Procedia Engineering最新文献

This paper will present findings from a longitudinal case study of the reconstruction of horizontal infrastructure networks in Christchurch, New Zealand, following the major earthquakes of 2010-2011. This involved exploring the role of governance in recovery and in particular, how funding mechanisms shape decisions for managing disaster risk. National policy on the funding of recovery that was geared towards direct replacement of existing infrastructure had a pivotal role in influencing design standards for infrastructure reconstruction. An outcome of this national policy, combined with constrained local financial resources, is that it was difficult to maximise the opportunity presented by a disaster to resolve the shortcomings of the existing infrastructure systems. This raises critical questions: whether it is appropriate to attempt to improve infrastructure in recovery and how local governments (or asset owners in general) may be better incentivised to invest proactively to reduce future disaster risk.

Special (yet limited) betterment funds were made available for the Christchurch reconstruction and similarly for post-flood reconstruction that was in progress at the same time in Queensland, Australia (which will also be explored in the paper). However, recent recovery funding reviews conducted in New Zealand and Australia have identified a need to investigate incentives to increase proactive investment to limit damage. This paper explores this proposition and presents some of the challenges faced with respect to building back better in Christchurch’s reconstruction and the subsequent lessons for developing future funding mechanisms for disaster recovery. It demonstrates the need for clearer terms of engagement between central government and local government, and how insurance mechanisms could play a more effective role.

An experimental system consisting of a spherical vessel with a horizontal pipe was established. By changing the pipe length, the effect that the ignition position has on methane explosion in an airtight spherical vessel with a pipe was studied, and the regularities of P_max, (dP/dt)_max and flame transmission were analyzed in detail. The results show that different ignition position leading to different propagation of flame and pressure wave. As the ignition position moved from the wall of vessel to the end of pipe, the P_max in the apparatus first increased, then decreased when ignition occurs behind the center of vessel, and finally increased when ignition occurs behind the middle of pipe. The same trend was observed for (dP/dt)_max. When ignited near the end of pipe, the P_max and (dP/dt)_max were large, and the explosion was the most dangerous. In addition, gas oscillation was observed during the explosion process in the pipe, and it was more serious when igniting at the wall of vessel, the center of vessel and the end of pipe. Furthermore, the influence that structure effect had on the gas explosion was determined. With ignition in spherical vessel, the longer the pipe is, the weaker the explosion intensity in vessel is, but the greater the explosion intensity in pipe is. With ignition in the pipe, the longer the pipe is, the greater the explosion intensities are in both the vessel and pipe. The influence that the ignition position has on a gas explosion was revealed, and the reason was analyzed. This research has great theoretical value and practical significance for preventing and controlling potentially disastrous accidents in complex units. The research results provide a theoretical foundation for antiknock and explosion venting in technical vessels and pipes.

Different categories of human beings have been affected due to a range of disasters in Sri Lanka. The effects of such disasters vary according to these categories, in particular, the effect on adolescents’ reports as vital. However, there is a dearth of research with regard to this in Sri Lanka. The aim of this study was to investigate the effect of the flood disaster at Rahula College in May 2016 on adolescents in terms of physical, educational, economical and interpersonal relations and mental aspects. The randomly selected sample considered of flood disaster affected students of grade 10-11; 25 males and 25 females. The quantitative data was collected using a survey questionnaire. The survey data was triangulated with semi- structured interviews with teachers (10) and students (6) and analyzed using SPSS. Fact findings revealed that the effect in terms of physical, mental, educational, economical and interpersonal relations on both girls and boys was at considerable amount. The majority have been affected by post trauma stress disorder (PTSD), whilst the effect of social problems was high among females than males. The support received from friends, school teachers, social workers and Media recorded as powerful in resolving most of the problems encountered by adolescents due to flood disaster. This study is offered insights of professional counselors, about how to design counseling programs on coping skills for disaster affected adolescents.

Providing high hardness, low friction coefficient, as well as, relatively good corrosion resistance, chromium-plated coatings are widely used for steel cylinder rods in marine environment. Nevertheless, a uniform network of microcracks in chromium coating is evolving under mechanical loadings during the service-life of cylinder rods. The propagation of these microcracks is in the origin of the premature corrosion of the steel substrate. The aim of the study was to evaluate the relationship between mechanical stresses, the evolution of the microcracks network and the corrosion resistance of chromium coatings. After monotonic pre-loading tests, it was demonstrated by microscopic observations that the microcracks propagated for stress levels higher than the yield stress of the substrate (520 MPa) and have passed instantly through the whole thickness of the coating and reached the steel substrate. The density of microcracks increases with the level of total strain, the inter-crack distance go from 80 µm at 1% of total strain to approximately 65 µm at 5%. Electrochemical measurements have shown that the higher the level of plastic strain applied during the mechanical loading, the more the corrosion potential of the sample decreases until reaching that of the steel substrate of approximately -0.65 V/ECS after 2 hours of immersion. The polarization curves also evidenced an increase in the corrosion current density with the strain level. Moreover, we note the absence of the characteristic passive region of the reference samples that have not undergone any loading. After cyclic loadings, no microcracks propagation was observed after 10⁴ cycles when maximal stress was lower than the yield stress. However, a decreasing of the corrosion potential was observed for samples which were submitted to a cyclic loading. Nevertheless, the current density and the characteristic passive region were not modified.

Currently, additive manufacturing with metals is an increasingly popular technique that allows the manufacturing of pieces of difficult shapes, nearly impossible to make with other techniques. Usually, these shapes try to optimize the solid to have the same strength with a lower weight. The fatigue behavior of the material of the components manufactured with this technique is a field in development. On the other hand, fretting fatigue is a common type of fatigue where a “stress concentration” appears due to the contact between two components. There are some procedures used to increase fatigue life in this situation (shot peening, surface knurling, etc.). This paper tries to analyze the possible beneficial effect on fatigue life of introducing voids inside the material in components under fretting, which is feasible now thanks to additive manufacturing. The problem under study is, for now, a 2D simplification where a cylinder is in contact with a half plane and a normal constant load and a variable tangential load are applied. This geometry has been numerically simulated, introducing a circular hole below the surface. The effect of this hole is to make the contact more elastic, which decreases the stresses near the surface. This work analyses and compares the stress and strain fields and Smith-Watson-Topper multiaxial fatigue parameter in the areas sensitives to fretting with respect to a case with homogeneous material (no internal voids). Various configurations changing different parameters like size and position of the hole, friction coefficient and the size of the slip zone have been considered. The problem analyzed in this paper is two-dimensional, therefore there would be no need to use additive manufacturing in a real situation. However, the results obtained in this paper indicate that it could also work in 3D. Actually, it is in a real three-dimensional problem where the additive manufacturing would be necessary for the introduction of voids inside the material to improve fatigue life.

Building partition wall, as one of the building partition constructions, and as one of the major renovation projects of the decoration and renovation engineering in commercial and official buildings, it often has an effect on the project’s fire safety. In this article, the type, structure and materials of partition walls are summarized in classification, factors affecting the fire performance of building partition walls are analyzed, and problems of partition walls in engineering and fire protection designing are illustrated and analyzed. International and national standards are analyzed. Through discussions on fire safety audit and setting of partition walls, the adverse effects of partition wall renovation projects on building structures, damage to fire prevention compartment, impact on evacuation route of people, smoke control design and on other fixed fire protection facilities, are discussed in this article. It can be seen from these projects, if building partition walls were designed improperly, it would do great harm to building fire safety. Therefore, it should be taken seriously in fire safety designing. Some suggestions on the problems in the application of partition wall engineering are proposed, which can provide references for fire prevention designing.

Organic peroxides are self-reactive substances that are susceptible to decomposition and redox reactions under external energy, causing catastrophic accidents such as fires and explosions. Self-accelerating decomposition temperature (SADT) is one of the most important parameters for describing the thermal hazard of organic peroxides in process industries. This study presented a quantitative structure-property relationship (QSPR) model to predict the SADT of 71 organic peroxides through their molecular structures. All molecular descriptors are calculated by DRAGON 6.0 software. Genetic algorithm (GA), along with multiple linear regression (MLR) was employed to select the optimal subset of descriptors. Two different models are developed by employing multiple linear regression (MLR) and support vector machine (SVM), respectively. Both models are considered to be valid and able to predict the SADT of organic peroxides through rigorous model validations. The average absolute error of the MLR model for the training set and test set is 7.976 ℃ and 8.585 ℃, while that for the SVM model is 5.676 ℃ and 8.172 ℃, respectively. The predicted results showed that the SVM model has an obvious superiority in prediction performance when comparing to the MLR one. This study could provide a new method for predicting the SADT of organic peroxides for engineering.

Natural disaster has led to adversity resulted from its physical (immediate on-set) and social (long-term) impact. Physical impacts majorly involved human casualties and loss or damages to properties and infrastructure. Meanwhile, among social impacts to society are the psychosocial, socio-demographic, socioeconomic, and socio-politic disturbances. Reducing the risk and impact of the disaster therefore, requires various efforts to prepare and empower the community through the implementation of disaster risk reduction (DRR) during and after a disaster as it is proven that the community themselves are first responders when disasters strike. An excellent example would be the Kobe earthquake where most of the victims survived due to prompt actions taken by members of their community. This indicates that a well-informed community i.e. with high level of awareness and sound knowledge on disaster preparedness and mitigation played crucial role in preventing greater incident of human casualties and reduce socio-economic loss to the community. Therefore, building a resilient community has become part of DRR initiatives. Review of literature, however, suggests that there are gaps in implementation due to lack of understanding of resilient community concept and suitable community-based approach in promoting a community resilience spirit towards disaster. This paper is prepared to discuss the framework considerations for building disaster resilient community in Malaysia from three (3) perspectives of DRR namely; (1) resilient community’s main capitals; (2) key drivers to community resilience and; (3) key deliverables of disaster-resilient community.

Additive manufacturing (AM) is a state of the art technology enabling fabrication of complex geometries, in addition to providing other advantages as compared to the traditional subtractive manufacturing methods. However, a wide variety of factors significantly influence fatigue behavior and structural performance of components made of AM metals. In addition to the fabrication process parameters, these include the effects of build direction, surface roughness, residual stresses, and heat treatment, and multiaxial stress states. At the microstructural level, defects such as pores and lack of fusion particles, as well as other microstructural features affect the behavior. In this paper, first a brief review of the aforementioned factors affecting the fatigue behavior will be presented. Then some experimental multiaxial fatigue data for selective laser melting (SLM), which is a powder bed fusion (PBF) metal AM process, of a common Ti alloy (Ti-6Al-4V) with applications in many industries are presented and discussed. The effects of surface finish, heat treatment, and stress state will be evaluated, as well as failure mechanisms in different life regimes and the role of defects. Finally, some additional factors that must be considered before wide acceptance of the AM technology in critical load bearing applications will be addressed.

By thermogravimetric (TG) experiments under 5 oxygen concentrations of 21.0, 40.0, 50.0, 60.0, 80.0% and 5 heating rates of 20.0, 30.0, 40.0, 50.0, 60.0 ℃/min, the combustion characteristics of jet coal and influences of oxygen concentrations and heating rates on them were investigated. Results show that the pyrolysis processes of jet coals consist of 3 segments of water evaporation, structure oxidation and mass-gaining, self-ignition and induced combustion and carbonization that lie in temperature ranges of 65.0~150.0 ℃, 150.0~290.0 ℃ and 290.0~650.0 ℃, respectively. Huainan jet coal samples burn more easily as universal ignition index increases. At constant heating rate, self-ignition temperature tends to decrease by 10.1~19.4 % with increasing oxygen concentration from 21.0 % to 80.0 %. However, the variation trend of oxidation process includes a slight rise when variation trend begins to fall. At constant oxygen concentration, the self-ignition temperature transformes into high temperature direction and lead to thermal lag effect. Values of Coal-oxidation time at various oxygen concentration levels decreased by 63.1~65.8 % at heating rates from 20.0 to 60.0 ℃/min. Accordingly, the coal-oxidation process is accelerated. A new index (R_S) named coal-oxidation difficulty level index to evaluate the lag effect of coal-oxidation process was proposed. Fitting results of three dimensionless parameters confirmed that the risk of spontaneous combustion determined by the coal-oxidation process still remains growing up although self-ignition temperature produces thermal lags with increasing heating rates.