The Research Of The Whiplash Effect Of Frame Structure

Due to the use of functional requirements, towers are frequently constructed at tops of most constructions at present, such as room for water tank or elevator and steel tower. But under the circumstance of earthquake, these towers would have some earthquake damage, and might cause serious influence to the main structures. Therefore, it is of significant importance for the actual engineering to research and analyze the different whiplash effect with different tower height and prevent or reduce its impact on the main structure.Using ANSYS software, this thesis gives four models (model one is the main structure of the building and three others are the structures with different tower height), does the modal and spectrum analysis and elastic analysis to each model and compares the results so as to obtain the influence of seismic responses of structures with different tower height. Through the research and analysis of the four models, this thesis has reached several conclusions as following:1. The thesis has drawn each natural frequency and modal participation factor through modal analysis of the four models. We know that, for the same model, the natural frequency changes with increasing modal order; the higher the tower is, the larger the structure of each modal natural frequency is (the larger cycle). In addition, the height of the tower will affect the structure of the main modes, turning into a high-level from low-level. Therefore, to some extent, it needs to be paid attention to the impact of the higher modes to building structure.2. Through the response spectrum analysis of each model from horizontal direction, the thesis has drawn layer displacement angle, floors and horizontal displacement of the seismic forces. The maximum deformation occurs at the corner of the top level of each model. The location of maximum deformation transfers into the top comer of the tower with towers settings. This suggests that the towers settings will increase the seismic response of the structure at the top.The growth of tower height makes the horizontal displacement of the top floor of the structure significantly larger and influences the displacement of floors below the top level; the towers settings change the displacement angle curve, the higher the tower is, the more complex the curve is.The towers settings have slight effect on the floor level of the bottom of the structure seismic forces and great effect on the top of the main structure, the higher the tower is, the greater the growth rate of the floor seismic force is, which is caused by the whiplash effect of towers, the higher towers is, the more obvious the whiplash effect is.3. Through the elastic time history analysis of each model on the Y-direction, the thesis has reached the conclusion that, for the same model, different seismic wave could obtain different maximum displacement and different acceleration. The higher of tower, the greater of displacement and acceleration, the amplification of the acceleration is more obvious which is bad for the structure. So choose a variety of seismic wave can better grasp the earthquake response of the structure.4. It can get that the results have little difference between spectrum analysis and time history analysis.This thesis has offered a method for the research of the influence of tower settings and changes of tower height to the main structure, which will be of assistance for the engineering design in the following years.