Analysis and Optimisation of Seismic Performance of Bridge Structures -- Zhoushan Cross-sea Bridge as an Example

Abstract

Bridges are an important part of the transport system, and structural damages (destructions) to bridges caused by seismic hazards
can result in social and economic losses. In order to reduce the losses caused by earthquakes, it is necessary to effectively assess the seismic
level of bridge structures and enhance the seismic capacity of bridge structures. Taking a highway bridge across the sea as the research object
in this paper, a finite element modelling method considering the pile-soil-structure interaction and the pile diameter effect is proposed; the
seismic susceptibility analysis of the bridge structure is investigated, and the system susceptibility is taken as the goal to optimize the parameters of the seismic isolation bearing; and the rule of change of the system susceptibility of the bridge over time during the service life is explored. The main research work carried out in this paper is as follows:
??(1) Introduced the analysis theory of seismic susceptibility of structure, gave the analysis steps of component seismic susceptibility and
system seismic susceptibility, and compared and analysed the different methods of the analysis of system susceptibility of bridge structure.
??(2) The influence of pile diameter effect on the seismic vulnerability of bridges was studied. Based on the finite element analysis platform, three kinds of finite element models were established: a model that considers both pile-soil-structure interaction and pile diameter effect; a model that considers pile-soil-structure interaction but not pile diameter effect; and a simplified model of pier bottom junction. The
seismic response of the bridge structure is obtained by incremental dynamic analysis (IDA), which gives the seismic susceptibility curve of
the bridge structure. The calculation results of the three models are compared and analysed to illustrate the significance of considering the
pile diameter effect.
??(3) The objective function of seismic susceptibility of the bridge system is established, and the mechanical parameters of the seismic
isolation bearing are optimised. Considering the characteristic strength and initial stiffness of the lead-core rubber bearing as the optimisation
variables, the influence law of the bearing parameters on the seismic vulnerability of the bridge system is obtained through the dynamic time
course analysis, and the reasonable interval of the bearing parameters is determined. In order to effectively reduce the calculation cost and
improve the calculation efficiency, Gaussian process model is used to replace the time-consuming power time analysis to obtain the optimised
design results.
??(4) The seismic susceptibility curve of the time-varying system of the bridge considering the corrosive effect of chloride ions is established. Based on the diffusion mechanism of chloride ions in concrete, the degradation of steel reinforcement and concrete under chloride
corrosion is analysed. Finite element models of bridge structures in different periods are established. At the same time, the changes in the limit
state of bridge piers and columns at different service life are considered, and the system susceptibility curves of bridge structures at different
time nodes are obtained. The Gaussian process model is used to establish the time-varying surface of the seismic susceptibility of the bridge
structure during the service life.