Study on the effects of rupture directivity on seismic behaviour of hybrid skeletal systems of eccentrically braced frames with knee rods

The dual steel resistant skeleton is one of the functional structural systems for resisting against lateral forces induced by earthquakes that in addition to the enhanced ductility possesses high stiffness, dynamic stability, and redundancy. Behavioural pattern of dual resisting systems is based on shear and bending performance modes. This research includes a study on the nonlinear seismic behaviour of dual eccentrically braced resisting frames with knee rods. The extent of the effectiveness of knee bracing has been assessed based on nonlinear time history analyses of the structure subjected to severe three-component earthquake records. A strong near-field ground motion possesses particular characteristics. The existence of high amplitude and long period pulses in recorded strong ground motions along with the severe accumulation of kinetic energy and its short release time, are of noticeable differences between near-field and far-field earthquake records. The particular objective of this research is to evaluate the amplitude of variations in maximum responses and to determine the time history of absolute acceleration, relative displacement, and relative velocity of floors along with the base shear of the studied models. Analysing the results indicate an observable appearance of the effects of large coherent velocity pulses presented in the time history of near-field earthquake records, on the relative lateral displacement of floors and on the rapid propagation of plastic hinge mechanism throughout the primary elements of dual resistant skeleton.