Fibre Reinforced Polymers (FRPs) are extensively employed to strengthen existing structures because of their several advantages over other strengthening techniques. On the other hand, the premature debonding of FRP reduces its effectiveness in strengthening steel structures. Anchoring FRP composites is an effective solution to delay or even prevent their debonding. Very limited anchorage methods, however, have been introduced for FRP-strengthened steel structures and the need for an effective anchorage system remains. Fan anchor has been validated as one of the remedies against debonding failure in FRP-strengthened concrete structures. Considering the advantages that fan anchors offer, the use of fan anchors for FRP-strengthened steel structures is proposed and evaluated in this paper. Since FRP-steel joints have a different bond-slip law than FRP-concrete joints and the strengthened steel members are prone to buckling-debonding interactions, this study focuses on the efficiency of fan anchors in delaying FRP debonding by assuming that an adequate mechanical connection between the dowel and the steel substrate is provided. Three experimental studies involving shear, flexural and buckling strengthening of steel components were simulated through finite element modelling, and fan anchors were added to the models after validation. The effect of fan anchors on strength, failure mode and FRP's strain distribution of the models was examined. The study showed that the fan anchor was successfully able to delay debonding mode, which increased the strength and ductility and exploited a higher strain capacity of FRP plates.
Purpose The purpose of this paper is to examine the dynamical behavior of a combined three-story building with a 3D panel wall system including a soft story irregularity at the very first floor by doing a shaking table test. The upper two stories of the model were made out of the 3D panel system, while the first story was constructed only with moment-resisting RC frames. Design/methodology/approach Besides the experimental program, the numerical finite element method was implemented for the verification of the experimental results. In the experimental study, the building responses including the floors’ accelerations and drifts were considered, and the seismically vulnerable zones were reported and compared with that provided by the implemented FEM-based program. Findings After the shaking table test, the major cracks appeared at the end of each column and beam-column connections. Some negligible cracks were also visible around the beam-panel connections. However, no crack was seen in the upper stories. The lateral deformation of the studied building was investigated under the applied ELC25 and NGH135 earthquakes. Under the both aforementioned ground motion records, the first story drift was larger than two upper stories, since the moment-resisting frame was a soft story. The hysteretic relation between the shear and displacement for each story was studied. Under the applied ELC25 earthquake, the system remains linear and the stiffness of each story is obtainable as well. Originality/value This is the first time when the dynamical behavior of a combined system is studied and tested experimentally and numerically for data validation. Regarding the response of the assumed combined structure, the 3D panel system has a remarkable rigidity with respect to the conventional RC frames, also 3D panels have less weight than the moment-resisting frames.
During an earthquake, diagonal braces are designed to dissipate energy by yielding in tension and buckling in compression. However, local buckling occurring in the middle of the brace leads to immediate fracture. Aiming to strengthen braces against local buckling, this study proposes wrapping FRP sheets in the transverse direction. The e ect of FRP strengthening on the post-buckling behavior of Square Hollow Section (SHS) tubes has not been investigated. A numerical model was generated and veri ed by other previous researches. Then, a comprehensive parametric study was conducted, and the e ects of slenderness ratio, the number of FRP layers, and FRP coverage percentage on post-buckling response of the strengthened brace were explored within this study. Results indicated that utilizing FRP was certainly successful in mitigating local buckling mode of long SHS braces. Moreover, for short braces, applying enough FRP layers can change the mode of buckling from local to overall. Finally, an optimized length of FRP was proposed for brace strengthening in accordance with their slenderness ratio.
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