Damaged Areas Research Articles

Parametric Study on Structural Performance According to the Condition Grade of Open-cut Electric Power Tunnel

In this study, the structural performance of electric power tunnels was evaluated based on the type and degree of damage. For experimental performance evaluation, a power structure test specimen was designed with a state safety performance of grade D corresponding to a concrete damage area ratio of 44% and structural safety performance of grade D with a reduced cross-section of 25% of the main reinforcement of the upper slab. The electric power structures with grade D state safety performance and structural safety performance exhibited 63% load-bearing capacity compared to those without damage. Cracks occurred on the outside of the structure under the experimental conditions simulating the overburden load, implying the possibility of corrosion of the outer reinforcing bars of the real structure. Finite element analysis showed that reducing the area of the outer main rebar of the upper slab caused more significant reduction in the load-bearing capacity than that of the inner main rebar.

Comparative Assessment of Thermal Damage Induced by Bipolar Forceps in a Bovine Liver.

Bipolar electrocautery systems in neurosurgical procedures may induce thermal damage to adjacent tissues, especially neural tissues. Therefore, it is crucial to control thermal spread from the tips of bipolar forceps into adjacent tissues. The goal of this study was to compare the thermal damage induced in unintended adjacent tissues during coagulation with 6 different bipolar forceps. Fresh ex vivo bovine liver tissues were coagulated with 6 different bipolar forceps: Aesculap® nonstick, Atlas Choice™, ISOCOOL®, SilverGlide®, Spetzler™-Malis®, and VersaTru® (45 trials per bipolar forceps). For all forceps, coagulation was performed with a power setting of 35 Malis units, 1-mm tip spacing, and 3-second activation time. Tissue samples were evaluated for the extent of thermal damage (30 trials per bipolar forceps). Tissue temperatures were measured with thermocouples placed in the tissues (15 trials per bipolar forceps). The area and maximum depth of thermal damage were measured manually with image analysis software. The injury area induced by ISOCOOL® and Atlas Choice™ bipolar forceps was significantly less than that of the Aesculap® nonstick (P < .001), SilverGlide® (P < .001), Spetzler™-Malis® (P < .001), and VersaTru® (P < .001). The areas of thermal injury caused by the ISOCOOL® and Atlas Choice™ forceps were not statistically significantly different from each other (P = .08). Lesions from the ISOCOOL® and Atlas Choice™ forceps showed significantly less depth of injury than the Aesculap® nonstick (P = .001), SilverGlide® (P < .001), Spetzler™-Malis® (P < .001), and VersaTru® (P < .001). There was no statistically significant difference in the depth of thermal injury between the ISOCOOL® and Atlas Choice™ forceps (P = 1.0). Bipolar forceps that effectively limit excessive thermal dissipation reduce the risk of unintended injury to adjacent or peripheral tissues. In an ex vivo bovine liver model, coagulation tests with ISOCOOL® and Atlas Choice™ bipolar forceps resulted in less depth and lower mean injury areas compared with other forceps.

Apolipoprotein C3-rich low-density lipoprotein (AC3RL) exacerbates cerebral ischaemic stroke injury by increasing BBB leakage via LOX-1

Abstract Background Ischaemic stroke causes the abrupt reduction or cessation of blood flow to the brain results in a cascade of events that can compromise blood-brain barrier (BBB) integrity. We revealed that an increase in apolipoprotein C3 (ApoC3)-rich low-density lipoprotein (AC3RL) is associated with endothelial cell apoptosis and inflammatory responses, indicating that AC3RL is one of the risk factors for cardiovascular events. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) triggers a cascade of events within endothelial cells that leads to endothelial dysfunction. Purpose We aimed to investigate whether AC3RL affects BBB permeability via the LOX-1, and thus increases brain damage. Methods We collected the whole blood from normal and patients with ischaemic events and separated them by centrifugation. AC3RL were collected using FPLC. We performed middle cerebral artery occlusion (MCAO) surgery to induce ischaemic stroke using B6 (C57BL/6) and LOX-1-/- mice injected with AC3RL. Triphenyl tetrazolium chloride (TTC) and Evans blue stains were accessed to confirm brain injury and BBB permeability. Results FPLC results showed that patients with ischaemic events presented higher levels of AC3RL compared to normal people. TTC stain showed the increased area of ischaemic penumbra damage in B6 mice with AC3RL injection, and LOX-1-/- mice with AC3RL injection were significantly protected. Evans blue dye leakage was observed in the brain tissues of B6 mice with AC3RL injection. LOX-1-/- mice with AC3RL injection revealed a decrease in BBB permeability. The modified neurological severity score (mNSS) method revealed a significant rise in B6 mice with AC3RL injection, which suggested a decline in motor and nervous function. LOX-1-/- mice with AC3RL injection significantly improved in motor and neurological functioning. Conclusions We demonstrate that AC3RL, through its effects on LOX-1, is associated with an increased risk of BBB damage after stroke. Therefore, pharmacological inhibition of AC3RL-LOX-1 interaction will be the main strategy to reduce severe brain damage. Figure 1: (A) AC3RL percentage (%) in individuals. Normal: healthy people, Ischemic event: patients who have experienced an ischemic event. **p &amp;lt; 0.001 vs. Normal group. (B, C) TTC stain of brain tissue after euthanasia to pinpoint the site of brain damage. The white portion of the mice brains indicated the site of the injury. (D, E) Evans blue dye leakage study in mice brains exhibited BBB permeability changes. (F) Assessment of mice's motor and neurological performance using the mNSS. Data are expressed as the mean ± SEM. **p &amp;lt; 0.001, ****p &amp;lt; 0.0001 vs. sham group, ##p &amp;lt; 0.001 vs. B6 I.V. AC3RL group.Graphical abstractFigure 1.

Being a nurse during an earthquake that affected ten provinces: A qualitative study on experiences and expectations.

This study was conducted to determine the professional experiences and future expectations of nurses working in the most damaged areas during the first two weeks of the 2023 Turkey earthquake. The increase in the frequency and severity of disasters in recent years has strongly shown that nurses must be prepared to respond to all disasters. To prepare for disasters that require a multifaceted approach, the experiences of nurses serving in disasters should not be ignored. A hermeneutic phenomenological approach was used in this research. The study included 18 nurses who worked in the first two weeks of the disaster. Data were collected through semistructured in-depth interviews between April and May 2023. Four themes were identified from the analysis of the data: (1) personal challenges, (2) organizational challenges, (3) nursing during the disaster, and (4) expectations. The results showed that nurses needed psychosocial support intervention skills in disasters and that their psychological preparation and knowledge levels for disasters were insufficient. In addition, the study revealed that organizational preparation was inadequate and that all these factors affected nursing care. The knowledge and skills that nurses need for professional disaster management can be provided by updating undergraduate education, in-service training procedures, and related policies. Considering that ideal disaster management is possible with a multidisciplinary team, it is recommended that national disaster policies be reviewed.

Damage Diagnosis in RC Frames on a Frequency Domain Basis

Today, there are many methods for detecting damages in reinforced concrete structures, such as pushover analysis, energy-based analysis and nonlinear analysis in the time domain. These methods are used to determine the dynamic properties of the structure by using accelerometers and a number of measuring devices that determine the mechanical and physical properties of the structure. In this study, it is aimed to diagnose damage with a set of frequencies and corresponding amplitude values obtained from accelerometers that determine the dynamic properties of the structure, instead of these methods that create calculation complexity. In this study, firstly, the damaged elements and joint points of the 1-storey RC frame with a single opening in both directions were determined by pushover analysis, for which the finite element model was built in the SAP2000 program. Later, time history analyzes were carried out under the influence of acceleration data of the Pazarcık earthquake (Mw 7.7) that occurred on February 6. The results obtained in the time domain were converted into the frequency domain and some inferences were made regarding the damaged areas. The study results showed that if the amplitude drop decreases in the same frequency range at a node, damage occurs at that node. It has been determined that the damages occurring in the RC frame increase due to the decrease in amplitude.

A peridynamics approach modeling gas flow in porous media with damaged regions

The study of gas flow within porous media, particularly those characterized by complex pore-fracture networks, is critical for applications in fields such as shale gas engineering, gas extraction, and hydrogeology. This paper proposes a convenient and novel peridynamics approach to describe gas flow behavior in fracture regions and transition regions between fractured and intact regions in porous media, where the bonds naturally describe the interactions between material points in damaged areas. For implementation, we interpolate the permeability of the bonds in the transition region by using local damage values, and adopt a meshfree discretization approach that does not require additional mesh refinement for damaged or fractured regions. Numerical examples are provided and compared with the traditional finite element method to verify the accuracy and effectiveness of the proposed method.

3D-BIOPRINTING OF BONE TISSUE IN VITRO И IN SITU

Advanced techniques in bone tissue regeneration include innovative achievements in the field of tissue engineering, among which 3D bioprinting technology holds a special place. This method demonstrates significant progress, driven by its numerous advantages, confirmed through extensive scientific research. 3D bioprinting offers the capability of precise printing of bone transplants with specified geometry, incorporating necessary biomaterials such as cells and growth factors, which facilitates effective osteoinduction, osteoconduction, and vascularization. This review article analyzes various modern methods of bone tissue restoration, including the use of autotransplants, allotransplants, and synthetic bone transplants. Particular attention is paid to the latest innovations in 3D bioprinting, opening prospects for creating individualized bone tissues characterized by a high degree of biocompatibility and minimizing the need for invasive procedures. Additionally, the article presents the concept of in situ bioprinting, developed by Weiss and his colleagues in 2007, as a method of direct printing of bio-inks directly in the area of damage in a living organism. This progressive approach provides high precision in the restoration of tissue defects, regardless of their complexity and geometric features. Over the last decade, several successful clinical cases of using printed structures have been registered, demonstrating the significance of 3D bioprinting in treating life-threatening diseases, as well as in accelerating the regeneration process and creating tissue transplants for subsequent implantation.

Study on the coupled hydro-mechanical model of gas-induced dilation effects in bentonite

IntroductionGas migration in low-permeability buffer materials is a crucial aspect of nuclear waste disposal. This study focuses on Gaomiaozi bentonite to investigate its behavior under various conditions.MethodsWe developed a coupled hydro-mechanical model that incorporates damage mechanisms in bentonite under flexible boundary conditions. Utilizing the elastic theory of porous media, gas pressure was integrated into the soil's constitutive equation. The model accounted for damage effects on the elastic modulus and permeability, with damage variables defined by the Galileo and Coulomb–Mohr criteria. We conducted numerical simulations of the seepage and stress fields using COMSOL and MATLAB. Gas breakthrough tests were also performed on bentonite samples under controlled conditions.ResultsThe permeability obtained from gas breakthrough tests and numerical simulations was within a 10% error margin. The experimentally measured gas breakthrough pressure aligned closely with the predicted values, validating the model's applicability.DiscussionAnalysis revealed that increased dry density under flexible boundaries reduced the damage area and influenced gas breakthrough pressure. Specifically, at dry densities of 1.4 g/cm³, 1.6 g/cm³, and 1.7 g/cm³, the corresponding gas breakthrough pressures were 5.0 MPa, 6.0 MPa, and 6.5 MPa, respectively. At a dry density of 1.8 g/cm³ and an injection pressure of 10.0 MPa, no continuous seepage channels formed, indicating no gas breakthrough. This phenomenon is attributed to the greater tensile and compressive strengths associated with higher dry densities, which render the material less susceptible to damage from external forces.

Systematic Analysis of Image Restoration Methods Based on Deep Learning

In today's digital age, people often use images to convey information. However, during the process of sending images, they can become damaged for various reasons, causing the images to lose their original meaning. In such cases, image repair is necessary to restore the damaged areas to their original, undamaged appearance. Traditional image repair methods often struggle to produce effective results for highly damaged images. However, image repair using deep learning techniques can address these challenges effectively. This paper will detail the impact of image repair on Convolutional Neural Networks (CNN), Recurrent Neural Networks (RNN), Long Short-Term Memory networks (LSTM), Convolutional Recurrent Neural Networks (CRNN), and other models, as well as the advantages and disadvantages of each approach. From the data, it is evident that combining multiple models for image repair is the most effective method. This approach reduces the consumption of hardware resources and time required for image repair, thereby improving the overall efficiency of the process.

Modelling of enhanced gas extraction in low permeability coal seam by controllable shock wave fracturing

The controlled shock wave (CSW) fracturing is an effective method for enhancing permeability of coal seam to promote gas extraction. Based on Fick’s law, Darcy’s law, the ideal gas law and the Langmuir equation, a damage-seepage-deformation coupling mathematical model of CSW fracturing in coal seam combined with the maximum tensile stress and the Mohr-Coulomb criterion is established. This model is implemented into COMSOL Multiphysics to simulate the coal seam CSW fracturing and subsequent gas extraction. When the shock wave and isotropic in-situ stress are applied on the borehole wall, the coal damage zone is an annular shape, and the permeability in the damage zone increases sharply. The CSW can effectively increase the efficiency of gas extraction and reduce the gas pressure and gas content in coal seam. With the increase of CSW action times, the damage in coal mass reaches a threshold and tends to be stable after several shocks. The damage area and the gas extraction efficiency are positively correlated with the shock intensity. Under the anisotropic ground stress, the larger diversity of the stress in different directions is, the more obvious damage extension in the fractured coal along the maximum stress direction is. Ground stress can inhibit the extension of cracks in the CSW fractured coal seam. This inhibition effect becomes more obvious with the increase of in-situ stress. Parameters are substantiated of controlled shock wave impact on the coal seam, which ensures increased methane extraction from low-permeability reservoirs, are substantiated.

Fatigue Damage Monitoring of Composite Structures Based on Lamb Wave Propagation and Multi-Feature Fusion

To address the challenges associated with fatigue damage monitoring in load-bearing composite structures, we developed a method that utilizes Lamb wave propagation and partial least squares regression (PLSR) for effective monitoring. Initially, we extracted diverse characteristics from both the time and frequency domains of the Lamb wave signal to capture the essence of the damage. Subsequently, we constructed a PLSR model, leveraging Lamb wave multi-feature fusion, specifically tailored for in-service fatigue damage monitoring. The efficacy of our proposed approach in quantitatively monitoring fatigue damage was thoroughly validated through rigorous standard fatigue tests. In practical applications, our model effectively mitigated the impact of multicollinearity among feature variables on model accuracy. Furthermore, the PLSR model demonstrated superior accuracy compared to the PCR model, given an equal number of principal components. To strike a harmonious balance between efficiency and precision, we optimized the size of the feature variable. The results show that the optimized PLSR model achieved an R-squared value exceeding 97% in predicting the in-service damage area. This underscores the robustness and reliability of our method in accurately monitoring fatigue damage in load-bearing composite structures.

Corrosion Inhibition Effect of Mg-Al-pAB-LDH Coating for Steel in the Marine Environment

In this study, the surface of steel was coated with a Mg-Al-pAB-LDH coating in order to enhance its corrosion resistance in the marine environment. The crystal structure, micro-morphology, and chemical composition of the Mg-Al-pAB-LDH coating were characterised using physicochemical techniques. The corrosion protection performance in a simulated marine environment was evaluated through electrochemical methods. The results indicate that the Mg-Al-pAB-LDH coating effectively adsorbs chloride ions from the environment, thereby increasing the corrosion potential of the steel in chloride environments and reducing its corrosion current density. In addition, the Mg-Al-pAB-LDH coating applied to the surface of steel not only enhances the corrosion resistance in the marine environment but also possesses self-healing capabilities in areas of local damage to the steel surface.

Experimental and numerical investigation of the damage propagation in regularly arrayed short fiber reinforced composite laminates under low‐velocity impact

AbstractThe outstanding mechanical performance and flowability of unidirectionally arrayed chopped strands (UACSs) give them an advantage in the manufacture of engineering structures with complex geometry. For the application of practical structures, the impact responses and damage evolution of material under low‐velocity impact must be investigated in advance. In this study, UACS laminates and continuous carbon fiber laminates with a stacking sequence of [0/90]4s and a thickness of 2 mm were fabricated for low‐velocity impact tests at 7, 11, 15, and 20 J. The impact responses and postimpact intralaminar damage area were analyzed according to the experimental results, including impact load responses and ultrasound C‐scan inspections. Moreover, to predict the damage evolution of the internal structure, the 3D finite element models were constructed in ABAQUS using a progressive damage model (PDM) through a user‐material subroutine VUMAT. Compared with continuous carbon fiber laminates, the dissipated energy of UACS laminates increases by approximately 10.64% and 57.37% for the 15 and 20 J, respectively. However, the intralaminar damage area of UACS laminates decreased by 29.96% and 28.16% at 15 and 20 J, respectively, since the discontinuous slits in UACS laminates can guide damage paths and suppress damage propagation.Highlights The regularly arrayed short fiber reinforced composite was studied. Revealed the low‐velocity impact responses and predicted the damage evolution. UACS and CFRP laminates have comparable impact performance. Illustrated the slits design can suppress the damage to a relatively small area.

Rapid analysis method of helicopter fuselage bullet damage based on bullet penetration theory

Helicopter fuselage has a complex shape and structure. Numerical simulation analysis of helicopter fuselage bullet damage based on the finite element method is computationally intensive and takes a long time. It is difficult to quickly analyze and evaluate helicopter fuselage bullet damage in a complex multi-bomb environment. To this end, the bullet penetration theory and the bullet impact calculation model were coupled to establish a rapid analysis method for helicopter fuselage bullet damage, and the accuracy of the rapid analysis method was verified by comparing with test results and finite element numerical simulation results. Then the helicopter fuselage bomb coordinates, residual speed and fuselage damage area of the multi-bomb strike were studied. Research shows that the residual velocity calculated by the rapid analysis method is consistent with the test results; compared with the finite element numerical simulation of bullet damage, the maximum error of the projectile residual velocity calculated by the rapid analysis method is 4.7%, and the maximum error of the fuselage damage area is 9.56%, and the calculation time is reduced 92.1%. Computational efficiency is significantly improved. As the incident angle of the projectile increases, the residual velocity decreases and the damage area increases; when the incident angle of the projectile is too large, the projectile cannot penetrate the surface of the fuselage, causing sink-like sliding damage, causing a larger area of damage.

Regulatory Peptide Pro-Gly-Pro Accelerates Neuroregeneration of Primary Neuroglial Culture after Mechanical Injury in Scratch Test

The scratch test is used as an experimental in vitro model of mechanical damage to primary neuronal cultures to study the mechanisms of cell death in damaged areas. The involvement of NMDA receptors in processes leading to delayed neuronal death, due to calcium dysregulation and synchronous mitochondrial depolarization, has been previously demonstrated. In this study, we explored the neuroregenerative potential of Pro-Gly-Pro (PGP)—an endogenous regulatory peptide with neuroprotective and anti-inflammatory properties and a mild chemoattractant effect. Mechanical injury to the primary neuroglial culture in the form of a scratch caused acute disruption of calcium homeostasis and mitochondrial functions. This was accompanied by neuronal death alongside changes in the profile of neuronal markers (BDNF, NSE and GFAP). In another series of experiments, under subtoxic doses of glutamate (Glu, 33 μM), delayed changes in [Ca2+]i and ΔΨm, i.e., several days after scratch application, were more pronounced in cells in damaged neuroglial cultures. The percentage of cells that restored the initial level of [Ca2+]i (p &lt; 0.05) and the rate of recovery of ΔΨm (p &lt; 0.01) were decreased compared with undamaged cells. Prophylactic application of PGP (100 μM, once) prevented the increase in [Ca2+]i and the sharp drop in mitochondrial potential [ΔΨm] at the time of scratching. Treatment with PGP (30 μM, three or six days) reduced the delayed Glu-induced disturbances in calcium homeostasis and cell death. In the post-glutamate period, the surviving neurons more effectively restored the initial levels of [Ca2+]i (p &lt; 0.001) and Ψm (p &lt; 0.0001). PGP also increased intracellular levels of BDNF and reduced extracellular NSE. In the context of the peptide’s therapeutic effect, the recovery of the damaged neuronal network occurred faster due to reduced astrogliosis and increased migration of neurons to the scratch area. Thus, the peptide PGP has a neuroprotective effect, increasing the survival of neuroglial cells after mechanical trauma in vitro by reducing cellular calcium overload and preventing mitochondrial dysfunction. Additionally, the tripeptide limits the post-traumatic consequences of mechanical damage: it reduces astrogliosis and promotes neuronal regeneration.

Effect of Kangfuxin liquid combined with triamcinolone acetonide in oral submucosal fibrous degeneration

Purpose: To investigate the effect of Kangfuxin liquid combined with triamcinolone acetonide in the treatment of oral submucous fibrous degeneration. Methods: A total of 140 patients with oral submucosal fibrous degeneration admitted to the outpatient clinic of Haiyan County Stomatological Hospital, China from June 2020 to June 2023 were divided equally into study and control groups. The study group received Kangfuxin liquid in addition to 1 mL triamcinolone acetonide (40 mg/mL) while the control group received 1 mL triamcinolone acetonide; therapeutic effects were compared after 4 weeks of treatment. Visual analogue scale (VAS) score, serum transforming growth factor (TGF-β1), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels were determined. Also, whole blood viscosity (WBV), plasma viscosity (PV), erythrocyte sedimentation rate (ESR), and incidence of adverse reactions were evaluated. Result: The study group showed significantly reduced pain levels compared to the control group, as well as lower mucosal damage areas and improved mouth opening after 4 weeks of treatment compared to control group (p &lt; 0.05). Also, the study group showed significantly lower TGF-β1, TNF-α and IL-6 compared to control group after treatment (p &lt; 0.05). It showed significantly lower WBV, PV, and ESR compared to control group (p &lt; 0.05). Furthermore, the study group showed significantly lower incidence of adverse reactions than the control group (p &lt; 0.05). Conclusion: Kangfuxin liquid, when combined with triamcinolone acetonide, lowers pain, reduces the levels of STGF-β1, improves hemorheology, and produces minimal adverse effects compared to triamcinolone alone. Future studies should focus on long-term outcomes to better assess the therapeutic potential of this combined regimen.

Influence of different mining locations on deformation characteristics of overlying strata on gently anti-dip high-steep mining slope.

High-steep gently inclined mining slopes, prevalent globally, often suffer significant deformation, leading to landslides due to numerous goafs. This research investigates the critical role of goaf location in controlling deformation, failure mechanisms, and disaster evolution, vital for safe mining practices. Through field investigations and model generalization in Guizhou, a physical model test method was used to study three positions of goafs: under the shoulder and foot of the slope, under the slope shoulder, and within the slope. Findings highlight the stronger influence of the goaf's mutual position with the slope shoulder on slope and overburden deformation and failure compared to the slope toe. Deformation and failure modes evolve from collapse toppling to collapse slip and collapse settlement as the goaf shifts from the near slope surface to inside of the slope. Statistical analysis of fracture distribution in the goaf's overlying strata reveals damage increase with larger goafs, following a Gaussian distribution, with concentrated damage in the middle. The study identifies the maximum damage area, influenced by the horizontal distance between the goaf center and slope shoulder. These insights advance understanding of overburden rock deformation in gently inclined high-steep mining slopes.

Obstetric and gynecological management in a patient with abnormal invasion of the placenta (placenta percreta)

Pathological placental invasion is a dangerous anomaly during pregnancy, which causes increased maternal morbidity and mortality. Patients with abnormal placental invasion may experience life-threatening uterine bleeding during delivery, particularly in cases of placenta percreta. This often requires surgical intervention, specifically a hysterectomy, which some researchers refer to as the “gold standard” treatment for pathological placental invasion, with rates ranging from 47% to 77.8%. Conversely, other researchers recommend a conservative approach, involving the complete removal of the placenta percreta, excision of damaged areas on the uterine walls and bladder, and metroplasty and restoration of the integrity of the. This article presents a clinical case of a 40-year-old patient with a complicated obstetric history, including abnormal placental invasion (placenta percreta) involving the anterior wall of the uterus and the bladder. Delayed diagnosis of such pathology leads to inappropriate treatment and, consequently, acute massive bleeding, posing a risk to the patient’s health and life. The applied comprehensive diagnostic and therapeutic measures facilitated the preservation of the pelvic organs and restoration of the patient’s reproductive function.

Seismic behavior and failure analysis of prefabricated foamed concrete composite walls for passive houses

In view of the lack of research on the failure mode and seismic behavior of high-performance insulation walls utilizing lightweight concrete as the structural material, this study presents experimental findings from a seismic behavior investigation of prefabricate foamed concrete composite walls (PFCCWs) for passive house in China. The PFCCWs incorporate low thermal conductivity and high-strength foamed concrete, polyurethane, decorative magnesium straw slabs to provide excellent thermal and mechanical properties for prefabricated passive houses in hot summer and cold winter area. The seismic behavior of PFCCWs under different influence factors were elaborated using quasi-static test data and observation of external damage. The lightweight and porous nature of foamed concrete leads to significant crack formation during failure. The findings suggest that the skin effect of magnesium straw slabs and polyurethane impedes crack development and improve the load-bearing capacity with ductility enhancement. Additionally, reducing the aspect ratio and substituting post-cast column concrete with common concrete are effective to improve the seismic behavior. The window opening changes the worst damage area of the wall and notably weakens the seismic behavior. The enhanced integrity of cast-in-place wall leads to the difference in the failure mechanism and increases in load-bearing and deformation capacities. Meanwhile, design suggestions for the foamed concrete insulation walls are also proposed by comparing the failure mode and hysteretic response of various wall types.

Assessment of damage prediction models for composite laminates under single and repeated low-velocity impacts

The aim is to explore the influence of damage initiation criteria and evolution methods on the damage prediction for composite laminates under single and repeated low-velocity impacts. A 3D finite element model is established to analyze the impact behavior of laminate, and a damage analysis process including the initiation determination, progressive evolution, and constitutive relationship is designed. Hashin criterion based on tensile strain for matrix is modified by an empirical assumption method. Besides, the quantitative evolution of damage area during impact is studied, which provides a new perspective for elucidating the damage mechanism. The numerical model is first validated against the available experimental data. The influence of initiation criteria and evolution methods on damage prediction is then performed in two-phase research. The first phase discusses the prediction capabilities of different combinations under single impact. In the second phase, a method for removing residual vibrations under repeated impacts is proposed. The differences caused by the removal and non-removal of residual vibrations are analyzed, and the sensitivity of these differences to various combinations is discussed. Results show that the numerical prediction agrees well with the experiment in dynamic mechanical response curve. Combining Hashin-Strain criterion with linear equivalent strain method and Puck criterion with exponential equivalent displacement method yields optimal results. Moreover, the sensitivity to differences caused by the residual vibrations effects is related to the initiation criterion, and the evolution method.