Evaluation of seismic behaviour of Cheomseongdae using dynamic centrifuge model test

Cheomseongdae is known to be the oldest astronomical observatory in Asia. According to historical records, the Gyeongju area, where Cheomseongdae is located, suffered from numerous medium-scale earthquakes. Cheomseongdae has a masonry structure, which is apparently vulnerable to horizontal dynamic loads such as earthquakes. However, despite its appearance, features such as the filler of the lower half, inner irregular-shaped stones which can induce high frictional resistance, eight long horizontal tie stones inside the artefact, and a grid of interlocking headstones increase its resistance to horizontal dynamic loads. Dynamic centrifuge model tests were performed on Cheomseongdae in order to evaluate the seismic response characteristics of this architectural heritage structure. Model tests were executed on two 1/15-scale models: one which was an exact duplicate of the original Cheomseongdae and the other without the long horizontal tie stones and grid of interlocking headstones. On the basis of the amplification patterns in the time and frequency domains, the differences in seismic behaviour between the two Cheomseongdae models, and a broken stone at the 19th layer during tests, the long horizontal tie stones and headstones were found to increase the seismic resistance within Cheomseongdae and provide a glimpse of the 'seismic design' of our ancestors.