Nonlinear Simulation Analysis On Lateral-resisting Performance Of RC Frame-shear Wall Structure Considering Accidental Eccentricity

Rotational components of ground motion,or structural asymmetry caused by unforeseen factors(like construction tolerances),induces eccentric torsional response of building subject to earthquake.At present,accidental eccentricity is the term used in general code provisions to account for aforementioned uncertainties,and taken as a percentage(5% or 10%)of the building dimension perpendicular to the direction of excitation.Researchers have made remarkable achievements on evaluation of code value and design necessity for accidental eccentricity,whereas the influence of which on lateral-resisting performance and lateral-torsional stiffness degeneration of RC frame-shear structure,are rarely mentioned.The accidental eccentricities are simulated and altered by scaling up and down two sides of horizontal seismic forces acting on a symmetrical structural model,with ratio value ranging from 0% to 15%(spacing of 1%).In addition,the scenario of eccentricities occurring on adjacent storeys in the opposite direction is considered,for the case of models with 5% and 10% eccentricities.A simulation program based on theory of degenerated 3-D solid virtual laminated element,is adopted to conduct the analysis on 18 ten-storey RC frame-shear wall structures,given that the accuracy of the method which involves slab-beam-column interactions was further demonstrated through a test example.The results show that:(1)the existence of accidental eccentricity reduces the ultimate lateral load-carrying capacity of RC frame-shear wall structure,and aggravates global damage with more cracks forming at structural components perpendicular to motion direction;(2)the structural ductility versus accidental eccentricity curve is a zigzag-shaped curve,with slow growth and sharp decline;(3)eccentricities are offset by their reversed counterparts on adjacent storeys,and the ultimate lateral load-carrying capacity of structure increase while ductility decrease,compared to models with equivalent eccentricities all in the same direction.Aforementioned models with accidental eccentricity ratios of 0%,5%,and 10% are selected to investigate the mechanism of torsional and lateral stiffness degradation,as well as pattern of shear forces redistribution.From the analysis results,the conclusions can be drawn that 10% accidental eccentricity has a significant impact on the process of shear forces redistribution among certain storeys,and slow down the rate of stiffness degradation of frames on “stiff” side;that in comparison with torsional stiffness,the global degradation of lateral stiffness instead is more vulnerable to the negative influence of accidental eccentricity.