Reseach On The Calculate Method Of Stiffness On Step-terrace Structure And The Plastic Seismic Performance

The structure of the hillside building will always make the constraint at elevation at the bottom of the building great different for the height of the ground is different. Step-terrace structure is a kind of ground structure. In this structure, the bottom surface of a building is set on the ground bases which are at different elevations, and beneath the highest ground point, the floors are set up according to the floor height. In the vertical, the apparent irregularity exists between the lateral resistant ability of lateral force-resisting elements of this structure and the inner of the floors, which makes the function of this structure is different from regular ones..This paper talks about the step terrace structure. It will start with the single-span, restricted frame with unequal bottoms, and use the method of mechanics to deduce the expression for the stiffness of the lateral-resisting element under this structure and analyze the effect factors and characteristics of the lateral-resisting element; secondly, it will transfer the step terrace structure into restricted structures with unequal bottoms, and carry out the calculate method of stiffness of the bottom according to the principle that the stiffness will be the same after two models are transformed with each other; finally, it will do the Push-over analysis with the FEA software, and study the plastic seismic performance under the horizontal load.The major conclusions are as following:1. Due to the unequal restrictions of the hillside building on the bottom,the striking angle of the column on its end will get apparent differences. Application on the D-value method to calculate the lateral-resisting stiffness with bring about great error.This article arises the calculation method under the consideration of the aforementioned factor ,which is based on the theoretical derivation of the unequal stricted frames.After that,some examples are made to prove the validity.2.With the affection of the unequal restrictions on the step-terrace structure at the bottom,the distribution of the lateral-resisting stiffness on the structure comes to be non–homogeneous both along the vertical and horizontal directions. Compared with the conventional structure, the performance gets even more unfavourable and antiseismic.3.To increase the stiffness ratio of the step-terrace structure at the bottom will be favourable to make full use of the dissipative ability of the upper elements. Meanwhile,it will avoid the bottom of the strcture becoming apparent flimsy layer.So,controlling of the stiffness ratio between layers at the bottom is one of the key factors during the design of step-terrace structures.4.The stiffness of the ground elements is stronger while the deformability is relatively weaker in the step-terrace structures.The deformability could be improved if the former's stiffness is improved properly,which will also abate the excessively concentraion of elastic-plastic deformations on weaken parts, make more components into elastic-plastic statement, improve the overal deformability and dissipative ability,and advantageous to improve the intergral seismic performance of the structure.