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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 1-8 of 8 Abstracts search results
April 1, 1989
B. O. Aalami and F. G. Barth
Based on extensive observations and a survey of the performance of unbonded post-tensioned buildings, paper presents a categorization of the common cracks in beams and slabs, and the principal causes of crack formation due to restraining effects of supporting structures are discussed in detail. Current methods of crack formation control are also presented and evaluated, and the consequences of cracks on serviceability and strength of post-tensioned buildings are reviewed. In addition, recommendations are made for crack mitigation and maintenance of buildings that are post-tensioned with unbonded tendons.
P. R. Chadrabarti
An attempt is made to study the crack formation, crack propagation, and the postcracking behavior until failure of four-panel prestressed concrete flat plates having two-way continuous parabolically draped unbonded post-tensioning tendons. The test specimens closely simulate the corner panels of an actual flat plate floor system having simple supports along the edges. The simple support system is similar to that provided by ledger beams or walls. The effect of added mild steel on the crack initiation, crack propagation, crack width control, and postcracking behavior is also studied. Recommendations are also made for further research.
E. G. Nawy
Discusses the stresses, strains, and development of bursting cracks at the end block anchorage zones of post-tensioned prestressed concrete beams. It covers the two stages of loading, namely, the longitudinal prestressing loading stage and the additional transverse loading at the third span point applied during the beam testing stage. The effects of the transverse shear force on the stress/strain distributions and end block cracking of concentrically and eccentrically post-tensioned beams with rectangular anchorage blocks were studied. A three-dimensional embeddable strain gage tripod frame was developed and fabricated in this investigation to measure the interior strains in the anchorage blocks of 15 beams subjected first to initial prestressing and subsequently to additional transverse shear loading. Surface concrete strains were also measured through the use of strain rosettes mounted on the concrete surface at critical locations in the anchor blocks.
J. A. Burgess, J. E. Breen and R. W. Poston
An experimental investigation was conducted to examine cracking of post-tensioned bridge deck anchorage zones with closely spaced anchors. The test program included full-scale tests of bridge deck anchorage zones with single and closely spaced anchorages. Half of the test specimens contained additional spiral anchorage zone reinforcement. The test results indicate that when the anchorages are closely spaced, a previously stressed anchor tends to precompress the anchorage zone of an adjacent anchor and slightly increases its cracking load. In heavily reinforced bridge decks, additional spiral anchorage zone reinforcement provides only a slight to moderate increase in the anchorage zone cracking or ultimate load. Predicted cracking loads based on ACI-PTI's allowable stress provisions were generally conservative for single and closely spaced bridge deck anchorages.
M. N. Hassoun and K. Sahebjam
Aim is the study of the cracking of partially prestressed concrete beams under increasing load up to failure. Different combinations of prestressed and nonprestressed steel were used. The strength of the nonprestressed steel varied between 40 and 250 ksi. Spacings and crack widths were measured and reported. An expression is introduced to calculate the maximum crack width of partially prestressed concrete flexural members.
M. H. Harajli and A. E. Naaman
Study was conducted to evaluate cracking in partially prestressed concrete beams under both static and cyclic fatigue loading. It comprises two parts: an experimental investigation and an analytical modeling of crack width increase under cyclic fatigue loading. In the experimental part, 12 different sets of beams were tested in four-point bending. Each set comprised two identical beams. One beam was tested to failure under monotonically increasing load, while the second beam was tested in fatigue at a constant load range simulating full live load. In the analytical part of the study, a model for computing the increase in crack width under cyclic fatigue loading is developed. The model accounts for the effect of change in steel stress due to cyclic creep of concrete in compression, the increase in slip due to bond redistribution, concrete shrinkage, and cyclic creep of concrete in tension. Results predicted by the model were found to be in good agreement with the experimental results observed in this study, as well as results reported elsewhere.
More prestressed beams incorporating mild steel reinforcement are built today with allowance of tension in the concrete, that is, partial prestressing. Consequently, a study of their cracking behavior and control of the crack width and distribution are significant. Available experimental data on the cracking behavior of prestressed beams is limited. Because of the importance of serviceability behavior of these elements, several experimental and analytical investigations have been undertaken and expressions proposed. Simple mathematical expressions have been developed. The proposed expressions for evaluating crack widths in partially prestressed beams at working load and overload have been developed in terms of the controlling parameters, namely, the variation in the steel reinforcement and percentage of the prestressing tendons and the nonprestressed reinforcement. The mathematical model is applied to tests on 20 simply supported pretensioned 9 ft span beams, 4 two-span continuous beams of effective 9 ft span, and 22 simply supported post-tensioned beams of 7 ft, 6 in. span. The major controlling parameters were the variation in the steel reinforcement percentage of the prestressed tendons and the nonprestressed reinforcement. The effect of concrete cover was incorporated in the value of the concrete area in tension.
Editors: Grant T. Halvorsen and Ned H. Burns
Cracking in Prestressed Concrete Structures has been compiled to provide further insight into the problems and solutions of cracking in prestressed concrete." This ACI Special Publication consists of seven papers reflecting the perspectives of both research and practice. Cracking in Prestressed Concrete Structures provides the know-how you need to build durable, crack-free, prestressed concrete structures.
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