Journal of the Korean Geotechnical Society ISSN:1229-2427(Print) 2288-646X(Online) 한국지반공학회 논문집

According to the revision of the Housing Act in 2013, it has been possible to carry out an apartment remodeling project involving two to three floor vertical extension. The remodeling project with vertical extension requires foundation  reinforcement because structural safety due to additional load and enhanced seismic criteria must be met. In this case, structural analysis is performed to analyze the load distributed to existing PC pile and reinforced additional pile. The vertical stiffness () of the pile is required for structural analysis, but the research on the 20～30 year old PC pile stiffness is very limited. In this paper, the stiffness of the PC pile in accordance with the change of diameter and length was analyzed by examining the results of 38 field pile load tests performed during the construction of the apartments in the 1990’s. As a result of the analysis, the pile stiffness decreases with the increase of the length-diameter ratio (). In addition, the results of on-site pile load test are compared with the coefficient ‘a’ for estimating pile stiffness proposed in Korea Highway Bridge Design Standard (2008) and the Pile Foundation Design Guideline of Korea Railroad Corporation (2012). It shows that ‘a’ obtained through the estimation of the literature is very similar to the field test results in the range of .