Xiaoli Jiang

Residual ultimate strength of offshore metallic pipelines with structural damage – a literature review

Abstract The latest research progress on residual ultimate strength of metallic pipelines with structural damage is presented through literature survey. The investigated pipe diameter-to-thickness ratios majorly lie between 20 and 50, which are typically applicable in deep water. Influential parameters in terms of pipe load, installation process and material that affect the ultimate strength of pipes are categorised. Structural damage including dent, metal loss and crack is identified and efforts are made to summarise critical damage factors such as dent length and crack depth. Furthermore, research and prediction methods on pipe residual ultimate strength in terms of experimental tests, numerical simulations and analytical predictions are summarised and discussed. Specific details on how to introduce, simplify and simulate structural damage are presented and discussed. It is expected that the mechanism of residual ultimate strength of metallic pipes with structural damage can be clarified through this study so that guidance will be provided for researchers in this field.

Crack Monitoring Method for an FRP-Strengthened Steel Structure Based on an Antenna Sensor

Fiber-reinforced polymer (FRP) has been increasingly applied to steel structures for structural strengthening or crack repair, given its high strength-to-weight ratio and high stiffness-to-weight ratio. Cracks in steel structures are the dominant hidden threats to structural safety. However, it is difficult to monitor structural cracks under FRP coverage and there is little related research. In this paper, a crack monitoring method for an FRP-strengthened steel structure deploying a microstrip antenna sensor is presented. A theoretical model of the dual-substrate antenna sensor with FRP is established and the sensitivity of crack monitoring is studied. The effects of the weak conductivity of carbon fiber reinforced polymers (CFRPs) on the performance of crack monitoring are analyzed via contrast experiments. The effects of FRP thickness on the performance of the antenna sensor are studied. The influence of structural strain on crack detection coupling is studied through strain–crack coupling experiments. The results indicate that the antenna sensor can detect cracks in steel structures covered by FRP (including CFRP). FRP thickness affects the antenna sensor’s performance significantly, while the effects of strain can be ignored. The results provide a new approach for crack monitoring of FRP-strengthened steel structures with extensive application prospects.

Numerical investigation of residual ultimate strength of dented metallic pipes subjected to pure bending

ABSTRACT A dent is one of the main structural damages that may affect ultimate strength. In this paper, the residual ultimate strength of dented metallic pipes subjected to a bending moment is quantitatively investigated. The numerical model is developed accounting for the variation of the dent length (ld), dent depth (dd), dent width (wd), dent rotation angle (θd) and dent location based on ABAQUS Python. The numerical model is validated by test results from a four-point bending test. Subsequently, a parametric investigation is performed on the effects of wave-type initial imperfection, D/t and dent geometrical parameters. It is found that both ld and dd have a significant effect on the residual ultimate strength of dented metallic pipes, while the effect of wd is slight. Finally, an empirical formula with respect to ld and dd has been proposed for the prediction of bending moment, which can be deployed for practical purposes.

PSO-based method for safe sailing route and efficient speeds decision-support for sea-going ships encountering accidents

Maritime accidents and incidents, such as ship to ship collision or ship grounding, most often occur near ports due to the intensive water traffic and shallow water depth. The occurrence of those accidents place a port in a very dangerous situation, since the port could suffer from a high risk of blockage of port entry, and the consequent economic loss can be substantial. In the case of maritime accidents, it is of great significance for sea-going ships outside of the accident zone to determine a safe and smooth sailing route and efficient speeds at a busy port, thus to reduce the risk of blockage and the economic loss of the port, whilst not disturbing the current emergency logistic response system. In this regard, a decision-making method for safe and smooth sailing route and efficient speeds for sea-going ships encountering an accident can be very valuable. Because of the high nonlinearity of these decisions, PSO algorithm is used to search the safe and smooth sailing route and efficient speeds. The study results show that the proposed method can effectively achieve the safe and smooth sailing route and efficient speeds for ships encountering an accident, thus to be more economic and reduce the risky chance of blockage of the port entry.

Study on route division for ship energy efficiency optimization based on big environment data

In the case of the global energy crisis and the higher sound of energy saving and emission reduction, how to take effective management measures of ship energy efficiency to achieve the goal of energy saving and emission reduction, put forward a new challenge for the development of shipping technology. The application of big data technology provides a new idea for the research of ship energy efficiency optimization management. The energy efficiency management level of the operating ship can be improved by the analysis and mining of the big data. In this paper, a big data analysis platform for ship energy efficiency management based on the widely used Hadoop platform architecture is designed. Afterward, due to the huge amount of involved data on the energy efficiency management which has exceeded the processing ability of traditional solutions, the big data analysis method is used to achieve the route division according to environmental factors, thus to lay the foundation for speed optimization in different segments of a route. Finally, a simple decision-making method of optimal engine speed based on the result of route division is proposed, which could improve ship energy efficiency and hence reduce CO2 emission.

Image processing algorithms for crack detection in welded structures via pulsed eddy current thermal imaging

As the common metal structure type, welded structures are widely used in civil infrastructure, bridges, ships and engineering machinery. Fatigue cracks often originate in welds enduring intense stress concentration or in welding defects under long-term continuous alternating loading [1]. Once these cracks propagate to a critical length, the structural integrity will be challenged. As a result, welding cracks detection is significant in engineering applications.

An Application of the IoT in Belt Conveyor Systems

The Internet of Things and Big data these days means big business. Monitoring Belt Conveyor Systems used to be performed by means of inspectors and off line. These days the developments are towards fully automated inspection systems. The IoT enables that more information from sensor systems becomes available that was not available in the past. Theoretically this means that monitoring Belt Conveyor systems 24/7 should become reality and down-time and unexpected maintenance a thing of the past. All these sensor systems produce a vast amount of information. Big data implies a combination of databases too large and/or too diverse to maintain by regular database management systems. Big data plays an ever-increasing role these days. This paper discusses an application of the IoT in bulk solid handling and transportation systems and the utilization of big data. It discusses recent developments and a case study.

A Novel Adaptive Negotiation Strategy for Agricultural Supply Chain Centered on Third Party Logistics

Agricultural supply chain is in general open and dynamic attributed and negotiation is a key strategy to realize collaboration among different entities involved. However, traditional static and offline negotiation strategy may not function well, an agricultural supply chain centered on third party logistics will provide a new collaborative relationship among agricultural materials suppliers, agricultural cooperatives, farmers, agricultural products demanders and third party logistics providers. This paper proposes a novel adaptive negotiation strategy for agricultural supply chain centered on third party logistics. The negotiation strategy consists of an evaluation function in terms of integrity and risk preferences, a concession function in terms of concession preference, time and resources, and a generation function in terms of opponent’s behaviors. Afterwards, an procedure was proposed to solve the negotiation strategy. Finally, a simulation experiment was employed to verify the effectiveness of the negotiation strategy.

Ultimate Strength of Damaged Stiffened Panels Subjected to Uniaxial Compressive Loads Accounting for Impact Induced Residual Stress and Deformation

In case of ship accidents, the ship’s hull will inevitably suffer from damages such as holes, cracks, dent etc., which will threaten the structural safety of ship. It is essential to study the ultimate strength of damaged ships in order to facilitate the decision-making process of ship salvage. There are considerable publications on the subject, however, the impact of the induced residual stress and deformation are normally excluded in those studies. This paper therefore aims at investigating the effect of the impact induced residual stress and deformation on the ultimate strength of a stiffened panel through application of a nonlinear Finite Element Analysis (FEA) method. Firstly, a literature review on ultimate strength of damaged ships is presented. Secondly, a nonlinear numerical simulation is adopted to investigate the ultimate strength of stiffened panels accounting for residual stress and deformation. this procedure consists of two stages: the impact stage and the static stage. The results of the numerical simulation of both stages are validated through the results of experiments and simulations available in literature. Afterwards, a series of case studies are performed deploying the validated numerical method. Finally, a closed form expression to predict the ultimate strength accounting for impact induced residual stress and deformation is proposed based on direct simulation. Results show that the combined effect of impact induced residual stress and deformation can significantly reduce structures’ load carrying capacity. The maximum reduction ratio reaches 37% in local stiffened panel. The method of removal of all the plastic deformation area is generally too conservative to predict the ultimate strength of a damaged local stiffened panel, which will underestimate the residual load carrying capacity of ships considerably.Copyright