Search results for: strucural failure

Authors: Saad A. Bakheet, Ashraf A. Younees, Abdalsamia M. Falah

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The main purpose of this study is to the occurrence of several failures in four-meter diameter pre-restressed concrete cylinder pipes, which transport a huge quantity of water from the Libyan Sahara Desert to the populated coastal area in the north. This study will help to address the problems related to corrosion of the pre-stressed concrete cylinder pipes and methods of controlling it. The methodologies used depended on reviewing the design and fabrication of pre-stressed concrete cylinder pipes and studying the cause of the corrosion, which resulted in the failure of the pre-stressed concrete cylinder pipe Man-Made River project in Libya. The chloride-induced corrosion penetrating through the mortar coat was the main reason for corrosion. The beginning of the occurrence of corrosion, its causes, and the mechanisms of its development in pre-stressed concrete pipes since 1937 have been reviewed and are continuing until now. Manufacturing technology control corrosion and all associated problems and technology to control it have been demonstrated, including variables during manufacture, the use of a modified coating, and cathodic protection systems. It has been revised and is still based on international standards. The development of these standards and the change in some of their technical contents reflect the world's interest in the problems of corrosion and the cost of maintenance and replacement.

Keywords: PCCP corrosion, international standard, coating system, failure assessment

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Authors: Ahmad Shukri Mohd Noor, Emma Ahmad Sirajudin, Rabiei Mamat

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Pertaining to a particular Marine interest, the process of data sampling could take years before a study can be concluded. Therefore, the need for a robust backup system for the data is invariably implicit. In recent advancement of Marine applications, more functionalities and tools are integrated to assist the work of the researchers. It is anticipated that this modality will continue as research scope widens and intensifies and at the same to follow suit with current technologies and lifestyles. The convenience to collect and share information these days also applies to the work in Marine research. Therefore, Marine system designers should be aware that high availability is a necessary attribute in Marine repository applications as well as a robust backup system for the data. In this paper, the approach to high availability is related both to hardware and software but the focus is more on software. We consider a NABTIC repository system that is primitively built on a single server and does not have replicated components. First, the system is decomposed into separate modules. The modules are placed on multiple servers to create a distributed system. Redundancy is added by placing the copies of the modules on different servers using Neighbor Caring Environment System(NCES) technique. NCER is utilizing parallel replication components mechanism. A background monitoring is established to check servers’ heartbeats to confirm their aliveness. At the same time, a critical adaptive threshold is maintained to make sure a failure is timely detected using Adaptive Fault Detection (AFD). A confirmed failure will set the recovery mode where a selection process will be done before a fail-over server is instructed. In effect, the Marine repository service is continued as the fail-over masks a recent failure. The performance of the new prototype is tested and is confirmed to be more highly available. Furthermore, the downtime is not noticeable as service is immediately restored automatically. The Marine repository system is said to have achieved fault tolerance.

Keywords: availability, fault detection, replication, fault tolerance, marine application

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Authors: Maria M. Giannakou, Athanasios K. Ziliaskopoulos

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Transmission pipelines carrying natural gas are often routed through populated cities, industrial and environmentally sensitive areas. While the need for these networks is unquestionable, there are serious concerns about the risk these lifeline networks pose to the people, to their habitat and to the critical infrastructures, especially in view of natural disasters such as earthquakes. This work presents an Integrated Pipeline Risk Management methodology (IPRM) for assessing the hazard associated with a natural gas pipeline failure due to natural or manmade disasters. IPRM aims to optimize the allocation of the available resources to countermeasures in order to minimize the impacts of pipeline failure to humans, the environment, the infrastructure and the economic activity. A proposed knapsack mathematical programming formulation is introduced that optimally selects the proper mitigation policies based on the estimated cost – benefit ratios. The proposed model is demonstrated with a small numerical example. The vulnerability analysis of these pipelines and the quantification of consequences from such failures can be useful for natural gas industries on deciding which mitigation measures to implement on the existing pipeline networks with the minimum cost in an acceptable level of hazard.

Keywords: cost benefit analysis, knapsack problem, natural gas distribution network, risk management, risk mitigation

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Authors: Madhavi-Priya Singh, Liam Lowe, Farouk Arnaout, Ludmilla Pillay, Giordan Perez, Luke Mischker, Steve Costa

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Introduction: An Emergency Department consultant identified the failure of medical students to complete the task of clerking a patient in its entirety. As six medical students on our first clinical placement, we recognised our own failure and endeavored to examine why this failure was consistent among all medical students that had been given this task, despite our best motivations as adult learners. Aim: Our aim is to understand and investigate the elements which impeded our ability to learn and perform as medical students in the clinical environment, with reference to the prescribed task. We also aim to generate a discussion around the delivery of medical education with potential solutions to these barriers. Methods: Six medical students gathered together to have a comprehensive reflective discussion to identify possible factors leading to the failure of the task. First, we thoroughly analysed the delivery of the instructions with reference to the literature to identify potential flaws. We then examined personal, social, ethical, and cultural factors which may have impacted our ability to complete the task in its entirety. Results: Through collation of our shared experiences, with support from discussion in the field of medical education and ethics, we identified two major areas that impacted our ability to complete the set task. First, we experienced an ethical conflict where we believed the inconvenience and potential harm inflicted on patients did not justify the positive impact the patient interaction would have on our medical learning. Second, we identified a lack of confidence stemming from multiple factors, including the conflict between preclinical and clinical learning, perceptions of perfectionism in the culture of medicine, and the influence of upward social comparison. Discussion: After discussions, we found that the various factors we identified exacerbated the fears and doubts we already had about our own abilities and that of the medical education system. This doubt led us to avoid completing certain aspects of the tasks that were prescribed and further reinforced our vulnerability and perceived incompetence. Exploration of philosophical theories identified the importance of the role of doubt in education. We propose the need for further discussion around incorporating both pedagogic and andragogic teaching styles in clinical medical education and the acceptance of doubt as a driver of our learning. Conclusion: Doubt will continue to permeate our thoughts and actions no matter what. The moral or psychological distress that arises from this is the key motivating factor for our avoidance of tasks. If we accept this doubt and education embraces this doubt, it will no longer linger in the shadows as a negative and restrictive emotion but fuel a brighter dialogue and positive learning experience, ultimately assisting us in achieving our full potential.

Keywords: ethics, medical student, doubt, medical education, faith

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Authors: Ariful Islam, Showkat Ahmad Lone

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Statistical distributions have long been employed in the assessment of semiconductor devices and product reliability. The power function-distribution is one of the most important distributions in the modern reliability practice and can be frequently preferred over mathematically more complex distributions, such as the Weibull and the lognormal, because of its simplicity. Moreover, it may exhibit a better fit for failure data and provide more appropriate information about reliability and hazard rates in some circumstances. This study deals with estimating information about failure times of items under step-stress partially accelerated life tests for competing risk based on adoptive type-I progressive hybrid censoring criteria. The life data of the units under test is assumed to follow Mukherjee-Islam distribution. The point and interval maximum-likelihood estimations are obtained for distribution parameters and tampering coefficient. The performances of the resulting estimators of the developed model parameters are evaluated and investigated by using a simulation algorithm.

Keywords: adoptive progressive hybrid censoring, competing risk, mukherjee-islam distribution, partially accelerated life testing, simulation study

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Authors: Joseph Carl Macalintal, Erlinda Armovit

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Magnesium sulfate has been a mainstay in the management of preeclampsia and is associated with a decreased incidence of morbidity and mortality. The syndrome has an unpredictable course, sometimes rapidly evolving to full-blown disease. In patients with deteriorating status, it is indicated to terminate the pregnancy via cesarean section. The anesthesiologists would prefer to have the procedure done under regional anesthesia; however, there may be cases when neuraxial anesthesia is contraindicated, or a general anesthesia would permit prompt delivery of the fetus. A patient with severe preeclampsia was given magnesium sulfate intrapartum, wherein a primary cesarean section was indicated for arrest in cervical dilatation, and was performed under general anesthesia. The patient developed acute respiratory failure and the causes of this occurrence were investigated in this report. It was later found out that neither the hypermagnesemia nor the muscle relaxant alone caused the patient’s condition but the interaction between the two. The patient was managed expectantly at the intensive care unit (ICU) and was eventually extubated during the 1st post-operative day. Knowledge of this drug interaction would allow obstetricians to advise their patients and their family about the possibility of prolonged intubation and ICU admission. This would also bring to the anesthesiologists’ attention the need to decrease the dose of muscle relaxant and to prepare drugs for immediate decurarisation.

Keywords: eclampsia, magnesium sulfate, preeclampsia, rocuronium bromide

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Authors: Hooman Dabirmanesh, Mahmoud Ghazavi, Kazem Barkhordari

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A finite element modeling for determination of the bearing capacity of caissons subjected to inclined loads is presented in this paper. The model investigates the uplift capacity of the caisson with varying cross sectional area. To this aim, the behavior of the soil is assumed to be elasto-plastic, and its failure is controlled by Modified Cam-Clay failure criterion. The simulation takes into account the couple analysis. The approach is verified using available data from other research work especially centrifuge data. Parametric studies are subsequently performed to investigate the effect of contributing parameters such as aspect ratio of the caisson, the loading rate, the loading direction angle, and points where the external load is applied. In addition, the influence of the caisson geometry is taken into account. The results show the bearing capacity of the caisson increases with increasing the taper angle. Hence, the pullout capacity will increase using the same material. In addition, the bearing capacity of caissons strongly depends on the suction that is generated at tip and in sealed surface on top of caisson. Other results concerning the influencing factors will be presented.

Keywords: aspect ratio, finite element method, inclined load, modified Cam clay, taper angle, undrained condition

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Authors: Amina Unis, Samah S. El Basateeny, Noha A. H. Nassef

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Introduction: Acute Renal Failure (ARF) is one of the most common problems encountered in hospitalized critically ill patients. In recent years great effort has been focused on the introduction of herbal medicine as a novel therapeutic agent for prevention of ARF. Hence, the current study was designed to investigate the effect of Green Coffee Bean Extract (GCBE) on gentamicin induced ARF in rats. Methods: The study was conducted on 60 male rats divided into six equal groups. Group 1 served as normal control group and GCBE was administered for 7 days at a dose of 20 mg/kg/day in group 2 and 40 mg/kg/day in group 3 to test the effect of GCBE on normal kidneys. ARF was induced by a daily intraperitoneal injection of gentamicin (80 mg/kg) for 7 days in group 4 (model group), group 5 (GCBE 20 mg/kg/day) and group 6 (GCBE 20 mg/kg/day). All rats were sacrificed after 7 days and blood was withdrawn for kidney function tests. Kidneys were removed for determination of renal oxidative stress markers and histopathological examination. Results: The present study showed that rats that received oral GCBE for 7 days without induction of ARF showed no significant change in all the assessed parameters in comparison to the normal control group, while rats in the groups that received oral GCBE for 7 days with induction of ARF showed a significant improvement in kidney functions tests (decrease in serum urea, serum creatinine, and blood urea nitrogen) when compared to the ARF model group. Moreover, there was significant amelioration in renal oxidative stress markers (renal malondialdehyde, renal superoxide dismutase) and renal histopathological changes in the GCBE treated groups along induction of ARF when compared to ARF model group. The most significant improvement was reported in the group where GCBE was administered for 7 days in a dose 40 mg/kg/day, along with induction of ARF. Conclusion: GCBE has a potential role in ameliorating renal damage involved in ARF mostly through its antioxidant effect.

Keywords: green coffee bean extract, gentamicin, acute renal failure, pharmacology

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Authors: Armin Solemanifar, Arthur Wilkinson, Kinjalkumar Patel

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Carbon fibre (CF) - polymer laminate composites have very low densities (approximately 40% lower than aluminium), high strength and high stiffness but in terms of toughness properties they often require modifications. For example, adding rubbers or thermoplastics toughening agents are common ways of improving the interlaminar fracture toughness of initially brittle thermoset composite matrices. The main aim of this project was to toughen CF-epoxy resin laminate composites using hybrid CF-fabrics incorporating Innegra™ a commercial highly-oriented polypropylene (PP) fibre, in which more than 90% of its crystal orientation is parallel to the fibre axis. In this study, the damage tolerance of hybrid (carbon-Innegra, CI) composites was investigated. Laminate composites were produced by resin-infusion using: pure CF fabric; fabrics with different ratios of commingled CI, and two different types of pure Innegra fabrics (Innegra 1 and Innegra 2). Dynamic mechanical thermal analysis (DMTA) was used to measure the glass transition temperature (Tg) of the composite matrix and values of flexural storage modulus versus temperature. Mechanical testing included drop-weight impact, compression-after-impact (CAI), and interlaminar (short-beam) shear strength (ILSS). Ultrasonic C-Scan imaging was used to determine the impact damage area and scanning electron microscopy (SEM) to observe the fracture mechanisms that occur during failure of the composites. For all composites, 8 layers of fabrics were used with a quasi-isotropic sequence of [-45°, 0°, +45°, 90°]s. DMTA showed the Tg of all composites to be approximately same (123 ±3°C) and that flexural storage modulus (before the onset of Tg) was the highest for the pure CF composite while the lowest were for the Innegra 1 and 2 composites. Short-beam shear strength of the commingled composites was higher than other composites, while for Innegra 1 and 2 composites only inelastic deformation failure was observed during the short-beam test. During impact, the Innegra 1 composite withstood up to 40 J without any perforation while for the CF perforation occurred at 10 J. The rate of reduction in compression strength upon increasing the impact energy was lowest for the Innegra 1 and 2 composites, while CF showed the highest rate. On the other hand, the compressive strength of the CF composite was highest of all the composites at all impacted energy levels. The predominant failure modes for Innegra composites observed in cross-sections of fractured specimens were fibre pull-out, micro-buckling, and fibre plastic deformation; while fibre breakage and matrix delamination were a major failure observed in the commingled composites due to the more brittle behaviour of CF. Thus, Innegra fibres toughened the CF composites but only at the expense of reducing compressive strength.

Keywords: hybrid composite, thermoplastic fibre, compression strength, damage tolerance

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Authors: Pierre van Tonder, Christoff Kruger

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Modular concrete elements are used for retaining walls to provide lateral support. Depending on the retaining wall layout, these precast panels may be interlocking and may be tied into the soil backfill via geosynthetic strips. This study investigates the ultimate pull-out load increase, which is possible by adding varied diameter supplementary reinforcement through embedded anchor loops within concrete retaining wall panels. Full-scale panels used in practice have four embedded anchor points. However, only one anchor loop was embedded in the center of the experimental panels. The experimental panels had the same thickness but a smaller footprint (600mm x 600mm x 140mm) area than the full-sized panels to accommodate the space limitations of the laboratory and experimental setup. The experimental panels were also cast without any bending reinforcement as would typically be obtained in the full-scale panels. The exclusion of these reinforcements was purposefully neglected to evaluate the impact of a single bar reinforcement through the center of the anchor loops. The reinforcement bars had of 8 mm, 10 mm, 12 mm, and 12 mm. 30 samples of concrete panels with embedded anchor loops were tested. The panels were supported on the edges and the anchor loops were subjected to an increasing tensile force using an Instron piston. Failures that occurred were loop failures and panel failures and a mixture thereof. There was an increase in ultimate load vs. increasing diameter as expected, but this relationship persisted until the reinforcement diameter exceeded 10 mm. For diameters larger than 10 mm, the ultimate failure load starts to decrease due to the dependency of the reinforcement bond strength to the concrete matrix. Overall, the reinforced panels showed a 14 to 23% increase in the factor of safety. Using anchor loops of 66kN ultimate load together with Y10 steel reinforcement with bent ends had shown the most promising results in reducing concrete panel pull-out failure. The Y10 reinforcement had shown, on average, a 24% increase in ultimate load achieved. Previous research has investigated supplementary reinforcement around the anchor loops. This paper extends this investigation by evaluating supplementary reinforcement placed through the panel anchor loops.

Keywords: supplementary reinforcement, anchor loops, retaining panels, reinforced concrete, pull-out failure

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Authors: Mohammad Sheikhalishahi, Vahid Ebrahimipour, Amir Hossein Radman-Kian

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This paper proposes an Ontology framework for knowledge modeling and representation of the equipment integrity process in a typical oil and gas production plant. Our aim is to construct a knowledge modeling that facilitates translation, interpretation, and conversion of human-readable integrity interpretation into computer-readable representation. The framework provides a function structure related to fault propagation using ISO 14224 and ISO 15926 OWL-Lite/ Resource Description Framework (RDF) to obtain a generic system-level model of asset integrity that can be utilized in the integrity engineering process during the equipment life cycle. It employs standard terminology developed by ISO 15926 and ISO 14224 to map textual descriptions of equipment failure and then convert it to a causality-driven logic by semantic interpretation and computer-based representation using Lite/RDF. The framework applied for an offshore gas riser. The result shows that the approach can cross-link the failure-related integrity words and domain-specific logic to obtain a representation structure of equipment integrity with causality inference based on semantic extraction of inspection report context.

Keywords: asset integrity modeling, interoperability, OWL, RDF/XML

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Authors: Xianjia Meng, Chuanyong Qu

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Compact bone produces fatigue damage under the inevitable physiological load. The accumulation of fatigue damage can change the bone’s micro-structure at different scales and cause the catastrophic failure eventually. However, most tests were limited to the macroscopic modulus of bone and there is a need to assess the microscopic modulus during fatigue progress. In this paper, nano-identation was used to investigate the bone specimen subjected to four point bending. The microscopic modulus of the same area were measured at different degrees of damage including fracture. So microscopic damage can be divided into three stages: first, the modulus decreased rapidly and then They fell slowly, before fracture the decline became fast again. After fracture, the average modulus decreased by 20%. The results of inner and outer planes explained the influence of compressive and tensile loads on modulus. Both the compressive and tensile moduli decreased with the accumulation of damage. They reached the minimum at ending and increased after fracture. The modulus evolution under different strains were revealed by the side. They all fell slowly and then fast with the accumulation of damage. The fractured results indicated that the elastic modulus decreased obviously at the high strain while decreased less at the low strain. During the fatigue progress, there was a significant difference in modulus at low degree of damage. However, the dispersed modulus tended to be similar at high degree of damage, but they became different again after the failure.

Keywords: fatigue damage, fracture, microscopic modulus, bone, nano-identation

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Authors: Deog-Gyu Seo, Jin-Soo Ahn

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Objectives: Recently, the development of adhesive primers on stable bonding between zirconia and resin cement has been on the increase. The bond strength of zirconia-resin cement can be effectively increased with the treatment of primer composed of the adhesive monomer that can chemically bond with the oxide layer, which forms on the surface of zirconia. 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) that contains phosphate ester and acidic monomer 4-methacryloxyethyl trimellitic anhydride(4-META) have been suggested as monomers that can form chemical bond with the surface oxide layer of zirconia. Also, these suggested monomers have proved to be effective zirconia surface treatment for bonding to resin cement. The purpose of this study is to evaluate the effects of primer treatment on the bond strength of Zirconia-resin cement by using three different kinds of primers on the market. Methods: Zirconia blocks were prepared into 60 disk-shaped specimens by using a diamond saw. Specimens were divided into four different groups: first three groups were treated with zirconiaLiner(Sun Medical Co., Ltd., Furutaka-cho, Moriyama, Shiga, Japan), Alloy primer (Kuraray Noritake Dental Inc., Sakaju, Kurashiki, Okayama, Japan), and Universal primer (Tokuyama dental Corp., Taitou, Taitou-ku, Tokyo, Japan) respectively. The last group was the control with no surface treatment. Dual cured resin cement (Biscem, Bisco Inc., Schaumburg, IL, USA) was luted to each group of specimens. And then, shear bond strengths were measured by universal tesing machine. The significance of the result was statistically analyzed by one-way ANOVA and Tukey test. The failure sites in each group were inspected under a magnifier. Results: Mean shear bond strength were 0.60, 1.39, 1.03, 1.38 MPa for control, Zirconia Liner (ZL), Alloy primer (AP), Universal primer (UP), respectively. Groups with application of each of the three primers showed significantly higher shear bond strength compared to the control group (p < 0.05). Among the three groups with the treatment, ZL and UP showed significantly higher shear bond strength than AP (p < 0.05), and there were no significant differences in mean shear bond strength between ZL and UP (p < 0.05). While the most specimens of control groups showed adhesive failure (80%), the most specimens of three primer-treated groups showed cohesive or mixed failure (80%).

Keywords: primer, resin cement, shear bond strength, zirconia

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Authors: Baba Iddrisu Musah

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Many Ghanaians, including the rich and downtrodden, elite and unlettered, rural and urban dwellers, politicians and civil servants, in one way or the other, believe in and practice witchcraft. The existence of witches’ camp in northern Ghana, the rise of Pentecostal churches, especially in southern Ghana with the penchant to cleanse people of witchcraft, as well as media reports of witchcraft imputations assuming wider dimensions in the country, often classified as a citadel of democracy, good governance and human rights in Africa, buttress the pervasive nature of belief in and the practice of witchcraft in the country. This is in spite of the fact that tremendous efforts, especially by British colonial authorities, were made to regulate witchcraft beliefs and its associated practices. Informed by Western values and philosophy, witchcraft was considered by colonial authorities as illogical and unscientific. This paper, which is largely a review of existing literature, supplemented by archival information from the national archives of Ghana, focuses on the nature of witchcraft regulation in Ghana’s pre-colonial and colonial past, as well as immediately after Ghana obtained her independence in 1957. This article concludes by rhetorically questioning whether or not believing in and the practice of witchcraft in contemporary Ghana in general, and the existence of witches’ camps in the northern region of the country are attributed to the failure of past regulations, as well as the failure of present government policies.

Keywords: colonial, natives, regulation, witchcraft

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Authors: Hayle Makda Gebru

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Companies are inevitable for society. They are the building blocks of every development in a country aimed at producing continuous goods and services for the people and, in turn, obliged to pay taxes, which enhances the economy of the nation. For the proper functioning of companies, their relationship with their stakeholders must be secure. The major stakeholders are suppliers, consumers, employees, creditors, etc. The law plays an important role in enhancing the relationship between these different stakeholders. If the law fails to keep track of the relationship, both the company and stakeholders remain unprotected. As a result, the potential benefits are prejudiced. This paper makes a comparative analysis of the types and formation of companies under the Transitional Commercial Code of Eritrea and the Company Law of the Peoples Republic of China. In particular, the paper addresses the legal lacuna under the TCrCE on handling the failure of shareholders to pay the promised capital. So, the methodology of the study is entirely analyzing the two countries' laws using practical cases. After analyzing the practical problems on the ground using real cases, this paper calls on Eritrea to update its outdated Commercial Code to give proper protection to the stakeholders.

Keywords: companies, company law of the People's Republic of China, transitional commercial code of Eritrea, protection of stakeholders, failure to pay the promised capital

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Authors: Navdeep Kaur

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The primary focus of this study is to answer “What is the role of corporate governance in corporate failures? Does poor corporate governance lead to corporate failures? If so, how?”. In doing so, the study examines the literature from multiple fields, including corporate governance, corporate failures and organizational decision making, and presents a research gap to analyze and explore the relationship between corporate governance practices and corporate failures through a behavioral lens. In approaching this, a qualitative research methodology is adopted to analyze the failure of Enron Corporation (United States). The research considered the case study organizations as the primary unit of analysis and the decision-makers as the secondary unit of analysis. Based on this research approach, the study reports the analytical results drawn from extensive and triangulated secondary data. The study then interprets the results in the context of the theoretical synthesis. The study contributes towards filling a gap in the research and presents a behaviourally plausible decision centered model of the role of corporate governance in corporate failures. The model highlights the critical role of the behavioral aspects of corporate governance decision making in corporate failures and focuses attention on the under-explored aspects of corporate governance decision making. The study also suggests a further understanding of ‘A Behavioral Theory of the Firm’ in relation to corporate failures.

Keywords: behavior, corporate failure, corporate governance, decision making, values

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Authors: Krunal Thakar

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Wire ropes combine high tensile strength and flexibility as compared to other general steel products. They are used in various application areas such as cranes, mining, elevators, bridges, cable cars, etc. The earliest reported use of wire ropes was for mining hoist application in 1830s. Over the period, there have been substantial advancement in the design of wire ropes for various application areas. Under operational conditions, wire ropes are subjected to varying tensile loads and bending loads resulting in material wear and eventual structural failure due to fretting fatigue. The conventional inspection methods to determine wire failure is only limited to outer wires of rope. However, till date, there is no effective mathematical model to examine the inter wire contact forces and wear characteristics. The scope of this paper is to present a computational simulation technique to evaluate inter wire contact forces and wear, which are in many cases responsible for rope failure. Two different type of ropes, IWRC-6xFi(29) and U3xSeS(48) were taken for structural strength evaluation and wear prediction. Both ropes have a double helix twisted wire profile as per JIS standards and are mainly used in cranes. CAD models of both ropes were developed in general purpose design software using in house developed formulation to generate double helix profile. Numerical simulation was done under two different load cases (a) Axial Tension and (b) Bending over Sheave. Different parameters such as stresses, contact forces, wear depth, load-elongation, etc., were investigated and compared between both ropes. Numerical simulation method facilitates the detailed investigation of inter wire contact and wear characteristics. In addition, various selection parameters like sheave diameter, rope diameter, helix angle, swaging, maximum load carrying capacity, etc., can be quickly analyzed.

Keywords: steel wire ropes, numerical simulation, material wear, structural strength, axial tension, bending over sheave

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Authors: Shota Nagata, Kazuya Okubo, Toru Fujii

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The purpose of this study is to investigate the proper condition in extracting carbon fibers as the reinforcement of composite molded by injection method. Recycled carbon fibers were extracted from wasted CFRP by pyrolyzing epoxy matrix of CFRP under air atmosphere at different temperature conditions 400, 600 and 800°C in this study. Recycled carbon fiber reinforced polypropylene (RCF/PP) pellets were prepared using twin screw extruder. The RCF/PP specimens were molded into dumbbell shaped specimens using injection molding machine. The tensile strength of recycled carbon fiber was decreased with rising pyrolysis temperature from 400 to 800°C. However, superior mechanical properties of tensile strength, tensile modulus and fracture strain of RCF/PP specimen were obtained when the extracting temperature was 600°C. Almost fibers in RCF/PP specimens were aligned in the mold filling direction in this study when the extracting temperature was 600°C. To discuss the results, the failure mechanisms of RCF/PP specimens was shown schematically. Finally, it was concluded that the temperature condition at 600°C should be selected in extracting carbon fibers as the reinforcement of RCF/PP composite molded by injection method.

Keywords: CFRP, recycled carbon fiber, injection molding, mechanical properties, fiber orientation, failure mechanism

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Authors: Mohamed Aniss El-Gamal

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For decades, the Global South has been facing many challenges in the fields of heritage conservation and local development. These challenges continue to increase due to rapid urbanization in historical cities, thus resulting in complicated juxtaposed contexts of heritage resources and deteriorated dwellings, where slum areas are dotted with heritage structures. While the majority of cases show the incapacity of national and local governments to deal with such contexts, few others managed to demonstrate how different levels of government can play complementary roles in the cooperation with local and international institutions as well as involving local community to achieve an integrated strategy and overcome the challenge. This paper discusses heritage conservation and local development strategies in reference to a number of case studies in cities of the Global south, i.e. Porto Alegre, Agra, Cairo and Mumbai. It further investigates main key aspects of success and failure through cross case studies analysis (Matrix). This study could help create a delineation of an integrated strategy for undertaking future interventions in similar contexts. Integrated strategies are needed to overcome the gap between heritage conservation and local development, maintaining the value of heritage structures and ensuring the quality of life for communities residing in its surroundings.

Keywords: heritage conservation, local development, the global south, regional development

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Authors: H. S. S. Abou El-Mal, H. E. M. Sallam

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This paper presents experimental and analytical study on the behavior of repaired and strengthened shear critical RC beams using externally bonded CFRP bi-directional fabrics. The use of CFRP sheets to repair or strengthen RC beams has been repetitively studied and proven feasible. However, the use of combined repair techniques and applying that method to both plain and FRC beams can maximize the shear capacity of RC shear deficient beams. A total of twelve slender beams were tested under four-point bending. The test parameters included CFRP layout, number of layers and fiber direction, injecting cracks before applying repairing sheets, enhancing the flexural capacity to differentiate between shear repair and strengthening techniques, and concrete matrix types. The findings revealed that applying CFRP sheets increased the overall shear capacity, the amount and orientation of wrapping is of prime importance in both repairing and strengthening, CFRP wrapping could change the failure mode from shear to flexural shear, the use of crack injection combined to CFRP wrapping further improved the shear capacity while, applying the previous method to FRC beams enhanced both shear capacity and failure ductility. Acceptable agreement was found between predicted shear capacities using the Canadian code and the experimental results of the current study.

Keywords: CFRP, FRC, repair, shear strengthening

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Authors: Shilpesh R. Rajpurohit, Harshit K. Dave

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Fused deposition modeling (FDM) gains popularity in recent times, due to its capability to create prototype as well as functional end use product directly from CAD file. Parts fabricated using FDM process have mechanical properties comparable with those of injection-molded parts. However, performance of the FDM part is severally affected by the poor mechanical properties of the part due to nature of layered structure of printed part. Mechanical properties of the part can be improved by proper selection of process variables. In the present study, a comparative study between unidirectional and bidirectional raster angle has been carried out at a combination of different layer height and raster width. Unidirectional raster angle varied at five different levels, and bidirectional raster angle has been varied at three different levels. Fabrication of tensile specimen and tensile testing of specimen has been conducted according to ASTM D638 standard. From the results, it can be observed that higher tensile strength has been obtained at 0° raster angle followed by 45°/45° raster angle, while lower tensile strength has been obtained at 90° raster angle. Analysis of fractured surface revealed that failure takes place along with raster deposition direction for unidirectional and zigzag failure can be observed for bidirectional raster angle.

Keywords: additive manufacturing, fused deposition modeling, unidirectional, bidirectional, raster angle, tensile strength

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Authors: Prakash Singh

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The focus of this study is on the use of the SWEAT analysis approach to determine how effectively a school, as an organization, has implemented its curriculum. To gauge the feelings of the teaching staff, unstructured interviews were employed in this study, asking the participants for their ideas and opinions on each of the three identified aspects of the school: instructional materials, media and technology; teachers’ professional competencies; and the curriculum. This investigation was based on the five key components of the SWEAT model: strengths, weaknesses, expectations, abilities, and tensions. The findings of this exploratory study evoke the significance of the SWEAT achievement model as a tool for strategic analysis to be undertaken in any organization. The findings further affirm the usefulness of this analytical tool for human resource development. Employees have expectations, but competency gaps in their professional abilities may hinder them from fulfilling their tasks in terms of their job description. Also, tensions in the working environment can contribute to their experiences of tobephobia (fear of failure). The SWEAT analysis approach detects such shortcomings in any organization and can therefore culminate in the development of programmes to address such concerns. The strategic SWEAT analysis process can provide a clear distinction between success and failure, and between mediocrity and excellence in organizations. However, more research needs to be done on the effectiveness of the SWEAT analysis approach as a strategic analytical tool.

Keywords: SWEAT analysis, strategic analysis, tobephobia, competency gaps

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Authors: Sarah Elsayed Mohammed, Lamiaa Ahmed Ahmed, Mahmoud Mohammed Khattab

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Aim: The aim of the present study was to investigate whether combined nicorandil and bone marrow-derived mesenchymal stem cells (BMDMSC) treatment could offer an additional benefit in ameliorating isoproterenol (ISO)-induced heart failure in rats. Methods: ISO (85 and 170 mg/kg/day) was injected subcutaneously for 2 successive days, respectively. By day 3, electrocardiographic changes were recorded and serum was separated for determination of CK-MB level for confirmation of myocardial damage. Nicorandil (3 mg/kg/day) was then given orally with or without a single i.v. BMDMSC administration. Electrocardiography and echocardiography were recorded 2 weeks after beginning of treatment. Rats were then sacrificed and ventricles were isolated for estimation of vascular endothelial growth factor (VEGF), tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β) contents, caspase-3 activity as well as inducible nitric oxide synthase (iNOS) and connexin-43 protein expressions. Moreover, histological analysis of myocardial fibrosis was performed and cryosections were done for estimation of homing of BMDMSC. Results: ISO induced a significant increase in ventricles/body weight ratio, left ventricular end diastolic (LVEDD) and systolic dimensions (LVESD), ST segment and QRS duration. Moreover, myocardial fibrosis as well as VEGF, TNF-α and TGF-β contents were significantly increased. On the other hand, connexin-43 protein expression was significantly decreased, while caspase-3 and iNOS protein expressions were significantly increased. Combined therapy provided additional improvement compared to cell treatment alone towards reducing cardiac hypertrophy, fibrosis and inflammation. Furthermore, combined therapy induced significant increase in angiogenesis and BMDMSC homing and prevented ISO induced changes in iNOS, connexin-43 and caspase-3 protein expressions. Conclusion: Combined nicorandil/BMDMSC treatment was superior to BMDMSC alone towards preventing ISO-induced heart failure in rats.

Keywords: fibrosis, isoproterenol, mesenchymal stem cells, nicorandil

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Authors: Nipun Manirajan, Heeralal Gargama, Sushil Guhe, Manoj Prabhakaran

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In railway industry, train sets are designed based on contractual requirements (mission profile), where reliability targets are measured in terms of mean distance between failures (MDBF). However, during the beginning of revenue services, trains do not achieve the designed mission profile distance (mileage) within the timeframe due to infrastructure constraints, scarcity of commuters or other operational challenges thereby not respecting the original design inputs. Since trains do not run sufficiently and do not achieve the designed mileage within the specified time, car builder has a risk of not achieving the contractual MDBF target. This paper proposes a constant failure rate based model to deal with the situations where mileage accumulation is not a part of the design mission profile. The model provides appropriate MDBF target to be demonstrated based on actual accumulated mileage. A case study of rolling stock running in the field is undertaken to analyze the failure data and MDBF target demonstration during low mileage accumulation. The results of case study prove that with the proposed method, reliability targets are achieved under low mileage accumulation.

Keywords: mean distance between failures, mileage-based reliability, reliability target appropriations, rolling stock reliability

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Authors: Zhenyu Yang, Qiunan Chen, Xiaocheng Huang

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Reliable prediction of tunnel collapse remains a prominent challenge in the field of civil engineering. In this study, leveraging the nonlinear Hoek-Brown failure criterion and the upper-bound theorem, an analytical solution for the collapse surface of shallowly buried circular tunnels was derived, taking into account the coupled effects of surface loads and pore water pressures. Initially, surface loads and pore water pressures were introduced as external force factors, equating the energy dissipation rate to the external force, yielding our objective function. Subsequently, the variational method was employed for optimization, and the outcomes were juxtaposed with previous research findings. Furthermore, we utilized the deduced equation set to systematically analyze the influence of various rock mass parameters on collapse shape and extent. To validate our analytical solutions, a comparison with prior studies was executed. The corroboration underscored the efficacy of our proposed methodology, offering invaluable insights for collapse risk assessment in practical engineering applications.

Keywords: tunnel roof stability, analytical solution, hoek–brown failure criterion, limit analysis

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Authors: A. Y. Purnama, N. Yasufuku

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The bridge structure is a building that has to be maintained, especially for the elastomeric bearing. The girder of the bridge needs to be lifted upward to maintain this elastomeric bearing, that needs high cost. Nowadays, integral abutment bridges are becoming popular. The integral abutment bridge is less costly because the elastomeric bearings are eliminated, which reduces the construction cost and maintenance costs. However, when this elastomeric bearing removed, the girder movement due to environmental thermal forces directly support by pile foundation, and it needs to be considered in the design. In case of pile foundation in a stiff soil, in the top area of the pile cannot move freely due to the fixed condition by soil stiffness. Pre-bored pile system can be used to increase the flexibility of pile foundation using a pre-bored hole that filled with elastic materials, but the behavior of soil-pile interaction and soil response due to this system is still rarely explained. In this paper, an experimental study using small-scale laboratory model test conducted in a half size model. Single flexible pile model embedded in sandy soil with the pre-bored ring, which filled with the filler material. The testing box made from an acrylic glass panel as observation area of the pile shaft to monitor the displacement of the pile during the lateral loading. The failure behavior of the soil inside the pre-bored ring and around the pile shaft was investigated to determine the point of pile rotation and the movement of this point due to the pre-bored ring system along the pile shaft. Digital images were used to capture the deformations of the soil and pile foundation during the loading from the acrylic glass on the side of the testing box. The results were presented in the form of lateral load resistance charts against the pile shaft displacement. The failure pattern result also established due to the cyclic lateral loading. The movement of the rotational point was measured due to the pre-bored system filled with appropriate filler material. Based on the findings, design considerations for pre-bored pile system due to cyclic lateral loading can be introduced.

Keywords: failure behavior, pre-bored pile system, cyclic lateral loading, sandy soil

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Authors: N. V. Nikhil, S. R. Lee, Do Won Park

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Korean peninsula receives about two third of the annual rainfall during summer season. The extreme rainfall pattern due to typhoon and heavy rainfall results in severe mountain disasters among which 55% of them are debris flows, a major natural hazard especially when occurring around major settlement areas. The basic mechanism underlined for this kind of failure is the unsaturated shallow slope failure by reduction of matric suction due to infiltration of water and liquefaction of the failed mass due to generation of positive pore water pressure leading to abrupt loss of strength and commencement of flow. However only an empirical model cannot simulate this complex mechanism. Hence, we have employed an empirical-physical based approach for hazard analysis of debris flow using TRIGRS, a debris flow initiation criteria and DAN3D in mountain Woonmyun, South Korea. Debris flow initiation criteria is required to discern the potential landslides which can transform into debris flow. DAN-3D, being a new model, does not have the calibrated values of rheology parameters for Korean conditions. Thus, in our analysis we have used the recent 2011 debris flow event in mountain Woonmyun san for calibration of both TRIGRS model and DAN-3D, thereafter identifying and predicting the debris flow initiation points, path, run out velocity, and area of spreading for future extreme rainfall based scenarios.

Keywords: debris flow, DAN-3D, extreme rainfall, hazard analysis

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Authors: Aymen H. Khalil, Ashraf M. Heniegal, Bassam A. Abdelsalam

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There are many problems related to cantilever slabs such as the time-dependent deformation, corrosion problems of steel reinforcement, and lack of experimental studies on the strength of strengthened cantilever slabs. This paper presents an investigation to evaluate the behavior of reinforced concrete cantilever slabs after strengthening with different techniques. Six medium scale specimens, divided into three groups, were tested along with a control slab. The first group consists of two specimens which were repaired and strengthened using reinforced concrete jacket above with and without shear connector bars, whereas the second group contained two slabs which were strengthened using two strips of two layers of glass fiber reinforced polymer (GFRP) covering 60% and 90% from the cantilever length. The last group involves two specimens strengthened with two steel plates. In one specimen, the steel plates were glued to the surface using epoxy resin. The second specimen, the steel plates were affixed to the concrete surface using expansion bolts. The loading was conducted in two phases. Firstly, the samples were subjected to 40% of the ultimate load of the control slab. Secondly, the specimens reloaded after being strengthened up to failure. The load-deflection, steel strain, concrete strain, failure mode, toughness, and ductility index are discussed in this paper.

Keywords: repair, strengthened, GFRP layers, reloaded, jacketing, cantilever slabs

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Authors: Tam Viet Hoang

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With a plethora of new mobility services and payment systems found in our cities and across modern public transportation systems, several cities globally have turned to common ticketing systems to help navigate this complexity. Helping to create time and space-differentiated fare structures and tariff schemes, common ticketing systems can optimize transport utilization rates, achieve cost efficiencies, and provide key incentives to specific target groups. However, not all cities and transportation systems have enjoyed a smooth journey towards the adoption, roll-out, and servicing of common ticketing systems, with both the experiences of success and failure being attributed to a wide variety of critical factors. Using case study research as a methodology and cities as the main unit of analysis, this research will seek to address the fundamental question of “what are the critical factors for the success and failure of common ticketing systems?” Using rail/train systems as the entry point for this study will start by providing a background to the evolution of transport ticketing and justify the improvements in operational efficiency that can be achieved through common ticketing systems. Examining the socio-economic benefits of common ticketing, the research will also help to articulate the value derived for different key identified stakeholder groups. By reviewing case studies of the implementation of common ticketing systems in different cities, the research will explore lessons learned from cities with the aim to elicit factors to ensure seamless connectivity integrated e-ticketing platforms. In an increasingly digital age and where cities are now coming online, this paper seeks to unpack these critical factors, undertaking case study research drawing from literature and lived experiences. Offering us a better understanding of the enabling environment and ideal mixture of ingredients to facilitate the successful roll-out of a common ticketing system, interviews will be conducted with transport operators from several selected cities to better appreciate the challenges and strategies employed to overcome those challenges in relation to common ticketing systems. Meanwhile, as we begin to see the introduction of new mobile applications and user interfaces to facilitate ticketing and payment as part of the transport journey, we take stock of numerous policy challenges ahead and implications on city-wide and system-wide urban planning. It is hoped that this study will help to identify the critical factors for the success and failure of common ticketing systems for cities set to embark on their implementation while serving to fine-tune processes in those cities where common ticketing systems are already in place. Outcomes from the study will help to facilitate an improved understanding of common pitfalls and essential milestones towards the roll-out of a common ticketing system for railway systems, especially for emerging countries where mass rapid transit transport systems are being considered or in the process of construction.

Keywords: common ticketing, public transport, urban strategies, Bangkok, Fukuoka, Sydney

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Authors: Leon Pan

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The first programming course within post-secondary education has long been recognized as a challenging endeavor for both educators and students alike. Historically, these courses have exhibited high failure rates and a notable number of dropouts. Instructors often lament students' lack of effort in their coursework, and students often express frustration that the teaching methods employed are not effective. Drawing inspiration from the successful principles of Extreme Programming, this study introduces an approach—the Extremes-based teaching model — aimed at enhancing the teaching of introductory programming courses. To empirically determine the effectiveness of the model, a comparison was made between a section taught using the extreme-based model and another utilizing traditional teaching methods. Notably, the extreme-based teaching class required students to work collaboratively on projects while also demanding continuous assessment and performance enhancement within groups. This paper details the application of the extreme-based model within the post-secondary online classroom context and presents the compelling results that emphasize its effectiveness in advancing the teaching and learning experiences. The extreme-based model led to a significant increase of 13.46 points in the weighted total average and a commendable 10% reduction in the failure rate.

Keywords: extreme-based teaching model, innovative pedagogical methods, project-based learning, team-based learning

Procedia PDF Downloads 59