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    Behavior of FRP-Retrofitted Joints Built with Plain Bars and Low-Strength Concrete
    (Asce-Amer Soc Civil Engineers, 2011) Ilki, Alper; Bedirhanoglu, Idris; Kumbasar, Nahit
    Two series of tests on eight full-scale exterior beam-column joint subassemblages built with plain bars and low-strength concrete were conducted. No transverse reinforcement was present in the joint cores. In the first series of tests, which included three specimens, the behavior of joints before fiber-reinforced polymer (FRP) retrofitting was investigated. In the second series, which included five specimens, the behavior of the FRP-retrofitted joints was investigated. The six specimens consisted of a column, an in-plane beam, a transverse beam, and a slab part, and two specimens were plane members without transverse beams and slabs. The utilized retrofitting scheme is easily applicable for actual exterior beam-column joints, even in the presence of a transverse beam and a slab. Two types of strength limitation were observed for specimens in the first series. The strength of the specimen with beam longitudinal bars sufficiently anchored to the joint core was limited by the shear strength of the joint. The strengths of the other two specimens were limited by the slip of the beams' longitudinal bars at their anchorages. In the second series of tests, significantly better performance was obtained both in terms of shear strength and ductility, provided that the slip of the beam bars was prevented. Furthermore, by using a simple theoretical algorithm based on truss analogy, the strength and deformability characteristics of the tested reference and FRP-retrofitted joints are predicted with reasonable accuracy. The same algorithm is used for predicting the joint shear strength of specimens tested by other researchers, and satisfactory agreement is obtained between the predictions and test results. DOI: 10.1061/(ASCE)CC.1943-5614.0000156. (C) 2011 American Society of Civil Engineers.
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    Precast fiber reinforced cementitious composites for seismic retrofit of deficient rc joints - A pilot study
    (Elsevier Sci Ltd, 2013) Bedirhanoglu, Idris; Ilki, Alper; Kumbasar, Nahit
    The objective of this study was to investigate the seismic behavior of deficient reinforced concrete exterior beam-column joints constructed with low-strength concrete and plain reinforcing bars before and after retrofitting with prefabricated HPFRCC (high-performance fiber-reinforced cementitious composite) panels. For this purpose, four full-scale beam-column-slab-transverse beam sub-assemblies were tested under constant column axial load and reversed static cyclic lateral loads. Before these full-scale tests, four simple panel specimens, which were built to represent the joint cores, were also tested under diagonal tension before and after retrofitting with prefabricated HPFRCC panels. Both types of tests showed that retrofitting with prefabricated HPFRCC panels provided considerable enhancement, both in strength and in displacement capacity, provided that the panels were properly anchored to the joint core and the slippage of the beam longitudinal bars in the joint core was prevented. In the analytical part of the study, the strengths of the reference and retrofitted panels, tested under diagonal tension, were predicted quite accurately using non-linear finite element analysis. Furthermore, Mohr's circle and strut-and-tie modeling was used to obtain the complete load-displacement relationships of the reference and retrofitted joint sub-assemblies. (C) 2013 Elsevier Ltd. All rights reserved.