The 'Housing Act (‘14.04), which permits the remodeling of old apartment buildings, has been implemented. In particular, vertical remodeling is generally implemented by adding 2~3 floors above the top floor of existing apartments. Technically, it is necessary to reinforce the existing pile due to the increase of vertical, horizontal, seismic load, etc. However, the existing piles are loaded simultaneously and so each pile was constructed at limited base space for application of reinforcement method. The bearing capacity of existing piles decreases due to vertical expansion so the bearing capacity of the piles must be confirmed by the indirect method(laboratory test etc.) in the first safety diagnosis and by the direct method(field test etc.) in the second safety diagnosis.

Abstract
 1. 서 론
 2. 문헌에 따른 말뚝의 강성(스프링계수)평가
 3. 수치해석을 이용한 말뚝의 강성(스프링계수)평가
 4. 결 론
 참고문헌

• 박경한(한국시설안전공단 진단본부 교량·터널안전실) | Park, Kyung Han 교신저자
• 이태형(한국시설안전공단 진단본부 교량·터널안전실) | Lee, Tae Hyung
• 정수형(한국시설안전공단 진단본부) | Jung, Soo Hyung