Lack Of Confinement Research Articles

Tire Encasement and Granular Column Stability

Abstract Granular columns derive their load capacity from the confinement offered by the surrounding soil. However, lateral support can be problematic in extremely soft soil. Granular columns, when embedded in very soft clay, may bulge because of a lack of confinement offered by the surrounding soil. To avoid these problems, additional confinement can be provided by using geogrid or geosynthetic encasement. This study investigates a method of encasement construction with the aim of using waste tires to build columns. Without any recycling pretreatment, waste tires were used as material for stone encasement. Tires were stacked vertically to form a column frame structure and were bonded together using infinite screws and tightened with bolts. The diameter of the stone columns was that of a nominal car tire in all tests. A similar geosynthetically encased stone column with identical geometrical properties was also tested. Load tests were performed on both geotextile and tire-encased columns in a clay bed medium under incremental surcharge loads. To measure the bucking deformations of the column section using photogrammetric methods, unconfined loading tests were conducted under the same loading conditions. Results obtained from small-scale laboratory tests show that tire encasement makes the stone columns stiffer and stronger than traditional geotextile-encased stone columns.

Cell-Free DNA: An Underestimated Source of Antibiotic Resistance Gene Dissemination at the Interface Between Human Activities and Downstream Environments in the Context of Wastewater Reuse.

The dissemination of antimicrobial resistance (AMR) is one of the biggest challenges faced by mankind in the public health domains. It is currently favored by a lack of confinement between waste disposal and food production in the environmental compartment. To date, much effort has been devoted into the elucidation and control of cell-associated propagation of AMR. However, substantial knowledge gaps remain on the contribution of cell-free DNA to promote horizontal transfers of resistance genes in wastewater and downstream environments. Cell free DNA, which covers free extracellular DNA (exDNA) as well as DNA encapsulated in vesicles or bacteriophages, can persist after disinfection and promote gene transfer in the absence of physical and temporal contact between a donor and recipient bacteria. The increasing water scarcity associated to climatic change requires developing innovative wastewater reuse practices and, concomitantly, a robust evaluation of AMR occurrence by implementing treatment technologies able to exert a stringent control on AMR propagation in downstream environments exposed to treated or non-treated wastewater. This necessarily implies understanding the fate of ARGs on various forms of cell-free DNA, especially during treatment processes that are permissive to their formation. We propose that comprehensive approaches, investigating both the occurrence of ARGs and their compartmentalization in different forms of cellular or cell-free associated DNA should be established for each treatment technology. This should then allow selecting and tuning technologies for their capacity to limit the propagation of ARGs in any of their forms.

Backyard poultry production in Chile: animal health management and contribution to food access in an upper middle-income country

Backyard production systems (BPS) that involve poultry are a good way to improve food security and poverty alleviation. Few studies have been carried out to quantify the contribution of poultry production to these households and the constraints they might face if a priority animal disease enters these systems. This study aims to characterize the poultry-rearing BPS in central Chile and to identify socio-economic factors associated to households’ consumption of poultry. Data was collected from 384 BPS through a face-to-face semi-structured questionnaire. Value chain framework associated with BPS poultry rearing and cash flow analysis of BPS was done to identify the inputs/outputs of the system and to know the profitability of the system. Multiple linear regression was performed to identify the BPS and household factors associated to poultry consumption. The results of this study suggest that BPS in central Chile have biosecurity deficiencies such as: lack of confinement, lack of veterinary assistance and incorrect handling of dead animals. Cash flow analysis indicated that 62% of the BPS had a positive balance from production. Distance to closest market and per capita income were factors associated to poultry value to farmers. Different factors were significant predictors of household poultry consumption. Positive predictors of consumption were identified as: (i) older owners, (ii) higher transportation price to closest market, (iii) larger flock size (iv) birds raised by women and (v) owning a car. On the contrary, (i) higher per capita income and (ii) bigger household size predicted a reduction in consumption. The results indicate the importance of BPS to low-income families and those living in remote areas while also highlighting the vulnerability of these systems to disease risks.

Seismic performance evaluation of GLD beam–column sub-assemblages of three different scenarios

Gravity load designed (GLD) structures exhibit poor seismic performance due to inadequate reinforcement to cater for the seismic forces, lack of confinement, poor joint strength, improper anchorage, presence of weak column and strong beams. These structures are also susceptible to environmental impact leading to corrosion of reinforcement which would further degrade their seismic performance. In RC structures, beam–column joints are crucial members and dissipate the seismic energy imparted to the structure. Hence in this study, two typical cases of GLD (i) uncorroded GLD and (ii) corrosion affected GLD (corroded) exterior beam–column sub-assemblages subjected to reverse cyclic loading are investigated and compared. Reinforcement corrosion of one of the GLD specimens is accelerated by the impressed current technique. Based on the investigation on uncorroded GLD and corrosion affected GLD beam–column specimens, it is noted that the corrosion has significant effect on the seismic performance in terms of loss of energy dissipation, strength- and stiffness- degradation. To improve the seismic performance of uncorroded GLD specimens, a low invasive single steel haunch upgradation scheme (SHUS) is proposed in this study. The maximum load carried by steel haunch upgraded GLD specimen is about 30% higher than that of GLD specimen. Hence, it is noted that by implementing the proposed upgradation scheme for GLD beam–column sub-assemblage, remarkable improvement in the seismic response can be achieved. The present study provides insight into the behaviour of steel haunch upgraded GLD specimen and would also pave the way for formulating seismic upgradation of even corroded GLD beam–column sub-assemblage.

CYCLIC BEHAVIOUR OF LIGHTLY REINFORCED CONCRETE COLUMNS WITH NON-DUCTILE LAP SPLICES

Experimental testing of lightly reinforced concrete column was conducted to investigate the collapse behavior of such column under cyclic lateral loading. Six column specimens, which have low longitudinal reinforcement and lack of confinement, were detailed with no lap splice, and non-ductile lap splice within or outside critical region. Placing the short, unconfined column's lap splice within critical region caused peak moment to fall short under its nominal moment capacity. In contrast, moment capacity of the specimen containing non-ductile lap splice outside critical region was in close agreement with those of specimen without lap splice. However, its inelastic damage region was moving away from the beam-column interface, resulted in degradation of drift capacity and rapid degradation of lateral strength. The presence of non-ductile lap splice outside critical region also potentially shift column's collapse mechanism from flexure to flexure-shear critical. The ability of lightly reinforced concrete columns to maintain its axial load carrying capacity to large drift ratios despite heavy damage and significant loss of lateral load carrying capacity indicates that lap splice failure does not create sudden collapse hazard.

Influence of Rock Properties in Estimating Rock Strength for Shallow Underground Structures in Weak Rocks

DOI: 10.17014/ijog.5.2.93-105Two popular rock strength criteria, the linear Coulomb and non-linear Hoek-Brown, are widely used in underground designs. These two criteria may be applied differently depending on rock conditions. Weak rocks may have different properties compared to hard rocks. Both criteria have been applied in a current research to practically determine the applicability of the criteria in estimating the strength of weak rock masses of five shallow underground structures. Results show that both criteria are able to model the strength of the five weak rock masses, but as expected the criteria provide quite different values for each type of rocks. The strength of rock masses around underground structures depends on uniaxial compressive strength and confinement; but the linear criterion very much depends on shear characteristics of rock materials. Whereas, the non-linear criterion relies on the geological strength index (GSI). Although the GSI may have served practical descriptions for rock masses, some difficulties were found when using the GSI for very weak pyroclastic rocks. The GSI seems to provide underestimated indexes for these rock types. Estimations show that the non-linear criterion may not really exhibit curved strength envelopes rather linear in some sense, for five weak rock masses. Thus in general, when an underground structure is reasonably shallow, has a lack of confinement, and where the shear behaviour dominates rock failures, the linear criterion is more preferable than the non-linear criterion in modelling the strength of weak rock masses.

Bidirectional shake table testing of RC columns retrofitted and repaired with shape memory alloy spirals

Under the extreme threats of strong earthquakes, bridge columns are required to remain functional to ensure the safety and structural integrity of the entire bridge system. However, many existing bridges designed according to old seismic design provisions lack flexural ductility due to insufficient concrete confinement. Lack of confinement in old bridges is often addressed through providing supplementary external passive confinement. Recently, an active confinement technique using Shape Memory Alloys (SMAs) has been proposed as a more effective alternative to conventional passive confinement methods. In this study, the application of SMA confinement in seismic retrofitting and emergency repair of RC bridge columns is examined experimentally through a series of shake table tests. Two 1/6-scale RC columns, retrofitted and repaired with SMA spirals, are tested simultaneously under bidirectional test motions with varying intensity. Test results show that SMA confinement is highly effective in mitigating the seismic damage and improving the seismic performance of retrofitted and repaired RC columns subjected to strong earthquakes.

21.04: Vibration characteristics of an existing high‐rise building in Montreal and the effects of retrofit

ABSTRACTThe study described in this paper refers to seismic assessment and retrofit of an existing 10‐storey reinforced concrete office building designed and built at the beginning of the 20 century. When this building with a height of 38.95 m was completed it was the highest in downtown Montreal. According to FEMA 547 classification, the typology of this building structure is associated to model building type “C3”. Consequently, this type of non‐ductile frame building with an insignificant amount of masonry walls is relatively weak and unable to carry the seismic forces when subjected to ground motions from a potential earthquake magnitude. The main deficiencies of this structural system are: poor lateral confinement and shear resistance of columns, the location of lap splices and the number of reinforcing bars often inadequate, the lack of confinement and shear reinforcement in joints, poor anchorage of longitudinal reinforcement of beams into joints and shear resistance of beams. Due to lack of seismic detailing, the common retrofit measure recommended in ASCE/SEI 41–13 for this building is to add new lateral force‐resisting systems designed according to current code and standard provisions. Hence, in this case, the most cost‐effective retrofit solution is to add a steel structure designed to withstand seismic forces while responding to serviceability criteria required to preserve the non‐reinforced masonry facades facing the main streets and the facades ornaments.

The QCD Phase-Diagram Obtained from the NJL and the Extended-NJL Models for Quark and Hadron Phases

We analyse the hadron/quark phase transition described by the Nambu-Jona-Lasinio (NJL) model [quark phase] and the extended Nambu-Jona-Lasinio model (eNJL) [hadron phase]. While the original formulation of the NJL model is not capable of describing hadronic properties due to its lack of confinement, it can be extended with a scalar-vector interaction so it exhibits this property, the so-called eNJL model. As part of this analysis, we obtain the equations of state within the SU(2) versions of both models for the hadron and the quark phases and determine the binodal surface.

Impurity radiation in DEMO systems modelling

For fusion reactors with ITER divertor technology, it will be imperative to significantly reduce the heat flux into the divertor e.g. by seeded impurity radiation. This has to be done without affecting the accessibility of a high performance scenario. To assess the implications of seeded plasma impurities on DEMO design, we have developed an impurity radiation model for radiation inside the separatrix. Evaluating the validity of our model, we find the assumption of a local ionisation equilibrium to be appropriate for our purposes and the assumption of flat impurity profiles – even though not satisfactory – to represent the best currently possible. Benchmarking our model against other codes highlights the need to use up to date atomic loss function data.From the impurity radiation perspective, the main uncertainties in current DEMO design stem from the lack of confinement and L-H-threshold scalings that can be robustly extrapolated to highly radiative DEMO scenarios as well as the lack of appropriate models for the power flow from the separatrix into the divertor that include radiation in the scrape off layer. Despite these uncertainties in the model we can exclude that significant fuel dilution through seeded impurities (with Z≥ZAr) will be an issue for DEMO, but the controllability of highly radiative scenarios still needs to be coherently shown.

Numerical study of pillar stresses and interaction effects for twin rock caverns

SummaryLarge underground caverns are increasingly being considered for the construction of industrial facilities and transportation infrastructure in order to optimize the use of surface land in large urban cities. Due to the geological constraints underground, it is sometimes necessary to construct a cavern close to an existing cavern. Pillars serve as an underground support element in twin caverns, without which it is difficult to sustain the weight of the overburden materials. If the strength of a pillar is exceeded, it will fail, and the load that it carried will be transferred and thereby contribute to the collapse of the twin caverns. The lack of confinement in slender pillars also contributes to the complete collapse of pillars at relatively low stress magnitudes. From a design point of view, understanding the pillar failure mechanism and the interaction effect between twin caverns is essential. This paper presents a numerical investigation on the influence of various design parameters on twin cavern interaction. Pillar performances with respect to the changes to the maximum principal stress in the pillar, the peak vertical stress, and the peak principal stress difference in the pillar core are studied in order to examine the failure mechanisms and to identify situations in which there is significant cavern interaction and overlap of the plastic zones. Copyright © 2014 John Wiley & Sons, Ltd.

Performance of tall buildings in Viña del Mar in the 27 February 2010 offshore Maule, Chile earthquake

AbstractAfter the devastating offshore Maule, Chile earthquake of moment magnitude 8.8 on 27 February 2010, the Los Angeles Tall Buildings Structural Design Council (LATBSDC) organized a reconnaissance team to visit the Santiago, Concepción and Viña del Mar areas. This report summarizes the highlights of the damage observed in the Viña del Mar area on the coast 120 km west‐north‐west of Santiago and much closer to the subduction rupture zone than Santiago. A significant portion of Viña del Mar is uniquely situated on variable ground conditions, particularly in the area with most of the damaged buildings. The Viña del Mar area also included tall buildings constructed before and damaged by the large 3 March 1985 magnitude 7.8 Offshore Valparaiso earthquake, which were damaged again in the 2010 earthquake.The predominant observation in these buildings was the lack of confinement and ductile detailing of shear walls. The second observation was the high demand in the localized Viña del Mar area.The apparently high demand on buildings clustered in the Viña del Mar area may be an observation based on the damage since most of the taller structures in the area are somewhat clustered in Viña. But significant damage was not reported in Valparasio, which is largely, situated on higher ground which steps downward to a narrow flat area along the ocean. Similarly, significant damage was not reported in new buildings along the coast just North of Viña del Mar. The authors' conclusion based on these observations is that the ground conditions in Viña del Mar relate to the level of demand and the level of demand is higher.Demand is variable geoseismically but with the local history of many earthquakes from the same source zone, the characterization should be regularized. However, structural response is much better defined at least for confined elements with tested and predictable analytical characterization. Regardless, the detailing of reinforcing in reinforced concrete must relate to the expected demand and duration. In addition, the structural system and elements need to be designed and detailed to prepare a building to survive a higher unanticipated demand without collapse.However, despite the apparently large demands due to the large magnitude earthquake with strong aftershocks and the long duration of seismic motions, building collapses did not occur even with limited capability due to non‐ductile and non‐confined detailing. Copyright © 2010 John Wiley & Sons, Ltd.

Dog Breeding in New Providence, The Bahamas, and Its Potential Impact on the Roaming Dog Population I: Planned and Accidental

This article reports the first known study on dog breeding in an Afro-Caribbean community. The study obtained the information on 517 matings through interviews with dog caregivers. Few litters (6.8%) from mongrels (potcakes) resulted from planned matings, whereas 66.5% of matings between purebred dogs were planned. Confinement of the female is often inadequate, and roaming dogs may have been responsible for 24.8% of the litters. The lack of confinement of potcakes has resulted in the perception that potcakes are “responsible” for the companion animal (pet) overpopulation problem; however, potcakes made up the minority (29.4%) of the breeding females. Until regulations concerning dog breeding are introduced, caregivers can be expected to continue exploiting their nonhuman animals to supplement their incomes from the sale of puppies. A consequence of unregulated breeding may also be inbred offspring of “purebred” dogs as few self-styled “professional” breeders appeared to use dogs who were not their own.

Ultraviolet guiding hollow-core photonic crystal fiber

We present what we believe to be the first experimental demonstration of low-loss guiding of UV radiation in hollow-core photonic crystal fiber. The "kagomé" latticed fiber was designed to guide 0.355 microm wavelength radiation with approximately 2 dB/m loss. Moreover, an excellent agreement between modeling and experimental results was obtained. From this comparison it was inferred that propagation loss only arises from the lack of confinement, thereby indicating that such fibers may be designed for even shorter wavelengths where material loss prohibits the use of fused silica as a core material. As an example, a fiber was designed to be operated at 0.25 microm with 0.4 dB/m loss.

A Comparison of Bahamian Cat and Dog Caregivers on New Providence

This article offers the first comparison of actions and attitudes of Afro-Caribbean caregivers who keep only cats or only dogs. A total of 330 Bahamian caregivers found that women primarily keep cats; men primarily keep dogs. Cat keepers were more attached to their companion animals but no more sensitive toward nonhuman animal-welfare issues than dog keepers. When considering actions toward pets, the study noted few differences between the two types of caregivers. Both types reported low neutering rates and lack of confinement. Findings suggest that although both cat and dog caregivers thought themselves good pet caregivers, both types would benefit from animal-welfare education. In communities where cat populations pose a threat to indigenous wildlife and current care-keeping practices may be a cause for concern, caregivers may need education as to the implications of their actions. Given the similarity in dog-keeping practices in the West Indies, the findings about cat caregivers reported here may be applicable to other Afro-Caribbean communities. Further research on cats should be done to allow better understanding of the dynamics and behavior of cat populations on small islands.

Behaviour of Asphalt Concrete in Cyclic and Static Compression Creep Test with and without Lateral Confinement

ABSTRACT The paper presents results of the cyclic and static compression creep test conducted on asphalt concrete specimens with and without lateral confinement. Asphalt concrete containing three polymer modified bitumen and one pure bitumen was tested. The results have shown that behaviour of asphalt concrete tested with and without lateral confinement significantly differs. It has been found that in creep without confinement the cohesion of a mix is mainly responsible for its response to external load whereas in creep with lateral confinement both cohesion and internal friction of mineral aggregate play an important role. It has been proven that the creep test without lateral confinement overestimates the function of bitumen and underestimates the function of internal friction of aggregate. Lateral confinement is of the greatest importance in cyclic loading in which lack of confinement may very significantly increase creep of material. The creep rate at cyclic loading was found to be significantly higher that the creep rate at static loading of the same magnitude of acting stresses for the same material. The prediction of asphalt mix behaviour in a pavement structure and evaluation of asphalt mix quality based on the results of unconfined compression creep tests may not be fully reliable.

Emplacement mechanisms of contrasting debris avalanches at Volcán Mombacho (Nicaragua), provided by structural and facies analysis

We study the lithology, structure, and emplacement of two debris-avalanche deposits (DADs) with contrasting origins and materials from the Quaternary–Holocene Mombacho Volcano, Nicaragua. A clear comparison is possible because both DADs were emplaced onto similar nearly flat (3° slope) topography with no apparent barrier to transport. This lack of confinement allows us to study, in nature, the perfect case scenario of a freely spreading avalanche. In addition, there is good evidence that no substratum was incorporated in the events during flow, so facies changes are related only to internal dynamics. Mombacho shows evidence of at least three large flank collapses, producing the two well-preserved debris avalanches of this study; one on its northern flank, “Las Isletas,” directed northeast, and the other on its southern flank, “El Crater,” directed south. Other south-eastern features indicate that the debris-avalanche corresponding to the third collapse (La Danta) occurred before Las Isletas and El Crater events. The materials involved in each event were similar, except in their alteration state and in the amount of substrata initially included in the collapse. While “El Crater” avalanche shows no signs of substratum involvement and has characteristics of a hydrothermal weakening-related collapse, the “Las Isletas” avalanche involves significant substratum and was generated by gravity spreading-related failure. The latter avalanche may have interacted with Lake Nicaragua during transport, in which case its run-out could have been modified. Through a detailed morphological and structural description of the Mombacho avalanches, we provide two contrasting examples of non-eruptive volcanic flank collapse. We show that, remarkably, even with two distinct collapse mechanisms, the debris avalanches developed the same gross stratigraphy of a coarse layer above a fine layer. This fine layer provided a low friction basal slide layer. Whereas DAD layering and the run-outs are roughly similar, the distribution of structures is different and related to lithology: Las Isletas has clear proximal faults replaced distally by inter-hummock depressions where basal unit zones are exhumed, whereas El Crater has faults throughout, but the basal layer is hidden in the distal zone. Hummocky forms depend on material type, with steep hummocks being formed of coherent lava units, and low hummocks by matrix-rich units. In both avalanches, extensional structures predominate; the upper layers exclusively underwent longitudinal and lateral extension. This is consistent with evidence of only small amounts of block-to-block interactions during bulk horizontal spreading. The base of the moving mass accommodated transport by large amounts of simple shear. We suggest that contractional structures and inter-block collisions seen in many other avalanches are artifacts related to topographic confinement.

Influence of matrix properties on alkali silica reaction rates

Matrices with different cracking and confinement characteristics are utilized to isolate the important parameters that influence gel initiation and alkali silica reaction rate. The paper is divided into two parts. In Part I, the matrix exhibits crack growth resistance behavior which induces compressive stresses on the alkali silica gel and in addition prevents the alkali silica gel from leaving the reaction site, which slows down the alkali silica reaction rate and modifies the gel composition. In Part II the matrices are designed to provide little confinement and hence allow the alkali silica gel to expand almost freely. However, the matrices in Part II differ in their ability to allow the alkali silica gel to escape the reaction site. The results reveal that lack of confinement accelerates early gel formation whereas the lack of escape of alkali silica gel products away from the reaction site reduces the alkali silica reaction rate.

Nucleon dressing from dispersion relations

The phase structure of hadronic matter at high density relevant to the physics of compact stars and relativistic heavy-ion collisions is studied in a low-energy effective quark theory. The relevant phases that figure are (1) chiral condensation, (2) diquark color condensation (color superconductivity) and (3) induced Lorentz-symmetry breaking (“ISB”). For a reasonable strength for the effective four-Fermi current–current interaction implied by the low-energy effective quark theory for systems with a Fermi surface we find that the “ISB” phase sets in together with chiral symmetry restoration (with the vanishing quark condensate) at a moderate density while color superconductivity associated with scalar diquark condensation is pushed up to an asymptotic density. Consequently, color superconductivity seems rather unlikely in heavy-ion collisions although it may play a role in compact stars. Lack of confinement in the model makes the result of this analysis only qualitative but the hierarchy of the transitions we find seems to be quite robust.

Quark condensation, induced symmetry breaking and color superconductivity at high density

The phase structure of hadronic matter at high density relevant to the physics of compact stars and relativistic heavy-ion collisions is studied in a low-energy effective quark theory. The relevant phases that figure are (1) chiral condensation, (2) diquark color condensation (color superconductivity) and (3) induced Lorentz-symmetry breaking (“ISB”). For a reasonable strength for the effective four-Fermi current–current interaction implied by the low-energy effective quark theory for systems with a Fermi surface we find that the “ISB” phase sets in together with chiral symmetry restoration (with the vanishing quark condensate) at a moderate density while color superconductivity associated with scalar diquark condensation is pushed up to an asymptotic density. Consequently, color superconductivity seems rather unlikely in heavy-ion collisions although it may play a role in compact stars. Lack of confinement in the model makes the result of this analysis only qualitative but the hierarchy of the transitions we find seems to be quite robust.