded plate shells went from long span structures to being used inroof structures for dormitories at Washington State University. The main beams for thedormitories were pretensioned in a factory, while the secondary beams were post-tensioned on site. During the 1970’s, precast folded plate structures were beingconstructed throughout the United States for various types of buildings, one notablestructure is the Hangar for Allegheny Airlines at Logan Airport, Boston, Massachusetts.Then they disappeared in the United States. Some Possible reasons why folded plateconstruction stopped are numerous but the two main factors are the architecturalsolution, and the lack of understanding of folded plate structures on the part ofengineers and architects.
Post-tensioned concrete is a popular material used in the construction ofparking facilities due to economy and durability it offers. The flooring system in post-tensioned parking facilities generally consists of one-way post-tensioned slabssupported by post-tensioned beams cast monolithic with concrete columns formmoment frames. However, the building codes have restricted the use of post-tensionedconcrete as primary lateral load systems in high seismic regions due to concerns aboutductility, anchorage, bond, transfer lengths, grouting, characteristics of high strengthprestressing steel and level of prestressing. Until recently, building codes have insistedon the ductile non-prestressed steel as the sole reinforcement and have not permittedthe use of prestressing in ductile moment frames. This paper summarizes issues,advances and historical developments of code requirements concerning theprestressed or post-tensioned frames, followed by performance of parking facilitiesduring recent major earthquakes. Next, the paper provides an overview of the currentstate of seismic design process for post-tensioned parking facilities and its structuralsystems, subsystems and elements.
In the early 1940’s Prof. G. Magnel performed extensive researchprogrammes on real scale prestressed concrete beams at Ghent University (Belgium) inorder to elaborate design methods for this new material. He also developed his ownanchorage system which was used until the mid 60’s in Belgium. He gave manylectures in several countries in which he explained in a simple way the principles ofprestressed concrete. He was also instrumental in the design of the first prestressedconcrete bridge in the USA, the Walnut Lane Bridge in Philadelphia and he was theauthor of the first English textbook on prestressed concrete. He designed one of thefirst PC railway bridges in Europe and the first statically indeterminate PC bridge in theworld. In the 1950’s many engineers from abroad spent some time in Magnels lab inGhent to perform research and to get acquainted with practical realizations.
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