Study On Seismic Damage Of RC Frame Structure Under Uneven Settlement Of Foundation

Uneven settlement of foundations is one of the common engineering hazards.Uneven settlement of foundations not only affects the normal use of the building,but can also cause damage to the superstructure or even collapse.Therefore,the problem of uneven settlement of foundations has been an important research hotspot in the field of engineering,but most of the existing results focus on the static damage of structures under uneven settlement of foundations,and the research on the seismic performance and seismic damage of structures under uneven settlement of foundations is very limited.A systematic study on the seismic damage of structures under uneven settlement conditions is of great value for the assessment of the seismic performance of such structures and the determination of repair and strengthening solutions.Therefore,in this research article,a three-dimensional solid refinement finite element model is established using numerical simulation methods to carry out dynamic time course analysis against the background of the common foundation uneven settlement engineering disease in high intensity wet sinking loess areas.The model considers the cumulative effect of plastic damage of the structure,and analyses the deformation,energy dissipation,damage evolution process and the law of damage mode of reinforced concrete frame structure by varying different settlement areas,settlement volume and ground vibration intensity.The main research elements of this study are as follows:(1)The seismic response law of integral frame structure under the action of uneven foundation settlement and earthquake is discussed.Through the nonlinear analysis method,the influence of different settlement area and amount on the seismic response of the whole frame structure is simulated and calculated.The results show that the natural vibration period of the structure increases with the increase of the uneven settlement of the foundation.Under the condition of uneven settlement,the center of mass of the structure deviates from the rigid center,resulting in the increase of the torsional deformation of the structure under the action of earthquake,which further aggravates the earthquake damage degree of the structure.When the settlement increases,the structure displacement increases,but with the increase of the input seismic peak acceleration,the influence of uneven settlement on the structure displacement is gradually weakened.(2)According to the influence of the uneven settlement of the foundation on the energy dissipation of the whole frame structure,the proportion of the damping energy and the hysteresis energy of the structure under the different settlement conditions and the earthquake together in the total input energy of the earthquake is calculated.The results show that under the premise of a certain seismic input energy,with the increase of the uneven settlement of the foundation,the damping energy of the structure takes a smaller proportion of the total energy dissipation,and the hysteresis energy takes a larger proportion of the total energy dissipation,but the damping energy always takes a larger proportion of the total energy dissipation of the structure.(3)The development of seismic damage and unit damage ratio of whole frame structure under the condition of uneven settlement of foundation are analyzed.The results show that the uneven settlement of the foundation has a great influence on the seismic damage degree of the components in the settlement area and the adjacent areas of the settlement area.The damage degree of the components in the adjacent area of the settlement area is the most serious under the action of the uneven settlement of the foundation,and the damage degree of the components in the adjacent area is aggravated when the seismic excitation acts together.The unit damage ratio of the first floor of the structure is relatively large under the earthquake action,and the unit damage ratio of each floor of the structure gradually decreases with the increase of the floor.With the increase of the uneven settlement of the foundation,the damage proportion of each floor of the structure under the earthquake is increasing.(4)The damage evaluation criteria were established based on the concrete damage grade and damage variable,and the local components of the structure were divided into fine grids to compare the development of earthquake damage and the degree of earthquake damage of components under different settlement amounts.The results show that the damage degree of the frame column in the settlement area is weaker than that of the frame column without settlement due to the uneven settlement of the foundation,and the damage development is relatively lagging behind in the earthquake process.The seismic damage degree of the adjacent frame beam and floor in the settlement area shows a positive correlation with the settlement amount.