Optimum sizing of launching nose of prestressed concrete bridges

El diseño del pico de lanzamiento de un puente lanzado determina su proceso constructivo y, por lo tanto, también sus dimensiones. La optimización del pico de lanzamiento puede plantearse como primer paso para la mejora del diseño de un puente lanzado. El procedimiento convencional de diseño del pico de lanzamiento se basa en emplear la técnica de prueba y error para reducir el momento flector sobre el apoyo frontal del tablero de hormigón pretensado durante el proceso de lanzamiento. Esta forma de trabajo en ningún caso garantiza alcanzar la mejor de entre todas las soluciones posibles, pues se basa en la experiencia e intuición del proyectista, además de limitarse necesariamente a escasos tanteos. Dado que los puentes lanzados constituyen una tipología constructiva importante, deben incorporar todas las capacidades disponibles de innovación del diseño, entre las que se encuentra la optimización matemática. Este trabajo propone una formulación objetiva y rigurosa para optimizar el pico de lanzamiento de un puente lanzado adaptada a los condicionantes reales que tienen en la práctica los proyectistas de puentes. Comparando los resultados obtenidos mediante procedimientos convencionales y con técnicas de optimización se puede comprobar el grado de validez de algunas afirmaciones, que se dan por supuestas en los métodos clásicos de diseño de picos de lanzamiento, pero que en realidad no se sustentan en fundamento teórico alguno, demostrándose la utilidad de la optimización matemática para la mejora del diseño.The design of the launching nose of an incrementally launched bridge determines its constructive process and, therefore, also its dimensions. The optimization of the launching nose can raise as a first step to improve the design of a launched bridge. The conventional design process of a launching nose is based on trial and error method to reduce bending moment of prestressed concrete deck at the foremost support during launch. In this way, there is no guarantee that the obtained solution is the best among all the possible solutions since they all depend on the experience and intuition of a designer, and they are also restricted by a limited number of possible iterations. Given that launched bridges constitute an important constructive typology, all the available capacities of design innovation should be incorporated, among which it can be found numerical optimization. This research work proposes an objective and rigorous formulation to optimize a launching nose of launched bridge under real constraints that a bridge designer can encounter in practice. Comparing the results obtained by conventional process and that by optimization techniques, it can be verified that some of the assumptions, considered in classical design methods of a launching nose, are not based on any theoretical foundation. This fact demonstrates the utility of numerical optimization to improve a design.Peer Reviewe

A comparative analysis between FEM and Boundary Methods in bending of Plates

Two different methods of analysis of plate bending, FEM and BM are discussed in this paper. The plate behaviour is assumed to be represented by using the linear thin plate theory where the Poisson-Kirchoff assumption holds. The BM based in a weighted mean square error technique produced good results for the problem of plate bending. The computational effort demanded in the BM is smaller than the one needed in a FEM analysis for the same level of accuracy. The general application of the FEM cannot be matched by the BM. Particularly, different types of geometry (plates of arbitrary geometry) need a similar but not identical treatment in the BM. However, this loss of generality is counterbalanced by the computational efficiency gained in the BM in the solution achievemen

Carbonatos en suelos de la zona oriental de Gran Canaria

The study of three soil profiles in the aridic-xeric zone of Las Palmas island showed that: petrocalcic horizons are formed in pyroclastic episodes; these horizons are generally thick; the xeric zone frequently have polycyclic profiles and their carbonates have complex mineralogy; underlain basaltic rocks are scantly altered, and their joints are frequently filled by carbonates. These facts suggest that the development of these profiles is mostly Pleistocene, and the diffuse carbonates accumulation in depth obstructs the assessment of carbonatation processes

Amplificación del efecto destructivo de los desprendimientos rocosos por deslizamiento sobre suelos volcánicos (Tenerife y Madeira)

This work provides geomorphological and geotechnical observations on the amplification of the destructive behaviour of rock falls developed in rocky slopes with a soil rich in organic matter, which are both exposed to high rainfall regimes. The determinant factor of this process would be related to the low geotechnical quality that the organic matter gives to the soil, which experience a sudden change in its fabric related to the dynamic load, similar to those observed in the quick clays in the fjords of Norway

Tumores óseos del pie

El manejo de los tumores óseos es difícil, debido a sus diferentes formas y comportamientos y a su baja incidencia. El pie no escapa a este axioma, ya que los tumores en esta región anatómica son particularmente infrecuentes y pueden mostrar un comportamiento clínico y radiológico diferente del que evidencian en otras regiones del esqueleto. Los autores revisan, en primer lugar, los aspectos generales de los tumores óseos del pie, considerando su epidemiología, el proceder diagnóstico y pronóstico y las opciones terapéuticas, para luego pasar a examinar las particularidades regionales e histológicas de estas neoplasias en relación con su tratamiento.The management of bone tumours is difficult, both because of their varying forms and behaviours and because of their low incidence. The foot is no exception to this axiom, as tumours in this particular anatomic region are particularly infrequent and may exhibit a clinical and radiological behaviour completely at variance to that in other skeletal regions. The authors first review the general aspects of the bobe tumours of the foot, considering their epidemiology, the diagnostic procedure and prognosis and the therapeutic options, and then examine the regional and histologic peculiaritiesof these neoplasms as related to their therapeutic management

Approaches for Removal of PAHs in Soils: Bioaugmentation, Biostimulation and Bioattenuation

Polycyclic aromatic hydrocarbons (PAHs)‐contaminated soils have been a concern during last decades; consequently, physicochemical and biological technologies have emerged and evolved with the aim of remediating them. Particularly, biological technologies are considered promising since they are low cost, safe and environmentally friendly. However, their results so far have been diverse and scattered. This chapter includes a review of the current status on bioaugmentation, biostimulation and bioattenuation techniques, which have been applied in PAHs‐contaminated agricultural soils during the last decades. Successes and failures in PAHs remediation applied at microcosm and field levels are exhibited. Furthermore, the effects of microbial inoculum, the soil organic matter and the particle size of the aggregates on the PAHs’ availability and on the subsequent microbial biodegradation are reviewed. Finally, agricultural management systems are considered in the prediction of the behaviour and the end‐point of some contaminants, as well as in the success of applying a biological technique

Quintom fields from chiral anisotropic cosmology

In this paper we present an analysis of a chiral anisotropic cosmological scenario from the perspective of quintom fields. In this setup quintessence and phantom fields interact in a non-standard (chiral) way within an anisotropic Bianchi type I background. We present our examination from two fronts: classical and quantum approaches. In the classical program we find analytical solutions given by a particular choice of the emerged relevant parameters. Remarkably, we present an explanation of the ''big-bang'' singularity by means of a ''big-bounce''. Moreover, isotropization is in fact reached as the time evolves. On the quantum counterpart the Wheeler-DeWitt equation is analytically solved for various instances given by the same parameter space from the classical study, and we also include the factor ordering $\rm Q$. Having solutions in this scheme we compute the probability density, which is in effect damped as the volume function and the scalar fields evolve; and it also tends towards a flat FLRW framework when the factor ordering constant $\rm Q \ll 0$. This result might indicate that for a fixed set of parameters, the anisotropies quantum-mechanically vanish for very small values of the parameter $\rm Q$. Finally, classical and quantum solutions reduce to their flat FLRW counterparts when the anisotropies vanish.Comment: 14 pages, 4 figure

Abuse and discrimination towards indigenous people in public health care facilities: experiences from rural Guatemala

Background Health inequalities disproportionally affect indigenous people in Guatemala. Previous studies have noted that the disadvantageous situation of indigenous people is the result of complex and structural elements such as social exclusion, racism and discrimination. These elements need to be addressed in order to tackle the social determinants of health. This research was part of a larger participatory collaboration between Centro de Estudios para la Equidad y Gobernanza en los Servicios de Salud (CEGSS) and community based organizations aiming to implement social accountability in rural indigenous municipalities of Guatemala. Discrimination while seeking health care services in public facilities was ranked among the top three problems by communities and that should be addressed in the social accountability intervention. This study aimed to understand and categorize the episodes of discrimination as reported by indigenous communities. Methods A participatory approach was used, involving CEGSS’s researchers and field staff and community leaders. One focus group in one rural village of 13 different municipalities was implemented. Focus groups were aimed at identifying instances of mistreatment in health care services and documenting the account of those who were affected or who witnessed them. All of the 132 obtained episodes were transcribed and scrutinized using a thematic analysis. Results Episodes described by participants ranged from indifference to violence (psychological, symbolic, and physical), including coercion, mockery, deception and racism. Different expressions of discrimination and mistreatment associated to poverty, language barriers, gender, ethnicity and social class were narrated by participants. Conclusions Addressing mistreatment in public health settings will involve tackling the prevalent forms of discrimination, including racism. This will likely require profound, complex and sustained interventions at the programmatic and policy levels beyond the strict realm of public health services. Future studies should assess the magnitude of the occurrence of episodes of maltreatment and racism within indigenous areas and also explore the providers’ perceptions about the problem