Some studies have shown that the seasonally frozen soils have a significant effect on the dynamic properties of building structures, which will yield increases in the fundamental frequencies from summer to winter. The changes in frequencies, however, appear a wide range from 4% to 50%. The factors to control the magnitude of this effect are important for earthquake engineering since it determines if the frozen soil effect needs to take account when designing buildings in the cold regions. Three buildings in the similar climate condition are studied in this paper to compare this effect. Through instruments in the field the ambient noise and small earthquake-induced vibrations have been recorded and their dynamic properties are identified. The changes in the first frequency during various seasons are discussed. The further parametric study using FE models is conducted. The relative stiffness between superstructures and soils is founded as a key factor. A ratio coefficient is presented to relate the frequency change when the ground freezing. Another possible factor is the building configuration or foundation design, which determines if the heat inside the building migrates to the soils under and surrounding the building, and if frozen soils occur for individual buildings.
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