Intended Service Life Research Articles

Negative impact of vibration on process pipelines of a compressor station with electrically driven gas pumping units

Relevance. In gas industry, the amount of equipment that has outlived its intended service life is increasing every year. In accordance with the law “On Industrial Safety of Hazardous Production Facilities,” compressor stations are dangerous objects, the reliable operation of which largely determines the condition of main gas pipelines. Technological pipelines of a compressor station are important objects of this system. They are subject to strict requirements due to the action of static and dynamic loads on them. Reliability of compressor stations is based on the results of a study of the condition of the object and the main factors affecting increased wear of equipment. The solution to wear problem is timely monitoring of equipment, in particular level measurement and determining the causes of pipeline vibrations using vibration diagnostics methods, and frequency and modal analysis methods. Aim. To study the causes of increased dynamic loads on the technological piping that arise during the operation of electric and gas pumping units at a compressor station using vibration monitoring methods. Methods. Vibration monitoring methods to analyze the causes of increased vibration values in the process piping of a compressor station with an electric gas pumping unit. Results and conclusions. The authors have measured vibration in a wide frequency band and assessed the technological condition of the main equipment of the compressor station with EGPA-6.3/8200-56/1.44-R based on the regulatory documentation STO Gazprom 2-2.3-324-2009. The main frequencies of the root-mean-square value of the vibration velocity, at which the highest vibration values were observed, were identified, and a modal analysis was performed using ANSYS software. Based on the results of natural studies and modal analysis, it was concluded about the occurrence of resonant high-frequency oscillations, multiple of the rotor rotation frequency.

Parametric study for shear failure of bearing pads due to hurricane-induced wave loadings

The increasing frequency of extreme weather events, such as hurricanes and rising sea levels due to climate change, presents significant challenges to coastal infrastructure. With 42% of bridges in the United States exceeding 50 years of age, which surpasses their intended service life, there is a pressing need to assess their structural integrity, especially in coastal regions. This study focuses on evaluating the structural performance of bearing pads in coastal bridges under hurricane-induced wave loadings. Utilizing a combination of physics-based models (PBM), nonlinear modal time history analysis, and numerical validation, the research examines the hysteresis response of eight distinct bearing pad configurations. The findings indicate that reinforced circular bearing pads exhibit significantly greater shear displacements compared to plain elastomeric pads, underscoring the critical influence of shape factors on shear response. Fragility functions developed in the study illustrate the probability of shear failure, with reinforced circular pads showing a 28% higher likelihood of exceedance compared to rectangular plain pads. These results highlight the necessity for advanced design methodologies specifically for bearing pads to enhance the resilience of coastal infrastructure against severe hydrodynamic forces induced by hurricanes.

Machine learning prediction models for investigating vibration properties of epoxy resin under moisture conditions

Epoxy resins used in engineering applications are commonly exposed to wet environment during intended service life, which causes vibration property degradation and increasing risk of structural failure. In this work, vibration properties of epoxy resin plate under different moisture conditions are predicted with various sizes and boundary conditions using developed machine learning (ML) models. The dataset of epoxy vibration is established first, where values in the dataset are calculated with five moisture contents using previously developed meshless model. The dataset from meshless simulation is used to train ML models of epoxy vibration using six different algorithms, including support vector machine, decision tree, random forest, gradient boosting decision tree, extreme gradient boosting, and artificial neural network. It is found that the prediction model developed using extreme gradient boosting algorithm shows the highest accuracy of 99.9% and strong reliability. Using this model, vibration properties of epoxy resin with a series of sizes and boundary conditions are predicted under various moisture contents from dry case to saturated case, which deepens the understanding of the effects of wet environments on the vibration responses of epoxy resins. The results could be used for analysis of durability of epoxy resin, and the developed ML prediction models contribute to investigating vibration property of epoxy resin under different moisture conditions, which is crucial for ensuring durability of epoxy resin in wet environment.

Effect of Machining Parameters on the Surface Roughness of Medium Carbon Steel Using Lathe Machine

The service life of a machined part depends greatly on the quality of its surface roughness value. Depending on the requirements of the intended service life, machined parts may be smooth or rough. Therefore, the quality of surface finish of machined parts must be closely monitored by technicians, artisans and operators in the shop floor in order to achieve optimal output from machining operations. The quality of surface finish obtained through machining operations are affected by a number of factors. However, the most important factors are the cutting speed, feed rate and depth of cut. These are the parameters that directly affect the characteristics of the surface roughness value of a machined component. In this study, an investigation was carried out on the effect of machining parameters on the surface roughness of 0.3% medium carbon steel using the Lathe. All other factors inherent in the cutting operations was held as constant whilst the cutting parameters were intermittently varied. For each combination of cutting speed, feed rate and depth of cut, the corresponding value for surface roughness was measured and recorded. The methods of analyses chosen for this study were artificial neural network, response surface methodology and the factorial design. Findings from the study show that the result from artificial neural network and the factorial design method exhibited similar patterns with the results of previous studies which recorded that feed rate was the most significant parameter affecting surface roughness. Also, findings revealed that increasing feed rate, cutting speed and depth of cut would result in a corresponding increase in the surface roughness values. Results obtained through response surface methodology generally did not agree with most of the findings of previous works in literature. Based on the predictive capabilities of the three models, statistical metrics indicated that the ANN model was found to be the best model with a coefficient of determination of 0.9979 and a mean square error of 0.003017. This was followed by the factorial design model with a coefficient of determination of 0.9298 and a mean square error of 0.0980. The model from the response surface methodology came last with a coefficient of determination of 0.9600 and a MSE of 0.1008. From the findings, it is strongly recommended that values of feed rate must be systematically selected during machining operations and the models developed could be used to predict the surface roughness of 0.3% medium carbon steel by technicians and artisans on the shop floor.

Lifetime assessment for riser systems

As marine renewable energy technologies developing, there is a growing need for energy transportation systems. During offshore operations, deep sea risers can be subjected to excessive environmental loadings, causing operational risks. In this study, hydrodynamic loads, caused by in situ sea currents, acting on a riser under real-world sea conditions were modelled and examined, with experimental data being used as a calibration tool. Major safety problems for various offshore energy systems being an accurate assessment of excessive riser external loads, under influence of local sea currents, and hence resulting vortex induced vibrations (VIV).The method outlined in this study may be applied to complex sustainable energy systems, that are exposed to environmental loads, throughout the whole period of their intended service life. Approach advocated in this study offers practical way to estimate failure risks for nonlinear multidimensional dynamic offshore riser systems in an easy yet accurate manner.With regard to defense technology, risers and umbilicals play an important role for modern submarine operations.

Durability Enhancement Effect of Silica Fume on the Bond Behavior of Concrete-PCM Composites under Environmental Conditions.

The long-term performance of the concrete-polymer cement mortar (PCM) interface under environmental exposure is crucial to the safety of the PCM overlaying method as the environmental exposure of the repaired structures caused further degradation of the interface, leading to a significant reduction in intended service life. This study investigates the durability enhancement effect of silica fume of the concrete-PCM interface, considering an individual action of elevated temperature (e.g., 60 °C) [constant (short and moderate duration) and cyclic conditions] and moisture content [continuous immersion and wetting/drying (W/D) cycle]. Our previous research confirmed that the use of silica fume forms more C-S-H with strong binding force and enhances the interfacial bonding strength due to the denser microstructure at the interface, and it is expected to be utilized for durability purposes under the aforementioned exposure conditions. Under all elevated temperature exposure conditions, the reduction percentage of the interfacial performance corresponding to the respective reference specimens reduced significantly with the inclusion of silica fume with overlay material. The occurrence of interface fracture at lower load and a greater number of pure interface fracture modes observed in normal PCM specimens compared to modified PCM specimens indicates a positive influence of higher adhesion with better durability of modified PCM overlay with substrate concrete. Under both conditions of moisture content, significant reduction in interfacial strength was observed in normal PCM specimens. In all cases, the reducing ratio of interfacial strength was higher in normal PCM compared to modified PCM, indicating a positive influence of silica fume under moisture content. Furthermore, silica fume inclusion shifts the fracture mode from pure interfacial fracture to composite fracture mode, indicating a positive response of silica fume to improve the resistance of interface fracture under moisture content. Conclusively, the use of silica fume improves concrete-overlay layer adhesion and enhances the bonding durability under environmental exposure.

Influence of Operating Conditions on a Cast-Iron Manhole Cover

Manhole covers must provide adequate strength and durability over the intended service life. In addition to operating loads, the lifespan of cast-iron manhole covers is strongly influenced by the conditions of installation and cover placement after opening or closing. These can include a vertical displacement from the plane of the carriageway during installation or the settlement of the terrain around the cover afterwards. After opening and closing the cover, the lid often only partially touches the support surface due to stones or other impurities caught on the surface or under the cover. These events can significantly affect the lifespan of the cover. In this study, an improved geometry of the cast-iron cover is proposed and analysed from an operational strength point of view. Initially, the geometry and potential critical points were scrutinized, and typical loads on the cover were determined. A numerical model was then set to simulate the behaviour during typical operation. In the simulations, the impact of the critical scenarios was analysed by dividing the impact parameters into individual levels. The simulation results reveal the suitability of the improved cover geometry.

A review on smart aggregate based structural health monitoring

Concrete structures are prone to damage and deterioration in their health due to environmental effects, aging, etc., leading to failure prior to their intended service life. Structural Health Monitoring (SHM) is an innovative technique adopted for assessing the structural health, damage identification and assessing the residual life of the structure. The conventional techniques have proved to be inefficient as they required prior information about the vicinity of the damage and accessibility to the damaged region of the structure. The development of various sensors such as fiber optical sensor (FOS), piezoelectric transducers have proved to efficient. This study presents the introduction and the fundamental concept of the latest sensor in trend in the domain of SHM, the piezoceramic-based Smart Aggregate(SA). The applications of SA under various loadings for concrete structures have been reviewed. Also, the damage indices developed for 1-D and 2-D structural components for assessing the damage status in the structure have been summarized. It was established that the smart aggregate is capable of damage detection, health monitoring (concrete columns, shear wall, frames) and impact detection(concrete piles).

(Invited) Management Systems for Lithium-Ion Batteries

Battery management systems (BMS) for large Li-ion batteries are, of themselves, complex systems. The complexity starts with voltage measurement for individual cells. Large batteries may have 96, 192, or more, series connected cells, so requiring complex wiring harnesses. The high noise environment provides additional challenges for wiring and also analog front end and analog to digital conversion system design. For safety, and to help with state-of-charge (SOC) estimation, temperature sensors must be located throughout the battery. A computational infrastructure estimates SOC for each cell. The estimate is typically based on cell voltage, measured current, estimated cell resistance, integrated current and temperature. Additionally, cell capacity imbalance, whether present from the start or evolved over time, must be corrected.This talk will attempt to provide some insight into BMS design for mass-produced large batteries. The applications, whether for electric vehicles (EV) or stationary storage, are generally safety critical, so placing additional demands on the BMS. Typically, the BMS also manages the interaction between the battery and the remainder of the system. It sets limits for allowed charge and discharge currents and can interrupt current and disconnect the battery if limits are exceeded. This area will also be addressed, with a particular focus on fusing challenges for EV applications. Power transfer of 500 kW or more may be required. Depending on the application this may be for only a few seconds, or it may be indefinite. In additional to safety, reliability is also critical. For example, the many required cell connections must remain intact for the intended service life of the installation. This will be addressed, touching also on design of the overall battery pack.

(Invited) Management Systems for Lithium-Ion Batteries

Battery Management Systems (BMS) for large Li-ion batteries are, of themselves, complex systems. The complexity starts with voltage measurement for individual cells. Large batteries may have 96, 192, or more, series connected cells, so requiring complex wiring harnesses. The high noise environment provides additional challenges for wiring and also analog front end and analog to digital conversion system design. For safety, and also to help with State of Charge (SOC) estimation, temperature sensors must be located throughout the battery. A computational infrastructure estimates SOC for each cell. The estimate is typically based on cell voltage, measured current, estimated cell resistance, integrated current and temperature. Additionally, the effects of cell capacity imbalance, whether present from the start, or evolved over time, must be mitigated. This paper will attempt to provide some insight into BMS design for mass produced large batteries. The applications, whether for Electric Vehicles (EV) or Stationary Storage, are generally safety critical, so placing additional demands on the BMS. Typically, the BMS also manages the interaction between the battery and the remainder of the system. It sets limits for allowed charge and discharge currents and has the ability to interrupt current and disconnect the battery if limits are exceeded. In additional to safety, reliability is also critical. For example, the many required cell connections must remain intact for the intended service life of the installation. This will be addressed, touching also on design of the overall battery pack.

Self-healing mixed matrix membranes containing metal-organic frameworks.

Mixed-matrix membranes (MMMs) provide a means to formulate metal-organic frameworks (MOFs) into processable films that can help to advance their use in various applications. Conventional MMMs are inherently susceptible to craze or tear upon exposure to impact, cutting, bending, or stretching, which can limit their intended service life and usage. Herein, a simple, efficient, and scalable in situ fabrication approach was used to prepare self-healing MMMs containing Zr(iv)-based MOFs. The ability of these MMMs to self-heal at room temperature is based on the reversible hydrolysis of boronic-ester conjugates. Thiol-ene 'photo-click' polymerization yielded robust MMMs with ∼30 wt% MOF loading and mechanical strength that varied based on the size of MOF particles. The MMMs could undergo repeated self-healing with good retention of mechanical strength. In addition, the MMMs were catalytically active toward the degradation of the chemical warfare agent (CWA) simulant dimethyl-4-nitrophenyl phosphate (DMNP) with no change in activity after two damage-healing cycles.

The environmental impact of service life-extending repair for corrosion damaged reinforced concrete balconies: a case study in a coastal context

Nowadays a vast number of concrete structures are approaching the end of their expected service life. The need for sustainable rehabilitation (maintenance and repair) is urgent and due to the expected deterioration of buildings and civil structures, there will be a great need for preventive and/or curative interventions in the near future. More than 2/3 of the damage to reinforced concrete structures is linked to reinforcement corrosion, which can affect the durability of the structure and the residual load-bearing capacity. With the necessary transition towards a circular economy and the Sustainable Development Goals in mind, it is important to deviate from considering only the technical requirements and initial costs during the design of concrete structures. Hence, the environmental impact over the entire life cycle and the intended service life extension need to be considered as well. A typical residential building in a Belgian coastal environment with damaged reinforced concrete balconies is selected as case study to evaluate different frequently used repair techniques (i.e. patch repair, conventional repair, galvanic cathodic protection, impressed current cathodic protection and total replacement) by means of a life cycle assessment. Several sensitivities are mapped by analysing the influence of the intended service life extension, the volume and configuration of the construction, the repair mortar composition and the application of coating/waterproofing. It was stressed that these uncertainties could have a substantial effect on the environmental impact and highlight the domains where further research is needed (e.g. assumed life span and composition of repairs). Due to this manner, it is not possible to identify one environmental optimal repair method. However, for a short service life extension (e.g. 5y) small interventions like patch repair seem to be more sustainable while methods like cathodic protection and conventional repair are preferable for longer service life extensions (e.g. 40y).

An objective assessment strategy for industrial reinforced concrete structures – Case study

Due to the booming construction wave between the 60´s and 80´s, a lot of reinforced concrete structures are now approaching their intended service life design. Concerning the industrial sector, an unforeseen shutdown of production processes due to urgent maintenance or repair actions of reinforced concrete structures can have major consequences for owners and managers. Therefore, it is important that they get a clear view of the current state of their structures in order to shift towards a more proactive maintenance. In order to recognize and assess both classic and more complex damage phenomena, a scientific approach to translate collected field data towards a service life and inherent repair strategies for the concrete structure is adopted by means of an in-house developed data analysis tool DIMCoSt (Durability Information Model for Concrete Structures). The objective assessment strategy is described in this paper by means of a case study. The subject of the case study is concrete storage silos. Although the applied methodology is mainly universal, each case has its own emphasis that must be considered regarding the decision-making process based on the owner’s or manager’s requirements. By means of this case, a scientifically based approach is presented which leads to objective decision-making regarding asset management and planning of maintenance or renovation activities.

ANALYSIS OF PECULIARITIES OF PASSENGER CAR BODY WEAR

The article considers the issues of analysis of the patterns of operation of the loadbearingelements of the body of carriage. A comparative analysis of the size and nature of theoperation of structural elements of carriages of different types and years of their construction.In recent years, there has been a significant aging of the operational fleet of carriage. Atnowadays, carriages of various models and their modifications with an extended service life, whichis approaching the limit, are in operation on the railway network of Ukraine.The technical, economic and ecological indicators of transport, the degree of reliability andtraffic safety depend on the age of the carriages. At nowadays, the level of development of technicalmeans and technology of repair and restoration of rolling stock is increasing fast.To increase the competitiveness of rail passenger transport, it is necessary to overcome thehigh degree of wear of the carriages fleet of JSC «Ukrzaliznytsia». Because of the lack of domesticand the complete absence of foreign investment in the railways, the tendency to increase physicaldepreciation and obsolescence of fixed assets is progressing. According to the data of the branch of«Passenger Company» JSC «Ukrzaliznytsia» in 2020 the inventory includes is almost 5 thousandcarriages, most of which have served their intended service life. As a result, the current wear of thecarriages fleet is approaching 92 %.Most of the carriages fleet was built in the 70s and 90s of the last century at car plants inGermany and Russia. Due to the constant lack of funding, the fleet of carriages of JSC«Ukrzaliznytsia»was renewed at a slow pace. Every year the carriages fleet wears out and ages. Thisreduces the competitiveness of railways, which negatively effects on quantity of passenger traffic.Naturally, carriages should not only create the necessary level of comfort, but also ensure trafficsafety and high reliability in operation. The results of the study made it possible to consider the issueof further use of carriages, which are most affected by corrosion.

Duroplastic gap filling materials in preloaded bolted connections

AbstractIn steel structures, bolted connections are preloaded either for load‐bearing capacity reasons or for serviceability reasons. Single and multi‐section connections of wind turbines, offshore plants, bridges etc. are typical application examples.Gap formation due to production‐ and assembly‐related imperfections poses a risk for a controlled application of the required preload level, which is vital for slip‐resistant and fatigue loaded connections. Furthermore, it might significantly affect the desired behaviour of the connection or even lead to premature failure. For this reason, EN 1090‐2 provides regulations on the allowable gap formation and even prescribes measures to avoid negative outcomes. One of the possibilities for a gap compensation are gap filling materials, also known as liquid shim or load transfer materials, such as MM1018 of DIAMANT Metallplastic GmbH, Germany, a two‐component composite system filled with special metallic materials.Currently, systematic investigations into the application of duroplastic gap filling materials in preloaded bolted connections are carried out in the frame of the German cooperation project “Bri‐San‐T ‐ DuroFüllSta”. Herein, the slip factor is experimentally determined according to EN 1090 2, Annex G under variation of application type, gap thickness, curing time, temperature and surface condition. Furthermore, relaxation tests are carried out to determine possible preload losses over the intended service life of the structure.The presented contribution intends to provide an insight into the main properties of duroplastic gap filling materials with regard to their application in preloaded bolted connections under various conditions.

Loss of preload in preloaded bolted connections over the service life

AbstractThe design of slip‐resistant connections and fatigue loaded tension connections according to the categories B/C and E of EN 1993‐1‐8 relies on a specified preload level of the bolted connections which has to be ensured over the whole service life of the structure. However, it is well known that preload losses occur after tightening due to several reasons: e. g. setting effects, creep and cyclic loading. In order to ensure not only the operational safety but also the load bearing behaviour of preloaded bolted connections, those influencing factors have to be estimated and considered reasonably.For this reason, systematic investigations were carried out to determine the system reserves due to different tightening methods and preload losses. Herein, preload losses due to setting effects, creep and cyclic loading were experimentally determined, evaluated and extrapolated to the intended service life considering two clamping length ratios Zt/d ≈ 5 and Zt/d ≈ 2 as well as five surface conditions. Furthermore, different types of M20 bolting assemblies and tightening methods were used.The main findings and conclusions are presented and discussed in the paper. On this basis, a critical review of the current regulations and recommendations for improvements can be given. Besides all other interesting results, it could be shown that only the combined method turned out to possess enough system reserves (over 30 % in relation to the required preload level) for covering possible preload losses especially for coated surfaces for the service life of the structure.

Investigating the nonlinear performance of corroded reinforced concrete beams

Reinforced concrete beams are one of the primary horizontal members that undergo large flexural stresses in a reinforced concrete structure. According to capacity design concept, the beams are designed to suffer damage before the columns of the structure. However, such damage in beams and subsequent failure sometimes occurs prematurely if the rebars in the beam have undergone corrosion. Corrosion of reinforcement is one of the primary factors responsible for degradation of RC structure that significantly affects its intended service life. The present study is an effort to assess the performance of corroded RC beams considering the primary effects, such as bond strength degradation, spalling stresses induced on concrete surrounding rebars, and reduction in the cross-sectional area of the rebars. A 3D nonlinear finite element model has been developed to simulate the corrosion induced spalling stress along with bending stress. The effect of the combined bending and spalling stresses are identified for the corroded RC beam. An attempt is also made to consider the effect of sustained loading and an optimum level of corrosion is proposed up to which maintenance and repair work can be executed at a minimum cost for corroded RC beams.

Total Repair Cost Simulation Considering Multiple Probabilistic Measures and Service Life

In this study, the total maintenance cost for public houses in South Korea was analyzed, and the effect of each repair process on the total maintenance cost was evaluated with probabilistic and deterministic methods. In the probabilistic method, quality of repair materials and construction skills were considered in the variability of extended service life through repair, while the deterministic method considered it by simple summation of repair step. The repair cost was analyzed considering the coefficient of variation (COV) of extended service life, so the reasonable total maintenance cost was able to be evaluated. Since the results through the probabilistic method provided a continuous cost line, a reasonable repair strategy was carried out by simply changing the intended service life of the structure. The repair cost was additionally analyzed with constant COV (0.15) of each repair process for considering various situations. The analysis results with a COV of 0.15 exhibited a slightly higher maintenance cost than those with current COV. The total maintenance costs can be adjusted if the initial repair timing is extended to the largest possible extent for the highest-repair-cost process since the total repair cost is dominated by the process with the highest repair cost.

Interaction between global warming potential, durability, and structural properties of fiber-reinforced concrete with high waste materials inclusion

Concrete production requires significant consumption of raw materials and is a major contributor to global greenhouse gas emissions. Because concrete is placed in varied, damage-inducing conditions, its durability performance is crucial for allowing the material to reach its intended service life and avoid premature replacement. In this multidisciplinary research program, a concrete is developed for both reduced environmental impact and enhanced durability compared to conventional solutions. These goals are realized through a novel combination of design parameters: recycled concrete aggregates (RCA) that increase reuse of construction demolition waste; a high-volume fly ash (HVFA) matrix that further incorporates industrial waste products while reducing portland cement content; and internal fiber reinforcement that increases composite crack resistance. The resulting high-performance concrete, designated as green hybrid fiber-reinforced concrete (GHyFRC), contains 39% waste materials by volume and is evaluated by life cycle assessment (LCA), exposure to a corrosive environment for 4.3 years, and structural loading. Corrosion activity of steel rebar embedded within GHyFRC was reduced through the low chloride permeability of a high-volume fly ash matrix and fiber reinforcement that limited crack propagation, maintaining the low designed matrix permeability. GHyFRC can be a more sustainable alternative to concrete under certain conditions by contributing to greater retention of flexural strength after corrosion has begun and lowering global warming potential (GWP) when normalized by flexural strength.

Molecular dynamics-based multiscale nonlinear vibrations of PMMA/CNT composite plates

Poly (methyl methacrylate) (PMMA)/carbon nanotube (CNT) composite plates have been extensively used in aviation and aerospace fields. During intended service life, the PMMA/CNT composite structure is prone to severe vibration, which leads to the formation of cracks and the fracture of structures. In order to achieve vibration attenuation, it requires a fundamental understanding of the vibration behavior of composite structures. Here, a molecular dynamics (MD) based multiscale approach is developed to analyze the nonlinear vibration behavior of PMMA/CNT composite plate. Molecular simulations are performed to capture the mechanical properties of the composite and constituents, including longitudinal, transverse, and shear moduli of single-walled CNT (SWCNT) segment, PMMA matrix, and PMMA/SWCNT nanocomposite. The MD simulation results are substituted into the extended rule of mixtures to derive the related efficiency parameters, which are used as the fundamental inputs in a meshless approach to predict the nonlinear vibration of macroscale functionally graded (FG)-based composite plates. According to the macroscale simulation, it is found that the arrangement of CNTs has a significant influence on the nonlinear vibration of FG-based composite plates. The developed multiscale approach provides an efficient paradigm of investigating the macroscopic behavior of composite structure in consideration of the mechanical response from microscopic constituents.