Abstract
Rapid drill-string tripping causes transient pressure fluctuations, triggering complex fluid-structure interac-tion (FSI) in the wellbore. This study uses FSI theory to model stress distribution and deformation under such loads. We develop and validate a three-dimensional numerical model—capable of simultaneous transient pressure and structural stress simulation—with laboratory and field data. Simulations across inclinations from 0o to 90o and varying tripping speeds show that pressure waves propagate with reflection and attenua-tion, with higher inclinations reducing attenuation. Pulsating pressures generate axial tensile stress, while drill-string inertia induces bending and lateral deformation. Bottom constraints critically affect stress: a rigid bottom raises peak stress by over 60%, whereas a free bottom has minimal impact. Above ~15o inclination, bottom-constraint effects weaken sharply. Sensitivity analyses recommend slower tripping, optimized fluid properties to damp surges, and reinforced casing in critical zones to enhance integrity. Applied to a high-pressure gas well in eastern Sichuan, the model accurately predicted transient pressures and stress patterns matching field monitoring. This work improves understanding of pressurestructure interactions in wellbores and informs safety measures in high-risk drilling.
Address
Ren Chen, Yanping You, Wei Zhang, Yanqing Chen, Liangzhu Yan: College of Energy (Modern Shale Gas Industry College), Chengdu University of Technology, Chengdu 610059, Sichuan, China; CNPC Chuanqing Drilling Engineering Company, Chengdu 610059, Sichuan, China; National Key Laboratory of Oil and Gas Reservoir Geology and Development Engineering, Chengdu 610059, Sichuan, China
Abstract
This paper investigates the seismic response of a concrete liquid storage structure for sewage treatment on different site types. By considering fluid-structure-soil interaction, the study examines the dynamic responses of the structure under multi-dimensional seismic action in various sites. The results indicate that the stress of the structure changes with the decrease of the shear wave velocity of the site type. The study shows that the shear wave velocity of the site type has a significant impact on the seismic response of the structure. However, the internal and external liquid sloshing wave height is not affected by the shear wave velocity of the site type. The liquid sloshing velocity increases and then decreases, which leads to a decrease in the hydrodynamic pressure of the internal and external liquid. The study also reveals that the principal stress of the structure increases under multi-dimensional seismic action, while the vertical seismic action has little effect on the sloshing wave height of internal and external liquids. When isolation bearings are adopted, the maximum principal stress of the structure is reduced by 49.3%; in addition, as the shear wave velocity of the site decreases, the seismic isolation efficiency of the isolation layer also decreases.
Key Words
fluid-structure-soil interaction; liquid-storage structure; multi-dimensional seismic excitation; seismic isolation; site soil type
Address
Lei Qi, Tianyu Wang, Bo Sun, Bo Wang, Longlong Yang: Gansu Province Gully Fixing and Tableland Protection Engineering Research Center, Longdong University, Qingyang 745000, China
Xuansheng Cheng: Western China Technical Centre of Seismic Dissipation and Isolation, Lanzhou University of Technology, Lanzhou 730050, China
Abstract
This study conducts an in-depth analysis of the thermal buckling and post-buckling behavior of functionally graded graphene platelet reinforced composite (FG-GPLRC) plates under thermal loading, with a particular focus on the combined effects of interfacial damage and initial geometric imperfection. Firstly, a displacement field model capable of characterizing interfacial damage features is considered. By considering two different temperature fields, the thermal post-buckling equilibrium equations incorporating interfacial damage effects are derived based on the generalized variational principle. Subsequently, a numerical computational approach combining the finite difference method and iteration method is employed. Finally, through a series of numerical simulations, the influence mechanisms of parameters such as interfacial damage severity, initial geometric imperfections, and material properties are systematically investigated. The results reveal that interfacial damage significantly reduces the critical buckling temperature and thermal post-buckling response, while initial geometric imperfection eliminates the bifurcation phenomenon observed in the post-buckling path response.
Abstract
The reinforcement design for openings in reinforced concrete (RC) deep beams presents a notable challenge in structural engineering. This study centers on RC deep beams with square openings, aiming to assess the reliability of empirical design methods and introduce an innovative topology optimization-based approach for additional reinforcement design. Through experimental data acquisition and nonlinear finite-element simulations, the research systematically explores how key parameters, such as opening location, size, load-bearing capacity, and failure mechanism—impact structural performance. Findings reveal that the distance between openings and the "direct pressure path", along with opening size, are critical factors affecting force transfer in these beams. A multilevel rebar diameter topology optimization technique is presented, and the optimal initial reinforcement configuration for openings is determined useing simulation results, leading to the development of a novel design method for opening reinforcement. Numerical examples of deep beams under single-point loading are employed to compare the new method with the strut-and-tie model (STM). The results show that deep beams with openings designed via the proposed method have significant advantages in stiffness retention, ultimate load capacity, and ultimate elastoplastic deformation capacity. Moreover, the method effectively optimizes the distribution of tensile damage in concrete, enhances the load-bearing capacity around openings, and maximizes steel strength utilization. This research offers an improved approach for designing RC deep beams with square openings, providing valuable insights and methods to advance related fields by overcoming the limitations of traditional design approaches with a more efficient and reliable solution.
Key Words
RC deep beam; reinforcement design; shear capacity; square openings; topology optimization
Address
Xianda Chen, Huzhi Zhang, Mingyu Wang, Kefei Li: School of Civil Engineering, Hunan University of Science and Technology, Xiangtan, 411201, China
Hui Chen: College of Civil Engineering, Hunan University, Changsha, 410082, China
Abstract
Traditional seismic support and hanger systems often suffer from issues such as uneven stress distribution, inefficient material utilization, and limited energy-dissipation capacity, which compromise their seismic performance. This study proposes a new-type seismic support and hanger system through structural optimization to address these challenges. The traditional system, characterized by C-shaped channel steel and single-ear connectors, was analyzed using finite-element methods, revealing significant stress concentration and suboptimal load-bearing efficiency. To overcome these limitations, the new-type system replaces the C-shaped channel steel with square steel tubes and adopts double-ear connectors, transforming the load-bearing components from eccentric to axial loading. This modification ensures more uniform stress distribution, reduces stress concentration, and improves material utilization. Experimental and numerical simulations demonstrate that the new-type system achieves a two-stage energy-dissipation mechanism: frictional dissipation during bolt slippage and plastic dissipation after slippage, significantly enhancing its seismic resilience. Compared to the traditional system, the new design exhibits higher load-bearing capacity, superior energy-dissipation performance, and a 10% reduction in steel consumption. These improvements align with modern engineering demands for sustainability and efficiency. The findings provide valuable insights for the design of seismic support systems, offering a robust solution for enhancing the resilience of civil infrastructure against seismic hazards.
Key Words
energy dissipation; finite-element analysis; material utilization; seismic support and hanger; stress concentration; structural optimization
Address
Jiexian Luo, Huzhi Zhang, Kechen Yu, Zhandong Chen, Xianglong Xiao, Ziyou Chen: School of Civil Engineering, Hunan University of Science and Technology, Xiangtan, 411201, China
Yiming Xu: Hunan Weifu Automotive Parts Co. Ltd., Xiangtan, 411100, China
Abstract
This study presents a deterministic analytic protocol for consequence-severity screening that focuses on evaluating the behaviour of screening methods rather than on probabilistic risk estimation. The protocol represents escalation potential using interpretable structural context descriptors and geospatial exposure proxies, and evaluates screening outputs using rank-stability and screening-efficiency metrics. The analytic metrics include Spearman rank correlation, top-k overlap (Jaccard similarity), grade reclassification rates, and candidate inflation to quantify how modelling choices and baseline definitions expand or contract prioritised candidate sets. Corridor-scale decision utility is reported using contiguous high-grade clusters rather than isolated section scores. The protocol is demonstrated on the Gyeongbu High-Speed Line (Republic of Korea) under alternative segmentation resolutions (500 m and 1 km) and grading variants. Results show that combined structural-exposure screening yields more compact candidate sets than structural-only or exposure-only baselines while remaining robust to key analytical choices. It is intended for prioritisation and does not estimate derailment probability, calibrate losses, or constitute a full risk assessment.
Address
Jaehoon Lim, Seong Keun Kang: System Safety Research Department, Korea Railroad Research Institute, Uiwang-si, Gyenggi-do, 16105, Korea
Kyumin Na: Department of Mechanical Design Engineering, Pukyong National University, Busan, 48547, Korea
Hyunkyu Jun, Chanwoo Park: System Safety Research Department, Korea Railroad Research Institute, Uiwang-si, Gyenggi-do, 16105, Korea
Jung Sik Kong: School of Civil, Environmental, and Architectural Engineering, Korea University, Seoul, 02841, Korea
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