Research Of Elastoplastic Second-order Stability Of Steel-asphalt Isolation Device And Its Engineering Application

Isolation technology has a long history.The base isolation technology that emerged in the 1960 s has undergone a lot of research,experiments and engineering practices at home and abroad,especially the test of strong earthquakes,which proves that this is an effective way to reduce the loss of building structures.Compared with traditional seismic methods,seismic isolation technology has its unique strengths,and its promotion and application prospects are huge.It has developed very rapidly in recent years.Earthquakes are a kind of natural disaster that is extremely sudden and has great destructiveness.It is related to human life and property safety.China has a vast area of land,about 70% of which is in the earthquake zone.Moreover,China is a big country with unbalanced development.In the construction process of houses in many villages and towns,due to lack of earthquake awareness,it has not done the n ecessary earthquake resistance,so that the buildings are easily damaged or even collapsed when a minor earthquake occurs.Our research group has proposed a new type of seismic isolation technology that is economical,safe,simple,and effective in isolation from the contradiction between the high price of conventional seismic isolation technology and the backwardness of economic conditions in rural areas in China.In order to give full play to the bearing capacity of isolated vertical reinforcement under frequent earthquakes,the elast ic-plastic second-order instability of steel-asphalt isolation device was studied.Through the method of finding the nonlinear curvature by the equivalent bending moment,a linear or nonlinear relationship between the real bending moment and the real curva ture of the vertical reinforcement was obtained under any vertical load and horizontal load.Then,using the principle of virtual force and plane strain assumption,the two order pushover analysis method of elastic-plastic static loading with gradual increase of vertical and horizontal loads was used to make the two order elastic-plastic instability calculation for the vertical steel bar under various working conditions,on the basis of two order elastic instability design theory of steel-asphalt isolation device.Ultimate bearing capacity of isolated vertical steel bars under various working conditions was obtained,and then the fitting algorithm of the ultimate bearing capacity of the isolated vertical steel bar under various working conditions was obtained,and then a design method for the two order instability of the elastic-plastic deformation of the steel-asphalt isolation device was proposed.The reliability of the design method was verified by shaking table test on a variety of working conditions.The results show that when the section bending moment of the end section of the isolated steel bar is much more than the elastic limit bending moment,the depth of the fiber in the edge of the cross section enters the plastic,the specimen is still not slump or tilted,and the steel bar still keeps normal work and has sufficient safety reserve.Therefore,according to this method,the calculation of the two order instability ultimate bearing capacity of the elastic-plastic deformation of the steel-asphalt isolation device is partial to the safety.Under this design method,the ultimate bending moment of the end of the steel bar can be improved 1.25~1.6 times under various working conditions.Therefore,the theoretical bearing capacity of the steel-asphalt isolation device is improved,which makes the seismic isolation steel less used,the total stiffness smaller and the isolation effect better.In addition,based on the existing results of this technology,combined with the research content of this paper,the design ideas and design flow of the steel-asphalt isolation device are explained.Finally,taking the design of a three-story house as an example,the design flow of the steel-asphalt isolation device was gradually demonstrated.