A modelling method of exposed column bases of steel buildings is proposed, and influence of modelling to the dynamic behavior of building structures is discussed. Exposed column bases are widely used as connection components, which can fix low to mid rise steel buildings to foundations. Most of these components transmit internal forces by contact and friction. The relationship between overturning moment and rotational angle can vary from linear elastic, non-linear elastic to elastoplastic according to the increase of input loads[1]. Since rotational behavior of exposed column base can affect bending moment distribution of 1st-story columns, which shall withstand the largest story shear force, appropriate modelling of column bases is important to assess dynamic responses under large seismic inputs of steel building structures accurately. Here, a 3-story steel building, which is the specimen of shake-table test conducted at E-Defense, NIED, Japan[2], is taken as the target structure. One column of the target structure is extracted and its exposed column base and 1st-story column are discretized by using solid finite elements. Other components are modelled by using beam elements. It is shown by comparing the numerical and experimental results that the fundamental frequency and relationship between bending moment and rotational angle of the numerical model correspond well. It is also shown that the proposed model can reproduce the input-dependency of rotational property of the column base, and assess the dynamic characteristics of the target structure under various types of input motions. REFERENCES [1] K. Sato, et al., A study on anchorage of column base using casted steel base plate -HIBASE- Parts 2 and 3, Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, Structures, pp.2031-2034, 1981 (in Japanese) [2] NIED, Experimental Study on Seismic Measures for Steel Frame Buildings damaged by Past Earthquakes, E-Defense Test Data Archive (ASEBI), E201303, https://doi.org/10.17598/NIED.0020-E201303