Engineering Damage Research Articles

Enhancing Functionality and Minimizing Damage of Air Valves in Pipelines Using FRP Sheets

Pipelines play a vital role in ensuring the efficient and secure transportation of water, making their performance to keep the water continuously going vital. This research explores the influence of air valves on the localized damage and overall functionality of the pipelines. Air valves are critical components that help stabilize pressure and prevent vacuum formation. However, their installation can introduce structural weaknesses in localized areas. The study employs FEM modeling alongside field data from a collapsed bridge to assess the performance and damage in the vicinity of air valves. The findings reveal that strategic redesigns, such as optimizing air valve placement and reinforcing surrounding areas, can significantly enhance performance while mitigating local damage. Additionally, the research highlights the effectiveness of repair methods in increasing pipeline resistance to bending stresses and compares various repair and design approaches, providing new insights into mitigating structural damage in aqueduct bridges. This study addresses a critical gap in the literature, offering a thorough approach to understanding and addressing air valve-related damage in engineering.

A modular approach to 3D-printed bilayer composite scaffolds for osteochondral tissue engineering

Prolonged osteochondral tissue engineering damage can result in osteoarthritis and decreased quality of life. Multiphasic scaffolds, where different layers model different microenvironments, are a promising treatment approach, yet stable joining between layers during fabrication remains challenging. To overcome this problem, in this study, a bilayer scaffold for osteochondral tissue regeneration was fabricated using 3D printing technology which containing a layer of PCL/hydroxyapatite (HA) nanoparticles and another layer of PCL/gelatin with various concentrations of fibrin (10, 20 and 30 wt.%). These printed scaffolds were evaluated with SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared Spectroscopy) and mechanical properties. The results showed that the porous scaffolds fabricated with pore size of 210–255 µm. Following, the ductility increased with the further addition of fibrin in bilayer composites which showed these composites scaffolds are suitable for the cartilage part of osteochondral. Also, the contact angle results demonstrated the incorporation of fibrin in bilayer scaffolds based on PCL matrix, can lead to a decrease in contact angle and result in the improvement of hydrophilicity that confirmed by increasing the degradation rate of scaffolds containing further fibrin percentage. The bioactivity study of bilayer scaffolds indicated that both fibrin and hydroxyapatite can significantly improve the cell attachment on fabricated scaffolds. The MTT assay, DAPI and Alizarin red tests of bilayer composite scaffolds showed that samples containing 30% fibrin have the more biocompatibility than that of samples with 10 and 20% fibrin which indicated the potential of this bilayer scaffold for osteochondral tissue regeneration.Graphical

A first-principles study of the effects of temperature on the atomic and electronic structures of Mg-montmorillonite with H2O molecule adsorption

The interaction between water and soft rock rich in clay minerals is one of the main factors causing damage in soft rock tunnel engineering. The effects of temperature on the atomic structure and water absorption capacities of clay minerals cannot be ignored. In the present study, the influence of temperature on the microstructure of Mg-montmorillonite and the thermal stability of the Mg-montmorillonite (010) surface were calculated based on density functional theory. Furthermore, the adsorption properties of H2O molecules within different coverages (0 < Θ ≤ 1.0 ML) on the (010) surface were investigated in the temperature range of 0–900 K. First, the volume of Mg-montmorillonite expanded significantly with increasing temperature along the z-axis direction. The surface energy of the Mg-montmorillonite (010) surface decreased with increasing temperature, indicating that the high temperature weakened the interatomic interactions on the surface. Moreover, the calculations demonstrated that H2O molecules could still be stably adsorbed on the Mg-montmorillonite (010) surface at different temperatures, and the order of stable adsorption configurations for a single H2O molecule was hollow > bridge > interlayer bridge > top sites. With increasing coverage of H2O molecules, the adsorption energies increased for the top sites, while decreased for the bridge, hollow, and interlayer bridge sites at high temperature. In addition, the changes in atomic structure and electronic characteristics during water absorption were further explored by calculating the ICOHP, PDOS, and lattice relaxation.

Damage-driven framework for reliability assessment of steam turbine rotors operating under flexible conditions

The high-temperature rotating structures (HTRS), e.g., steam turbine rotors, often operate in extremely harsh environments with a flexible load condition during peak shaving of power system. In this work, a damage-driven framework for reliability assessment is developed in terms of the cumulative damage-damage threshold interference (CD-DT) principle, in which the cumulative damage and damage threshold are regarded as two random parameters to address uncertainties. The CD-DT principle is founded on the engineering damage theory and incorporates physics-of-failure into the probabilistic modeling of high-temperature structural reliability. Probabilistic damage analysis, correlation analysis of weak sites, system-level reliability analysis, and sensitivity analysis have been encompassed in this framework. Three numerical examples are used to verify the effectiveness and applicability of the proposed framework. Application to steam turbine rotor involving multiple weak sites with multi-damage modes illustrate the implementation procedures of the framework. Results show that the reliability-based design life of rotor decreases with the increases of start-stop frequency, the implementation of a two-shift operation would pose a threat to meeting the safety requirement of a 30-year design life. Furthermore, sensitivity analysis highlights the critical influences of initial rotor temperature and speed rising rate on rotor reliability, providing insights for operational maintenance and reliability optimization.

Evolution of Pore Structure and Fractal Characteristics in Red Sandstone under Cyclic Impact Loading

Fatigue damage can occur in surface rock engineering due to various factors, including earthquakes, blasting, and impacts. The underlying cause for the variations in physical and mechanical properties of the rock resulting from impact loading is the alteration in the internal pore structure. To investigate the evolution characteristics of the pore structure under impact fatigue damage, red sandstone subjected to cyclic impact compression by split Hopkinson pressure bar (SHPB) was analyzed using nuclear magnetic resonance (NMR) technology. The parameters describing the evolution of pore structure were obtained and quantified using fractal methods. The development of the pore structure in rocks subjected to cyclic impact was quantitatively analyzed, and two fractal evolution models based on pore size and pore connectivity were constructed. The results indicate that with an increasing number of impact loading cycles, the porosity of the red sandstone gradually increases, the T2 cutoff (T2c) value decreases, the most probable gray value of magnetic resonance imaging (MRI) increases, the pores’ connectivity is enhanced, and the fractal dimension decreases gradually. Moreover, the pore distribution space tends to transition from three-dimensional to two-dimensional, suggesting the expansion of dominant pores into clusters, forming microfractures or even macroscopic fissures. The findings provide valuable insights into the impact fatigue characteristics of rocks from a microscopic perspective and contribute to the evaluation of time-varying stability and the assessment of progressive damage in rock engineering.

Real-time seismic damage simulation for urban building portfolio based on basic building information and machine learning

Timely and accurate simulation of seismic damage of the urban building portfolio is essential for pre-earthquake planning and post-earthquake rescue. This study proposes a real-time seismic damage simulation method for the urban building portfolio based on the multiple degree-of-freedom (MDOF) shear and flexural-shear model established by basic building information and machine learning. The formulas for predicting periods of six types of structures are proposed, and the surrogate model-I for predicting the critical inter-story hysteretic parameters are established to optimize the MDOF models. The surrogate model-II is established to rapidly predict the engineering demand parameters and damage states of structures under earthquakes. Regarding the generalization capability, an incremental learning strategy is advised to guarantee the accuracy of the surrogate model-II in predicting the seismic damage of other urban building portfolios. The results in two city-scale cases show that the proposed method can achieve real-time seismic damage simulation of urban building portfolio with acceptable accuracy, and it's not necessary to retrain or only needs minor additional training on the existing surrogate model when applied to other urban building portfolios.

Damage characteristics of rock induced by unloading in hole under true triaxial boundary stresses: Experimental study

In order to study the effect of unloading of underground rock excavation on the stability of surrounding rock, the true triaxial compression (TTC) and coupled true triaxial compression and in-hole loading-unloading tests (TTC-HU) were conducted on hollow cubic rock (100mm × 100mm × 100mm). The experimental results indicate that the compressive strengths of the specimens increase as confining pressure increases in the equal biaxial stressand increase with increasing intermediate principal stresses in the unequal biaxial stress. At low confining pressure (σ < 30 MPa), the internal stress at unloading damage in the hole of hollow cubic specimen increases with the increase of the three-directional boundary stresses. At high confining pressure (σ ⩾ 30 MPa), the specimen will not be damaged during the entire unloading process in the hole. The damage mode of the specimen is dominated by tensile damage. The shape of the holes in the specimens did not significant change, and hole wall of specimen have layered destruction along the circumference in low confining pressure. In high confining pressure, the hole area of the specimen undergoes significant deformation damage, forming a V-groove along the direction of the minimum principal stress, and the wall of the hole is completely peeled off. This study can reasonably predict the actual engineering damage patterns and guide the optimization of surrounding rock support.

Key technologies for improving resilience of super-large diameter shield tunnel affected by large variable loads underneath the Yellow River

Environmental conditions may have a significant impact on the construction and operation of underground works, and sudden changes in environmental conditions may lead to underground engineering damage. Considering the Yellow River crossing tunnel on Huanggang Road in Jinan as an example, this paper analyzes the mechanical performance of the lining of the shield tunnel with an external diameter of 16.8 m, which faces the challenge of large variable loads in operation stage, such as deep riverbed erosion and deposition, large-scale heightening of river embankment, seasonal changes in groundwater level, and key technologies for improving the resilience of tunnel structure are proposed accordingly. The results can not only assist in the construction of the super-large-diameter shield tunnel project in Jinan City but also provide technical support for other shield tunnel projects crossing rivers, lakes, and seas.

Effects of modified organic material addition on soil and microbial communities in ecologically restored engineering slopes of the Qinghai-Tibetan plateau: A mesocosm study

Organic material plays an essential role in the ecological restoration of different types of surfaces with engineering damage in extremely fragile environments. An outdoor mesocosm experiment was conducted to explore the effects of modified organic material on chemical, physical properties and microbial communities of reconstructed soil in ecologically restored engineering slopes of the Qinghai-Tibetan plateau. The physical and chemical properties of the soil indicate that the addition of modified organic materials significantly improves soil nutrients. In this area, organic carbon increased by 1.87 g·kg−1 in the frame beam slopes compared with the control area, and the potassium content doubled. In addition, modified organic material effectively induced soil metabolism responses, mainly promoting the activities of soil enzymes like amylase, cellulase, urease, sucrase, and alkaline phosphatase. Moreover, addition of modified organic material noticeably changed the abundance and structure of microbial communities in soils. The enhanced concentrations of the signal molecules N-acylated-L-homoserine lactone and auto inductor peptide indicated that addition of modified organic materials significantly influenced quorum-sensing in soil microbial communities. There are differences in the soil improvement effects of different types of slopes, among which the frame grid beam has the best effect. These findings demonstrate the effect and underlying mechanisms of the addition of incorporating modified organic materials, primarily sodium carboxymethyl cellulose and anionic polyacrylamide, into the soil of engineering slopes. These results have extensive application prospects for ecological restoration in strict environments.

Damage assessment of High-Stress brittle surrounding rock masses in a deep Large-Span High-Sidewall underground Cavern: In situ measurement and numerical simulation

Excavation within high-stress brittle rock masses often encounters severe problem of structural damage in deep underground engineering, necessitating a significant scientific demand for accurately assessing the damage to surrounding rock masses through in-situ measurement and numerical simulations. This study reports detailed findings from an exhaustive investigation on the damage characteristics and underlying mechanisms in the high-stress brittle surrounding rock masses during excavation at the Shuangjiangkou (SJK) underground caverns. These findings were obtained through a comprehensive long-term in situ measurement using multi-point extensometer monitoring, borehole digital optical televiewer observing, and acoustic testing. Based on a deep understanding of the damage and failure mechanisms peculiar to the SJK high-stress brittle surrounding rock masses, a new damage index specifically designed for high-stress brittle rock masses was developed. This index is formulated by incorporating the failure approach concept into a modified Hoek−Brown criterion adapted for high-stress brittle rock masses. Comparison between the numerical predictions and in situ measuring results of the excavation damage zones during layered excavation of the SJK underground powerhouse revealed remarkable concordance. This consistency validates that the newly proposed damage index has good applicability and reliability for quantifying excavation-induced damage in high-stress brittle surrounding rock masses. These research findings are poised to provide valuable insights into the damage identification of brittle surrounding rock masses subjected to high-stress excavation, contributing to optimize excavation design and enhance the safety and sustainability of underground engineering projects.

Study on Damage Inference for Superstatic Trusses

Based on the damaged statically indeterminate truss, this study uses the Bayesian and Opensees methods to study and deduce the damage of damaged members. Multiple schemes are used for inference in order to compare multiple loading schemes to obtain the best loading scheme. By changing the error comparison, it can be found that the smaller the error, the more concentrated the posterior distribution, and the closer to the result. By changing the comparison of measuring points, it can be found that the closer the measuring points are to the damaged bar, the more concentrated the posterior distribution is, and the better the effect is. In combination with the prior distribution, increasing the number of cycles has little effect on the results. Through these comparisons, this study mainly finds out the key factors to infer structural damage in practical engineering, so that the damage inference of statically indeterminate truss can better serve the practical engineering.

Experimental investigation on the characteristics of the shock wave emitted by the cavitation bubble near the air bubble

This study explores the mitigation of cavitation damage in hydraulic engineering through air entrainment. The primary aim is to experimentally analyze the shock wave characteristics emitted by cavitation bubbles adjacent to air bubbles affixed to a tube nozzle. The schlieren optical system is utilized to visualize the shock wave, while a hydrophone measures its pressure. Experiments are conducted on cavitation bubbles induced by the spark-generated method in the vicinity of air bubbles, varying the dimensionless distances and sizes of the air bubbles. The results indicate that (1) The introduction of an air bubble noticeably changes the morphology, kinematic behavior, and shock wave features of the cavitation bubble. (2) Four distinct shock wave patterns are identified based on the quantity and shape of the shock wave, with variations in the cavitation bubble's collapsing behavior and shock wave characteristics across different patterns. (3) The dimensionless distance γ and size δ exert significant influence on the shock wave's quantity, pressure peak, shape, and energy. With γ decreases or δ increases, the shock wave quantity increases while the shock wave intensity decreases. This investigation of the interaction between cavitation bubbles and air bubbles is essential for elucidating the mechanism through which air entrainment mitigates cavitation damage.

Performance Assessment of Reinforced Concrete Bridges Under Coupled Horizontal and Vertical Ground Motions Using Fragility Surfaces

ABSTRACT The objective of this study is to explore the seismic fragility of reinforced concrete bridges, specifically in response to the vertical components of ground motions, utilizing fragility surfaces. The examination of bridge responses involves the application of optimally selected intensity measures through three-dimensional nonlinear time-history analyses, encompassing uncertainties in both superstructure materials and soil–structure interaction effects. In this investigation, an extended Probabilistic Seismic Demand Model (e-PSDM) is employed, leveraging fragility surfaces to concurrently consider vertical and horizontal excitations. The results obtained from this approach are compared with traditional fragility curves. This study emphasizes Pile-cap displacement and drift ratio as pivotal engineering damage parameters, acknowledging their sensitivity to the influences of both soil–structure interaction effects and vertical ground motion. The fragility surfaces derived from the study reveal a correlation between increased vertical spectral accelerations and elevated probabilities of surpassing both slight damage and collapse limit states. These observations underscore the critical significance and practical utility of fragility surfaces in the context of performance-based seismic assessment and design for reinforced concrete bridges. The findings from this research contribute valuable insights into the nuanced behaviour of reinforced concrete bridges under seismic conditions, emphasizing the relevance of incorporating vertical components in fragility assessments for a more comprehensive understanding of structural vulnerability.

Macroscopic and microscopic mechanical characteristics and crack propagation behavior of sandstone-like samples with single cracks under freeze–thaw cycles: Experimental and numerical simulation

In permafrost regions, rock engineering projects inevitably suffer from the effects of freeze–thaw (F-T) cycles under complex geographical and climatic conditions. Under F-T cycles, the damage and deterioration of macro- and microdefects, such as joints and cracks, in the rock will reduce the structural stability of the rock and even lead to frost damage in rock engineering. In this study, through indoor F-T cycle tests, uniaxial/triaxial compression tests, acoustic emission monitoring, and discrete element method (PFC 3D) modeling, the macro/microscopic mechanical characteristics and crack propagation behavior of sandstone-like samples with single cracks under F-T cycles were investigated. The results show that the compressive strength of sandstone-like samples with single cracks tends to decrease and then increase with an increasing crack angle and exhibits a stable decreasing trend with increasing F-T cycles, indicating a significant crack angle effect and F-T deterioration effect. Additionally, the confining pressure has an inhibiting effect on the F-T deterioration of samples, and there is a mutual inhibition relationship between the F-T deterioration effect and the crack angle effect. The characteristics of the acoustic emission signals during the loading process of sandstone-like samples with single cracks show good consistency with the stress–strain curves. The analysis of fracture mechanisms based on rise time/amplitude (RA) and average frequency (AF) is consistent with the macroscopic failure modes observed in the experiments. Moreover, with an increase in the number of F-T cycles, the number of tension cracks in the sandstone-like samples with single cracks increases, while the number of shear cracks decreases. The crack propagation behavior of sandstone-like samples with single cracks obtained through discrete element simulations (PFC 3D) is mainly divided into four stages: Stage I - initial calm stage, Stage II - crack initiation stage, Stage III - crack propagation stage, and Stage IV - failure stage. The simulated mechanical properties and failure modes agree well with the experimental results, and five crack propagation modes of sandstone-like samples with single cracks under F-T cycles were proposed: direct tension (DT), relative tension (RT), shear-tension (ST), direct shear (DS) and relative shear (RS).

Characteristics of loess wind sorting and its structural mechanical significance

As loose sediment transported and deposited by wind, changes in the grain size of loess is the main source of changes in its macromechanical properties, mesostructural characteristics and microparticle effects. However, at present, there is almost no relevant research on the relationship between grain size and structural mechanics of wind-sorted loess, which significantly restricts the in-depth understanding of the mechanism and evolution of geological disasters and resulting engineering damage. In this paper, grain size optimization is performed by a wind sorting device developed in this laboratory to reveal the intrinsic mechanism associated with sorting, structural mechanics and particle interactions. The results show that the average grain size is positively correlated with the wind speed and negatively correlated with the transport distance. Further study finds that the grain size of aeolian loess consists of superimposed medium and fine particle fractions with good distribution sorting and coarse particle fractions with poor distribution sorting. Under the same conditions of water content and dry density, cohesion increases with increasing transport distance and wind speed. However, the internal friction angle first decreases and then slowly increases during the whole wind transport process. Fine particle content is the decisive factor for the change in shear parameters. Microscopic analysis shows that the contact mode, pore characteristics, azimuth of particles and variations in coarse, medium and fine ternary particle accumulations are closely related to the grain size distribution caused by wind sorting. The negative (loosening, wall, wedge) and positive (filling, adsorption) effects in these microstructures correspond to the structural characteristics of soil at different transport distances, and different structural characteristics correspond to different mechanical properties. This correspondence fully reveals the close relationship between the grain size characteristics produced by wind sorting and structural mechanics. This study helps to elucidate the relationship between grain size variation and mechanical characteristics of aeolian loess and provides theoretical references for relevant applications in the fields of geological and geotechnical engineering.

A novel molecular modeling approach for simulating asphalt-aggregate debonding: Considering interfacial moisture migration

The asphalt-aggregate debonding behavior in moisture environments is a fundamental but unresolved issue in pavement engineering. In this study, a novel molecular dynamics (MD) modeling method was developed to address this challenge. Compared with previous layered modeling methods, the new method considers the moisture diffusion and migration at the interface, which better reflects the real debonding process. Based on the results, we found a layered diffusion phenomenon at the interface, which significantly affects the efficiency of moisture migration and interfacial debonding. The strong interactions between water molecules and alkaline aggregates (represented by calcite) restrict the interfacial moisture diffusion and migration, making it more resistant to moisture damage than acidic aggregates (represented by quartz). This study highlights the limitations of energy-based parameters obtained from the layered modeling method and resolves a long-standing controversy over whether calcite or quartz is more susceptible to water damage. Findings from this research contribute to comprehending the fundamental debonding mechanisms and provide an atomic-level perspective to investigate moisture damage in pavement engineering.

Investigation on the frost heave-induced pressure and hydro-thermal processes in freezing soil under rigid constraint and hydraulic pressure

Frost damage in engineering is closely related to hydraulic pressure in artificial freezing ground areas and cold regions; however, limited studies have focused on this relationship. To clarify the evolution of frost heave-induced pressure (FHIP) and its effect on engineering stability, unidirectional freezing tests are performed under rigid constraint and various hydraulic pressures. The results indicate that the development of the FHIP is induced by ice growth. Meanwhile, the FHIP increases with hydraulic pressure, which consequently increases the pore water pressure (PWP) at the base of the warmest ice lens. When the PWP on both sides of the frozen fringe reaches equilibrium, the water stops migrating, ice stops growing, and FHIP stops increasing. The frozen fringe is captured via X-ray computed tomography, and a model for calculating the maximum FHIP is developed based on the frozen fringe theory. The model is validated and compared with the experimental results. The increased FHIP prevents water migration in freezing soil by increasing the soil density and decreasing the segregation temperature of the frozen fringe. Additionally, the factors contributing to the increase in FHIP are discussed, and an application of this study to engineering design and maintenance in cold regions is proposed.

A research on excavation compensation theory for large deformation disaster control and a review on the multiphysical–multiscale responses of salt rock for underground gas storage

A research on excavation compensation theory for large deformation disaster control and a review on the multiphysical–multiscale responses of salt rock for underground gas storage

Towards Determining an Engineering Stress-Strain Curve and Damage of the Cylindrical Lithium-Ion Battery Using the Cylindrical Indentation Test

Mechanical internal short circuit (ISC) is one of the significant safety issues in lithium-ion battery design. As a result, it is possible to subject LIB cells to thorough mechanical abuse tests to determine when and why failure may occur. The indentation test is a recommended loading condition for evaluating mechanical damage and ISC. In this study, 18,650 cylindrical battery cells underwent indentation tests and a voltage reduction following the peak force identified by the ISC. Due to the complexity of the contact surface shape between two cylinders (LIB cell and indenter), a new phenomenological analytical model is proposed to measure the projected contact area, which the FEM model confirms. Moreover, the stress-strain curve and Young’s modulus reduction were calculated from the load-depth data. In contrast to previously published models, the model developed in this paper assumes anisotropic hyperelasticity (the transversely isotropic case) and predicts the growing load-carrying capacity (scalar damage), whose variation is regulated by the Caputo-Almeida fractional derivative.

Damage Model and the Influence Factors of Mitigation Engineering against Glacial Debris Flow in the Parlung River Basin, SE Tibetan Plateau

Understanding the damage mechanism of glacial debris flow mitigation systems is crucial for the risk prevention and assessment of the 200 km traffic corridor in the Southeast of the Tibetan Plateau, where the Sichuan-Tibet railway and expressway have been planned. Based on the phenomena, position and residual efficiency of damaged engineering, our analysis of satellite imagery and field investigation in multitype spatial reveals the damage types and influencing factors of glacial debris flow mitigation engineering. An evaluation model which can be used to estimate the engineering damage grade is established by using the relationship between mono engineering works and mitigation systems. In the new model, the engineering damage is divided into five grades: undamaged, slightly damaged, relatively damaged, seriously damaged, and totally damaged. For glacial debris flow in the Parlung river basin, the five grades of damage of mitigation works account for 8.70%, 34.78%, 21.74%, 13.04% and 21.74%, respectively. Furthermore, the soil source type and channel profile gradient are the key factors in engineering damage. Design defect of profile gradient is the controlling factor of damage in drainage channel engineering. Based on those results, an engineering damage model is established, which can provide an important reference for risk reduction and prevention of hazards due to the increasing development of traffic engineering.