The purpose of this study is to analyze the cause of damage to the three storied stone pagoda of Bulguksa temple in GyeongJu. This report is attempted to making reinforcement and conservation plan through investigating and analyzing the cause of damage to that. The damage is caused by occurring of stress, degrading of stone strength, changing of underground soil structure, natural disasters and so on. Compressive stress, shear stress, bending stress and lateral pressure affected to the pagoda since built up. Ultrasonic examination data tells the strength of the stone. According to this result, strength of the stereobate stone materials is enough to support the weight of the upper ones. But we could found many other factors of the damage could consider, for example the problems occurred on building the pagoda construction and the weakness of the stone material(soft rock). And many environmental factors being changed in soil structure(subsidence of soil and degradation of bearing power of soil and freezing and melting of soil) can be seen as the cause of the damage. Natural disasters like earthquake, lightning and heavy rain were also thought to give direct impact to the damage. At last Concentration of compressive stress caused the crack and exfoliation on the stone materials and shear stress, bending stress and lateral pressure were main causes of the stereobate stone materials shearing.

Abstract
1. 머리말
2. 불국사 삼층석탑 현황
    2-1. 석탑의 형태 및 구성
    2-2. 파손현황
3. 파손원인
    3-1. 응력발생
    3-2. 석재강도 저하
    3-3. 지반구조 변화
    3-4. 자연재해
    3-5. 파손원인에 대한 대응책
4. 맺음말
References

• 지성진(국립문화재연구소 건축문화재연구실 학예연구사) | Ji, Sung-Jin Corresponding author