Dynamic Characteristics and Dynamic Response of Timber Footbridges to Dynamic Human Activities

Abstract

The dynamic action of footbridge users in different forms of activity (especially during walking and running) may cause an excessive vibration of the footbridge deck and may disturb the comfort of use of the structure. The dynamic susceptibility of the footbridges varies depending on the construction material used to build the footbridge and the typical construction solutions (construction details) resulting from the construction material used. The paper presents the basic dynamic characteristics of timber footbridges of various structural solutions, collected during dynamic field tests of these structures. The obtained results indicate relatively high dynamic resistance of timber footbridges to the dynamic loads generated by users under normal conditions of use. In addition, the results show that in the case of timber footbridges, it is possible to consider changing the requirements of international standards defining the range of natural frequencies sensitive to the dynamic impact of users. In the case of timber footbridges, characterized by a relatively high self-weight (compared to steel footbridges), high stiffness and high damping, it is possible to consider changing the requirements for performing forced vibration analyses only for structures with fundamental vertical vibration frequency 𝑓 3.0 Hz instead of the currently defined 𝑓 5.0 Hz.