Earthquake Response Analysis Of Communication Towers Fixed On The Top Of Buildings

In order to reduce the construction cost and satisfy the signal quality requirements, the communication towers are usually built on the top of existing buildings. These protrusions of buildings generally suffer serious damage under destructive earthquake. After the earthquake, the communication system is damaged, but the communication requirement dramatically increases at the same time. The residents in disaster area need internal communication for self-help, and the outside needs the damage information as soon as possible. This situation causes the congestion of communication. The destruction of communication brings great difficulties to the local people self-aid and the government’s emergency response action. This article is based on the damage examples of communication tower in earthquakes. The reason of the communication tower’s whiplash effect was studied. It is necessary to reduce the communication tower under the action of earthquake seismic effect through reasonable design and site selection.For the seismic response of communication tower, one of key points is the whiplash effect. The whiplash effect of communication tower on the top of exited buildings is analyzed in this paper. Communication tower’s whiplash effect happens when the communication tower’s natural vibration periods is close to the main structure’s. The several analysis methods for the seismic response of protrusion of buildings supposed by the design codes or other researchers are introduced and compared.Two communication towers’　and different layer structures’　FEM models are established in this paper. These composite structures are analyzed by the modal analysis, vibration mode decomposition response spectrum method and linear time history analysis. The variation trend of the periods of the composite structure, the seismic response of the communication tower and the main structure are studied with model analysis. Site categories’ and the main structure layer’s influence to communication towers’and the main structures’seismic response are also analyzed. At last, the seismic responses of these composite structures are studied by linear time history analysis method, inputting three different typical seismic acceleration records. The results are similar to the results obtained by mode decomposition response spectrum method.The research results show that the seismic response of communication tower can be reduced and the reliability of communication towers can be guaranteed by the reasonable seismic design and site selection.