Structural Performance Of Reinforced Concrete Beams Strengthened With Steel Plates Under Pure Torsion

Strengthening of concrete members with externally fixed plates has been recognized as a viable means of improving the performance and strength of the structures.The present study is focused on improving the torsional strength of composite reinforced concrete-steel beams by means of bolting steel plates to their shear sides.The experimental work includes an investigation of thirteen reinforced concrete beams under pure torsion.The present study deals with the effect of some important parameters;these include the steel plate's thickness,steel plate's height and the spacing between shear connectors.Test results of beams discussed are based on torque-twist behavior,beam longitudinal elongation behaviour and the influence of the variables considered in the test program on cracking torque,ultimate torque and failure modes.The results revealed that the cracking torque,ultimate torque,global stiffness of beam and beam ductility for all composite beams increase with the increase of the plate's thickness,plate's height and number of shear connecters.Torsional moments and angles of twist are affected by the steel plate's thickness more than the steel plate's height.While the composite beams elongation was affected by the number of shear connectors more than both steel plates height and plates thickness.The ABAQUS6.10 nonlinear finite element software is used to model the above examples.Twelve model B1-B12 with steel plate thickness,steel plate height and pin spacing(total number)are respectively established,and the model BN in the beam is not added.The specific corresponding relation is shown in the following table,and then the finite element analysis under torsional loading is carried out.Comparing the test values of the yield torque and the ultimate torque to the finite element analysis,the amplitude of the variation coefficient Tyb/Tya is 0.83 and 0.92 respectively,which shows that the constitutive model,interaction and loading mode used in the model can reflect the actual situation.According to the numerical simulation results,it is obvious that the yield torque and ultimate torque of the beams strengthened with steel plates are higher than those of the non steel beams.Under the same stub spacing and steel plate thickness,the stiffness of the reinforced beams with different plate height is closer to the elastic stage.The increase of the torsion stiffness with the steel plate height is more obvious after the yield torque.The thickness of the steel plate has a significant influence on the limit torque,and the effect of the pin spacing decrease is similar to the encrypt stirrup.It effectively inhibits the deformation of the beam.