The Effect Of The Small Tower On The Main Structure In High-Rise Building

The high-rise buildings often set a small tower on the top roof for the function needs. The small towers which are beyond the top floor include stairways, elevators and steel tower. Because of its stiffness and mass is much smaller than the main structure, which in strong wind or seismic motions have a significant "whiplash effect", making it far exceeds the dynamic response of the main structure's. Previous earthquake damages show that under earthquake, the small tower will have serious damage or collapse while the main structure without damage, or damage of the case of very light.At present, seismic design of tall buildings with a small tower, generally separate the small tower and the main structure and calculate respectively. In China, the seismic design of the tower under earthquake use the increased factor to considered "whiplash effect". The main structure is generally not considered the impact of the tower. The main structural elements which is directly connected with the tower included in the tower when calculate the seismic impact under earthquake. However, the high-rise buildings which has a tower, while the vibration of the tower is bound to has the strong reaction to the main structure, so effect the dynamic characteristics and dynamic response of the main structure.In this paper, finite element analysis software SAP2000 model analysis is conducted. Analysis and comparison of three models:high-rise building with a small tower on the roof which the main structure and the tower work together; the tower placed in the ground; high-rise building without a tower. The following major elements:1. Find out why high-rise buildings with a small tower when vibration generated the whiplash effect.2. Using Mode response spectrum method to analyze the effect of the higher modes on on the seismic response of tall buildings with a small tower.3. Consider the following factors:different location of the small tower, different height of the small tower, different stiffness of the small tower, different height of the main structure. Models were established to compare the effect of these different factors on the dynamic response of the main structure and the tower.