Fundamental natural frequency of an integral bridge system considering soil structure interaction effects

Fundamental Natural Frequency (FNF) is the lowest natural frequency at which a structural and mechanical system vibrates. For those systems, knowing FNF is crucial to avoid resonance, which can lead to excessive vibrations and potential failure. Therefore, the main objective of this paper is to determine FNF of Integral Bridge (IB) system considering Soil-Structure Interaction (SSI) effects. To achieve this aim, FNFs of the studied system are obtained by developing Finite Element Models (FEMs) in the ANSYS program. The results which uncover in the following, help designer to know effective factors on stiffness of the IB. The results show FNFs of the IB decrease significant with increasing spans of the studied models (for all cases: onespan bridge, two-spans bridge and three-spans bridge) from 10 m to 15 m and 20 m, by an average of 20.75% and 52.85%, respectively. Also, FNFs of the studied models reduce with increasing number of spans from one span to two and three spans, by an average of 13.6% and 20.2%, respectively. In addition, FNFs of the studied models decrease with increasing width of the IB from 7.05 m to 10.7 m and 14.35 m, by an average of 6.7% and 11.1%, respectively. Furthermore, FNFs of the IB change with changing thickness of abutment, deck and wing walls, only by maximum 8.18%. In the end, FNFs of one-span bridge, twospans bridge, and three-spans bridge show increase with considering SSI effects, by 48.9%, 34.7%, and 20.4%, respectively.