Tension of reinforced concrete prisms: round robin analysis and tests on bond : a report from an investigation arranged by RILEM technical committee 147-FMB fracture mechanics to anchorage and bond
2001 (English)Report (Other academic)
Results are presented from a RILEM Round Robin Investigation. It deals with tension stiffening of reinforcement bars embedded in concrete tie elements. Seven groups of researches have performed some 50 tests and analyses. Parameters discussed are: cover thickness, crack spacing, bar size, tension stiffening of naked reinforcing bars, and influence of concrete strain softening. Similar trends were seen in the different tests and most of the applied theoretical models give reasonable results. The general behaviour is similar, although there seems to be some differences between the tested cracking loads. The models used are able to predict the bond behaviour in a correct way: analytical models based on the tension softening of concrete; bond-slip relations; as well as finite element methods with inner softening bands. The CEB-FIP Model Code can be used for design purposes and gives straight-forward predictions. The following new and/or refined insights were obtained from the tests: Cover thickness and crack spacing. - The number and spacing of visible cracks are more or less proportional to the thickness of the concrete cover. Bar diameter size effect. - There is a small tendency to a proportionally lower tension stiffening effect for larger bar sizes but the scatter is too large to secure definite conclusions. Longitudinal splitting and yielding of reinforcement. - Longitudinal splitting cracks occurred close to and after yielding of the reinforcement. Tension stiffening of naked reinforcing bars. - A new hypothesis of a tension stiffening of the bare reinforcing bar has been presented. Concrete strength and strain softening - The crack opening resistance is given by the tension softening curve of the concrete. By addition of fibres to the concrete matrix, the curve is changed, and the crack opening resistance is improved without necessarily changing other properties of the concrete. The chosen amount and type of fibers do not necessarily have much influence on the tensile strength, and the same crack patterns will be obtained on elements with the same geometry. The shape of the load-deformation curve, however, is considerably changed compared to that of the plain concrete. This is due to the enhanced crack-opening resistance, whereas the stiffening effect seems to depend on the crack spacing and consequently on the cover thickness and the degree of confinement it provides.
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2001. , 243 p.
Research report / Luleå University of Technology, ISSN 1402-1528 ; 2001:13
Research subject Structural Engineering
IdentifiersURN: urn:nbn:se:ltu:diva-23707Local ID: 817b7ef0-71c2-11db-962b-000ea68e967bOAI: oai:DiVA.org:ltu-23707DiVA: diva2:996756
Godkänd; 2001; 20061111 (ysko)2016-09-292016-09-29Bibliographically approved