Cumulative Damage Index Research Articles

Performance of corroded RC beam–column joints repaired using a hybrid scheme with HSFRC and stirrups replacement

AbstractThe present study proposes a new technique for retrofitting corroded beam–column joints (BCJs) using high‐strength fiber reinforced concrete (HSFRC) and stirrups replacement. The entire corrosion‐affected concrete was removed and replaced with HSFRC. The corroded reinforcing bars were cleaned and treated to resist the progression of the corrosion mechanism. The severely pitted stirrups were replaced with new stirrups. Four exterior BCJ specimens were tested under seismic loading to determine the effectiveness of the proposed retrofitting scheme. The efficacy of the proposed retrofitting scheme is determined in terms of the hysteresis response, stiffness degradation, cumulative energy dissipation, ductility, and damage index. A significant delay in the fracture of severely pitted reinforcing bars was experienced for the corrosion‐damaged retrofitted specimens compared to the corroded unretrofitted specimen. The cumulative energy dissipation of the corroded unretrofitted and corroded retrofitted specimens was 0.4 and 1.3 times that of the reference specimen, respectively, indicating the effectiveness of the retrofitting strategy, as both specimens had similar corrosion rates. The test results indicated that the proposed retrofitting technique effectively improved the seismic performance of the corrosion‐damaged BCJs.

A data-driven approach for structural integrity assessment of prestressed concrete containment vessel considering the effect of vertical ground motions

As a final barrier against the release of radioactive material, the prestressed concrete containment vessel (PCCV) plays an important role in the nuclear power plant (NPP). When subjected to seismic loads, its structural performance requires high structural integrity. During an earthquake, the PCCV experiences ground motions (GMs) consisting of horizontal and vertical components in a global coordinate system, and its structural integrity is probably overestimated if only the horizontal component is considered in numerical analyses. In this study, a novel cumulative damage index is first employed to quantitatively assess the structural integrity of PCCVs. Accordingly, the failure probability of structural integrity of the PCCV is investigated by incremental dynamic analysis (IDA) and further seismic fragility analysis considering the effect of vertical ground motions (VGMs). The results show that the effect of VGMs on structural integrity of PCCVs is gradually non-negligible with the increase of vertical intensity. Moreover, an accurate cumulative damage prediction model for the PCCV is established based on eight mainstream machine learning (ML) algorithms, and the necessity of incorporating vertical intensity measures (IMs) in ML models is investigated. The results show that the ML model considering the vertical IMs is superior in capturing the cumulative damage of the PCCVs. The best estimates are obtained by GB with R2 of 0.912, MAE of 1.301, MSE of 6.186, and RMSE value of 2.487. Finally, the SHapley Additive exPlanation (SHAP) method is adopted for interpreting the prediction results of the optimal ML model to assess the effect of each IM and its interactions on the generalization performance of the model. The proposed ML-based cumulative damage prediction model for PCCVs considering the effect of VGMs enables an accurate quantitative assessment on structural integrity of PCCVs. This provides an important reference for evaluating the potential environmental hazard due to the leaking of radioactive materials.

Fatigue damage monitoring of composite laminates based on acoustic emission and digital image correlation techniques

Timely and effective health evaluation of carbon fiber reinforced polymer (CFRP) structures under dynamic fatigue loading is one of the key issues of CFRP in practical engineering applications. This paper uses a combination of acoustic emission (AE) and digital image correlation (DIC) to study the fatigue behavior of CFRP open-hole laminated beams with different stacking sequences under pure tensile loading, and analyze the influence of different damage mechanisms on the ultimate fatigue failure of the specimens. Two parameters, AE hit rate and absolute AE energy, are used to characterize the stiffness degradation behavior of CFRP structures. The strain field distribution characteristics during the damage failure of specimens with different stacking sequences are discussed in association with DIC. Based on the data obtained by AE and DIC, the damage modes of two types of layered CFRP laminated beams are identified by combining principal component analysis (PCA) and the K-means++ algorithm. The clustering results are consistent with the microscopic image results of the fracture surface. The identified modes are employed to characterize the dynamic evolution of fatigue damage in CFRP, and the contribution of different damage modes to the ultimate fatigue failure of the specimens is analyzed using cumulative damage index (CDI) values.

Fatigue life prediction of a Durga flyover bridge at vijayawada using wireless sensors

It is essential to inspect and assess any fatigue damage to the components of a structure in order to determine how long it will last. This is necessary for constructions such as concrete bridges, which are subjected to fluctuating loads with high intensity and frequency. This study presents a computer application method for calculating the fatigue life of the Durga flyover (reinforced concrete) bridge. The damage to bridge components can be evaluated based on the dynamics of the interaction between the bridge and vehicles caused by actual traffic. The computer code initially calculates the fluctuation of stresses caused by the passage of various types of vehicles in a given segment of a bridge. The other module has a continuous set of loads to measure the strains and calculate the stress variations across the section components. The rainflow method is used to count stress cycles owing to the fact that the peak intensities of the stress cycles are not steady, and the appropriate S-N curves are utilized to determine the damage caused by each cycle. In this analysis, the stress range amplitude waveform and fatigue toughness characteristics of bridge elements were employed to systematically detect continuous bridge girder fatigue damage. The most severe flexural stresses induced by vehicles were detected, and a stress-range frequency waveform was created while accounting for the total traffic volume. Linear damage accumulation theory was used to calculate the cumulative damage index and bridge fatigue life. The Miner's rule was used to calculate the overall damage caused by the passage of the vehicles. The major factors affecting the fatigue life are the effects of the span, pavement quality, increase in the speed of operation, weight, and suspension characteristics of the bridge.

Alexithymia in systemic lupus erythematosus: A cross sectional study in a Brazilian sample.

Alexithymia is considered as a reduced capacity to be aware of, to clearly recognize, and to define one's feelings with a limited fantasy and a concrete, externally oriented cognitive style. Some studies have stated that alexithymia is more common in systemic lupus erythematosus patients (SLE) than in general population but there is a paucity of studies in such context. To study the prevalence of alexithymia in a sample of SLE patients looking for associated epidemiological and clinical findings and its relationship to quality of life. Cross-sectional study in 93 SLE patients collecting clinical, epidemiological, and serological data, data on quality of life by 12 item short health survey (SF-12), and alexithymia by Toronto scale (TAS-26). Disease's cumulative damage was measured by Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage index. In this sample (90.3% females and median age of 46years), 55.9% had alexithymia; 22/92 (23.9%) did not and 19/93 (20.4%) had inconclusive results. Alexithymia presence had a positive association with age (p = 0.01) and a negative association with presence of glomerulonephritis (25% vs 59%; p = 0.005) and glucocorticoid use (19.2% vs 59.0%; p = 0.0007). A negative correlation of TAS-26 was observed with mental domain of (r = -0.46; p < 0.0001) and physical domain (r = -0.32; p = 0.004) of SF-12, but not with cumulative damage index. We found a high prevalence of alexithymia in this sample of SLE patients that negatively associated with quality of life, but not with cumulative damage index.

Structural fatigue reliability evaluation based on probability analysis of the number of zero-crossings of stochastic response process

Structural fatigue failure is closely related to the number of stress cycles. Therefore, the number of the intersections between stochastic response process and zero-boundary is a key problem in structural fatigue reliability analysis. In this paper, the relationship between the number of the multiple intersections and the fatigue cumulative damage index is derived according to the Miner rule-based high cycle fatigue random cumulative damage index. Then, use random walk to approximately simulate Wiener process, and get the first intersection probability between Wiener process and the zero-boundary. Next, further utilize the renewal process to solve the distribution law of the number of intersections between the Wiener process and the zero-boundary in a period of time. Finally, based on the fatigue failure criterion considering the randomness of the failure threshold, the calculation formula the structural fatigue reliability is derived. As a practical example, the fatigue reliabilities of the key part of Metro Bogie under different operation periods are analyzed using the proposed method.

In-Service Reliability Assessment of Turbine Blade Thermal Barrier Coatings Based on a Novel Cumulative Damage Index Model

Abstract Thermal barrier coating (TBC) has been used widely on turbine blades to provide temperature and oxidation protection. With the turbine inlet temperature continuously increasing, TBCs have become more likely to oxide spallation, leading to premature failure of blade metal substrates. Thus, It is necessary to accurately evaluate the in-service reliability of TBCs for blade life assessment and engine operation safety. Nowadays, it is common to dynamically record aero-engine operating and performance data, called dynamic covariate data, which provides periodic snapshots for obtaining reliability information of engine components. Nevertheless, existing TBC life prediction models that pay adequate attention to dynamic covariate information are rare. This paper focuses on using limited failure samples with associated dynamic covariate data to make in-service reliability assessments of TBCs through a proposed cumulative damage index model. For the demonstration of the proposed approach, an integrated TBC life simulation approach has been introduced, which comprises engine performance, blade thermal, TBC damage, and damage accumulation models. The case study shows that the proposed cumulative damage index model-based method provides more stable and accurate results than the traditional statistical method based on failure-time data.

Determining relevant traits for selecting landrace accessions of Phaseolus lunatus L. for insect resistance.

Plant-insect interactions are a determining factor for sustainable crop production. Although plants can resist or tolerate herbivorous insects to varying degrees, even with the use of pesticides, insects can reduce plant net productivity by as much as 20%, so sustainable strategies for pest control with less dependence on chemicals are needed. Selecting plants with optimal resistance and photosynthetic traits can help minimize damage and maintain productivity. Here, 27 landrace accessions of lima beans, Phaseolus lunatus L., from the Yucatan Peninsula were evaluated in the field for morphological resistance traits, photosynthetic characteristics, insect damage and seed yield. Variation was found in physical leaf traits (number, area, and dry mass of leaves; trichome density, specific leaf thickness and hardness) and in physiological traits (photosynthetic rate, stomatal conductance, intercellular carbon, water-use efficiency, and transpiration). Five accessions (JMC1325, JMC1288, JMC1339, JMC1208 and JMC1264) had the lowest index for cumulative damage with the highest seed yield, although RDA analysis uncovered two accessions (JMC1339, JMC1288) with strong positive association of seed yield and the cumulative damage index with leaf production, specific leaf area (SLA) and total leaf area. Leaf traits, including SLA and total leaf area are important drivers for optimizing seed yield. This study identified 12 important morphological and physiological leaf traits for selecting landrace accessions of P. lunatus for high yields (regardless of damage level) to achieve sustainable, environmentally safe crop production.

A Hybrid Approach for Fusing Physics and Data for Failure Prediction

This work describes the architecture for developing physics of failure models, derived as a function of machine sensor data, and integrating with data pertaining to other relevant factors like geography, manufacturing, environment, customer and inspection information, that are not easily modeled using physics principles. The mechanics of the system is characterized using surrogate models for stress and metal temperature based on results from multiple non-linear finite element simulations. A cumulative damage index measure has been formulated that quantifies the health of the component. To address deficiencies in the simulation results, a model tuning framework is designed to improve the accuracy of the model. Despite the model tuning, un-modelled sources of variation can lead to insufficient model accuracy. It is required to incorporate these un-modelled effects so as to improve the model performance. A novel machine learning based model fusion approach has been presented that can combine physics model predictions with other data sources that are difficult to incorporate in a physics framework. This approach has been applied to a gas turbine hot section turbine blade failure prediction example.

Investigate of damage index of coupled steel plate shear walls (C-SPSW) system under seismic loading

In the analysis of damage to a structure after the occurrence of a destructive event, it is impossible to estimate the exact amount of damage to any part of the structure. Therefore, it is necessary to introduce failure indicators to assess the amount of damage to structural elements. For this purpose, in this study, the damage caused to the coupled-steel plate shear wall (C-SPSW) system under earthquake load was investigated. In this paper, three damage index of park and Ang, ductility and drift using numerical methods upon multi-story C-SPSW systems are investigated. Following the validation of the numerical simulation through a comparison of the experimental results and numerical predictions, a parametric study was performed to evaluate the damage indexes. Comparative results of the hysteresis curves obtained from the finite element analysis with the experimental curves indicated that the finite element model offered a good prediction of the hysteresis behavior of C-SPSW. In the parametric study, Thirty prototype multi-story C-SPSW systems with different the height of the structures were designed, modeled, and using nonlinear seismic analysis. The results show that the use of cumulative damage indices, which is a combination of several different failure parameters, it predicts the vulnerability of structures more realistically.

Experimental investigation on cumulative damage indices for steel members under ultra-low-cycle loading

Notched bending specimens and axial load specimens were tested under different ultra-low cycle loadings to investigate the plastic deformation capacity and plastic energy capacity of steel members. A total of 53 experiments were performed in cyclic axial and bending configurations. The effect of notch shape, the order of mixed amplitudes, the average deformation of the amplitude, and the environmental temperature on plastic deformation capacity of steel members are studied. Four cumulative damage indices, including the ductility damage index, the normalized plastic energy damage index, the max-side ductility damage index, and the max-side normalized plastic energy damage index were compared for ductile fracture evaluation of these specimens under different ultra-low cycle loadings. The results indicated that the standard deviation of the normalized plastic energy damage index is the smallest among the four damage indices, which shows the lowest data dispersity. The max-side ductility damage index is larger than the ductility damage index, and the max-side normalized plastic energy damage index is larger than the normalized plastic energy damage index, both achieving a safety evaluation. Among the four damage indices, the max-side normalized plastic energy damage index achieves the maximum reliability.

EXPERIMENTAL STUDY ON THE COMPRESSIVE STRENGTH OF CONCRETE UNDERGOING FREEZE-THAW CYCLE ACTIONS WITH DIFFERENT ULTRALOW TEMPERATURE RANGES

Through freeze-thaw cycle action experiments of concrete with ultralow temperature ranges of 10℃ to -40, 10 to℃℃ -80 and 10 to℃℃ -160,℃ the effect of different ultralow temperature ranges on the concrete compressive strength is investigated. From these test results, it can be shown that for the specimens undergoing various freeze-thaw cycles at different ultralow temperature ranges, their failure modes are basically in a double cone shape when they are loaded at upper and lower limit temperatures. But the sound during their destruction processes and failure conditions are different. The variation regularity of the compressive strength of concrete undergoing freeze-thaw cycle actions under ultralow temperatures is obviously different from that at natural environment temperature. The effect of the freeze-thaw cycle action for various ultralow temperature ranges on the concrete compressive strength is also different. The concrete compressive strength will increase at the initial stage of the freeze-thaw cycle action for these temperature ranges with the lower limit temperatures which are relatively higher. After that, they fluctuate and trend to a deteriorating state with the increase in number of freeze-thaw cycles. There are obvious differences among different ultralow temperature ranges for the single freeze-thaw cycle action damage index and the cumulative freeze-thaw cycle action damage index of concrete. For the temperature ranges with the lower limit temperatures which are relatively higher, they are still positive after experiencing more freeze-thaw cycles at lower limit temperatures, but are always negative after several freeze-thaw cycles for those with the lower limit temperatures which are relatively lower. It shows that the cumulative damage of concrete due to the freeze-thaw cycle action for the latter is more severe than that for the former. The results in this paper can provide references for reliably designing concrete structures of liquefied natural gas storage tanks and so on.

Seismic reliability analysis of structures based on cumulative damage failure mechanism

Non-stationary random seismic response and reliability of multi-degree of freedom hysteretic structure system are studied based on the cumulative damage failure mechanism. First, dynamic Eqs. of multi-degree of freedom hysteretic structure system under earthquake action are established. Secondly, the random seismic response of a multi-degree freedom hysteretic structure system is investigated by the combination of virtual excitation and precise integration. Finally, according to the damage state level of structural, the different damage state probability of high-rise frame structure is calculated based on the boundary value of the cumulative damage index in the seismic intensity earthquake area. The results show that under the same earthquake intensity and the same floor quality and stiffness, the lower the floor is, the greater the damage probability of the building structure is; if the structural floor stiffness changes abruptly, the weak layer will be formed, and the cumulative damage probability will be the largest, and the reliability index will be relatively small. Meanwhile, with the increase of fortification intensity, the reliability of three-level structure fortification is also significantly reduced. This method can solve the problem of non-stationary random seismic response and reliability of high-rise buildings, and it has high efficiency and practicability. It is instructive for structural performance design and estimating the age of the structure.

Effect of residual displacement and sequence of events on Design Force Ratio spectrum

In the areas of high seismicity, where several medium-to-strong events may occur before the design event, the cumulative damage due to earthquake events expected during the design life of the structure should be kept within safe limits. This may be achieved by raising the design force level corresponding to the largest seismic event anticipated during the design life of the structure by a factor known as Design Force Ratio (DFR). This study is an attempt to generalize the existing DFR spectrum by modifying how the damage during an event is computed and how the power spectral density function (PSDF) of the ground motion process for that event is estimated. As the existing models do not estimate incremental damage during an event of a sequence, the modified Park-Ang damage model is proposed to be modified further such that its estimates for the individual events add up to the cumulative damage index for the entire sequence as well as the effects of residual displacements are accounted for. The proposed model can estimate additional damage due to an event (in a multiple-event situation) without requiring the excitation time-history. The generalized procedure for DFR spectrum is based on using this model and the concept of spectrum-compatible PSDF. A numerical study on a hypothetical seismic environment shows that the DFR spectrum is very sensitive to the directions of the residual displacements and that all residual displacements should be assumed in the same direction for a conservative estimate of the DFR spectrum. It is also shown that in that case, the event with maximum damage potential should be assumed to occur as the last event in the sequence in order to maximize the cumulative damage.

Experimental Study of Composite Members in Spatial Grid Structure Subjected to Ultralow‐Cyclic Axial Force

This paper presents the results of ultralow‐cycle fatigue tests for three full‐scale assemblies consisting of steel tubes and bolt‐sphere joints, which are widely used in public buildings. Each assembly was tested six times under a varying loading history. The ultralow‐cycle fatigue performance was investigated considering the joint stiffness and loading history. The deformation patterns, hysteretic characteristics, skeleton curves, bearing‐capacity degradation features, cumulative energy dissipation, and cumulative damage index of the assembly were obtained and analysed. The results show that the joint stiffness and loading system have a significant effect on the ultralow‐cycle fatigue performance of the assembly. Based on these results, an equation that describes the relationship between the cumulative damage index and the bearing degradation of the assembly for an ultralow‐cycle fatigue test was derived.

Comparison of CFRP and GFRP Wraps on Reducing Seismic Damage of Deficient Reinforced Concrete Structures

The effectiveness of glass/carbon fibre reinforced polymer (GFRP/CFRP) wraps at plastic hinges has been confirmed; however, their respective effectiveness on reducing seismic damage of deficient reinforced concrete structures has hardly been compared. The current study aims at this comparison, providing some useful information to realise the better FRP for confinement retrofitting of reinforced concrete structures poorly confined due to deficient transverse reinforcement. Four- and eight-storey poorly confined reinforced concrete frames were selected to represent low- and mid-rise building structures, respectively. These deficient frames were then strengthened by CFRP/GFRP wraps via external confinement. Inelastic time history and cumulative damage analyses of the original, CFRP- and GFRP-retrofitted frames were performed. The damages of CFRP- and GFRP-retrofitted frames were compared with each other and with the damage of the original frame. The comparison results show that CFRP and GFRP wraps at plastic hinges substantially reduce damage. More importantly, GFRP wraps are more effective than CFRP wraps by reducing a higher amount of the cumulative damage index. The conclusions can help in deciding on the type of FRP to be used for confinement retrofitting of RC structures poorly confined due to deficient transverse reinforcement.

A study of the effect of transient stresses on the fatigue life of RF MEMS switches

AbstractFatigue affects the durability of radio frequency microelectromechanical systems (RF MEMS) devices. It is common to rely on actuation voltage cycles or resonant frequencies shift to estimate the fatigue life of MEMS devices. Actuation of moving mechanical parts within the device causes transient stresses because of transient vibration. Such stresses and stress cycles are difficult to account for when fatigue life is estimated by observing actuation voltage or resonant frequencies shift only. This work investigates the effect of transient stresses on the durability of RF MEMS switch, using a benchmarked finite element‐based structural dynamics model of the switch to generate the stress‐time history of the device. Principal normal stresses are calculated from raw stress data and ordered such that (σ1 ≥ σ2 ≥ σ3). Maximum principal stress amplitudes at pull‐in and pull‐out are calculated, and their corresponding number of cycles are determined by rainflow counting method. A Cumulative damage index (Dc) is determined using Miner's rule. This study revealed that, when transient stresses are taken into consideration, the cumulative damage caused by a single on‐off cycle, of the switch studied, is 1.031 × 10−6, and its life‐to‐failure is 9.7 × 105 on‐off cycles. Whereas the life‐to‐failure of the switch, without considering transient stresses, is approximately 10.3 × 108 cycles. Results are compared with published data for similar switches, and they are in good agreement.

On the structural energy distribution and cumulative damage in soil-embedded foundation-structure interaction systems

Repeated cyclic loading is well-known to have detrimental effects on inelastic response of structures. Distribution of structural energy and quantification of cumulative damage effects are very important components in performance-based seismic design approach. On the other hand, soil-foundation-structure interaction effects significantly influence inelastic response of structures through the soil contribution to modification of dynamic characteristics of the structure. Hence, this study focuses on structural energy distribution and cumulative damage effects in structures with embedded foundations considering collective effects of kinematic and inertial interactions. To achieve this goal, a soil-foundation-structure interaction system well suited for parametric study was considered: the soil surrounding the rigid foundation was modelled as a half-space, the embedded foundation was modelled using a stack of discrete disks and applying double cone model concept, and the structure was considered as a single-degree-of-freedom structure. The soil-foundation-structure interaction systems were defined according to key interaction dimensionless parameters and were then analysed subjected to 40 non-pulse far-fault ground motions. It is found that SFSI effects significantly alter total energy, viscous damping energy, and hysteretic damping energy of the structure. The results also show that considering only inertial interaction increases cumulative damage index of the structure while inclusion of kinematic interaction has a decreasing effect. Furthermore, practice-oriented correction factors to cumulative damage index of fixed-base structures are proposed to return cumulative damage index of soil-foundation-structure systems. This study can find use in damage evaluation of existing structures with embedded foundation on soft soils.

More adequate seismic design force pattern for yielding structures considering structural and ground motion uncertainties effects

SummaryIn the present paper, a new algorithm to achieve optimum lateral load pattern for inelastic steel shear‐building structures is proposed and the efficiency of the proposed algorithm in terms of convergence speed and stability is investigated. Then, by conducting this algorithm on 28,800 elastic and inelastic steel shear‐building structures having different dynamic characteristics subjected to 40 design compatible earthquakes, a new seismic force pattern incorporating higher modes effect is proposed, and the adequacy of the proposed load pattern is parametrically investigated on the basis of the concepts of structural weight and dissipated energy and cumulative damage index. Through conducting numerous nonlinear dynamic analyses, the effects of uncertainties in story shear strength, structural fundamental period, and damping ratio by using the Monte Carlo simulation are parametrically investigated. Result indicates that optimum structures are in general more sensitive to the random variation of fundamental period and story lateral strength, whereas up to 40% of damping ratio variation does not affect the seismic performance of the optimum design frames. Finally, compared with recently proposed optimum structures without consideration of higher modes and code‐complaint design structures, the proposed mean optimum designed buildings of this study exhibit up to 42% less cumulative damage under the design earthquakes.

Application of a PCM-rich concrete overlay to control thermal induced curling stresses in concrete pavements

This study aims to evaluate the application of a Phase Change Material (PCM) rich concrete overlay to reduce curling stresses in concrete pavements. Curling stresses are the results of temperature gradient in pavements, and are comparable to the stresses that are induced by traffic loads. The weather conditions, which have a cyclic nature, are the source of curling stresses, and they cause cyclic tensile and compressive stresses in pavements. This phenomenon causes fatigue damage in concrete pavements and reduces their service life. The PCMs have a high latent heat of fusion and can increase the thermal inertia of concrete. When PCM is used in a concrete overlay, it tends to moderate the temperature gradient in the slab, and thus mitigate the curling stresses. The efficiency of the proposed PCM-rich overlay was evaluated under the real climatic conditions of three different cities in the US. The findings of this research demonstrated that the cumulative fatigue Damage Index (DI) resulted from repetitive curling stresses can be up to 22% in a concrete slab with the service life of 35 years. However, using a 7.6 cm bonded concrete overlay with 25 vol% PCM can moderate the curling stresses so much that the effect of curling induced fatigue damage would be virtually negligible.