The Seismic Performances Study On The Transverse Column Grid-intensive Spring Vibration-isolated Foundation Of Turbo-generator

With the increase of turbo generator’s installed capacity,the infrastructure which supports turbine becomes complex.Two-column pillars in turbine foundation of the past large power plants is common.But as the installed capacity becomes larger,both equipment and disturbing force of steam turbine have increased substantially,so the structural scheme that turns two-column into four-column partly is introduced.Because of the changes in structural form,traditional design methods cannot guarantee safe operation of the unit when an earthquake occurs,which calls for special research.This paper takes a 2x1 100MW spring vibration isolation foundation of turbo generator as the prototype,a scaled model of 1:8 is designed and constructed,and the following research work is carried out:First,through the excitation test,the natural vibration characteristic parameters of the spring vibration isolation foundation are obtained,including natural frequencies,vibration modes and damping ratios.It is worth noting that this model is equipped with a condenser and the low-order vibration modes of the condenser are obtained,creating conditions for dynamic response analysis of the condenser.The numerical model of the spring vibration isolation foundation and the non vibration isolation model under the same conditions are established by ABAQUS software.The two types of structures’ dynamic characteristics are compared,it fully illustrates the important role of spring vibration isolators in improving structural dynamic characteristics.Second,by using hammering method to test the dynamic stiffness of the cross beams,the dynamic stiffness curve of each bearing seat in the range of 25Hz±5%are obtained.Through the pseudo dynamic test of 7 degree frequently occurred earthquake、7 degree basic earthquake and 7 degree rare earthquake,the seismic response of structure is obtained.It includes platen speed time history,acceleration time history,restoring force time history,displacement time history;displacement time histories of the capital、the condenser and other critical locations;time history of the strain,crack distribution and development etc.The results show that:the dynamic stiffness values of each bearing seat are greater than 4*106kN/m which meets the requirement of the manufacturer.under the action of 7 degree frequent seismic and basic intensity seismic,platen displacement is small,the strain of steel bar is far less than the yield strain.The inter story displacement angle is less than the limit value of elastic inter story displacement angle according to the "Seismic Design of Buildings".The structural deformation is still basically in elastic range.Under 7 degree rare earthquake,the structure shows a certain elastic-plastic,the maximum strain of steel bar has not yet reached the yield strain.The inter story displacement angle is less than the limit value of the elastic-plastic displacement angle.The deformation of columns located in where the density changes in column-grid is much smaller than the others.That’s favorable to the structure.As a whole,this column grid-intensive foundation is in line with the"seismic design code" standard.The transverse column grid-intensive makes full use of the characteristics of continuous beams to decrease bending moments,avoiding layout form of bulky corner columns,thus the mechanics performance is more evenly.and creating a flexible space for the process.