考虑环境腐蚀的海上施工栈桥承载性能分析

Analysis of Load Bearing Capacity of Offshore Trestle Considering Environmental Corrosion

为研究环境腐蚀对波流共同作用下的海上施工栈桥承载性能的影响,以平潭海峡公铁大桥海上施工栈桥为背景,建立考虑杆件弹塑性、节点局部柔性和环境腐蚀的栈桥有限元模型,采用非线性分析方法计算栈桥在不同波流条件、不同腐蚀时间下的承载力,对其波流承载性能进行分析。结果表明:栈桥极限波流承载力随着腐蚀时间增长而减小,腐蚀时间为20年时承载力下降48%并趋于稳定;通过提出的腐蚀时间与极限承载能力的数学关系可快速获取不同影响参数下海上施工栈桥的损伤临界线,提高了评估效率;考虑腐蚀后,在相同重现期波流荷载作用下,结构损伤程度会明显加重。该栈桥在100年一遇波流作用下,服役6年内只会出现轻微损伤,服役7年后可能会出现中度损伤,11年后可能会出现严重损伤。

With the case of trestle used in the construction of Pingtan Straits Rail-cum-Road Bridge,the influence of environmental corrosion on the load bearing capacity of offshore trestle under the combined action of waves and currents is studied.A finite element model was established,taking into account the elastoplasticity of members,local flexibility of nodes and environmental corrosion.The non-linear analysis method was used to calculate the load bearing capacity of the trestle under different wave and current conditions and different corrosion exposure time.The results show that the load bearing capacity of the ultimate load bearing capacity of the offshore trestle decreases as the exposure time increases,the load bearing capacity can be reduced by 48%after 20 years exposure,and tends to be stable.Based on the mathmatic relationship between the corrosion exposure time and ultimate load bearing capacity,the damage critical line of the offshore trestle with different influential factors can be obtained,and the evaluation efficiency is improved.When the corrosion is considered,the damage degree of the trestle will be significantly escalated under the action of waves and currents of same return period.Under the action of waves and currents of 100-year return period,the trestle will suffer minor damage after serving for 6 years,but medium-degree damge after serving for 7 years and severe damage after serving for 11 years.