2025 Volume 81 Issue 13 Article ID: 24-13533
The behavior of structures such as bridges and viaducts during earthquakes includes not only horizontal motion but also rotational motion. Additionally, it has been understood that the behavior of ancillary equipment and vehicles on these structures during earthquakes is influenced by not only the horizontal motion at the top of the structure but also its rotational motion. Therefore, this study aims to understand the fundamental mechanisms of seismic rotational behavior for single-column and rigid-frame structures, theoretically deriving the rotational-horizontal ratio kθ (rotation angle θ/ horizontal displacement δ) at the top of the structure. In this analysis, fixed-ground conditions were assumed, and the girder mass was modeled as a concentrated mass. Comparing the values of the rotational-horizontal ratio kθ between single-column and rigid-frame structures, the ratio for the rigid-frame structure was found to be less than half that of the single-column structure. Furthermore, through frequency response analysis, the frequency dependence of the rotational-horizontal ratio kθ was also identified.
