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The technical research committee on continuous fiber (CF) sheet in the Japan Society of Civil Engineers (JSCE) has been engaged in making a new design system for concrete structures retrofitted with externally-bonded CF sheets since 1998. This paper presents the framework and some tentative contents of the design system. The system is on the basis of the concept of performance-based design, in which a structure to be retrofitted is systematically verified if it can satisfy any required performance items during the residual service life. Performance items of structures are verified in terms of the verification index which represents each performance item quantitatively. Evaluation methods for several performance items under development are shown in this paper regarding structural safety and serviceability of structures. The importance of precise prediction of peeling-off of CF sheet from concrete is emphasized. In the verification process of performance items, time-dependent performance changes due to environmental and loading attack are taken into account, so that structural and durability design are unified in a rational way.

AFRP tensile elements (bars, strands etc.) can be successfully applied for the pre-tensioning of precast concrete members, for post-tensioning tendons, ground anchors etc. In such applications, the AFRP may come into permanent contact with the alkaline pore solution of concrete or cementitious grout. Many tests prove that such aggressive environment may seriously damage the stressed AFRP and significantly abbreviate its lifetime due to premature stress rupture. The stress rupture strength of FRP is the relevant durability property to ensure the serviceability and safety of a structural concrete member during its service life. The stress rupture behaviour is usually studied on stressed AFRP bars placed in aggressive solutions etc.. It is though evident that such severe environment does not realistically reflect the true environment of AFRP in dense concrete and grout. It is was therefore the aim of the authors to develop - on basis of experiments in several stages and by theoretical studies - an engineering model for the prediction of the stress rupture strength of stressed AFRP in concrete or grout. This model was verified by tests. Provided the stress rupture strength of AFRP in dry air or in alkaline solution etc. was experimentally established afore-hand, the parameters of the mean stress rupture relationship can be sharpened. Additional deliberations are however necessary to transfer the model into the real environment of concrete or grout around the FRP element. Suitable procedures are presented.

Using the database consisting of 236 R/C column specimens conducted in Japan, the characteristic behaviors of strengthening by fiber wrapping were analyzed. The following findings were obtained: (1) The amount of shear reinforcement, the span to depth ratio, the axial compressive stress level influence on the strength and deformation capacities of retrofitted columns by fiber sheet wrapping (2) Shear strength of retrofitted columns can be predicted by previous design equations based on the strut and tie models as same as for usual R/C columns, in which the effective fiber strains of about 1% is appropriate. (3) There are few test data about the confining effect of fiber sheet wrapping on bond resistance of longitudinal bars. Further research effort is required to evaluate the shear strength of columns governed by the splitting of cover concrete along longitudinal bars. (4) The ductility ratio can be roughly estimated as a function of the shear to flexural strength ratio. (5) For the specimens with plain round longitudinal bars, the previous equations based on the strut and tie model cannot be applied because of the poor bond capacity.

This paper discusses the procedure and results from in-situ load tests performed on strengthened double tee beams in a precast parking garage. The load tests were performed to evaluate and confirm the performance of the double tees after the members had been strengthened in shear. Carbon FRP sheets were used as shear reinforcement at a 0/90° combination on the stem of each double tee. Load tests were performed on twenty double tees at various locations and floor levels of the parking structure. Each complete load test, including assembling and dismantling of the test equipment, was completed in approximately three hours. Results indicate that the shear strengthening systems increased the capacity of the double tee beams to meet the design load requirements.

In this paper the results of a series of tests, which were carried out using a total of 16 specimens of reinforced concrete (R/C) columns having wing walls retrofitted with fiber reinforced polymer (FRP) sheets as shear reinforcement, are described. In this work, the FRP sheets were adhered with epoxy resin. The specimens before retrofit were designed by the abolished Japanese seismic code before 1971. The primary test variables were the widths of the wing walls stretching from the columns, the kind of FRP sheets and its amount as shear reinforcement. It was observed that all specimens failed in a shear mode except for one specimen and that the ultimate shear strengths increased linearly in proportion to the amount of the fiber as shear reinforcement. ( i.e., the product of tensile strength and equivalent reinforcement ratio which corresponds to an replaced rectangular cross section of the column and the wing walls as a whole.) Based on the test results of regression analysis, an equation to evaluate the ultimate shear strength of R/C columns having wing walls retrofitted with FRP sheets is proposed.