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Local site conditions may pose a significant influence on the seismic responses of submarine pipelines by altering both the offshore motion propagation and soil-structure interaction (SSI). This paper aims to provide an in-depth understanding of the influence regularity of local site conditions on the seismic performance of free-spanning submarine pipelines (FSSPs). For this purpose, a suite of underwater shaking table tests were performed to investigate the seismic responses of FSSP subjected to the offshore spatial motions at three site categories. Response comparison factor (chi R.ij${\chi }_{R.ij}$) is defined to quantify the structural response discrepancies caused by the seismic inputs at different sites. The test results indicate that responses of the studied model FSSP gradually increase as spatial offshore motions at softer soil sites are employed as inputs; and the values of chi R.ij${\chi }_{R.ij}$ vary with a maximum magnitude of up to 40%-60% for different response indices when the site soil changes from fine sand to clay. Subsequently, the corresponding numerical simulations are carried out to reproduce the seismic responses of the test model. The experimental and numerical results meet a good agreement, indicating that the developed numerical modeling method can accurately predict the seismic responses of FSSPs. Following this verified modeling method and using the p-y approach to address the SSI effect, fragility surfaces of the studied FSSP are derived in terms of PGA and site parameter VS30${V}_{S30}$ (shear-wave velocity in the top 30 m of the soil profile) via probabilistic seismic demand analyses. The impact of local site conditions on the seismic performance of the FSSP is quantitatively examined by comparing the fragility curves corresponding to various VS30${V}_{S30}$. Furthermore, a fast seismic damage assessment method is proposed for efficiently evaluating the performance of FSSPs buried in various offshore soil conditions. This approach proves beneficial for designers and decision-makers, enabling accurate estimation of seismic damage and facilitating the implementation of post-earthquake maintenance measures for FSSPs.

期刊论文 2024-11-01 DOI: 10.1002/eqe.4216 ISSN: 0098-8847

Pitting corrosion is normally distributed randomly along the pipeline, which is the source of the uncertainty affecting the ultimate bearing capacity of the submarine pipelines. So the Monte Carlo method is employed to study the effect of pitting corrosion on the upheaval buckling behavior of the pipeline. A corroded pipeline model with randomly distributed pitting corrosion is utilized to captures the intricate realities of corrosion scenarios. Multiple corrosion models with distinct artificial patterns have been meticulously crafted. Additionally, a new pipeline element based on Euler-Bernoulli beam theory is extended considering corroded sections, pipe -soil interactions, axial load, initial imperfections, and other major factors. Moreover, the bearing capacity, vertical deformation and stress of the pipeline under corrosion is discussed thoroughly, wherein a Newton- Raphson typed numerical analysis procedure is utilized for nonlinear analysis of the upheaval buckling of pipelines. The influence of corrosion parameters such as the corrosion depth, corrosion ratio and area loss ratio on mechanical properties of the submarine pipelines is further analyzed in detail. It's indicated that varying patterns of corrosion distribution, despite exhibiting identical corrosion parameters, can result in distinct reduction factors and vertical buckling displacements. Copyright (c) 2024 by The Hong Kong Institute of Steel Construction. All rights reserved.

期刊论文 2024-03-01 DOI: 10.18057/IJASC.2024.20.1.10 ISSN: 1816-112X

As an essential component for the transportation of oceanic oil and gas supplies, it is crucial to ensure the efficient operation of submarine pipelines. The fatigue failure of submarine pipelines occurs frequently under the combined effects of currents, waves and soil. Firstly, a pipe-soil interaction suspended pipeline model was developed, which could be used to simulate the mechanical behavior of pipes and the dynamic response of the combined loads of waves and currents. Then, the effects of soil properties, current direction and suspended length on the stress distribution and dynamic mechanical response of submarine suspended pipelines were investigated. In addition, the vibration characteristics of suspended pipelines affected by soil were revealed. At last, according to the vortex-induced resonance evaluation and fatigue life assessment method, the critical length of suspended pipelines for the Bohai sea was determined. The results show that the stress change in the center of the suspended reaches the most significant for the pipeline with a length of less than 20m. When the suspended length exceeds 20m of the pipeline, the connection between the suspended and the buried shows the most dramatic stress fluctuations. Meanwhile, the cumulative damage of the submarine suspended pipeline entering the soil becomes the maximum, and fatigue failure often occurs in this position. The results are expected to provide an important theoretical basis in safe operation and repair decision of submarine pipeline.

期刊论文 2024-01-01
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