Study On The Key Technology Of Existing,Masonry Buildings Reinforcement On Soft Ground

With decades of research and practical experience,the application of seismic isolation technology has become mature.The type of building sites like ?,?,? is appropriate for seismic Isolation design,and a better base type should be chose.The reason is many engineering experiences in and outside our country show that extension of period of the structure on soft soil ground will likely increase the seismic response.Isolated structure is generally.not recommended built on soft soil base like ? in Our country.But,there is a large number of soft soil sites in our country,such as tianjin and Shanghai has a sizable buildings built on soft soil ground,corresponding development is demanded.Therefore,research on isolation technology in the field such as ? is essential.In order to discuss the key techniques of seismic reinforcement for existing masonry buildings on soft soil sites,the main research work(and conclusions)of this paper is as follows:1):Using the analysis software of finite element ETABS,a 5-span 6-layer brick wall with natural rubber isolation bearing of different diameters is established.With the design value of the maximum shear stress of the wall less than the shear strength of masonry structure as the target,We explore the reasonable size of the joists and give the recommended value;On this basis,the reasonable range of vertical stiffness difference of adjacent supports is studied and the recommended value is give.In general,the larger the span,the smaller the ratio of the height and span of the wall,the worse for reducing the shear stress of the wall;The lower limit of vertical stiffness of adjacent supports decreases with the increase of the ratio of high and span.of the wall.2):In combination with the conclusions in the previous chapter,the analysis software of finite element ETABS was used to establish the three-dimensional masonry structure model,and the seismic isolation model and non-seismic model of natural rubber isolation bearing with different diameters on the foundation were simulated numerically,and the influence of the length of period of seismic wave(the typeof site)on the seismic response of the structure was discussed:Under middle-class Seismic action,theaverage shear force response of the first layer and the average response of the damping coefficient both increase with the increase of the diameter of the bearing,which does not change with the change of the soft.The damping coefficient is greater than 0.4,and even close to 1 in some soft soil sites.It is concluded that the key to seismic isolation in soft soil sites is the use of elastic sliding plate bearings and the use of combination of different kinds of bearings.And it is possible to remove the roof of the isolation layer,this conclusion does not change with the site.Under middle-class Seismic action,theaverage shear force response of the first layer and the average response of the damping coefficient both increase with the increase of the diameter of the bearing,which does not change with the change of the soft.The damping coefficient is greater than 0.4,and even close to 1 in some soft soil sites.It is concluded that the key to seismic isolation in soft soil sites is the use of elastic sliding plate bearings and the use of combination of different kinds of bearings.And it is possible to remove the roof of the isolation layer,this conclusion does not change with the site.Under severe earthquake action,in the hard ground soil,displacement of isolation layer decreases as the isolation layer stiffness increase,and on soft ground soil,through the layers of displacement is not obviously decreases with increasing isolation layer stiffness,when the level of isolation bearing stiffness in somecertain value,the displacement of isolation layer increases with the stiffness increases,which is different from the two indicators of mean shear force and damping coefficient of the first layer.3):With a masonry buildings model of aseismic reinforcement engineering using the finite element analysis software SAP2000 for isolation of key technology,the use of elastic slide bearing on soft soil ground is a key to the success of isolation,in order to reduce the displacement of isolation layer under severe earthquake action there shall be equipped with the damping energy dissipation of lead core rubber isolation bearings,the soft soil ground isolation should consider the combination of a variety of types of isolation bearings.The time history analysis of the isolated structure model after removing the roof of the isolation layer in the actual project shows that the displacement of the bearings are little affected by the absence of the roof of the isolation layer.