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This paper presents an experimental study on seismic repair of damaged square reinforced concrete columns with poor lap splices, 90-degree hooks and widely spaced transverse bars in plastic hinge regions according to ACI detailing (pre.1971) and (318-02) using GFRP wraps. Three specimens were tested in “as built” condition and retested after they were repaired by glass fiberreinforced plastic sheets. They were tested under numerous reversed lateral cyclic loading with a constant axial load ratio. FRP composite wraps were used for repairing of concrete columns in critically stressed areas near the column footings. Physical and mechanical properties of composite wraps are described. Seismic performance and ductility of the repaired columns in terms of the hysteretic response are evaluated and compared with those of the original columns. The results indicated that GFRP wraps can be an effective repair measure for poorly confined R/C columns due to short splice length and widely spaced ties with 90-degree anchorage hooks. Both flexural strength and ductility of repaired columns were improved by increasing the existing confinement in critical regions of them.

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During the past years the use of buckling restrained braces (BRBs) have had a dramatic growth due to their better performance comparing to conventional braces. BRBs have more ductility and energy absorption capacity by excluding the overall brace buckling. However, even these kinds of braces have some problems restricting their use in some projects, i.e. high tolerance of applying unbonding material, concrete placing difficulties and their weight. Accordingly, many researchers have conducted experiments to find the possibility of shortening or even eliminating the infill material of the braces. The following study has addressed the effect of debonding material friction ratio, shortening the concrete fill, and finally eliminating it if possible, by reshaping the core element with constant section area. The operated analysis has been carried out both numerically and experimentally. ABAQUS finite element software was applied for numerical analysis and the results were verified by an experimental study in two groups of models each including four full-scale brace models. With a constant core section area, results revealed that without the risk of buckling, the concrete cover length could be reduced. With a special core profile, the infill may be fully omitted and the restrainer would be made up of only a steel tube, which may happen without any changes made to the cross sectional area of the core profile.