Search

Effective implementation of the static friction of sliding isolators in object-oriented software for structural design has not yet been achieved, and use of the dynamic friction only for design is common practice. A modeling strategy to account for the contribution of static friction under unidirectional ground motion histories has been developed and used to assess its effects on the response of a building isolated with curved surface sliders. Under low-to-moderate intensity earthquakes, disregarding static friction can lead to unpredictable response of the isolation system and result in a non-conservative evaluation of accelerations and forces transferred to the superstructure. [ABSTRACT FROM AUTHOR]

Luminaire poles are commonly installed along highways to provide proper illumination in critical areas. When placing light poles in close proximity to guardrail, the poles may affect the guardrail's ability to safely contain and redirect vehicles. The interaction between a deflected guardrail system and a closely-positioned light pole may create unwanted stiffening or hinging of the barrier system around the pole. The pole may also present a snag hazard to impacting vehicles and induce vehicle instabilities. In this study, the barrier clearance distance, i.e. the lateral offset away from a breakaway light pole was investigated and evaluated. The minimum safe lateral offset away from the pole with respect to the Midwest Guardrail System (MGS) was determined to be 508 mm (20 in.) through crash testing and computer simulation with non-linear finite-element analysis. Two full-scale crash tests were conducted according to the American Association of State Highway Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) impact safety criteria. In test no. ILT-1, a 2268-kg (5000-lb) pickup truck impacted the combination MGS with light pole system laterally offset 508 mm (20 in.) from back of posts at a speed of 100.7 km/h (62.6 mph) and an angle of 25.0°. In test no. ILT-1, the pickup truck was captured and safely redirected while impacting the light pole and disengaging the pole away from the base. In test no. ILT-2, a 1098-kg (2420-lb) small car impacted the combination MGS with light pole system laterally offset 508 mm (20 in.) from back of posts at a speed of 100.9 km/h (62.7 mph) and an angle of 25.6°. In test no. ILT-2, the car was safely contained and redirected while minimally contacting the light pole. The MGS with a lateral pole offset of 508 mm (20 in.) away from back of posts to front face of pole provided an acceptable safety performance to MASH TL-3 when critically impacted by a pickup truck and a small car. Thus, a minimum offset of 508 mm (20 in.) between the back of the MGS post and front face of the breakaway pole was sufficient to assure a safe performance of the MGS during vehicle impacts without undesired interaction with the pole. Accordingly, guidance for the safe pole placement behind the MGS was provided. [ABSTRACT FROM AUTHOR]

Scales grown on chromia forming alloys in CO2 are less protective than those developed during exposure to oxygen or air. Reaction with CO2 leads to faster chromia scale growth, the more rapid onset of breakaway and internal carburisation of the alloy. Conventional and laser Raman microscopy studies of Fe-Cr alloys show that local fluctuations in scale thickness are associated with varying degrees of chromium depletion. Local conversion of Cr2O3 to spinel leads to rapid outward iron diffusion and nucleation of Fe-rich oxide nodules. A TEM investigation reveals that reaction in CO2 produces finer grained Cr2O3, inward scale growth and more rapid scaling, as well as internal carburisation. Appropriate silicon additions to the alloys lead to the formation of a thin, glassy silica layer beneath the chromia, greatly slowed chromia thickening rates and the prevention of carburisation. Atom probe tomography is used to locate carbon within the chromia. [ABSTRACT FROM AUTHOR]

Scales grown on chromia forming alloys in CO2 are less protective than those developed during exposure to oxygen or air. Reaction with CO2 leads to faster chromia scale growth, the more rapid onset of breakaway and internal carburisation of the alloy. Conventional and laser Raman microscopy studies of Fe-Cr alloys show that local fluctuations in scale thickness are associated with varying degrees of chromium depletion. Local conversion of Cr2O3 to spinel leads to rapid outward iron diffusion and nucleation of Fe-rich oxide nodules. A TEM investigation reveals that reaction in CO2 produces finer grained Cr2O3, inward scale growth and more rapid scaling, as well as internal carburisation. Appropriate silicon additions to the alloys lead to the formation of a thin, glassy silica layer beneath the chromia, greatly slowed chromia thickening rates and the prevention of carburisation. Atom probe tomography is used to locate carbon within the chromia. [ABSTRACT FROM AUTHOR]

Background: Violence to mental health staff is a major problem in the UK. Breakaway training may improve knowledge, attitudes, and stress. It is unknown if breakaway training is effective in clinical environments.Aim: To audit the effectiveness of breakaway training in a sample of clinically-based mental health nurses in a medium secure forensic mental health unit.Method: Audit using a cross-sectional design with an opportunistic sample of 47 clinically-based mental health nursing staff in a forensic medium secure unit. Participants had previously been trained in breakaway techniques. They were approached by the audit team on the ward and randomly selected one of five possible life-threatening assaults that they then had to break away from. Measures were blind ratings by breakaway trainers of the participant's correct use of technique and time. Where participants were unable to break away after 10 seconds the scenario was stopped. Descriptive analysis of the sample and inter-rater agreement of breakaway trainers' ratings were conducted.Results: None of the sample had used a breakaway technique in the preceding 12 months; 40% (19/47) were unable to break away from a life-threatening assault within a 10-second period; 60% did not employ the correct breakaway technique.Conclusion: The effectiveness of breakaway training is questionable given that 40% of the sample were unable to break away from a life-threatening hold in time. Further replication is required. [ABSTRACT FROM AUTHOR]