故宫神武门动力特性及地震反应研究

Study on Dynamical Character and Seismic Response of Shen-Wu Gate in the Forbidden City

中国古建筑以木结构为主,千百年来历经多次地震考验而保持完好。为研究古建筑的抗震性能,以故宫神武门为例,通过引入反映古建筑榫卯及斗连接的半刚性节点单元,建立了有限元模型;通过模态分析,获得了神武门的主要频率和振型;通过输入三向Elcentro波(加速度峰值400gal),研究了典型节点的地震响应曲线,并讨论了斗、榫卯节点、侧脚及基底约束等构造对神武门抗震性能的影响。研究表明:神武门的基频为1.07Hz,振动形式以平动为主,在8度罕遇地震作用下,结构产生的变形很大,但能够保持稳定的振动状态;斗、榫卯节点、侧脚等构造均有利于神武门发挥其抗震性能。

Chinese ancient buildings are mainly made of wood, for thousands of years they have experienced sorts of earthquakes but remain intact. In order to study aseismic character of Chinese ancient buildings, Shen-Wu Gate in the Forbidden City is taken as an example. By introducing 2-node spring element which can simulate Tou-Kung and Tenon-Mortise joints, finite element model of Shen-Wu Gate is built. By modal analysis, the main frequencies and modes of Shen-Wu Gate are obtained;Then Elecentro waves in 3 directions （peak value reaches 400gal each） are imposed on the model, and seismic response of typical nodes and elements are studied. Aseismic constitutions such as Tou- Kung, Tenon-Mortise joint, Cejiao, base conditions and so on are also discussed. The results show that the base frequency of Shen-Wu Gate is 1.07Hz,whose main modes are of translation; Under 8-degree intensity of setdomly occurred earthquake, it produces large displacement but remains stable vibration status;Constitutions such as Cejiao, Tou-Kung, Tenon-Mortise joints and so on are all helpful for seismic resistance.