Effect Of Local Damage Research Articles

폭발에 의한 국부손상이 철근콘크리트 보의 휨강도에 미치는 영향과 전단 철근 배근에 따른 폭발저항 성능

폭발에 의한 국부손상이 철근콘크리트 보의 휨강도에 미치는 영향과 전단 철근 배근에 따른 폭발저항 성능

The Effect of Light Ion Irradiation on 4H-SiC MPS Power Diode Characteristics: Experiment and Simulation

In this article, the effect of local radiation damage on the electrical characteristics of 1700 V 4H-SiC Merged-Pin Schottky (MPS) diode have been investigated. Radiation defects introduced by irradiation with 670 keV protons were placed into the low-doped n-type epi-layer and their influence on diode characteristics were characterized by capacitance DLTS, C-V profiling and I-V measurements. Simulation model accounting for the effect of proton irradiation was developed, calibrated and used for analysis of underlying effects and temperature dependencies. Results show that the forward voltage drop and breakdown voltage is insensitive to the position of the damage region when the defect peak is placed far away from the Schottky metal contact of the MPS diode. However, when the damage region approaches to the p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> regions, forward voltage drop degrades significantly. For fluences higher than 3.3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">- 2</sup> , the acceptor concentration in the peak region achieves donor doping level of the epi-layer and a sharp increase in the diode forward voltage drop is observed. Acceptor centers introduced by proton irradiation also slightly increase the breakdown voltage while decreasing the leakage current at voltages close to the MPS diode breakdown ( > 2000 V).

Effects of local structural damage in a steel truss bridge on internal dynamic coupling and modal damping

Structural health monitoring of steel truss bridge based on changes in modal properties was investigated in this study. Vibration measurements with five sensors were conducted at an existing Warren truss bridge with partial fractures in diagonal members before and after an emergency repair work. Modal properties identified by the Eigensystem Realization Algorithm showed evidences of increases in modal damping due to the damage in diagonal member. In order to understand the dynamic behavior of the bridge and possible mechanism of those increases in modal damping, theoretical modal analysis was conducted with three dimensional frame models. It was found that vibrations of the main truss could be coupled internally with local vibrations of diagonal members and the degree of coupling could change with structural changes in diagonal members. Additional vibration measurements with fifteen sensors were then conducted so as to understand the consistency of those theoretical findings with the actual dynamic behavior. Modal properties experimentally identified showed that the damping change caused by the damage in diagonal member described above could have occurred in a diagonal-coupled mode. The results in this study imply that damages in diagonal members could be detected from changes in modal damping of diagonal-coupled modes.

Damage localization in composite lattice truss core sandwich structures based on vibration characteristics

Although much effort has been devoted to explore the behavior of the composite lattice truss core sandwich structures, little research has been undertaken into non-destructive evaluation (NDE) and health control of this new structure. This article presents the development of a baseline-free NDE method to determine the debonding of truss bar in composite lattice truss core sandwich structures. The method is proposed based on the uniform load surface (ULS) curvature, and developed according to the synergy of gapped smoothing method (GSM) and Teager energy operator (TEO), which is denoted as GSM-TEO method. The effects of local damage on the vibration characteristics of different composite lattice truss core sandwich structures are firstly investigated, and then, experiment and numerical simulation are conducted to assess the performance of the proposed method. It is demonstrated that the GSM-TEO method is reliable and applicable for damage localization in composite lattice truss core sandwich structures.

Indications of radiation damage in ferredoxin microcrystals using high-intensity X-FEL beams.

Proteins that contain metal cofactors are expected to be highly radiation sensitive since the degree of X-ray absorption correlates with the presence of high-atomic-number elements and X-ray energy. To explore the effects of local damage in serial femtosecond crystallography (SFX), Clostridium ferredoxin was used as a model system. The protein contains two [4Fe-4S] clusters that serve as sensitive probes for radiation-induced electronic and structural changes. High-dose room-temperature SFX datasets were collected at the Linac Coherent Light Source of ferredoxin microcrystals. Difference electron density maps calculated from high-dose SFX and synchrotron data show peaks at the iron positions of the clusters, indicative of decrease of atomic scattering factors due to ionization. The electron density of the two [4Fe-4S] clusters differs in the FEL data, but not in the synchrotron data. Since the clusters differ in their detailed architecture, this observation is suggestive of an influence of the molecular bonding and geometry on the atomic displacement dynamics following initial photoionization. The experiments are complemented by plasma code calculations.

Study on the Similarity Laws for Local Damage Effects in a Concrete Target under the Impact of Projectiles

The local destruction and deformation characteristics of a concrete target impacted by a rigid projectile were analyzed, and the similarity laws for local damage effects in the concrete target were studied utilizing the rigid-plastic, internal friction, and modified hydrodynamic models. For a thin target, the impact factor is the only factor controlling the low-velocity impact process. For a thick target impacted by a projectile at intermediate velocity, internal friction is the main factor contributing to the energy dissipation. The impact factor, the toughness factor, and the dynamic factor together determine the penetration process. However, for a thick target impacted at high velocity, the impact factor and hardness factor together determine the penetration process. The penetration depth shows a 2/3 power relationship with impact velocity. For thick targets, similarity laws change along with impact velocity. The radii ratio between the projectile and penetration tunnel is proportional to the projectile’s diameter for intermediate velocity impact and only shows a relationship with the impact velocity for high velocity penetration.

폭발 손상을 입은 강섬유 및 FRP 시트 보강 철근콘크리트 보의 국부손상 및 잔류성능 평가

본 연구에서는 폭발에 의한 국부손상이 철근콘크리트 보의 잔류 휨강도 및 연성에 미치는 영향을 알아보기 위하여 160×290×2200㎜의 철근콘크리트 보에 대하여 근접 폭발 시험과 정하중 휨시험을 수행하였다. 또한 이 시험을 통해 강섬유 및 FRP 시트로 보강한 철근콘크리트 보의 폭발저항성능을 평가하였다. 장약량 1㎏, 이격거리 0.1m의 폭발 시험을 수행하였으며, 시험 후 시험체의 crater, spall 지름과 무게손실(weight loss)을 측정하여 시험체의 국부손상을 평가하였다. 또한 폭발하중을 받지 않은 시험체와 폭발하중을 받아 국부손상이 발생한 시험체의 정하중 휨시험을 수행하여 휨강도 및 연성지수를 측정하였다. 시험결과, 보통콘크리트 시험체(NC)는 비교적 큰 crater와 spall이 발생하였으며 국부손상에 의한 무게 손실이 23.5㎏ 발생하였다. 반면 강섬유보강콘크리트 시험체(SFRC)와 FRP 시트 보강 시험체(NC-F, NC-FS)는 NC에 비해 crater 크기와 무게손실이 감소하며 향상된 폭발저항성능을 나타내었다. 또한 폭발하중에 의해 국부손상이 발생한 시험체들은 휨강도와 연성지수가 감소하였다. 특히 NC는 잔류 휨강도가 기존 강도에 비해 크게 감소하였고 압축철근의 좌굴현상이 나타나며 취성적으로 파괴되었다. 강섬유와 FRP 시트로 보강한 시험체의 경우 잔류 휨강도 및 연성지수가 NC에 비해 증가하였다. 이를 통해 폭발이 발생할 경우, 충분한 이격거리를 확보하지 못하면 장약량이 적더라도 구조부재에 심각한 국부손상을 발생 시킬 수 있다는 것을 알 수 있었으며, 강섬유와 FRP 시트에 의한 보강 방법이 폭발저항성능을 향상시킨다는 것을 확인할 수 있었다.

Effect of Local Damage Caused by Overweight Trucks on the Durability of Steel Bridges

AbstractOver the lifetime of a bridge, traffic loads cause numerous stress-strain cycles within its components which in turn lead to the slow accumulation of damage in them. The rate of progression of this damage with time is affected by several human-induced and natural factors such as volume and type of traffic loads, environmental conditions, and maintenance practices. Traffic volume and truck weights have been steadily increasing with the growth and technical development of the freight industry. With increased truck weight limits being anticipated in the future, a detailed study of the potential detrimental effects of such increases, especially due to overweight trucks, on the durability of bridges has become necessary. In this paper, a computational approach is presented to assess the effect of different load-related and environmental factors on the durability of steel bridge components using detailed finite-element (FE) models that were calibrated using data from inspection reports of real bridges. ...

Statistics based localized damage detection using vibration response

Damage detection is a challenging, complex, and at the same time very important research topic in civil engineering. Identifying the location and severity of damage in a structure, as well as the global effects of local damage on the performance of the structure are fundamental elements of damage detection algorithms. Local damage detection is essential for structural health monitoring since local damages can propagate and become detrimental to the functionality of the entire structure. Existing studies present several methods which utilize sensor data, and track global changes in the structure. The challenging issue for these methods is to be sensitive enough in identifYing local damage. Autoregressive models with exogenous terms (ARX) are a popular class of modeling approaches which are the basis for a large group of local damage detection algorithms. This study presents an algorithm, called Influence-based Damage Detection Algorithm (IDDA), which is developed for identification of local damage based on regression of the vibration responses. The formulation of the algorithm and the post-processing statistical framework is presented and its performance is validated through implementation on an experimental beam-column connection which is instrumented by dense-clustered wired and wireless sensor networks. While implementing the algorithm, two different sensor networks with different sensing qualities are utilized and the results are compared. Based on the comparison of the results, the effect of sensor noise on the performance of the proposed algorithm is observed and discussed in this paper.

Variations in the effects of local foliar damage on life span of individual leaves of downy birch (Betula pubescens)

Although the premature abscission of leaves damaged by herbivores has been discovered decades ago, the reduction in leaf life span caused by herbivory remains poorly documented, and the sources of variation in the magnitude of this effect have only rarely been studied. We aimed at exploring the effects of several herbivore species (at their background densities) and simulated herbivory on the leaf life span of downy birch, Betula pubescens Ehrh. Leaves damaged by herbivores abscised on average 12.6 days earlier and punched leaves 3.5 days earlier than the intact leaves of the control shoots. Different herbivores reduced the life span of the birch leaves from 0% to 27% depending on the intensity and timing of the damage but not on the insect feeding guild. The reduction in leaf life span was greater when the damage was imposed on expanding and growing leaves compared with mature leaves. However, the effect of herbivore species remained significant after accounting for intensity and timing of damage. This fact, together with greater reduction in leaf life span due to natural herbivory compared with mechanical damage, indicates that premature abscission in response to injury is considerably enhanced by insect-specific elicitors.

Effects of local damage on vibration characteristics of composite pyramidal truss core sandwich structure

The effects of local damage on the natural frequencies and the corresponding vibration modes of composite pyramidal truss core sandwich structures are studied in the present paper. Hot press molding method is used to fabricate intact and damaged pyramidal truss core sandwich structures, and modal testing is carried out to obtain their natural frequencies. A FEM model is also constructed to investigate their vibration characteristics numerically. It is found that the calculated natural frequencies are in relatively good agreement with the measured results. By using the experimentally validated FEM model, a series of numerical analyses are conducted to further explore the effects of damage extent, damage location, damage form on the vibration characteristics of composite pyramidal truss core sandwich structures as well as the influence of boundary conditions. The conclusion derived from this study is expected to be useful for analyzing practical problems related to structural health monitoring of composite lattice sandwich structures.

Dynamic Response for Collision Load between Over-Height Truck and Curved Beam Bridge

In recent years, ultra-urban road overpass vehicle impact beam incident after another. High beam impact of vehicles on the overpass bridge safety impact has become another important issue. High trucks at home and abroad on the curve of reinforced concrete beam bridge working effect of the impact is still insufficient. Based on high-precision linear dynamic finite element simulation analysis, research under the action of high vehicle collision, reinforced concrete curved girder Bridges of local damage effect and the overall distortion performance. The results showed that: high vehicles on the bridge superstructure imposed impact impulse and punching power led bridge superstructure is hitting zone produce local cracks. Damage caused by different impact velocity varied.

PolyVinyliDene Fluoride (PVDF) Material Based Energy Harvesting from Train and Damaged Bridge Interaction

This paper investigates the potential use of PolyVinyliDene Fluoride (PVDF) for the purposes of damage detection for infrastructural elements, primarily for bridge elements. PVDF based sensors have been created and characterised in the laboratory in this regard. Finite element analysis of vehicle-bridge interactions with varying damage are carried out. The energy harvesting signatures of realistic trains are assessed and quantified for the modelled bridge. The effect of localized damage on the finite element model and its subsequent relationship with energy harvesting from the calibrated PVDF based sensors are investigated using the harvesting signatures of realistic trains. This approach is useful in terms of designing new generation smart bridge structures and for possible retrofit of existing structures. The use of train-bridge interaction ensures that the damage detection is carried out while the bridge is under operational conditions. Consequently, there is minimal to no impact on the existing operation of the bridge or the transport network during damage detection. The paper is expected to be useful for practicing engineers and researchers in the field of application of new materials in the next generation of bridge structures.

The Effect of Local Damage on Energy Absorption of Steel Frame Buildings During Earthquake

Progressive collapse is a kind of failure in which whole or large part of a structure collapse when a local damage occurs and distributes to other parts. Many researchers focus on the column removal analysis and study of the structure behavior under effect of gravity loads, so these investigations are mostly carried out on the tall building. Earthquake inspections indicate structural element can be damaged during earthquakes and this initial damage distributes to the other parts, so seismic progressive is proposed as a research issue. In this article, seismic progressive collapse of a steel-frame building is investigated. A local damage in a part of the structure was created by weakening a column intentionally so, the initial damage was navigated toward a part of structure then the lateral loads were applied to the model and the structure behavior subjected to seismic progressive collapse is evaluated. In the next step, the effect of differentiating length and numbers of spans in both directions is studied and finally structure failure pattern cased by seismic progressive collapse is obtained.

Effect of local damage on the behavior of a laboratory-scale steel truss bridge

This paper presents an investigation into the performance of a steel truss bridge subjected to local damage. An experimental program with 16 damage scenarios is conducted to study the behavior of damaged truss systems. A three-dimensional numerical model is developed to predict the test results. Static and dynamic responses of the damaged trusses are compared with those of the control. Various technical aspects are studied, including damage quantification using a damage index, load rating, variation of strain energy, modal analysis, and structural safety based on simple reliability theory. Service performance of the truss bridge is significantly influenced by local damage (i.e., damage index >0.5) and the load-carrying capacity is exponentially reduced with the increased damage index. A high mode shape such as the 4th mode is of use to diagnose local damage in the truss system. The global safety index derived using deflection characteristics is an indicator to indirectly detect the presence of local damage in the system. Stress redistribution among the constituent truss members is found to be insignificant, except for those adjacent to the damage. The global safety index of the system based on deflection characteristics is an indicator to diagnose the presence of local damage. The need for developing a repair method that can address the global redundancy of a damaged truss bridge is highlighted.

Jararhagin, a hemorrhagic snake venom metalloproteinase from Bothrops jararaca

Jararhagin is a metalloproteinase isolated from Bothrops jararaca snake venom, which has been extensively studied. These studies showed its involvement on most of the systemic and local damaging effects of snakebite envenomings. In this review we comment on the major targets of jararhagin as the vascular endothelium, platelets and coagulation factors and also its action on other cell systems as inflammatory cells and their mediators, cancer and cell signaling. The mechanisms of jararhagin action are discussed together with structural features essential for the expression of its biological activities. The studies reviewed here denote jararhagin as a prototype for studies of snake venom metalloproteinases, bringing new insights into cellular-matrix interactions and adding for the improvement of snakebite treatment.

The effect of localized damage on the behavior of composites with periodic microstructure

The effect of localized stationary and progressive damage on the behavior of elastic composites with periodic microstructure is investigated. To this end, an analysis that combines continuum damage mechanics considerations together with three different approaches is presented and applied. In the first one the representative cell method is employed according to which the periodic composite domain is reduced, in conjunction with the discrete Fourier transform to a finite domain problem of a single cell. Appropriate far-field boundary conditions in the transform domain are applied in conjunction with the high-fidelity generalized method of cells micromechanical model which forms the second approach. The third approach consists of the application of the higher-order theory for the computation of the elastic field in the transform domain. An inverse transform provides the actual field. The effect of damage is included in the analysis in the form of eigenstresses which are a priori unknown. Hence an iterative procedure is employed to obtain a convergent solution. Several verifications of the proposed theory by comparisons with closed-form solutions have been presented. Results show the effect of stationary damaged regions as well as the development of cracks in the composite. It is demonstrated that standard micromechanical analysis based on the analysis of the repeating unit cell of the periodic composite with evolving damage cannot predict its actual behavior when a localized damage is involved.

Damage identification in Euler frames

The present paper examines the effect of local damage in elastic frames composed by Euler beams. The direct problems of undamaged and damaged frames are studied using the Wittrick–Williams algorithm. The related inverse problems of identifying material parameters in the undamaged structure and damage parameters, i.e. location and intensity, in the damaged frame are studied using procedures based on the comparison of numerical and pseudo-experimental natural frequencies. It is shown that the material parameters can be reliably determined and, with reference to the damaged frame, important considerations on the number of frequencies required in order to evaluate damage parameters are outlined. The sensitivity of the proposed procedure to experimental errors is also studied.

Effect of Local Damage on the Performance of Structures

Abstract. The dynamic behavior of structure subjected to local damage is investigated using conceptional removal methods recommended in the General Services Administration (GSA) guidelines. Two types of local damage are considered, namely, the speed and location of failure. The study is conducted on designed seven-story prototype buildings by applying dynamic liner analysis. Based on the simulation, it is concluded that dynamic effects are important considerations properly representing structural behavior in a robustness analysis of structure. The results also show that corner column play more important role in prevention of structural collapse than interior column. The resulting information would be valuable for protecting structures.

Modelling and Numerical Simulation of the Dynamics of Glaciers Including Local Damage Effects

A numerical model to compute the dynamics of glaciers is presented. Ice damage due to cracks or crevasses can be taken into account whenever needed. This model allows simulations of the past and future retreat of glaciers, the calving process or the break-off of hanging glaciers. All these phenomena are strongly affected by climate change.