Impact Factors of Bridges based on Natural Frequency for Various Superstructure Types

摘要

As the characteristics of dynamic loadings on bridges changes its influence should be appropriately taken into account during a design process. This study utilized the measured impact factor data from 256 bridges and found about 32% exceeded the design criteria of the impact factor which was based on a span length. This study aims to suggest new design criteria for an impact factor which is based on a natural frequency rather than the span length. In order for easier estimation of the natural frequency of the bridges, equations were suggested to calculate natural frequencies with respect to different types of superstructure by using the statistical regression. The impact factors computed based on the suggest methods were compared to the field measured impact factors. The suggested calculation method herein provided very reliable results of the impact factors. It was also found that the impact factor criteria from the suggested method provided more conservative values regarding the structural performance of bridges under dynamic loadings.