Damage State Research Articles

Research on the fatigue performance of continuous beam bridges with vibration-mixed steel fiber-reinforced concrete

To address the fatigue damage issues in continuous beam bridges under vehicle loads, a method using vibration-mixed steel fiber-reinforced concrete to improve critical vulnerable areas of the bridge is proposed, thereby enhancing the bridge’s fatigue resistance. Fatigue performance and micro electron microscopy tests were designed for vibration-mixed steel fiber-reinforced concrete, analyzing its damage conditions and microstructural changes under 0 to 2 million cyclic loads, and the key mechanical parameters of the concrete were determined. Based on this, a numerical analysis model was established to simulate the fatigue damage of continuous beam bridges under moving vehicle loads. The results show that piers made with vibration-mixed steel fiber-reinforced concrete exhibit a 56.86% reduction in compressive damage compared to conventional piers, a reduction in stiffness damage range, and a 29.35% increase in fatigue life.

Damage regularity and multifractal analysis of sol-gel reflection coating of KDP crystal under low UV irradiation flux.

This study employed multifractal analysis to investigate the changes in surface morphology of SiO2 anti-reflective coatings prepared on KDP substrates using the sol-gel method, under various conditions of ultraviolet (UV) irradiance. The coatings were successfully fabricated, and the chemical structure of the SiO2 sol was comprehensively characterized using Solid-State Nuclear Magnetic Resonance (SSNMR) technology. Under low UV irradiance (4 J/cm2), repeated experiments revealed a crack-induced mechanism of surface fatigue damage. Utilizing Scanning Electron Microscopy (SEM), the study discovered the induction effect of initial crack defects in UV-damaged coatings and established a damage model. Furthermore, Atomic Force Microscopy (AFM) was used to acquire images of the coatings' surface morphology at different damage levels, which were analyzed using the multifractal spectrum f(α). This analysis confirmed the multifractal nature of the coatings both before and after damage. This study identified significant effects of UV irradiation on the width of the multifractal spectrum and Δf, indicating that the SiO2 anti-reflective coatings exhibit multifractal characteristics under various damage states. The coatings displayed a pattern of decreasing and then increasing singularity spectrum width, height distribution unevenness, and surface roughness with increasing damage. This study demonstrates that multifractal analysis is an effective tool for describing the complexity of the surface morphology of sol-gel-derived anti-reflective coatings for the first time and for validating their multifractal properties across different stages of UV damage. HIGHLIGHTS: Damage dynamic process of KDP crystal sol-gel coating was described by SEM&AFM; The crack propagation mechanism of sol-gel coating under UV radiation is proposed; The damage evolution of sol-gel coating was described by multifractal analysis.

Salidroside and exercise performance in healthy active young adults - an exploratory, randomized, double-blind, placebo-controlled study.

Rhodiola rosea extract is purported to improve physical performance and support resilience to stress. Salidroside is considered to be one of the main constituents responsible for the ergogenic actions of R. rosea. However, R. rosea extract contains relatively little salidroside and cultivation of R. rosea is challenging as it is mainly found in high-altitude, cold regions. Additionally, the R. rosea plant is subject to conservation concerns because of its growing popularity. The purpose of this exploratory study was to evaluate the short-term effects of pure, biosynthetic salidroside supplementation on exercise performance, mood state, and markers of inflammation and muscle damage in healthy active young adults. Fifty participants (30 M, 20F; 21 ± 4 yrs; 173 ± 8 cm; 74 ± 13 kg) were randomly assigned to either salidroside (60 mg/day for 16 days) or placebo supplementation and underwent peak oxygen uptake (VO2 peak), intermittent time-to-exhaustion (TTE), and local muscular endurance assessments, along with mood state evaluations using the Profile of Mood States (POMS). Blood samples were analyzed for erythropoietin, myoglobin, creatine kinase-MM, and C-reactive protein. Salidroside supplementation enhanced overall percent predicted oxygen uptake during high-intensity intermittent exercise (p < 0.01). An increase in serum myoglobin was observed 24 hours following exercise in the placebo group (p = 0.02) compared with baseline whereas no statistically significant increase was observed for the salidroside group indicating reduced exercise-induced muscle damage. Placebo group experienced a decrease in number of intervals performed during the TTE test (p = 0.03), and a decrease in friendliness (p < 0.01) and an increase in fatigue-inertia (p < 0.01) as reported by POMS. The salidroside group exhibited stable mood states and maintained performance levels during the time-to-exhaustion test. Salidroside supplementation may enhance oxygen utilization and mitigate exercise-induced muscle damage and fatigue, warranting further research on its long-term effects and potential as an adaptogen for active individuals.

Damage monitoring on inter-lamination of GFRP via the resistance change of the MWCNT@GF sensor

The paper aimed to investigate the performance of multi-walled carbon nanotube-coated GF (MWCNT@GF) sensors on interlayer shear damage monitoring and sensing capability of glass fiber-reinforced polymers (GFRPs) based on the resistance change under short beam shear (SBS) load. The MWCNT@GF sensor, manufactured by physical vapor deposition (PVD), was embedded into the neutral layer of laminates to form an in-situ sensing network in different directions and positions. “The MWCNT@GF sensor, manufactured by physical vapor deposition (PVD), was embedded into the neutral layer of laminates to form an in-situ sensing network.” “With the help of Keithley 2700 programmable electrometer and the 3D-digital image correlation(3D-DIC), monotonic and cyclic tests were carried out.” The monotonic test found that the off-axis sensor is more sensitive to shear failure than the on-axis sensor because of its lower shear strength. In addition, the qualitative relationship between shear damage and relative resistance was established by selecting crucial moments. In the cyclical test, the relative resistance of off-axis sensors presented a cyclic mode under cyclic load. Furthermore, the relative resistance under the first 20 cyclic loads was similar to that under monotonic loads. “Furthermore, the relative resistance under the first 20 cyclic loads was similar to that under monotonic loads, which shows that the sensor has superior sensing ability. Finally, the quantitative relation between shear damage and relative resistance was established.” “That means MWCNT@GF sensors can be used to reasonably evaluate the damage state and further evaluate the service performance, reliability and remaining life of the structure.”

Mapping structural damage to material damage for analysis of urban buildings considering actual damage states

Mapping structural damage to material damage for analysis of urban buildings considering actual damage states

A molecular dynamics study on microscopic mechanism of nano-polished single crystal copper

Molecular dynamics simulations are performed to investigate the microscopic mechanism of diamond abrasive grain (DAG) polishing on the surface of single crystal copper (SCC). In this paper, the polishing parameters including the incident angle and the polishing force applied to the DAG are varied to analyze the surface morphology, friction and subsurface damage state of the workpiece. The polishing process on scratched SCC surface was also investigated. It is found that variations in the incident angle and the polishing force have significant effects on the swarf formation and internal structure of the workpiece. At small incident angle, unstable DAG motion and obvious friction fluctuations is observed. As the incident angle becomes larger, the sliding of the DAG on the workpiece surface becomes stable, and the friction force undergoes transition from the rapid growth to the stabilization phase. However, the fluctuation of dislocation density increases with the incident angle. As the polishing force increases, the sliding distance required to reach the peak of dislocation density becomes longer. In addition, the friction as well as the dislocation density show different characteristics on the scratched surface compared to the smooth surface.

In Situ Ultrasonic Characterization of Hydrogen Damage Evolution in X80 Pipeline Steel

A nondestructive evaluation of the hydrogen damage of materials in a hydrogen environment is important for monitoring the running conditions of various pieces of equipment. In this work, a new thermostatic electrolytic hydrogenation in situ ultrasonic test system (In Situ TEH-UT) was developed. The system operates by combining cross-correlation delay estimation and frequency domain amplitude estimation and hence improves measurement accuracy with respect to ultrasonic propagation time and amplitude, allowing in situ ultrasonic evaluation of the hydrogen-charging process in X80 pipeline steel. The experimental results show that under a 30 mA/cm2 hydrogen-charging current, the hydrogen saturation time of X80 pipeline steel is 800 min. Between 0 and 800 min, the attenuation coefficient and amplitude attenuation both demonstrate a strong linear relationship with the hydrogen-charging time. After 800 min, the attenuation coefficient and amplitude attenuation do not change further, while the attenuation coefficient fluctuates greatly. Through the characterization of the microstructures of the materials analyzed, it was found that hydrogen-induced cracks (HICs) constituted the main reason for the change in the ultrasonic parameters, and the mechanism behind the hydrogen-induced damage layer (HIDL) was determined. This study provides reference significance for clarifying the change mechanism of ultrasonic parameters under hydrogen damage conditions and determining the extent of hydrogen damage using an ultrasonic technique.

Protective effect of Glycyrrhizic Acid against diclofenac-induced renal damage in male albino rats

Acute renal injury is a serious condition of severe damage to the kidney tissue resulting from various causes. Some medicinal plants have been used to treat certain renal injury. The purpose of the current investigation was to determine the protective effect of Glycyrrhizic acid (GA) on kidney function in rat models with induced kidney damage by Diclofenac sodium (Voltarene®, 50 mg coated tablets). Glycyrrhizic acid was given at doses of 200 and 400 mg/kg/day orally for 30 days. Its protective effect was evaluated by renal function tests . The result showed significant decreased the elevation of urea , serum creatinine and uric acid. Also, The result show significant decrease in total cholesterol, triglyceride concentration and low-density lipoprotein, and a significant increase in high-density lipoprotein concentration. Therefore, GA can be used for the prevention and treatment of renal damage and some kidney and liver disorders.

A direct energy-based design method for damping control reinforced concrete structure: methodology and application

Energy-based seismic design, which integrates both the accumulated hysteretic energy and plastic deformation of the structure, provides a more comprehensive evaluation of structural seismic performance compared to other performance-based seismic design methods. In damping control structures, the distribution of hysteretic energy is clearly defined, with the expected positions for energy dissipation and damage concentrated in the dampers. This facilitates the application of an energy-based design method in such structures. This research presented a novel direct energy-based design (DEBD) method for damping control reinforced concrete (RC) structures, following the principle that the energy dissipation capacity of the structural members and dampers exceeds the hysteretic energy dissipation demand. With this principle, an energy-based damage index, which is directly correlated with structural damage state, was introduced. Subsequently, a detailed energy-based design process was provided. To achieve the desired seismic performance, the required energy dissipation capacity of dampers was determined using a pre-select damage index, and thereby, identifying the design parameters of the dampers. Finally, to validate the feasibility of the proposed design method, an 8-story RC frame with friction dampers was chosen as an example. The energy dissipation capacity and damage state of the designed structure were evaluated through nonlinear time-history analyses, and the results demonstrate the successfully achievement of the predefined seismic performance.

Structural Online Damage Identification and Dynamic Reliability Prediction Method Based on Unscented Kalman Filter

As sensor monitoring technology continues to evolve, structural online monitoring and health management have found numerous applications across various fields. However, challenges remain concerning the real-time diagnosis of structural damage and the accuracy of dynamic reliability predictions. In this paper, a structural online damage identification and dynamic reliability prediction method based on Unscented Kalman Filter (UKF) is presented. Specifically, in the Wiener degradation process with random effects on structural performance, the structural damage identification is initially realized using UKF. Following that, the EM algorithm is employed for estimating the performance model parameters. Eventually, dynamic reliability prediction is realized based on conditional probability. The simulation results indicate that the method effectively estimates the damage state during the structure’s use while providing accurate, real-time, and dynamic reliability predictions for the system.

Characteristic stress response law and fracture precursor of granite under different dynamic disturbance damage conditions

Characteristic stress response law and fracture precursor of granite under different dynamic disturbance damage conditions

Effect of Time and Stress on Creep Damage Characteristics of Cement-Based Materials

In the realm of daily life, ensuring the safety of building structures and civil engineering projects remains a paramount research focus. The creep properties of materials significantly influence their long-term loading process. Specifically, creep load and creep time are pivotal factors that impact material creep damage, thereby playing a crucial role in assessing the safety of engineering endeavors and estimating aspects such as housing construction. This study undertakes creep damage tests on cement-based materials, subjecting them to varying creep loads and creep times, and subsequently conducts uniaxial compression tests on the specimens post-creep damage. The refined Nishihara model is employed for data fitting, facilitating the construction of a creep damage time-stress model. Concurrently, a Neural Network model is utilized to validate the experimental data. The findings indicate that both steady-state creep strain and steady-state creep rate exhibit discernible trends relative to creep load and creep time, effectively mirroring the alterations in creep damage experienced by the specimens. The refined Nishihara model proves adept at predicting and equating creep damage under diverse creep loads and creep times. Similarly, the trained Neural Network model demonstrates capability in measuring and estimating various creep damages. The study successfully explored the correlation between creep time and creep load, enabling the simulation of long-term creep damage within a shorter creep time and facilitating an analysis of its physical and mechanical properties, which is pivotal in predicting the safety of large-scale engineering projects. Concurrently, it advances research on material damage equivalence, offering insights and theoretical groundwork for developing a system to assess material damage equivalence under various damage conditions.

Component Restoration Models of Highway Bridges for Resilience Assessment: A Nationwide Expert-Opinion Survey Study and Application

This study performs a nationwide expert-opinion survey in Mainland China to establish component restoration models of highway bridges toward high-fidelity resilience assessment. To this end, a questionnaire based on component damage states is designed to collect expert opinions on key variables of the restoration models, including loss of functionality, traffic decision, idle time, repair strategy, and recovery time. More importantly, this study introduces the concept of repair-induced loss of functionality into the component restoration models, in addition to the traditional earthquake-induced loss of functionality. According to the survey results, both deterministic and probabilistic restoration models are developed, where the former is for practical application while the latter characterizes epistemic uncertainties in the key variables. Finally, a case study on a highway bridge with multiple types of vulnerable components is carried out to illustrate the application of the component restoration models for full bridge resilience assessment.

Study on thermal damage characteristics and micromechanical behavior of structures induced by spontaneous combustion of low-rank coal

Thermal damage induced by coal spontaneous combustion (CSC) has a significant impact on its development. In this study, low-rank coals were heat-treated (25–500 °C). Experiments such as nuclear magnetic resonance, scanning electron microscopy, and uniaxial compression were used to visualize and quantify the evolution of pore structure and structural strength during CSC. A multi-component discrete-element model of coal thermal fracture was developed and a sensitivity analysis of the micromechanical behavior of CSC was carried out. The results showed that during CSC, the micropores in coal gradually evolved into mesopores or macropores, and the pore diameter, porosity and permeability can be increased to 5.51 μ m, 21.05 % and 1.51 mD respectively with the temperature. Significant thermal damage occurred in low-rank coal at 100 °C, leading to a sharp decrease in its load-bearing capacity, which made it easier to reach the damage condition and produce more cracks. And then the thermal damage was fluctuating with the increase of temperature. From 100 °C to 500 °C, the micromechanical behavior of low-rank coal is similar, and the variation of the critical value with temperature is small. The study results can serve as a reference for controlling coal fires.

Rapid post-earthquake damage assessment of building portfolios through deep learning-based component-level image recognition

Frequent seismic events significantly heighten the likelihood of the building structure being impacted throughout its operational lifecycle. Seismic effects on these structures result in a notable reduction in structural safety and serviceability. Enabling the post-earthquake recovery of building structures necessitates a precise and swift assessment of earthquake-induced damage. The conventional method for assessing building damage involves collecting data through close manual observation or contact inspection. Although it can obtain relatively accurate results by combining evaluation specifications, it is time-consuming and labour-intensive. Deep learning (DL) is data-driven and employs computational methods for data processing. The image classification function of convolutional neural network (CNN) in DL brings great convenience to image data processing. It has been applied to various aspects of structural health monitoring/post-disaster assessment. However, most of the current studies focus on the component level and lack of a comprehensive perspective on the whole structure, which is not conducive to the judgment of the overall condition. Consequently, this paper proposes a rapid assessment method of the overall damage level of post-earthquake buildings based on component images and DL. Two component-level image classification models, component type and damage level, are firstly trained. Then, the images of the buildings to be evaluated after the earthquake are collected and classified. Combined with the weights of different component types and damage levels proposed, the overall condition scores and grades of the structures can be obtained by weighted calculation. The proposed method realizes an overall evaluation of the structural damage condition after seismic events, and further extends to the building portfolios, providing actionable guidance for subsequent personnel and fund allocation, rescue, and maintenance measures. Due to limitations in the dataset, such as the potential biases in the training dataset, the trained model is not perfect and faces challenges in distinguishing between minor and moderate damage. In the future, the dataset should update and ideally cover a wide range of building types, component types, and damage levels to ensure the model's robustness and applicability to various real-world scenarios.

Improving the seismic response of existing shear wall structures through experimentally validated high-performance RC retrofit

Since reinforced concrete (RC) multistory shear wall (MSSW) buildings comprise an essential part of modern urban built environments, it is vital to investigate the failure modes of existing SW systems through shake-table testing (STT) and propose effective techniques to mitigate their seismic risk. Thus, this study aims to enrich the literature with STT results of two-story shear wall (2SSW) specimens representing the lateral force-resisting system (LFRS) and construction practice of pre-seismic code MSSW structures before and after the retrofit. The study also experimentally verifies the effectiveness and modeling approach of a contemporary technique comprising thin high-performance reinforced concrete (HPRC) jackets and steel angles to enhance the SW buildings’ seismic performance. Following assessing the seismic response of an existing SW specimen through pre-STT dynamic simulation, the first phase of the STT campaign confirmed the vulnerability of the substandard 2SSW primarily to bond slip failure at the construction joint. The STT results of a second 2SSW specimen retrofitted with HPRC jackets and steel plates confirmed that the unfavorable failure mode at construction joints was delayed from 0.96 g to 1.44 g. At the same input ground motion intensity that triggered the bond slip for the substandard 2SSW, the maximum top drift ratio and chord rotation of the enhanced 2SSW specimen were significantly reduced by 93.5 % and 91 %, respectively. Finally, the effectiveness of the risk-mitigation technique when applied to a three-dimensional simulation model of a real-life SW building is confirmed through probabilistic seismic performance assessment. Under the most significant seismic events at the design-based earthquake (DBE), the probability of the continued occupancy damage state improved from 26 % to almost 100 %. Signs of damage, including impaired occupancy, structural damage, and collapse, were mitigated at DBE through the proposed measures to reduce the seismic risk of existing SW structures.

Operational Modal Analysis and Safety Assessment of a Historical Masonry Bell Tower

The seismic assessment of historical masonry bell towers is of significant interest, particularly in Italy, due to their widespread presence and inherent vulnerability given by their slenderness. According to technical codes and standard practice, the seismic evaluation of masonry bell towers can be conducted using a range of methodologies that vary in their level of detail. This paper presents a case study of a historical masonry bell tower located in the Caserta Province (Italy). Extensive investigative efforts were undertaken to determine the tower’s key geometric and structural characteristics, as well as to document ongoing damage phenomena. The dynamic behavior of the tower was assessed through ambient vibration testing, which enabled the identification of the principal modal shapes and corresponding frequencies, also highlighting peculiar dynamical characteristics caused by the damage conditions. Subsequently, the seismic assessment was carried out using both Level 1 (simplified mechanical) and Level 2 (kinematic limit analysis) methodologies. This assessment helped identify the most probable collapse mechanisms and laid the foundation for employing more advanced methodologies to design necessary retrofitting interventions. The study emphasizes the importance of Level 2 analyses for structures where out-of-plane failure mechanisms are likely due to pre-existing cracking. Both approaches provide less-than-unity acceleration factors, ranging from 0.45 for Level 1 (assuming non-ductile behavior) to 0.59 for Level 2, in this case specifically using the information available about existing cracking pattern.

Detection and assessment of post-earthquake functional building ceiling damage based on improved YOLOv8

Ceiling is one of the crucial non-structural components in public buildings, but it is susceptible to damage after earthquakes. For important functional buildings, rapid assessment of their safety, economic losses, and recoverability is crucial post-earthquake. However, the current detection and assessment of ceiling damage in earthquake-stricken areas heavily relies on manual efforts. Due to limitations in detection methods and technological levels, these manual efforts struggle to meet the requirements of speed, accuracy, and safety. In response to these challenges, this study proposes a post-earthquake functional building ceiling damage detection and assessment method based on GTS-YOLOv8. Firstly, a dataset containing 1059 real ceiling damage images is established, categorized into two damage types: “Panels Fallen" (PF) and “Complete Destruction" (CD). Next, Ghost convolution is introduced, combined with Swin Transformer blocks, and a novel Slim Neck structure is designed to enhance the YOLOv8 algorithm. The GTS-YOLOv8 object detection model is presented. On the established dataset, GTS-YOLOv8 achieves 92 % mAP50 and 72.2 % mAP50-95, surpassing the baseline YOLOv8 by 2.3 % and 4.1 %, respectively. The study investigates ceiling damage detection under different lighting conditions and shooting distances. The results indicate that the highest detection accuracy is achieved under well-lit conditions and when the shooting perspective covers the entire ceiling area. Finally, based on the research outcomes, a detection and assessment architecture is constructed, and a corresponding system is developed, capable of automatically determining the damage State based on ceiling damage detection results. This architecture provides a foundation for the rapid assessment of building safety, economic losses, and recoverability post-earthquake.

Seismic Fragility Analysis for Probabilistic Risk Assessment of Underground Structures

ABSTRACT The seismic assessment of urban tunnels, crucial for city infrastructure, particularly shallow tunnels in transportation systems, is vital for risk mitigation. This study focused on the Ahwaz twin tunnels in Iran, using incremental dynamic analysis and probabilistic risk assessment. Evaluating seismic behavior through 15 earthquake records, the study generated fragility curves for operational, minor, moderate, and extensive damage states. Results indicate a 99.5% probability of operational limit at a PGA of 0.35 g, with seismic risk assessment aligning with safety class 3 of the Swedish Transportation Administration.

Study on Damage Index for Beam–Column Joints with Flush End-Plate Connections

Experimental results from 109 flush end-plate (FEP) connections were analyzed to investigate the failure modes and damage index of FEP connections across various damage states. The present study was conducted in accordance with the performance design objectives specified in China’s GB50011-2010 Code for Seismic Design of Buildings. The observed rotation angles and corresponding rotation factors were systematically categorized using a probabilistic statistical approach, with the 95% confidence lower limit as the primary constraint. The damage states of FEP connections were classified as virtually undamaged, lightly damaged, moderately damaged, severely damaged, and joint failure. A minimum plate thickness of 12 mm and a minimum high-strength bolt diameter of 20 mm are recommended to be used for the FEP connections, in accordance with building codes in China, the United States, and Europe. Quasi-static tests of six FEP connections were conducted to validate the damage-state categorization. The results revealed that for connections undergoing moderate and severe damage, the mean rotation factor deviated from the theoretical values proposed in this study by 3.7% and 9.4%, respectively. Therefore, the damage state of FEP connections can be reliably predicted based on different rotation angles using the damage-state categorization presented herein.