Limited Damage Research Articles

Analysis of Temperatures Generated during Conventional Laser Irradiation of Root Canals-A Finite Element Study.

The success of endodontic treatment is dependent on the removal of bacteria. A modern strategy to reduce bacterial load is laser irradiation. During this procedure, there is a local increase in temperature with possible side effects. The aim of this study was to determine the thermal behavior of a maxillary first molar when performing the conventional irradiation technique using a diode laser. For this study, a 3D virtual model of a maxillary first molar was created. The preparation of the access cavity, the rotary instrumentation of the palatal root canal and the laser irradiation protocol were simulated. The model was exported in a finite element analysis program where the temperature and heat flux were studied. Temperature and heat flux maps were obtained, and the temperature increase on the internal wall of the root canal was analyzed. The maximum temperature value exceeded 400 °C and was maintained for less than 0.5 s. The obtained temperature maps support the bactericidal effect of diode laser and the limitation of damage to surrounding tissues. On internal root walls, the temperature reached several hundred degrees Celsius, but for very short durations. Conventional laser irradiation is an adjuvant method of decontamination of the endodontic system.

Experimental behavior and seismic performance assessment of Unbonded Post-tensioned Precast Concrete Walls for low-rise buildings

The current growth of the urban population has led to an increment in the housing demand, increasing the seismic exposure, especially in developing countries that struggle to provide efficient and safe housing solutions. To address this issue, it is necessary to develop structural systems that provide sufficient seismic performance while allowing reduced building time and cost. This paper presents the structural identification and seismic performance assessment of a structural system based on unbonded post-tensioned precast concrete walls. These structural walls are composed of precast concrete panels connected through shear connectors and post-tensioned using unbonded steel bars. Three unbonded post-tensioned precast concrete wall specimens were subjected to a cyclic loading test, obtaining several structural parameters from the analysis of the experimental campaign results. In addition, the seismic response of the proposed system was identified by characterizing its hysteretic behavior and by defining several experimental damage limit states. Based on these results, a numerical model was calibrated using the Pinching4 material of the OpenSees software. Finally, a numerical seismic performance assessment of the in-plane response was carried out by proposing an archetype building and using the FEMA P695 far-field ground motion set as seismic input. These analyses allowed the development of fragility functions of the diverse damage states observed on the tested specimens. The results show that the proposed structural system based on unbonded post-tensioned precast concrete walls is a feasible option for its implementation as a lateral load structural system on low-rise buildings, providing sufficient seismic capacity and allowing further improvements in its implementation.

Performance-based drift prediction of reinforced concrete shear wall using bagging ensemble method

Reinforced Concrete (RC) shear walls are one of the civil structures in nuclear power plants to resist lateral loads such as earthquakes and wind loads effectively. Risk-informed and performance-based regulation in the nuclear industry requires considering possible accidents and determining desirable performance on structures. As a result, rather than predicting only the ultimate capacity of structures, the prediction of performances on structures depending on different damage states or various accident scenarios have increasingly needed. This study aims to develop machine-learning models predicting drifts of the RC shear walls according to the damage limit states. The damage limit states are divided into four categories: the onset of cracking, yielding of rebars, crushing of concrete, and structural failure. The data on the drift of shear walls at each damage state are collected from the existing studies, and four regression machine-learning models are used to train the datasets. In addition, the bagging ensemble method is applied to improve the accuracy of the individual machine-learning models. The developed models are to predict the drifts of shear walls consisting of various cross-sections based on designated damage limit states in advance and help to determine the repairing methods according to damage levels to shear walls.

Evaluation of modelling uncertainties impact in older infilled frame RC structures

The seismic response of infilled frame reinforced concrete structures is affected by different sources of aleatory and epistemic uncertainties and is particularly sensitive to the modeling parameters evidenced by reported numerical and analytical studies. In the current study, a probabilistic sensitivity analysis is performed by nonlinear static (PNSA) and nonlinear dynamic analyses (PNDA) on a base-case infilled frame structure incorporating structural (beam, column) and non-structural (masonry infill) components behavior. Therefore, the state-of-the-art models of the most effective sources of nonlinear response employed herein as fiber section to depict the axial-moment interaction in frame components, bi-diagonal eccentric strut to capture the cracking and crushing of masonry infill, and the shear failure in columns caused by infill-frame interaction. Finally, results are illustrated by tornado plots incorporating probabilistic sensitivity to material and component parameters for operational (O), damage (D), life safety (L), and collapse (C) limit states. Results state that the building response is significantly affected by the modeling parameters of infill characteristics, mass source, and the damping of the structure.

Probabilistic Analysis of RC Buildings Based on Incremental Dynamic Analysis

Earthquake is a natural disaster that can induce immense damage to properties and human lives. Fragility curve, defined as the probability of reaching or exceeding a specific damage state under an earthquake excitation, provides a prediction of damage that may occur during an earthquake. Incremental Dynamic Analysis Curve (IDA curve) developed from Incremental Dynamic analysis can be considered as the initial step of fragility curve development. The present study summarises the development of IDA curve for a RC building considering maximum roof displacement and storey drift as Damage Measure (DM) and peak ground acceleration as Intensity Measure (IM). The fragility curves developed using incremental dynamic analysis provide an overview of the probability of exceedance of damage limits in an existing building when acted upon by different levels of earthquake excitations and the performance level can be improved by incorporating appropriate design changes.

Effectiveness of Pitfall Trap Colors in Monitoring Adults of Blister Beetle Meloe proscarabaeus Linnaeus, 1758 (Coleoptera: Meloidae) in Faba Bean Fields at El-Farafra Oasis Egypt

The blister beetles Meloe proscarabaeus Linnaeus, 1758 (Coleoptera: Meloidae), is a dangerous pest that threatens the agriculture of faba bean fields in El-Farafra Oasis, New Valley Governorate. In this study, an evaluation of the efficiency of different pit-fall trap colors for capturing adults of the blister beetles has been performed in faba bean (Vicia faba L.) fields. The experiment revealed that the green and red traps showed the highest number of captured beetles during the 2020 and 2021 seasons, which was highly significant to other traps’ colors. On the other hand, black, blue, gray, white, and yellow traps showed insignificant differences in the number of captured beetles. Concerning the sex of trapped beetles; it could be highlighted that the green trap attracted more female beetles than males with significant differences. Inversely, the red color trap attracted more males than females with significant differences. Approximately 40% of the captured beetle population was recorded in March, while only 11% were trapped in April. A Green pit-fall trap could be deemed a new estimating assay to suppress M. proscarabaeus adults in faba bean fields since the color trap variation affected the number of captured beetles. Therefore, color traps can be relied upon as an effective method in controlling beetles without the number of beetles reaching the limit of economic damage and in a manner that is safe for the environment

Lateral impact performance of wire ropes

Wire ropes are often used in flexible barriers or road engineering to resist lateral impact because of their good reliability, high economy, and construction convenience. However, their application under lateral impact lacks a systematic design approach. In this paper, to ensure the safe use of the structure, the lateral impact test of single wire ropes and wire rope nets is carried out, and the strain, displacement, and acceleration response are analyzed. In addition, the tensile mechanical properties of wire rope strands are determined through static tensile mechanical properties tests, which provide reasonable parameters for the constitutive model used in numerical simulations. Furthermore, considering the influence of wire rope pre-tension ratio, span ratio, and mass ratio, empirical formulas for longitudinal peak tensile force and lateral peak displacement are given. The results show that the wire rope mainly occurs local abrasion at the impact point, fracture, and end connection failure. It is worth noting that when the dimensionless lateral peak displacement (ωm) reaches 0.089, the wire rope breaks. Moreover, according to Lagrange Green’s strain theory, a theoretical calculation formula for the mid-span lateral limit displacement of wire rope under pre-tension is derived and compared with the simulated values of test members. Consequently, according to the damage degree of wire ropes, the damage limit value is determined. Finally, considering the tensile capacity of wire ropes and their displacement responses, a limit state function is proposed to evaluate the damage of existing components or to design new components.

Review of Methodologies for Displacement Checks in Modern Seismic Design Codes

This review paper discusses the procedures for evaluating the design displacement given in various design codes from seismically prone countries around the world (the United States, New Zealand, Chile, Japan, Greece, Italy, Iran, India, Turkey, and Romania). The limit displacements and the corresponding limit states are also presented and analyzed in this study besides the importance class factors considered in the selected seismic design codes. A presentation of the behavior factors necessary for evaluating the design value of the seismic action is also shown in this study. One of the observations of this review paper is that there are significant similarities in terms of the approach to the displacement check in the analyzed codes. In addition, it was observed that the displacement check is generally associated with the serviceability limit state (e.g., damage limitation). However, differences in terms of the mean return period for the serviceability check action were observed among the analyzed seismic design codes. Several aspects which have to be further adapted in the future versions of seismic design codes are also discussed in this review paper. One of the main aspects which must be further discussed is the enforcement of displacement limits, which are dependent on the structural system and on the importance of the class/height regime for the ultimate/serviceability limit state. In addition, the dependence of the TD control period on the probabilistic seismic hazard ordinates should be further discussed. Moreover, the pulse effects, which can affect both the acceleration and the displacement design of response spectra, should be accounted for as well in future generations of seismic codes. Finally, it appears necessary to perform a harmonization of the behavior factors employed in seismic design codes.

Seismic Risk of Weak First-Story RC Structures with Inerter Dampers Subjected to Narrow-Band Seismic Excitations

This study evaluates the seismic risk of weak first-story reinforced concrete (RC) structures retrofitted with inerter dampers at their ground level when subjected to narrow-band seismic excitations. The main advantages brought about by the ground-level inerters are the reductions in seismic demands (e.g., drifts, floor accelerations). This study shows that structures with inerters are reliable systems in terms of peak story drifts for large ground motions. For moderate ground-motion intensities, the opposite could occur, mainly for soft soil sites. The reliabilities of structures with inerter dampers at their ground level are in general higher for buildings under seismic intensities associated to limit state of incipient collapse, especially for low-height buildings. This could be reversed for intensities associated to the limit state of damage limitation. The findings of this study could guide practicing engineers to use inerter-based dampers in retrofitting ductile structures consisting of moment-resisting reinforced concrete (RC) frames subjected to narrow-band earthquake excitations in regions such as Mexico City.

Seismic capacity and performance of code-conforming single-story RC precast buildings considering multiple limit states and damage criteria

The seismic capacity and performance of code-conforming precast buildings is assessed in the study. The case study consists in single-story precast buildings designed according to Italian building code considering low to high seismicity sites and varying both geometry layout and soil conditions. The seismic behavior of the buildings is assessed through multiple-stripe analyses performed through nonlinear three-dimensional modeling. Fragility of the buildings is computed by considering several methods, and performance evaluation is based on capacity margin ratios, failure probabilities, and reliability indexes. Damage limitation, life safety prevention, and near collapse prevention performance levels are considered by accounting for multiple damage criteria and damage states, including both local and global approaches and both ductile and brittle failure of beam-to-column connections.The paper provides guidance for implementation of seismic capacity and performance evaluation of precast buildings according to latest advances, considering both European and US approaches. The study proves that the current code prescriptions might not supply adequate seismic performance, especially in the case of more critical soil conditions (i.e., C soil type compared to A soil type). A relatively critical performance was observed for damage limitation and life safety prevention performance levels, whereas collapse performance of the buildings was adequate. The extremely critical condition associated with brittle failure of the beam-to-column connection was also confirmed. The study stresses the need for an enhancement of current design requirements and highlights the need for further investigation into the adequacy of seismic performance of precast buildings and reliability of related code-conforming design.

Seismic fragility and risk assessment of self-centering wall structures with traditional and sliding joint infill walls

Self-centering (SC) precast wall structures have emerged as earthquake-resilient structural systems with excellent seismic performances characterized by low damage as well as negligible post-earthquake residual deformation. However, research on SC wall systems often ignores infill walls for simplicity, which results in difficulty to achieve an integrated resilient structural system. To fill this gap, this paper presents a comprehensive assessment of SC precast concrete wall structures with three different types of infill walls and compares the results with that without infill walls. The maximum inter-story drift, the peak floor acceleration, and the damage index of the considered systems at different seismic intensities are calculated through incremental dynamic analysis. The assessment is then expanded from fragility to risk by evaluating the probabilities of exceeding each potential limit state throughout the service life. Results show that, despite merely no damage to the SC wall itself, the integral system could sustain significant damage due to the damage to the infills attached. What’s more, with stronger infill walls, severer damage to the integral system is likely to be. Among the three infills considered in this study, the one with sliding joints performs the best from the perspective of damage, resulting in a smaller likelihood of 21%∼60% exceeding various damage limits than that of traditional infills. However, the sliding joint infill’s benefit in damage is at the expense of larger drift and slightly higher acceleration responses compared with traditional infills. It is concluded that the infills considered in this paper all have their drawbacks and new infills that combine the sliding mechanism (to reduce damage) and higher damping (to reduce drift and acceleration) are encouraged to develop an integrated resilient system.

Frequency‐Sensitivity of the seismic damage to suspended ceilings

AbstractSeismic damage to suspended ceilings was frequently reported even in minor to moderate earthquakes and caused problems to immediate occupancy and quick recovery of buildings. While peak floor acceleration (PFA) has been exclusively used as an intensity measure for suspended ceilings, this study introduces a shake table test on minimum subassemblies of suspended ceilings under sinusoidal excitation to critically assess the rationality of this practice. The test results show a significant frequency‐sensitivity of the ceiling damage that, depending on the dominant frequencies, an excitation of a lower PFA might cause much severer damage than that of a higher PFA. A numerical model that captures the nonlinear interaction of the individual components in a suspended ceiling, that is, the main and cross runners, ceiling panels, a hanger, and enclosure angles, is established and calibrated to simulate the frequency‐sensitive behavior observed in the shake table tests. The model is then extended for suspended ceilings of realistic dimensions. Three‐dimensional fragility spectra of suspended ceilings under sinusoidal excitations are proposed to relate the extent of seismic damage with not only the PFA but also the excitation frequency. Boundaries of damage limit states can be defined by taking two‐dimensional sections on the fragility spectra, based on which, the influence of key factors on ceiling damage characteristics is illustrated.

Analysis of the influence of CA mortar layer void on the dynamic performance of high-speed trains

The void of cement asphalt (CA) mortar layer will aggravate the abnormal vibration of high-speed trains at the void position and threaten the running safety. Few studies have been conducted on the effect of mortar layer void on the dynamic performance of slab track on bridges and the damage limits. Aiming at the practical problem of CA mortar layer void in track-bridge systems, a dynamic response calculation program for the train-track-bridge system is prepared based on the train-track-bridge interaction theory. A sample library of high-speed trains running performance indicators considering random initial track irregularity under CA mortar layer void conditions is constructed. The influence of void length on the dynamic performance of high-speed trains under two different CA mortar layer void conditions is investigated by means of sample upper bounds based on probability guarantee rate. The results show that the wheel load reduction rate and vertical acceleration of high-speed trains are more sensitive to changes in void length than the derailment coefficient. The effect of CA mortar layer void on the running performance index of high-speed trains is significantly enhanced after a certain critical void length value, railway maintenance should pay more attention to critical thresholds. The mid-span void and beam-end void length thresholds of CA mortar layer based on the probability guarantee rate decrease significantly with the increase in running speed while utilizing the wheel load reduction rate as the control index. However, the void position has little influence on the void length threshold. The void length threshold results can provide a basis for the CA mortar void limits.

Life‐cycle cost‐oriented multiobjective optimization of composite frames considering the slab effect

SummaryThe life‐cycle cost‐oriented design philosophy is a promising tool for building resilient cities as it helps in gaining insights into the impact of hazard‐induced damage and repair of civil and infrastructure systems. In this study, a socioeconomic parameter‐independent practical formulation was introduced for life‐cycle cost analysis by combining the economic loss rate associated with different damage limit states and cloud analysis‐based probabilistic seismic demand model. A framework for life‐cycle cost analysis‐based seismic design optimization was proposed using an emerging nature‐inspired algorithm, namely, the multiobjective cuckoo search. By considering an eight‐story prototype composite frame, the framework was used to determine the trade‐off design alternatives between competing optimization objectives. Conventional and improved fiber models were developed to comparatively evaluate the influence of the slab spatial composite effect on Pareto optimal designs. The key drivers of change in three cost indicators were identified using generalized linear models. The result indicates that the overstrength factor is the critical design parameter affecting the initial construction, seismic damage, and life‐cycle costs, with statistical significance at the 0.001 level.

Factors Impacting Rhizobium-legume Symbiotic Nitrogen Fixation with the Physiological and Genetic Responses to Overcome the Adverse Conditions: A Review

Symbiotic N2 fixation is essential for the plant’s growth because it can fix reactive nitrogen compounds in soil. However, all steps of this process can be hampered by several biotic and abiotic environmental factors. This study mainly focused on discussing the impacts of 12 major factors on this process by reviewing the significant numbers of research works. According to the information from these works, we found some significant physiological and genetic impacts caused by these factors like plasmid deletion, genomic mismanagement, abnormal molecular signals, toxicity, deficiency of minerals, deformation of rhizobial cells, protein denaturation, nucleic acid damage, acetylene reduction and nod factors limitation. Furthermore, expression of heat or acid shock proteins, internal buffering, genes spanning, extracellular immobilization, periplasmic allocation, change of lipopolysaccharides composition, intracellular accumulation of inorganic and organic solutes (Osmolyte) and activation of hydrogenase expression are shown by both micro and macro symbionts as a natural response to adapt to these stress conditions. Though the stress-tolerant strains like HR-3, HR-6, HR-10, HR-12, acta, actP, exoR, lpiA, actR, actS and phrR can be used to sense the external environment and make signals to change gene transcription during the adverse condition, the application of genetic engineering should be expanded more to promote the commercial inoculation by the production of novel stress-tolerant strains or modified genes of rhizobia and legumes.

Effectiveness of Design Procedures in Counteracting Second Order Effects in Steel Moment Resisting Frames

The seismic response of structures is always influenced by second order (P–Δ) effects. The importance of these effects becomes significant when the structure experiences large plastic deformations. Seismic codes indicate that P–Δ effects may be counteracted by means of an increase of the lateral strength required by a first order analysis, but the expressions of the Strength Amplification Factor (SAF) given in codes are often criticized by researchers. This paper proposes and validates a formulation of the SAF for Moment Resisting Frames (MRFs), which is a generalization of that derived in the past by some of the authors based on the response of SDOF systems. To this end, in a first stage of the research a set of steel MRFs is designed and analyzed neglecting P–Δ effects. The seismic response is determined by nonlinear static and incremental dynamic analyses and the mean annual frequency of exceedance of the Significant Damage (SD) and Near Collapse (NC) limit states is computed. In a second stage, each structure is re-designed and analyzed considering P–Δ effects. P–Δ effects are counteracted in design according to provisions of European, American and Canadian seismic codes or according to other formulations proposed in literature, such as that proposed by Bernal and that proposed by the authors. The accuracy of the design provisions accounting for P–Δ effects is determined by comparing the response of the structures designed in the first and in the second stages.

Impact of the Melt-Refining Process on the Performance of Sodium-Cooled Rotational Fuel-Shuffling Breed-and-Burn Reactors

This study assesses a Rotational Fuel-Shuffling Breed-and-Burn (RFBB) fast reactor that operates in breed-and-burn (B&B) mode with a rotational fuel-shuffling scheme and remains within the 200 displacements per atom (DPA) radiation damage constraint of currently verified cladding materials. The design is based on a commercial-scale fast burner reactor called the Super Power Reactor Innovative Small Module (S-PRISM) reactor. To reduce the high DPA values of discharged fuels, the melt-refining process developed in the Experimental Breeder Reactor-II (EBR-II) project is adopted in this study. The effects of the melt-refining process on the performance of the RFBB are investigated via five scenarios and compared with a core to which the melt-refining process is not applied: Scenario I, “Homogenization,” occurs without the removal of fission products (FPs) during the melt-refining process; Scenario II, “Homogenization and FP Removal,” occurs with the removal of FPs to a fraction similar to that in the melt-refining process developed in the EBR-II project; Scenario III, “Homogenization, FP Removal, and Make-Up,” is similar to Scenario II but makes up fuel losses with natural uranium; Scenario IV, “With 1% TRU [transuranics] Losses,” is similar to Scenario III but is evaluated with 1% of actinides not recovered; Scenario V, “With 10% TRU Losses,” is similar to Scenario III but is evaluated with 10% of actinides not recovered. The results show that it is neutronically and thermal hydraulically feasible to establish a B&B mode with the rotational fuel-shuffling scheme and by reconditioning the fuel whenever its cladding reaches its proven 200 DPA radiation damage limit. In Scenario V, the core is subcritical due to a large number of actinides not being recovered during the melt-refining process. The cores of the other scenarios are all critical. The cores of scenarios in which FPs are removed during the melt-refining process have higher excess reactivity than that of the core of Scenario I (“Homogenization”) and that of the core to which the melt-refining process is not applied. The numerical analyses also show that in scenarios that include making up fuel losses during melt refining, the core is fed with more natural uranium make-up fuel during operation and thus has lower burnup. Other characteristics, such as power density distributions, neutron flux profiles, and fertile and fissile nuclide density distributions, are all stable during operation.

Special braced stairs versus typical braced frames. New architectural‐structural‐seismic approach to stair design

SummaryThis paper presents a new approach to the project of steel buildings, mainly focused on the architectural, structural, and seismic design of stairs. The objective is to design a structural stair system capable of controlling seismic damage and contributing to the bracing system of the building. The article begins with a review of the seismic standard (ATC, FEMA, and EC8) on which the current design criteria for new buildings with stairs are based. The research is based on two spatial building models (A–B) with the same bracing elements but placed differently. Reference Model A follows classical design approaches. It means, stairs are considered nonstructural elements that do not influence the seismic behavior of the building. This structure corresponds to typical braced frames (IV‐CBF and EBF) according to EC8. Model B includes a stair system designed to help control the effects of inter‐story drifts and inertia forces. In this case, the same bracing elements of Model A were integrated into the stair structure of Model B. A comparative seismic behavior analysis of typically braced frames (A) versus specially braced stairs (B) is presented. The research was based on the static nonlinear (pushover) analysis and the capacity spectrum method (ATC‐40) according to the seismic performance levels (FEMA) and damage limitation (EC8). Finally, the braced stairs was verified via nonlinear time‐history analysis in order to better capture the structural safety of the evacuation routes and their influence on the behavior of the building. This deterministic analysis of the braced stairs verified satisfactory results compared to reference bracing systems.

An electro-optic continuous laser beam steering device based on an SBN75 crystal

The performance of electro-optics (EO) beam steering systems relies on the EO effect exhibited by certain crystals which is a refractive index change with an applied electric field. The very high EO coefficient and transparency, high optical damage limit, low conductivity, and comparatively low Curie temperature of SrxBa1-xNb2O6 (SBN) make this EO crystal very attractive for EO beam steering applications. In this study, an EO laser beam steering device based on a bulk Sr0.75Ba0.25Nb2O6 (SBN75) crystal grown at Teledyne Scientific was designed 1 . The SBN beam steerer was tested under different scenarios and the first and second EO effects and all linear EO coefficients of the SBN75 ( ) were measured based on the laser beam’s deflection angles and compared with the values reported in the literature. The results showed that Teledyne’s SBN75 crystal exhibited a primary EO effect of about 4 to 6% more than the value reported in the literature at the room temperature, the share of the secondary EO effect is less than 8% and the linear EO effect disappeared at 58 °C.

Sly-miR398 Participates in Cadmium Stress Acclimation by Regulating Antioxidant System and Cadmium Transport in Tomato (Solanum lycopersicum).

Cadmium (Cd) pollution is one of the major threats in agricultural production, and can cause oxidative damage and growth limitation in plants. MicroRNA398 (miR398) is involved in plant resistance to different stresses, and the post-transcriptional regulation of miR398 on CSDs plays a key role. Here, we report that miR398 was down-regulated in tomato in response to Cd stress. Simultaneously, CSD1 and SOD were up-regulated, with CSD2 unchanged, suggesting CSD1 is involved in miR398-induced regulation under Cd stress. In addition, the role of miR398 in Cd tolerance in tomato was evaluated using a transgenic line overexpressing MIR398 (miR398#OE) in which the down-expression of miR398 was disrupted. The results showed that Cd stress induced more significant growth inhibition, oxidative damage, and antioxidant enzymes disorder in miR398#OE than that in wild type (WT). Moreover, higher Cd concentration in the shoot and xylem sap, and net Cd influx rate, were observed in miR398#OE, which could be due to the increased Cd uptake genes (IRT1, IRT2, and NRAMP2) and decreased Cd compartmentalization gene HMA3. Overall, our results indicate that down-regulated miR398 plays a protective role in tomato against Cd stress by modulating the activity of antioxidant enzymes and Cd uptake and translocation.