Torsional Response Of The Superstructures By The Incident Waves

The direction of earthquake input in current seismic design is mostly horizontal.However,if the epicenter distance is small,the seismic wave input direction has a certain spatial angle with the horizontal plane.At this time,simplifying the seismic wave into horizontal is not in line with the actual situation.The torsional displacement response with inclined seismic waves cannot be ignored,and will cause the column and anti-lateral force component from the simple flexural-shear force state to the complex stress state.So the form of the component failure mode becomes unpredictable.Therefore,it is necessary to deeply study the torsional response of structure with inclined seismic waves.Firstly,the elastic wave theory is applied to deduce the acceleration of the torsion caused by seismic wave,and the torsional displacement is obtained by Wilson-? method.Then a two-dimensional soil model is established based on the infinite element artificial boundary theory,and the reliability is verified by a simple harmonic wave.Then,a three-dimensional finite element analysis model of the soil-embedded foundation was established.The numerical solution of the torsion was obtained and compared with the theoretical solution.Besides,the seismic results of free field soil are also analyzed,and the reliability of the model is verified.Finally,numerical simulations were performed.The factors that considered the torsion included the angle of the shear wave,the wave velocity,the structure height,the distance between adjacent structures,and the basic shape.In the study of each parameter,the influence on input motions for rigid embedded foundations is first analyzed,and then comes the influence of the parameter on structure.By controlling the variable method,and the following conclusions are drawn: The variation of the spatial incidence angle directly affects the torsional response of the foundation and the superstructure;the torsion decreases with the increase of the shear wave velocity under the same angle of incidence;the superstructure will have a larger torsional response when the frequency of incident wave is close to the univalent natural vibration frequency of the superstructure;Under the same space incident angle,the torsion of the superstructure is much greater than the torsional response of the basic input motion;the existence of the adjacent structures will increase its torsional response,and the increase of the torsion will be reduced with the increase of the adjacent structures distance;the larger the foundation shape coefficient,the greater the torsional response.