With the development of Elisha Otis’ elevator in 1853, the history of high-rise buildings begins. Since then the rapid development of the city and the increase in population due to the Industrial Revolution have led to the development of high-rise buildings in New York and Chicago, a choice for the efficient use of limited land due to overcrowding and expansion of the city. The development of high-rise buildings, which began mainly in the United States. However, since the 2000s, due to the development of construction technology and digital technology, high-rise buildings have become tangible in expressing the landmark symbolism of the country and the city in an environmentally friendly and irregular form as well as high competition.

The purpose of this study is to identify the core characteristics of irregular high-rise buildings and the present guidelines applicable to the initial design stage. In particular, the area of the ground layer core and components of the ground layer core, as well as the shape characteristics, are to be analyzed. The analysis of the characteristics of core planning of these unstructured skyscrapers is expected to serve as a basic material for the research as well as the practical guidelines applicable to the initial planning of unstructured high-rise buildings.

To analyze the characteristics of irregular high-rise buildigns cores, the buildings listed in the CTBUH were completed or under construction until 2018. In order to derive more objective analysis results, the examples included unstructured high-rise buildings corresponding to ‘buildings with more than 30 floors or 120 meters or more’

In the study, the basic data of the analysis of the ground layer for each purpose and type of unformatted high-rise buildings that have been completed or under construction have been established, and the guidelines for the initial design of core of unformatted high-rise buildings are provided based on this research. The result are as follows.

● First, in order to confirm the combination of plan type and core type of unstructured high-rise buildings use case, we analyzed the combination style through form cases according to each classified use design method.

● Second, the calculation of the core area of the ground layer of irregular high-rise buildings was carried out by Auto CAD based on the results of case analysis classified by usage and type of the aboce three chapters.

● Third, analyze the inside of the core structure wall by utilizing the adta drawn through Auto CAD. Analyze the components of the reference layer core to classify the major and minor components and then calculate the number of elements and the area of the elements placed in the ground layer for each case.

● Fourth, the previously developed core area and composition analysis were specified to analyze the area of the major components of the ground layer core and the effective ratio including the major components.

The results of this study, conducted in the above manner, are as follows : irregular high-rise buildings can be classified according to the shape or sue of the buildings. TAPER-Curve and TWIST forms are the most distributed of the unformatted forms composed of double bending, and the plane and core shapes of the ground layer are the most commonly used, such as rectangles and circles. The result is a trend of core area relative to the total floor area of the buildings. The classification of the effective ratio of ground layer cores by type of core indicates that the most commonly used core types for planning irregular high-rise buildings are square, round, and oval, with elliptical cores being the most efficient and relatively inefficient.

The results will help us understand the rational core plan during the initial design phase of an irregular high-rise buildings, expect the analysis results to be used as practical guidelines, and will also be used as basic data for the related research.