Rigid Barrier Research Articles

Dimensional Analysis of the Pounding Response of an Oscillator Considering Contact Duration

AbstractThe dynamic response of an elastic pounding oscillator subjected to harmonic excitation is investigated with dimensional analysis. To model the pounding process, a linear viscoelastic model is used to simulate the contact force. Through dimensional analysis, the peak structural response parameters of the pounding oscillator, including structural displacement, velocity, and penetration displacement, are characterized by a set of dimensionless terms (denoted by the Buckingham notation Π). The reduced Π-set explicitly describes the interaction between the oscillator and the rigid barrier. Analytical solutions to dimensionless contact time, displacement, and velocity response are derived in this study and are further verified against the numerical simulation. The effect of pounding on the oscillator’s response is illustrated using three well-divided spectral regions (i.e., amplified, deamplified, and unaffected regions), which are defined based on the dimensionless system frequency parameter Πω. Param...

Challenges to the Implementation of a New Framework for Safeguarding Financial Stability

Abstract There is probably no single economic concept that has attracted more attention and intrigued scientific and professional circles than financial stability. For over a decade now that have been efforts to establish the starting point in explaining this condition or characteristic of the financial system since some find that the key to defining financial stability lies in stability and others argue in favour of the opposite, instability. Unfortunately, no agreement has been reached on a universal definition that would be widely accepted at the international level. Consequently, this gave rise to open discussions on systemic risk, creating a framework for preserving financial stability, and the role of central banks in this process. This article analyses the results achieved in the development of a theoretical concept of financial stability and its practical implementation. A consensus has been reached on the necessity of removing rigid barriers between macro and prudential policies and on the necessity of their coordinated actions. The primary objectives of monetary and fiscal stability have been shifted towards preserving financial stability. The isolated macroprudential principle rightfully got the epithet of an archaic approach. Coordinated micro and macroprudential policies have definitely prevailed and become reality in many countries, including Montenegro. Created institutional frameworks for safeguarding financial stability at all levels - national, Pan-European and global - represent a challenge for further comparative studies.

Development and commissioning of FBG sensors for impact test of rock fall protective barrier

Purpose – This paper aims to present an effective sensing detection system based on fiber Bragg grating (FBG) sensing technology for protective barriers that have been effectively applied to intercept and stop rocks from falling onto railway tracks. . Determination of exact stress and deformation values during impact tests for key components of the protective barrier forms important criteria for quality control of these barriers. Monitoring changes in force along the protective barrier when deployed in field application allows for real-time disaster warning for collapse and falling rocks. Design/methodology/approach – In this paper, we propose a monitoring strategy for key components of a protective barrier. During performance tests, dynamic force and strain were measured for the steel strands and supporting I-beam, respectively. Design of a special elastic structure for the force transducer based on finite element analysis and tensile tests has been discussed here. Two types of FBG force transducers were manufactured based on the elastic structure. Four FBG force transducers and four FBG strain sensors were used for impact verification testing of a new rigid protective barrier with a design protection level of 25 KJ. Findings – Dynamic force and strain responses were obtained during an impact of free-falling block with a kinetic energy of 25 KJ. Originality/value – The FBG monitoring scheme can be extremely valuable for optimized design of the barrier and can provide real-time disaster warning in regions of collapse and falling rocks.

Further insight into the reaction FeO(+) + H2 → Fe(+) + H2O: temperature dependent kinetics, isotope effects, and statistical modeling.

The reactions of FeO(+) with H2, D2, and HD were studied in detail from 170 to 670 K by employing a variable temperature selected ion flow tube apparatus. High level electronic structure calculations were performed and compared to previous theoretical treatments. Statistical modeling of the temperature and isotope dependent rate constants was found to reproduce all data, suggesting the reaction could be well explained by efficient crossing from the sextet to quartet surface, with a rigid near thermoneutral barrier accounting for both the inefficiency and strong negative temperature dependence of the reactions over the measured range of thermal energies. The modeling equally well reproduced earlier guided ion beam results up to translational temperatures of about 4000 K.

Recent advances in vibro-impact dynamics and collision of ocean vessels

The treatment of ship impacts and collisions takes different approaches depending on the emphasis of each discipline. For example, dynamicists, physicist, and mathematicians are dealing with developing analytical models and mappings of vibro-impact systems. On the other hand, naval architects and ship designers are interested in developing design codes and structural assessments due to slamming loads, liquid sloshing impact loads in liquefied natural gas tanks and ship grounding accidents. The purpose of this review is to highlight the main differences of the two disciplines. It begins with a brief account of the theory of vibro-impact dynamics based on modeling and mapping of systems experiencing discontinuous changes in their state of motion due to collision. The main techniques used in modeling include power-law phenomenological modeling, Hertzian modeling, and non-smooth coordinate transformations originally developed by Zhuravlev and Ivanov. In view of their effectiveness, both Zhuravlev and Ivanov non-smooth coordinate transformations will be described and assessed for the case of ship roll dynamics experiencing impact with rigid barriers. These transformations have the advantage of converting the vibro-impact oscillator into an oscillator without barriers such that the corresponding equation of motion does not contain any impact term. One of the recent results dealing with the coefficient of restitution is that its value monotonically decreases with the impact velocity and not unique but random in nature. Slamming loads and grounding events of ocean waves acting on the bottom of high speed vessels will be assessed with reference to the ship structural damage. It will be noticed that naval architects and marine engineers are treating these problems using different approaches from those used by dynamicists. The problem of sloshing impact in liquefied natural gas cargo and related problems will be assessed based on the numerical and experimental results. It is important for vessel designers to determine the capacity of ships to resist random slamming loads, sloshing loading impact, grounding accidents and ships collisions.

Extraordinary acoustic transmission mediated by Helmholtz resonators

We demonstrate perfect transmission of sound through a rigid barrier embedded with Helmholtz resonators. The resonators are confined within a waveguide and they are oriented such that one neck protrudes onto each side of the barrier. Perfect sound transmission occurs even though the open area of the necks is less than 3% of the barrier area. Maximum transmission occurs at the resonant frequency of the Helmholtz resonator. Because the dimensions of the Helmholtz resonators are much smaller than the resonant wavelength, the transmission is independent of the direction of sound on the barrier and of the relative placement of the necks. Further, we show that the transmitted sound experiences a continuous phase transition of π radians as a function of frequency through resonance. In simulations of adjacent resonators with slightly offset resonance frequencies, the phase difference leads to destructive interference. By expanding the simulation to a linear array of tuned Helmholtz resonators we show that it is possible to create an acoustic lens. The ability of Helmholtz resonator arrays to manipulate the phase of a plane acoustic wave enables a new class of sonic beam-forming devices analogous to diffractive optics.

Development of compatibility assessments for full-width and offset frontal impact test procedures in FIMCAR

The goal of the project FIMCAR (Frontal Impact and Compatibility Assessment Research) was to define an integrated set of test procedures and associated metrics to assess a vehicle's frontal impact protection, which includes self- and partner-protection. For the development of the set, two different full-width tests (full-width deformable barrier [FWDB] test, full-width rigid barrier test) and three different offset tests (offset deformable barrier [ODB] test, progressive deformable barrier [PDB] test, moveable deformable barrier with the PDB barrier face [MPDB] test) have been investigated. Different compatibility assessment procedures were analysed and metrics for assessing structural interaction (structural alignment, vertical and horizontal load spreading) as well as several promising metrics for the PDB/MPDB barrier were developed.The final assessment approach consists of a combination of the most suitable full-width and offset tests. For the full-width test (FWDB), a metric was developed to address structural alignment based on load cell wall information in the first 40 ms of the test. For the offset test (ODB), the existing ECE R94 was chosen. Within the paper, an overview of the final assessment approach for the frontal impact test procedures and their development is given.

A Comparison of the NHTSA Research Offset Oblique and Small Overlap Impact Tests and the IIHS Moderate and Small Overlap Tests

The National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) have both developed crash test methodologies to address frontal collisions in which the vehicle's primary front structure is either partially engaged or not engaged at all. IIHS addresses Small Overlap crashes, cases in which the vehicle's primary front energy absorbing structure is not engaged, using a rigid static barrier with an overlap of 25% of the vehicle's width at an impact angle of 0°. The Institute's Moderate Overlap partially engages the vehicle's primary front energy absorbing structure using a deformable static barrier with 40% overlap at a 0° impact angle. The NHTSA has developed two research test methods which use a common moving deformable barrier impacting the vehicle with 20% overlap at a 7° impact angle and 35% overlap at a 15° impact angle respectively. In this paper, the authors present a case study in which an exemplar mid-size sedan was subjected to all four impact conditions. Following the NHTSA research procedures and IIHS protocols, the anthropomorphic test devices used in this study were THOR-NT (with LX instrumented lower legs) for the NHTSA research tests, and the Hybrid III AM50 for the IIHS tests. Differences with regards to resulting vehicle deformation, vehicle kinematics, and occupant kinematics were noted between the IIHS and NHTSA test methods and are discussed in this paper. Language: en

Evaluation of energy loss in motorcycle-to-car collisions

Kinetic energy loss during the impact between two vehicles is an essential parameter to assess the impact severity and for road accident reconstruction, since knowledge of this value allows us to estimate the collision closing speed. In this paper, an activity for the evaluation of the kinetic energy loss in collisions between two-wheeler vehicles and cars by means of semi-empirical methods is presented. Often in this field, as remarked in literature, the main difficulty lies in the evaluation of the energy loss for the car, on which usually localised deformations are produced, involving zones, near the wheels, for instance, having stiffness completely different from those on which crash tests are normally carried out. The work provides an initial analysis of crash tests between motorcycles and rigid barriers present in literature and a subsequent experimental work aimed at extending the records and assessing the influence on the impact of a braking motorcycle. Subsequently, a method is developed for the assessment of the energy loss of the car–motorcycle system and a campaign of crash tests conducted between the two types of vehicle for the validation of the model.

The HeartShield device reduces the risk for right ventricular damage in patients with deep sternal wound infection.

Right ventricular rupture, resulting in serious bleeding, is a life-threatening complication associated with negative-pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier between the heart and the sharp sternal edges has been successfully tested on pigs. In the present article, we demonstrate increased safety in NPWT through the use of the HeartShield device. Six patients were treated with a specially designed device in combination with NPWT. The device consists of a horizontally placed disk covered in foam. The back of the T-shaped device sticks up between the sternal edges and up above skin level. This part of the device is also covered in foam. Drainage is performed through two holes at the top of the device. The device and foam are changed every second to third day, and -120 mm Hg of continuous therapy is used. Six patients were treated with traditional NPWT, serving as control group. No signs of calluslike formation were seen on the right ventricle in the group treated with the HeartShield device. In the conventional NPWT control group, all six patients had calluslike formation (>1 × 2 cm2) on the anterior part of the right ventricle. All patients in the HeartShield group had grade 1 epicardial petechial bleeding (<0.5 cm2) on the right ventricle. In the control group, one patient had grade 1 (<0.5 cm2), three patients had grade 2 (0.5-2.0 cm2), and two patients had grade 3 (>2.0 cm2) epicardial petechial bleeding on the right ventricle. No major bleeding or mortality was observed in either group during the course of the study. The use of the HeartShield device significantly minimizes the contact between the right ventricle and the sternal edges, thereby decreasing the risk for life-threatening complications due to bleeding.

교량 및 노측용 SB5-B 등급 강성배리어 개발

교량 및 노측용 SB5-B 등급 강성배리어 개발

Dynamic fragmentation of solid particles interacting with a rigid barrier

Fragmentation of small solid particles as a result of collision with a rigid barrier is considered. It is shown that the application of the Griffith energy approach to dynamic fracture is characterized by specific surface energy differing from its value determined from static tests. The existence of the threshold fragmentation velocity is established and the method for its prediction is proposed. The method for experimental estimation of the fracture incubation time is also proposed.

Cervical collagen network remodeling in normal pregnancy and disrupted parturition in Antxr2 deficient mice.

The remodeling of the cervix from a rigid barrier into a compliant structure, which dilates to allow for delivery, is a critical process for a successful pregnancy. Changes in the mechanical properties of cervical tissue during remodeling are hypothesized to be related to the types of collagen crosslinks within the tissue. To further understand normal and abnormal cervical remodeling, we quantify the material properties and collagen crosslink density of cervical tissue throughout pregnancy from normal wild-type and Anthrax Toxin Receptor 2 knockout (Antxr2-/-) mice. Antxr2-/- females are known to have a parturition defect, in part, due to an excessive accumulation of extracellular matrix proteins in the cervix, particularly collagen. In this study, we determined the mechanical properties in gestation-timed cervical samples by osmotic loading and measured the density of mature collagen crosslink, pyridinoline (PYD), by liquid chromatography tandem mass spectrometry (LC-MSMS). The equilibrium material response of the tissue to loading was investigated using a hyperelastic material model where the stresses in the material are balanced by the osmotic swelling tendencies of the glycosaminoglycans and the tensile restoring forces of a randomly-oriented crosslinked collagen fiber network. This study shows that the swelling response of the cervical tissue increased with decreasing PYD density in normal remodeling. In the Antxr2-/- mice, there was no significant increase in swelling volume or significant decrease in crosslink density with advancing gestation. By comparing the ECM-mechanical response relationships in normal and disrupted parturition mouse models this study shows that a reduction of collagen crosslink density is related to cervical softening and contributes to the cervical remodeling process.

Relevance of the IIHS Small Overlap Crash Test in Europe

Modern cars often perform poorly in the new small overlap crash test of the Insurance Institute for Highway Safety (IIHS). This frontal impact replicates what happens, when only the front corner of the vehicle collides with another vehicle or an object such as a pillar or a tree. European vehicle manufacturers criticise that the IIHS small overlap crash test would not be relevant based on accident statistics and that two-way traffic collisions could not be reproduced with a rigid barrier. The DTC Dynamic Test Center AG in Switzerland did research on the relevance of the IIHS small overlap crash test in Europe. Therefore the reproducibility of the IIHS barrier in comparison with real two-way traffic collisions was examined. Three tests were performed with a randomly chosen Renault Scenic II using different test configurations. In a fourth test was the influence of the vehicle slip off from the barrier analysed implemented by design modifications on the test vehicle. Loads of the anthropomorphic test device (ATD) placed on the driving seat were measured during each test to draw conclusions on biomechanical stress and occupant protection. The results obtained show that a collision of real two-way traffic collision can be reproduced on a rigid barrier if the impact velocity is adapted on the involved vehicles. If a car is not designed for the IIHS small overlap crash test, speed reduction by main absorbing elements could be marginal and therefore significantly increase the biomechanical stress on the occupant. It has been shown that the vehicle slip off from the barrier could decrease the biomechanical stress but requires a frontal-/ side impact adapted restraint system. The front wheel must be prevented from penetrating the occupant foot well. To avoid injury risks of likely secondary collision further measures such as multifunctional airbags with sufficient residual energy should be taken. With regard to the analysed tests the conclusion was drawn that a slip off from the barrier in combination with necessary adaptions could decrease the injury risk. It can be concluded that the IIHS small overlap crash test is relevant for Europe due to the identified key gaps for occupant protection.

Pinned-Down Temporary Concrete Barrier with Transition Systems for Limited-Space Work Zone Applications

In work zones in which space to place a temporary concrete barrier (TCB) is limited (e.g., zones to expand or repair a bridge), the barrier must be restrained to prevent large, lateral deflection from vehicular impact. This paper presents the development and testing of a restrained, F-shaped TCB that has limited deflections. In addition, two transitions were developed: (a) from the freestanding, F-shaped barrier to the restrained barrier and (b) from the restrained barrier to a rigid concrete barrier. Details of the development and crash testing of these transitions are presented. The restrained TCB and its transitions were developed with the use of a simple pinned-down anchoring method. Steel pins were simply dropped into inclined holes that started from the toe of the barrier and continued a short distance into the underlying bridge deck or concrete pavement, and thus locked the barrier in place. The drop-pin method makes it easy to install the barrier, inspect for proper installation, and remove or relocate the temporary barrier in a work zone. The pinning method also results in minimal damage to the underlying bridge deck or concrete pavement. Thus the method is more desirable to use, as opposed to some anchoring systems that require through-deck bolting, which results in greater concrete damage and is difficult to install and relocate.

Integrin-Matrix Clusters Form Podosome-like Adhesions in the Absence of Traction Forces

SummaryMatrix-activated integrins can form different adhesion structures. We report that nontransformed fibroblasts develop podosome-like adhesions when spread on fluid Arg-Gly-Asp peptide (RGD)-lipid surfaces, whereas they habitually form focal adhesions on rigid RGD glass surfaces. Similar to classic macrophage podosomes, the podosome-like adhesions are protrusive and characterized by doughnut-shaped RGD rings that surround characteristic core components including F-actin, N-WASP, and Arp2/Arp3. Furthermore, there are 18 podosome markers in these adhesions, though they lack matrix metalloproteinases that characterize invadopodia and podosomes of Src-transformed cells. When nontransformed cells develop force on integrin-RGD clusters by pulling RGD lipids to prefabricated rigid barriers (metal lines spaced by 1–2 μm), these podosomes fail to form and instead form focal adhesions. The formation of podosomes on fluid surfaces is mediated by local activation of phosphoinositide 3-kinase (PI3K) and the production of phosphatidylinositol-(3,4,5)-triphosphate (PIP3) in a FAK/PYK2-dependent manner. Enrichment of PIP3 precedes N-WASP activation and the recruitment of RhoA-GAP ARAP3. We propose that adhesion structures can be modulated by traction force development and that production of PIP3 stimulates podosome formation and subsequent RhoA downregulation in the absence of traction force.

Analysis of Delta Velocity and PDOF by Means of Collision Partner and Structural Involvement in Real-Life Crash Pulses With Modern Passenger Cars

Objective: In the widely used National Automotive Sampling System (NASS)-Crashworthiness Data System (CDS) database, summary metrics that describe crashes are available. Crash angle or principal direction of force (PDOF) is estimated by the crash examiner and velocity changes (ΔV) in the x- and y-directions are calculated by the WinSMASH computer program using PDOF and results from rigid barrier crash testing combined with deformations of the crashed car. In recent years, results from event data recorders (EDRs) have been added to the database. The aim of this study is to compare both PDOF and ΔV between EDR measurements and WinSMASH calculations. Methods: NASS-CDS inclusion criteria were model-year 2000 through 2010 automobiles, frontal crashes with ΔV higher than 16 km/h, and the pulse entirely recorded in the EDR module. This resulted in 649 cases. The subject vehicles were further examined and characterized with regard to frontal structure engagement (large or small overlap) as well as collision properties of the partner (impact location; front, side, or back) or object. The EDR crash angle was calculated as the angle between the lateral and longitudinal ΔV at the time of peak longitudinal ΔV. This angle was compared to the NASS-CDS investigator's estimated PDOF with regard to structural engagement and the collision partner or object. Multiple linear regression was used to establish adjustment factors on ΔV and crash angle between the results calculated based on EDR recorded data and that estimated in NASS-CDS. Results: According to this study, simulation in the newest WinSMASH version (2008) underestimates EDR ΔV by 11 percent for large overlap crashes and 17 percent for small overlap impacts. The older WinSMASH version, used prior to 2008, underestimated each one of these two groups by an additional 7 percentage points. Another significant variable to enhance the prediction was whether the crash examiner had reported the WinSMASH estimated ΔV as low or high. In this study, none of the collision partner groups was significantly different compared to front-to-front impacts. However, with a larger data set a couple of configurations may very well be significantly different. In this study, the crash angle denoted by PDOF in the NASS database underestimates the crash angle calculated from recent EDR modules by 35 percent. Conclusion: On average the ΔV and crash angle are underestimated in NASS-CDS when analyzing the data based on collision partner/object and structural engagement. The largest difference is found in small overlap crashes and the least difference in collision scenarios similar to barrier tests. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

TRAINED AND COMPETENT PERSONNEL - A PREREQUISITE FOR SUSTAINABLE FOREST MANAGEMENT

A general discussion a/the requirements Jar training at professional, technician, andoperative levels in the Sri Lankan context. There should be I/O rigid barriers to thepromotion ofoutstanding indivtdualsfrom one level to another. There is a particularneed Jbr short courses to cater Jill' continuing education and training. Theestablishment ofa national training council is recommended.

In-Service Safety Performance Evaluation of Roadside Concrete Barriers

Safety-shaped concrete barriers have been the most widely used rigid roadside barriers to shield errant motorists from roadside hazards or obstacles. These barriers are designed to lift impacting vehicles up and thereby extend the duration of impact and reduce the peak decelerations on the vehicle. However, safety-shaped concrete barriers tend to produce rollovers due to excessive vehicle climbing. Vertical concrete barriers, on the other hand, do not have the advantage of reducing impact forces by lifting the vehicle up, but they do produce lower roll angles. The objective of this research was to evaluate which of these two barrier profiles is the safest based on real-world vehicle crash data. The safest profile was defined as the one that produced lower driver injury severity levels and rollover propensity. It was found that safety-shaped barriers are more likely to produce rollovers as compared to vertical barriers. It was also found that crashes involving safety-shaped barriers tended to result in more severe driver injury levels. This finding was not statistically significant though. However, rollovers were found to significantly increase driver injury severity levels. Therefore, it is believed that the expanded use of vertical concrete barriers should improve overall highway safety.

C‐reactive protein and leucocyte counts drop faster using the HeartShield® device in patients with DSWI

Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier disc (HeartShield™) has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up by the negative pressure and damaged by the sharp sternum bone edges. Seven patients treated with conventional NPWT and seven patients treated with NPWT with a protective barrier disc (HeartShield) were compared with regard to bacterial clearance and infection parameters including C-reactive protein levels and leucocyte counts. C-reactive protein levels and leucocyte counts dropped faster and bacterial clearance occurred earlier in the HeartShield® group compared with the conventional NPWT group. Negative biopsy cultures were shown after 3·1 ± 0·4 NPWT dressing changes in the HeartShield group, and after 5·4 ± 0·6 NPWT dressing changes in the conventional NPWT group (P < 0·001). All patients were followed up with clinical check-up after 3 months. None of the patients in the HeartShield group had any signs of reinfection such as deep sternal wound infection (DSWI) or sternal fistulas, whereas in the conventional NPWT group, two patients had signs of sternal fistulas that demanded hospitalisation. HeartShield hinders the right ventricle to come into contact with the sharp sternal edges during NPWT and thereby protects from heart damage. This study shows that using HeartShield is beneficial in treating patients with DSWI. Improved wound healing by HeartShield may be a result of the efficient drainage of wound effluents from the thoracic cavity.