Seismic performance of hybrid fibre reinforced Beam – Column joint
Author(s)– Perumal.P, Thanukumari.B
High Strength Concrete has become a very popular construction material which is directly related to recent development in concrete technology. The brittle nature of this High Strength Concrete results in sudden unpredictable failure. By using special hybrid fibre combinations of steel and polypropylene fibres, the explosive failure behaviour of High Strength Concrete (HSC) may be avoided. The main objective of this study is to investigate the effect of different proportions of hybrid fibre combinations (1.5% of steel fibre and 0 to 0.4% of polypropylene fibre) at the joint of exterior beam-column connections subjected to earthquake loading using M60 concrete. The hybrid fibre combinations of 1.5% of steel fibre and 0.2% of polypropylene fibre have best performance considering the strength, energy dissipation capacity and ductility factor. An attempt has been made to develop a new model by slightly modifying the previous models available in the literature for the joint shear strength. The proposed model was found to compare satisfactorily with the test results.
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Prediction of Joint Shear Strength of Concrete Beam-Column Joints Reinforced Internally with FRP Reinforcements
Author(s)– Saravanan Jagadeesan, Kumaran G
This experimental study primarily focuses on the joint shear strength of full scale size exterior concrete beam-column joint reinforced internally with Glass Fibre Reinforced Polymer (GFRP) reinforcements under monotonically increasing load on beams keeping constant load on columns. Four series of joints and totally eighteen numbers of such specimens are cast and tested for different parametric conditions like beam longitudinal reinforcement ratio, concrete strength, column reinforcement ratio, joint aspect ratio and influence of the joint stirrups at the joint. Also finite element modelling and analysis of GFRP reinforced concrete beam-column joints are performed to simulate the behaviour of the beam-column joints under various parametric conditions. Based on this study, a modified design equation is proposed for predicting the joint shear strength of the GFRP reinforced beam-column specimens based on the experimental results and the review of the prevailing design equations.
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Experimental Investigation on Behavior of Reinforced Concrete Beam Column Joints Retrofitted with GFRP–AFRP Hybrid Wrapping
Author(s)– Robert Ravi.S, Prince Arulraj.G
Upgradation to higher seismic zones of several cities and towns in the country has necessitated in evolving new retrofitting strategies. Recent earthquakes have demonstrated that most of the reinforced concrete structures were severely damaged during earthquakes and they need major repair works. One of the techniques of strengthening the reinforced concrete structural members is through external confinement by high strength fiber composites which can significantly enhance the strength and ductility which will result in large energy absorption capacity of structural members. Fiber materials are used to strengthen a variety of reinforced concrete elements to enhance the flexural, shear, and axial load carrying capacity of elements. Beam-column joints, being the lateral and vertical load resisting members in reinforced concrete structures are particularly vulnerable to failures during earthquakes and hence their retrofit is often the key to successful seismic retrofit strategy. The existing reinforced concrete beam-column joints which were designed as per code IS 456:2000 must be strengthened since they do not meet the requirements given in the ductility code IS 13920:1993. In this paper an attempt has been made to study the behavior of reinforced concrete beam-column joints retrofitted with glass-carbon hybrid fiber sheets. Three exterior reinforced concrete beam-column joint specimens (control) were cast and tested to failure. Two specimens had reinforcement details as per code IS 456:2000. The other specimen had reinforcement details as per code IS 13920:1993. An axial load was applied on the column. Push and pull load was applied at the free end of the cantilever beam till failure. The failed two beam-column joint specimens designed as per code IS 456:2000 were retrofitted with GFRP-AFRP/AFRP-GFRP hybrid fiber sheets wrapping to strengthen the specimens. The performance of the retrofitted beam-column joints was compared with the control beam-column joint specimens and the results are presented.
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