International Concrete Abstracts Portal

"The American Concrete Institute sponsored an unprecedented six technical sessions on FRP Reinforcement for Concrete at the Vancouver Conference on March 28-31, 1993. Speakers and attendees were present from Europe, Japan, Canada and the United States. The papers in this Special Publication are organized in the same subject areas as the conference. The subject topic areas and symposium sections are: 1. FRP Material Properties and Testing Methods 2. FRP Reinforcement for Reinforced Concrete 3. FRP Reinforcement for Prestressed Concrete 4. Analysis And Design 5. The Japanese National Project for FRP Development 6. Applications of FRP Reinforcement The 55 technical papers in this report represent the most comprehensive compilation to date of FRP research, design, and application information. A comparison of the papers provides an insight to the approach to the use and development of FRP reinforcement within the research communities of Europe, Japan and North America. The two symposium volumes are also significant because substantial portions of the extensive Japanese national research project have been translated into English. The Japanese papers provide an insight to both the magnitude of the technical work being conducted in Japan and the organization of the Japanese research program." Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP138

In concrete pretensioned with nonmetallic fiber reinforced plastic reinforcement (FRPR), the Hoyer effect leads to high splitting stresses due to confinement of radial deformations of bars or strands in the transfer zone. Incompatible linear temperature expansion can aggravate the splitting stresses. Bond in the transfer zone is heavily influenced by the confined radial expansion, as demonstrated by tests with bars in lightweight concrete. Very short transfer lengths (80 mm) have been measured. Three calculation approaches for splitting stresses are presented: the elasto-plastic, concrete deformation, and fracture energy approaches. The elasto-plastic model has been checked using a discrete element model that includes tensile softening of concrete. The presented formulas are confirmed by several tests on pretensioned prisms.

A comprehensive research program to investigate the suitability of a fiber reinforced plastic (FRP) for reinforced concrete is described. The investigation focuses on highway bridge decks and barrier walls. In determining the research needs, careful consideration has been given to the loads and environments to which highway bridges are subjected in northern North America. Short-term tension, creep, fatigue, and durability tests are being carried out on FRP specimens in the first phase of a three-phase program. Tests completed so far indicate a small yet noticeable change in strength and stiffness of FRP with change in temperature; small creep strain rates have been computed after 175 days of sustained loading, with satisfactory fatigue behavior under a tensile load cycling between 10 and 30 percent of the tensile strength.

FRP tensile elements exhibit the so-called creep rupture phenomenon when subjected to a high axial tensile stress. For this reason, the time of endurance until fracture that is dependent on the level of the permanent stress is the relation to be derived experimentally. The creep rupture phenomenon exists principally for all structural materials. However, experiments prove that for prestressing steel it is of no practical relevance: the usual permanent steel stresses that are in the range of 75 percent of characteristic tensile strength can be borne indefinitely without fracture or strength loss. However, this is not the case for FRP, whose stress rupture behavior is also influenced markedly by the micro-environment around the element and is dependent on the type of fiber and matrix employed. Paper presents an outline of the results known so far, the experimental techniques, methods of statistical evaluation, and forecast of the long-term behavior of specific FRP elements. It is shown that the characteristic stress rupture line is the essential basis for the derivation of the admissible permanent prestress of FRP tensile elements.

In Japan, FRP reinforcement has been regarded as the substitute structural material for steel bars in reinforced concrete elements. The Architectural Institute of Japan (AIJ) has formed the Committee of Continuous Fiber Composite Material to address the need for use of FRP in the future. Paper concerns evaluating FRP and FRP reinforced concrete elements from a structural viewpoint. The evaluation of new materials such as FRP outside the parameters of standard building codes is difficult. It is also potentially dangerous to evaluate a new material according to conventional standards. Therefore, this paper encompasses the tendency of present research and standards, together with suggestions to promote the future use of FRP and FRP reinforced concrete elements.