| The grounding modes of the upper and lower sides of the step-terrace frame structure are unequal,so the mechanical performance of the step-terrace frame structure is significantly different from that of the ordinary frame structure.The prominent problems of step-terrace frame structure in mountain area are uneven vertical stiffness,sudden change of floor bearing capacity and concentrated deformation of upper ground layer.Adding the swing wall can effectively control the overall deformation capacity of the step-terrace frame structure in mountainous area.The study shows that SSI effect obviously changes the dynamic characteristics of the structure.Therefore,SSI effect must have an important influence on the seismic performance of the frame swing wall structure system.Only by understanding this influence law and considering it in practical engineering,can the expected seismic performance be achieved Shock effect.However,the current design theory and analysis method of frame swing wall structure are based on the assumption of rigid foundation,without considering the influence of SSI effect on the dynamic response characteristics of the structure,it may overestimate the damping effect of frame swing wall structure,leading to structural insecurity.This thesis systematically studies the influence of SSI effect on the seismic performance of the frame-swing wall structure in mountainous area,and discusses the influence of different soil conditions,swing wall location,swing wall stiffness ratio,the number of floors and spans and the energy dissipation capacity of the structure on the seismic response of the structure.In order to verify the feasibility of SAP2000 model used in elastic-plastic analysis,the quasi-static test of the frame structure in mountain area completed by Chongqing University Laboratory is simulated.Based on SAP2000,a series of 7-degree(0.15g)mountain step-terrace frames and corresponding structural models considering SSI effect and additional sway wall are established to explore the influence of SSI effect on seismic performance of mountain step-terrace frame sway wall structure under different conditions.The main conclusions are as follows:(1)The seismic performance of the frame structure with or without SSI effect and with or without sway wall in the condition of medium soft soil and medium hard soil is compared and analyzed.It can be seen that SSI effect will prolong the natural vibration period of the structure.The softer the soil is,the greater the degree of extension is.After adding swing wall,the effect on the natural vibration period of the structure is small.SSI effect will increase the maximum story displacement,maximum inter story displacement angle,maximum story shear and beam column energy consumption.When SSI effect is not considered,the dynamic response of medium soft soil forward seismic wave to structure is much greater than that of medium hard soil forward seismic wave;when SSI effect is considered,the dynamic response of structure in medium soft soil condition is greater than that in medium hard soil condition.When the SSI effect is considered,the maximum story displacement,maximum inter story displacement angle,maximum story shear force and energy dissipation capacity of the frame swing wall structure are reduced,but the reduction is smaller than that without SSI effect.(2)The influence of the location of the swing wall on the seismic performance of the structure is discussed.When SSI effect is considered,the additional swing wall increases the SSI effect on the ground plane on the structure,and the degree of SSI effect varies with the location of swing wall.When the swing wall is set on the upper ground side,the deformation of the upper ground side of the frame structure is obviously improved.When considering the SSI effect,the deformation of the upper ground side is reduced,and the deformation of the top is increased.The structure deformation is ideal swing type,and the effect of SSI effect on the upper ground side is smaller than that of other layout methods.When the swing wall is set on the lower ground side,the maximum floor displacement of the upper ground side and the lower ground side is the same The curve of the maximum inter story displacement angle is a uniform inclined line,but the amplification effect of SSI effect on the maximum inter story displacement and the maximum inter story displacement angle of the upper ground plane is larger than that of other layout positions,so it will aggravate the concentrated failure phenomenon of the floor dropping frame structure,and the effect of SSI effect on the lower ground side is smaller than that of other layout methods;when the swing wall is set on the upper and lower ground sides,the control effect on the upper ground side is smaller The control effect of SSI effect on the lower grounding side is between that of the upper grounding side and the lower grounding side.(3)Because the structural stiffness will change when SSI effect is considered,the stiffness ratio of swing wall to structure will also affect the SSI effect of frame swing wall system.The control effect of swing wall on the weak floor of the frame structure with falling floors,that is,the upper ground floor and the upper floor of the upper ground floor,increases with the increase of the stiffness ratio,that is,the shear force of the weak floor decreases with the increase of the stiffness ratio;while the shear force of the top two floors of the frame swing wall structure with falling floors increases with the increase of the stiffness ratio,which makes the shear force of the whole floor more uniform,indicating that the swing wall is still weak when considering SSI effect However,the shear force originally concentrated in the weak layer can be evenly distributed to the upper layers,and the greater the stiffness ratio of the swing wall is,the more obvious the control effect is.When the SSI effect is not considered,the frame swing wall structure has a stable deformation mode when the swing wall stiffness ratio is 10.06%,and the shape of deformation curve changes little with the increase of stiffness ratio.When SSI effect is considered,the SSI effect increases with the increase of swing wall stiffness ratio.When the swing wall stiffness ratio is 14.56%,the frame swing wall structure begins to have stable deformation mode in medium soft soil;when the swing wall stiffness ratio is 20.17%,the frame swing wall structure begins to have stable deformation mode in medium hard soil.Therefore,the actual soil conditions should be considered in the design of frame swing wall stiffness ratio.(4)The number of story dropping and the number of story dropping span have different effects on the mass and stiffness of the frame swing wall structure.The change of the number of story dropping span has less effect on the frame swing wall structure considering SSI effect,and the change of story dropping number also changes the height of the sill.With the increase of story dropping number,the SSI effect of the structure is greater.(5)Compared with the case of rigid foundation,considering SSI effect,the proportion of hysteretic energy consumption of beams decreases,the proportion of hysteretic energy consumption of columns increases,and the proportion of beam column energy consumption decreases;after adding swing wall,the proportion of hysteretic energy consumption of beams increases,the proportion of hysteretic energy consumption of columns decreases,and the hysteretic energy consumption of beams and columns is more uniform The design concept of "strong column and weak beam" can be realized by increasing the ratio. |
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