| With the attention of our country to marine sovereignty and resources,the demand of cross-sea bridge construction is increasing.As an important hub of economic exchange in coastal cities,cross-sea bridges have great national strategic significance.Different from inland bridges,cross-sea bridges are faced with more severe environmental challenges,notably chloride ion erosion and hydrodynamic pressure,which seriously affect the seismic performance of bridges.Many bridges in China are located in areas with frequent earthquakes.As an important part of the bridge,the pier directly affects the service life of the bridge.At present,the research on chloride ion erosion and hydrodynamic pressure mainly focuses on the single factor,and the combined action of the two is rarely involved.Therefore,the research on the seismic performance and vulnerability of bridge piers under the combined action of the two is of great significance.The main work of this paper is as follows:(1)The finite element model of the cross-sea bridge pier was established using ABAQUS software,and the diameter and yield strength of the corroded steel bars were calculated based on the mechanism of chloride ion attack on the reinforced concrete structure.Based on this,the time-varying degradation performance parameters of the concrete in the core area were calculated and the concrete cracking time of the protective layer,and the influence of material deterioration on the constitutive relationship of the material in the model is considered,which provides the basis for the subsequent seismic analysis and vulnerability assessment of the pier.(2)According to the different deterioration conditions of bridge pier structure,XTRACT section analysis software was used to conduct moment-curvature analysis and ABAQUS software to conduct dynamic response analysis,and the influence of stirrup corrosion,longitudinal bar corrosion and longitudinal bar corrosion combined with stirrup corrosion on the seismic performance of bridge pier was studied.Research shows that the seismic capacity of the pier when considering the corrosion of stirrups and longitudinal reinforcements is far less than considering only the corrosion of stirrups or longitudinal reinforcements.(3)Selected 10 ground motion records that meet the site conditions,determine the displacement of the top pier as the pier damage index,the pushover analysis method is used to analyze the bridge piers and quantify the damage index of the cross-sea bridge piers.The IDA analysis method is used to analyze the nonlinear dynamic time history of the bridge piers,draw the time-varying vulnerability curve of the bridge piers,and evaluate the time-varying seismic vulnerability of the cross-sea bridge piers.(4)Based on the Morison equation,the influence of dynamic water pressure is simulated by using the additional mass method,and the influence of different water depths on the seismic dynamic response of bridge piers is analyzed.Seismic vulnerability curves of bridge piers at different water depths are established respectively to evaluate the seismic vulnerability of bridge piers with different water entry depths.(5)The seismic vulnerability of bridge piers under the combined action of chloride ion erosion and hydrodynamic pressure is analyzed.The results show that the vulnerability of bridge piers under the combined action of chloride ion erosion and hydrodynamic pressure is greater than that under the single factor.When the bridge pier has been in service for 25 years and the water penetration depth is 10m,in the process of adjusting the PGA from 0 to 1g,the piers with the combined effect of the two and the piers with only a single factor are considered in the state of minor,moderate,severe,and complete damage,the maximum difference in failure probability is 12.7%,12.7%,12.6%and 10.4%.After considering the hydrodynamic pressure,the seismic vulnerability of the pier with a short service time may be greater than that of the pier with a long service time. |
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