• Korean Journal of Heritage: History & Science
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• v.53 no.4
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• pp.100-117
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• 2020

National Treasure no. 101, the stupa of State Preceptor Jigwang from the Beopcheonsa Temple Site in Wonju has been transferred from place to place and reassembled several times since it was built. In particular, overall dismantling and repair was carried out in 1957 to restore parts damaged by bombing during the Korean War. Documented information on the repair process and materials used at that time does not exist. However, various types of metal materials used for this stupa have been identified during conservation work. Besides clamps anchor bolts, 9mm-thick circular rebars were mainly used for joining the parts of this stupa, while circular rebars and wires of various thicknesses were used for joining the parts with mortar restoration materials. Although deformed bars are typically used for stone pagodas classified as architectural structures, smooth circular rebars were used in this case. In terms of restoration using mortar, material shapes were transformed, bound alternately, and twisted irregularly to improve bonding strength and coherence in order to insert restoration materials and to bolster structural weaknesses. In addition, metallographic analysis showed the material to be hypo-eutectoid steel with low carbon content. Many non-metallic inclusions in the shape of drops of different sizes were included, which do not affect the whole elemental composition due to the very small quantities involved. Qualitative and EPMA analysis of Mn and S, which were not identified by SEM-EDS area analysis, established an even distribution of MnS in crystal grains of the microstructure, regardless of the shape of the samples. It is presumed that secondary homogenization and softening might have been conducted after manufacturing to facilitate the working process. Furthermore, in consideration of properties indicating that the thinner the steel is, the less carbon content contained and the greater the elasticity and elongation, it is judged that restoration work was ordered.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.6
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• pp.87-98
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• 2009

It is well known that reinforcement details in the plastic hinge region of bridge piers give the most important effects on the seismic performance of bridges, from investigations of bridge failures in many earthquake events and in laboratory tests. Longitudinal reinforcement details give larger effects than lateral reinforcement details do. The lap-spliced longitudinal steel shows slip during earthquake events, which results in low ductility and inadequate seismic performance. However, before the issue of the earthquake design code, a considerable number of bridge piers were constructed with lap-spliced longitudinal steel in the plastic hinge region. Therefore, a large amount of research has been conducted on the seismic performance and retrofit of circular and rectangular shaped bridge columns with lap-spliced longitudinal steel. However, research on wall type piers is very limited. This paper investigates the seismic performance of a pier wall by a quasi-static test in the weak axis direction and proposes a retrofit method. From the test with variables being the longitudinal steel detail and the transverse steel amount, it is shown that the currently used definition of yield displacement is not adequate. Therefore a new definition of yield displacement for the ductility investigation for a pier wall is proposed. In addition, a retrofit method by steel plates and bolts is proposed to improve ductility, and test results show that slip of the longitudinal steel is prevented by up to a considerably large displacement.

• Journal of the Korean GEO-environmental Society
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• v.17 no.11
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• pp.15-21
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• 2016

Nowadays, some studies have been performed for rockbolt method widely used in Korea. To make large slopes, tunnels or rock structures stable, supporting systems, such as anchor bolt, rock bolt which are developed recently, are commonly used. In this study, laboratory pullout tests were carried out to compare the characteristics of rock bolt that is most widely used with ones of rock bolt by newly developed circular model testers. Re-pullout test for the rock bolt in which loading and unloading cycles are repeated several times showed that the maximum pullout load is almost constant irrespective of the number of loading cycles, which may be due to no failure between rock bolt and filler that is filled with soils and concrete as a substitute. A development of rock bolt fillers as supporters using to protect people in tunnels and slopes is reviewed as a probable man-made hazard after excavation works. The functions of the grouted rock bolts associated with reinforcement effects also should be assessed in this study, which develop the sealing apparatus preventing from overflowing mortar out of a rock bolt hole for securing safety in the tunnel and slopes in order to secure stability named the sealing packer.