Vibration Serviceability Investigation of a Curved Footbridge

Abstract

An investigation of the dynamic behavior of a footbridge located at Jordan University of Science and Technology, Irbid, Jordan, is presented in this paper. The work includes the evaluation of vibrations serviceability and comfort criteria of the footbridge structure for which several pedestrians felt a level of discomfort when passing through. The authors conducted an experimental investigation in which they investigated various dynamic excitations (walking, jogging, and running with varying numbers of pedestrians). Nine different dynamic excitations were applied to the structure with one, two, five, eight, and nine pedestrians. It is recognized that the pedestrians exert both vertical and lateral dynamic forces on the footbridge structure; the maximum vertical and lateral accelerations as a result of various pedestrian excitations are compared to extensively used international vibration serviceability codes/guidelines. These guidelines are HIVOSS, British Standards 5400, Sétra, Ontario Highway Bridge Design Code, ISO-1992, Hong Kong Structures Design Manual for Highways and Railways, and Japanese Footbridge Design Code. Concerning vertical accelerations, for everyday walking, the structure is found acceptable for most of the codes and almost all dynamic excitations used in the study, whether there is only a single pedestrian or a group of pedestrians walking on the footbridge. There are a few dynamic excitations where the vertical accelerations exceed the comfort limits specified in the codes. Still, those are extreme excitations that would not occur during the daily use of the footbridge. Maximum accelerations (i.e., vertical and lateral) exceed the limiting criteria for the majority of relatively older codes, but for relatively recent standards (HIVOSS and Sétra), excitations are found to be acceptable with medium or minimum comfort classes. However, some dynamic excitations (running and synchronous walking excitations) are deemed unacceptable, although these are considered extreme excitations that would not occur during everyday footbridge use. The old or early used codes in the design of lightweight footbridges are concerned to study the serviceability of bridges under human-induced vibration and are used until nowadays, and the new codes are concerned to study the comfort criteria of bridges under human-induced vibration.