Seismic Performance Analysis Of RC Frames On The Slope Designed By Displacementbased Method Using Viscous Dampers

RC frame on the slope is a typical structure with two or more different embedding ends and vertical irregularity.The structures are easily damaged by torsional effect under seismic action.One of the problems which still puzzle many scholars and engineering designers is how to improve the seismic performance of structures on the slope.A new method which combines displacement-based design method and energy dissipipation technology to improve seismic performance is proposed in this paper.The damping coefficient of each floor is caculated using the method which is proportional to floor shear force,and the installation scheme of viscous dampers at each floor are determined by torsional parrameter of the frames.The seismic behavior of RC frames on the slope with different floor and spans number under upper embedding ends are investigated by dynamic time-history analysis results under different earthquake action.The main conclusions achieved are five points:(1)Due to the plane and vertical irregularities,there is torsion effect which is caused by earthquake action,especially perpendicular to the direction of the slope.The torsion effect of the structure on the slope can be effectively reduced by the displacement-based seismic design method with proper damper factors assign plan.(2)The damping effect of displacement-based seismic design method of RC frames on the slope can meet the prospective performance objective.The damping effect of the dampers which are designed by this method is slightly reduced with the increased number of floor and spans under upper embedding ends.But they can still meet the required performance targets(3)The whole degree of structural plastic development is reduced in the step-terrace RC frames which have earthquake resistant capability due to the energy dissipation fo dampers.Along the direction of the slope,the first and second floor upper the scape are the weak story of the structure.However perpendicular to the direction of the slope,the weak story is in different position.It should be noted that different directions lead to different weak stories,during the process of seismic design.(4)As the floor number goes up the story torsion ratio is reduced in the structure above upper embedding ends which means the story torsion ratio of the first floor above upper embedding ends is the largest.Compared with the same floor after structural vibration damping,the difference of the torsion ratio is small,when the span number under upper embedding ends is 5.So the damping effect is unobvious.However with the increasing number of spans under upper embedding ends,the torsion effect is enlarged,when the floor number under upper embedding ends is 3.(5)Compared with the structure in one-direction earthquake input,the torsion effect of structure in two-direction earthquake is a little bigger.RC frames on the slope designed by displacement-based method using viscous dampers can meet the prospective performance object.