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The reliable performance of composite tubes conveying nanofluid is an essential issue for robust design under dynamic loads. Further, the frequency failure mode of these structures is a considerable performance function to provide a balance between mass and stiffness of the structure. The ability of the first-order reliability method (FORM)-based finite-step adaptive length (FAL) is discussed for reliability analysis of composite tubes under frequency failure mode. The performances for efficiency and robustness to evaluate the failure probability FORM formulas are discussed. Therefore, the capability of FAL using the steepest descent sensitivity vector is compared with three FORM formulations that are extended by the steepest descent search direction for nanocomposite tubes conveying nanofluid. In this current work, the Navier scheme is employed for calculating the frequency failure mode. Furthermore, the robustness and efficiency related to the steepest descent FORM formulas of HL-RF, directional stability transformation method (DSTM), and finite-step length (FSL) are compared with FAL. Based on this discussion, FAL contains efficient formula in comparison with other FORM formulas. Moreover, it is found that FSL formulas as well as FAL formulas are more robust than HL-RF and DSTM. This structure's failure probability rises as the fluid velocity and pipe diameter increase.

Offshore structures are mainly associated with the oil and gas industry given that globally, nearly one-third of the oil and gas extracted worldwide comes from offshore sources. This situation is likely to continue to rise over the coming decades because of abundant deposits of oil and gas still present in the oceans and society's dependency on hydrocarbon fuels. Regardless, offshore wind shows promise and continues to rise at an exponential rate because it provides means for decarbonization while contributing to economic growth in many countries. As such, wind continuos to be a leading solution against climate change globally. To ensure that a structure will fulfill its function, fatigue design is crucial to ensure an adequate service life because it is responsible for more than 80% of structural failures, most of them catastrophic and without warning. This work aims to evaluate environmental loads and fatigue analysis in a jacket-type platform located in the North Sea. Wave data scatter has been provided, and using Morison's formula, the loads on the structure were used to achieve an applicable normal loading force. Then, a static and a dynamic fatigue analysis for the offshore jacket-type structure under consideration are evaluated and compared.

The wind resource offshore is often excellent due to a higher average wind speed and lower turbulence intensity. Jacket structures are the most common offshore platforms for extraction of oil and natural gas in relative low water depths. When the offshore resources run out, these structures must be displaced to another area containing underground resources or removed in the case of reaching their design life. Therefore, one possible procedure to reduce the carbon footprint on the planet, allowing society to rely on promising sources of ’clean’ energy while salvaging these oil and gas platforms, is to consider the transformation of these oil and gas platforms into offshore wind turbine support structures. The present research focus on the possibility of converting such structures for gas extraction into offshore platforms for wind turbines. In this study, a comparison between the behavior of horizontal and vertical axis wind turbines on the same offshore platform is presented. In this comparison, two different software programs are used: MATLAB and SAP2000. The model proposed is a new simplified tool used to study the structural analysis of the jacket structures, developed and summarized in 10 steps, adopted to evaluate the behavior of the platform with the wind tower configurations.

The paper deals with the subject of diagnostics and the quick repairs of long-term operated metallic materials. Special attention was paid to historical materials, where the structure (e.g., puddle iron) is different from modern structural steels. In such materials, the processes of microstructural degradation occur as a result of several decades of exposure, which could overpass 100 years. In some cases, their intensity can be potentially catastrophic. For this reason, the search for minimally invasive diagnostic methods is ongoing. In this paper, corrosion and fracture toughness tests were conducted, and the results of these studies were presented for two material states: post-operated and normalized (as a state &ldquo, restoring&rdquo, virgin state). Moreover, through the use of modern numerical methods, composite crack-resistant patches have been designed to reduce the stress intensity factors under cyclic loads. As a result, fatigue lifetime was extended (propagation phase) by more than 300%.

Maritime Engineering covers the investigation on safe and sustainable engineering in the salt-water environment and includes scientific and technical works regarding management, planning, design, analysis, construction, operation, maintenance and applied research related to renewable energy and oceanic engineering. In this journal are published articles from industry and academia that convey advanced research that those developing, designing or constructing schemes can begin to apply, as well as papers on good practices that others can learn from and use. The themed issue on Renewable Energy and Oceanic Structures, Part I, was intended to be a forum of discussion of the recent advances in the domain of the structural integrity, inspection, monitoring, repair, maintenance, fatigue, fracture mechanics, structural design, stability, safety, reliability, offshore materials technologies, computational fluid dynamics, ocean renewable energy and environment. Contributions were proposed from engineers, scientists, consultants among others, in the field of ocean, offshore, polar, artic, naval, marine renewable energy, subsea, marine environmental engineering, coastal and aquaculture engineering, as well as by other specialists interested in these fields. This issue of ICE's Maritime Engineering journal reflects on the following topics: structural integrity of offshore structures; dynamic response of pipelines under flexural loads; and finally, assessment of wave energy resources. The first paper (Rege and Pavlou, 2019) presents a procedure for modelling the stop hole induced fatigue crack growth delay for a crack propagating under mixed-mode I + II conditions. This procedure combines the S–N curve for fatigue crack initiation and the Paris law for fatigue crack propagation. The procedure is implemented to evaluate the structural integrity of a plate with circular hole used in offshore structures applications. In the second paper (Pavlou and Correia, 2019) proposed an exact solution for pipeline response under transient and harmonic loads. In this way, the authors modelled the fluid-pipe interaction under transient loading conditions through the equilibrium and motion partial differential equations. A system of 8 first-order coupled partial differential equations and the integral transforms are used for achieving an analytical solution. Additionally, the methodology is based on double integral transforms. The methodology proposed is applied for pipelines subjected to impact and harmonic loads, and their results are provided. The paper by Jiang et al. (2019) presents an assessment of wave energy resources in the South China Sea and prepares the basis of plans for developing and using wave energy at the referred region. Additionally, a guidance to site wave power stations as well as the design criteria for wave energy convertors are provided. According to this study, the results showed that areas with abundant and stable exploitable wave energy in the South China Sea, mainly between the Luzon Strait and the southeast of the Indo-China Peninsula, the annual average wave energy fluxes ranged from 10 to 18 kW/m. In this way, the authors have concluded that the wave energy resources and the frequency of high sea states need to be considered when choosing sites for wave energy farms.