Analysis method for seismic response of large-span CFST arch bridge considering arch forming process

Abstract:

In order to explore the influence mechanism of arch formation process on the seismic response of large-span concrete filled steel tube (CFST) arch bridges, the typical arch formation process and the stress accumulation history of the arch rib section are first explained. A nonlinear dynamic sequential analysis method is proposed for large-span CFST arch bridges considering the construction process, and the accuracy of the proposed method in obtaining the initial state of bridge is validated against Midas/Civil professional construction analysis module. The influence laws of the arch formation process are investigated from the perspectives of seismic responses of steel pipe and infilling concrete strains, as well as seismic response of the main arch displacement. Based on the "mediating effect analysis", the influencing mechanism of the arch formation process on the seismic response of large-span CFST arch bridges is addressed. Finally, a mapping relationship between the seismic strain responses of steel pipe and infilling concrete obtained with and without considering the arch formation process is established. A simplified corrective analysis method is proposed for seismic response of large-span CFST arch bridges. The research results indicate that the proposed analysis method can achieve accuracy very close to that of Midas/Civil professional construction analysis, with a peak stress error of only 6.8% for steel pipes and almost overlapping stress curves for infilling concrete. When considering the arch formation process of the main arch, the strain distribution of the steel pipe and infilling concrete no longer conforms to the plane section assumption. Under earthquakes, whether the arch formation process is considered leads to different elastic-plastic states in the CFST main arch, with the discrepancies increasing as the peak ground acceleration (PGA, a_PG) rises. When the plastic development degree of the main arch section is low, the differences in the initial state of the completed bridge are critically influential. Conversely, when the plastic development degree is high, the degree of material plasticity becomes the key influencing factor. The proposed simplified corrective analysis method has high accuracy, with average peak strain errors of only 2.9% for the steel pipes and 5.5% for the infilling concrete.