International Concrete Abstracts Portal

The development of Arapree, about fifteen years ago in the Netherlands, can be considered as one of the initiatives, which started the use of FRP reinforcement for concrete structures. Today, although no longer produced in the Netherlands, Arapree is still commercially available. Hence, over the years a considerable amount of information on the use of this type of AFRP has become available, including test data and practical experience. Several approaches have been developed regarding the design philosophy. Based on the information available to the authors, and their own experience concerning the use of Arapree, a design philosophy for concrete elements prestressed with Arapree is given in this paper.

Investigation of the long-term characteristics of the Highly Expansive Material (HEM) anchorage for CFRP strands is very important. In the post-tensioning type of prestressed concrete structures, considerations should be made for the loss of prestressing force due to the pull-out displacement which is caused by the creep of the HEM. The long-term characteristics of the HEM anchorage were investigated by creep test on five specimens. From the creep test, some important characteristics of HEM anchorage were observed, for example, time-dependent change of pull-out displacement at the loaded end, unit shear “q” distributions and the tensile force distributions “Tp”. An analytical relationship on how the long-term behavior of prestressing force can be predicted by using the measured values for the time-dependent change of pull-out displacement at the loaded end is presented. Also from the simulated results of this relationship, it was found that the loss of prestressing force is negligible in practice when the CFRP strand is 10 meters long. Normally the expansive pressure of HEM at prestressing is 50MPa. However, when the expansive pressure is 100MPa, the pull-out displacement at the loaded end and the loss of prestressing force can be reduced to more than the half of one with 50MPa.

In this paper, an experimental study on the frictional coefficient of fiber reinforced polymer (FRP) tendons is made and reported. Tests on FRP tendons fixed in cement mortar and confined with highly expansive material (HEM), and placed all together inside a steel sleeve pull-out test were conducted. Tests were carried out at various levels of confining pressure. The initial bond and the friction coefficient are presented for the FRP tendon with the surrounding HEM. A newly developed pressure transducer was placed in the same manner as the FRP tendon to monitor the confining pressure due to the HEM. The previous results are compared with the present one on Carbon FRP are reported using this monitoring system. The Vinyl on FRP is tested for the first time and the large size Carbon FRP are also introduced as they are prime candidates for use in practice.

Since the 1995 Hansin Earthquake, need of seismic retrofitting of existing structures has been strongly understood. Being expected to reduce inconvenience in retrofit work of buildings, some techniques using carbon and/or aramid fibers have been widely employed in Japan due to light weight, flexibility, non-welding, and easy handling. Many of these techniques aim to improve shear capacity and ductility of existing reinforced concrete columns and may be called “Standard Method” due to the almost common working procedure. The procedure includes (1) wrapping columns in the transverse direction using continuous fiber sheets, (2) impregnating epoxy resin into the sheets to make FRP composite, and (3) doing surface treatment or arrangement of concrete to prevent voids or wrinkles. This “Standard Method” of fiber wrapping has induced development of other methods that improve a working process or can be applied for other structural members. In the future, the fiber wrapping technique will be more spread, however, it requires an approved and common quality control method. An education program for retrofit engineers and craftsmen should be also established.

Design guidelines for reinforced concrete structures (RC) with fibre reinforced polymers (FRP) use the concept of partial safety factors to ensure that structural safety is attained. However, when partial safety factors are used for the design of FRP RC structures, the structural reliability levels are not known. It is very important that structural reliability targets are met, in particular when there is a change in the predominant mode of failure. Furthermore, the resistance-capacity margins between various failure modes are not known. The work reported in this paper investigates these safety-related uncertainties. The notional structural reliability levels of two FRP RC beams are evaluated for the flexural and shear failure mode. The resistance-capacity margins for these two failure modes are also evaluated. Finally, the effect of the partial safety factors on the type of the expected failure mode is investigated.