Studies On Aseismic Behavior Evaluation And Seismic Broken Mechanics Of Ancient Masonry Pagodas

The restoration and strengthening of Xi'an Xiang-ji Temple Pagoda is introduced in this paper. And then using finite element analysis tool ANSYS, the 3D solid finite element analysis model of Xiang-ji Temple Pagoda is established, and the modal analysis and earthquake response analysis of the pagoda are made. At last the aseismic behavior of Xiang-ji Temple Pagoda is evaluated, and the seismic broken mechnics of ancient masonry pagodas are discussed. Main works and conclusions are as follows:1. The destroy factors to ancient masonry pagodas were analysed, and the restoration and Strengthening of Xi'an Xiang-ji Temple Pagoda is introduced.2. The 3D solid finite element analysis model of Xiang-ji Temple Pagoda is established, and found that the determination of mortar grade could influence greatly to the analysis results of dynamic properties of pagoda.3. Using two methods which are "Judging by comparing with similar ancient pagodas' field test dynamic properties results" and "Judging by comparing with empirical formulas", this paper determined the credibility of the finite element model established by this paper.4. This paper put forward a method called "mainly evaluating to the overall structure judging by ultimate displacement, and supplemented by evaluating to constructional details judging by ultimate stress" to evaluate the earthquake response of ancient masonry pagodas.5. This paper put forward the two judgement criterias to determine the damaged states of ancient masonry pagodas: according to the elastic drift angle, and according to the principal tensile stess of masonry units.6. Ajusting and inputing EL-Centro wave, Taft wave and Lanzhou artificial wave, using time-history analyse method, this paper analysed the earthquake response of Xiang-ji Temple Pagoda, and then evaluated the aseismic behavior of Xiang-ji Temple Pagoda according to the above evaluating methods and judgement criterias. The results showed that:(1) Under 8 degree minor earthquake's action, the main structure of Xiang-ji Temple Pagoda will stay at elastic stage, almost no damage. But minor cracks will appear at the weak positions of Xiang-ji Temple Pagoda.(2) Under 8 degree seismic fortification intensity's action, the main structure of Xiang-ji Temple Pagoda will suffer serious damage, and the distruction state is very consistent with the real destruction state.(3) This paper inferred that the subsequent destruction state of Xiang-ji Temple Pagoda was made by a north-south 8 degree earthquake in the history.(4) The 8st layer and 9st layer are weak layers of Xiang-ji Temple Pagoda. The axle of the south facade, the top of the four arches of the bottom layer, and the position where pagoda facades contact with the ground are the weak positions of Xiang-ji Temple Pagoda.7. Researched how the damper will impact at the structure earthquake response, and found that: the structure earthquake response under EL-Centro wave is not as sensitive as the earthquake response under Taft wave; And when the damper be smaller, the earthquake response will be greater, the time when the greatest response appears will postpone.8. Concluded the seismic broken mechnics of ancient masonry pagodas, explained theoretically the earthquake damage phenomenon of ancient masonry pagodas.