Examinando por Materia "Soils"

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    Base shear determination using response-spectrum modal analysis of multi-degree-of-freedom systems with soil–structure interaction
    (Springer Netherlands, 2019-01-01) Arias H.; Jaramillo J.D.; Mecánica Aplicada
    Building codes and design guidelines, e.g. FEMA (NEHRP recommended seismic provisions for new buildings and other structures, FEMA P-1050, Washington, 2015) and ASCE (Minimum design loads for buildings and other structures ASCE/SEI 7-10/2010, Reston, 2010), describe the problem of multi-degree-of-freedom systems with soil-structure interaction (SSI). These systems are modeled like those having a fundamental degree of freedom on a foundation with lateral and rotational interactions and the other vibration modes isolated and supported on a fixed foundation. This model oversimplifies the problem, neglecting the effects of having all modes coupled in the foundation with SSI. A simple, easily programmable, SSI model in which all vibration modes are coupled an attached to an infinitely rigid shallow foundation subjected to soil excitation is introduced here. Initially, the total response of the coupled system is calculated. Then, using traditional procedures to combine modal responses, a simplified alternative methodology to find the total response of this coupled system is proposed. The new methodology is verified against a robust numerical technique, i.e. boundary elements method, using a wide variety of cases that combine several types of soils, building heights and two structural typologies: bending frames and shear walls. Finally, it is clear from the parametric study that current methodologies, based only on the interaction of the fundamental mode of vibration of the structure, in some cases has a significant influence on the total base shear of buildings, particularly in tall buildings founded in soft soils. © 2019, Springer Nature B.V.
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    Evaluación de la promoción de crecimiento de bacillus subtilis ea-cb0575 en cultivos de banano, crisantemo y café
    (Universidad EAFIT, 2014) Cuéllar Gaviria, Tatiana Zazini; Posada Uribe, Luisa Fernanda; Villegas Escobar, Valeska
    El desarrollo de productos biológicos con base en microorganismos benéficos para la agricultura no es un tema nuevo, sin embargo diversas estrategias para su aplicación y ampliación de su espectro de acción son ampliamente exploradas hoy en día, con el fin de lograr un mejor entendimiento de las condiciones que más beneficien su aplicación -- En este trabajo se evaluó el efecto de la inoculación de un bioinsumo con base en el Bacillus subtilis EA-CB0575 sobre la promoción del crecimiento en cultivos de banano, crisantemo y café -- Para la evaluación en el cultivo de banano, se realizó la inoculación del producto a nivel de raíz en plantas a partir de tres etapas fenológicas -- Los resultados de la evaluación mostraron que al inocular el producto desde la etapa de endurecimiento, hubo un aumento en las variables de longitud aérea (16%-31%), diámetro del pseudotallo (17%), número de hojas (19%-38%), peso seco aéreo (85%) y peso seco total (59%) durante las etapas tempranas del desarrollo -- Sin embargo, al evaluar estas plantas en etapa reproductiva, no se encontraron diferencias estadísticas entre los tratamientos -- Respecto a las plantas inoculadas en las etapas más avanzadas del desarrollo, no se identificaron diferencias significativas entre los tratamientos -- Por otra parte, al evaluar el efecto de la inoculación del bioinsumo en el cultivo de crisantemo se observó que al aplicar el bioformulado sobre esquejes hormonados con AIB hubo un aumento en el peso fresco radicular (27%-64%) cuando se aplicó el producto por medio de la inmersión de los esquejes; mientras que al inocular la suspensión del B. subtilis EA-CB0575 sobre el sustrato de germinación en esquejes no hormonados, se observó una disminución significativa en los tiempos de floración -- Por último, al evaluar el efecto de la inoculación de semillas de café con el bioformulado, se encontró que bajo las condiciones evaluadas, el producto no tuvo un efecto positivo en el crecimiento de las plantas a pesar de haber causado un cambio en la estructura radicular, en donde se observó que las plantas inoculadas con el producto aumentando en un 53% en el diámetro de la raíz principal
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    Human induced discharge diversion in a tropical delta and its environmental implications: The Patía River, Colombia
    (ELSEVIER SCIENCE BV, 2012-03-06) Restrepo, Juan D.; Kettner, Albert; Universidad EAFIT. Departamento de Geología; Ciencias del Mar
    The Patía River, the number one in terms of sediment yield ~1500tkm -2yr -1 draining the western South America, has the most extensive and well developed delta on the Pacific coast, measuring 1700km 2. During the Holocene, nature forced the Patía delta to the south; however, a major water diversion, starting in 1972, diverted the Patía flow to the Sanguianga River, the latter, a small stream draining internal lakes from the Pacific lowlands. This human induced discharge diversion shifted the active delta plain back to the north and changed the northern estuarine system into an active delta plain. Overall, major environmental consequences of this discharge diversion in terms of morphological changes along the delta coast and distributary channels, are evidenced by: (1) coastal retreat along the abandoned delta lobe; 63% of the southern shoreline is retreating at maximum rates of 7myr -1, with a corresponding coastal land loss of 106myr -1; (2) transgressive barrier islands with exposed peat soils in the surf zone; (3) abandonment of former active distributaries in the southern delta plain with associated closing of inlets and formation of ebb tidal deltas; (4) breaching events on barrier islands; and (5) distributary channel accretion in the northern delta plain by morphological processes such as sedimentation (also in crevasses), overbank flow, increasing width of levees, interdistributary channel fill, and colonization of pioneer mangrove. The Sanguianga Mangrove National Park (SMNP), the largest mangrove reserve in Colombia, measuring 800km 2, lies in this former estuary, where major hydrologic and sedimentation changes are occurring. Observed environmental changes in the SMNP, include (1) seaward advance of the sub-aqueous delta front at the Sanquianga inlet evidenced by an increase in tidal flat area from 5.4Mm 2 in 1986 to 14Mm 2 in 2001; (2) freshening conditions in the Sanguianga distributary channel, a hydrologic change that has shifted the upper estuarine region (salinity <1psu) downstream; (3) downstream advance of freshwater vegetation, which is invading channel banks in the lower and mixing estuarine zones; (4) die-off of approximately 5200ha of mangrove near the delta apex at Bocas de Satinga; and (5) recurrent periods of mangrove defoliation due to a warm plague. Further analysis indicate that during the past two decades, processes such as mangrove erosion in the delta shore, are the result of a short-term relative sea-level rise of 5.1mmyr -1 for the 1984-2006yr-period, after the devastating tsunami of 1979. In the Patía catchment, erosion rates have been more pronounced during the 1970-1980 and 1990-2000 decades, as a result of land degradation and deforestation. Preliminary results indicate that relative resent anthropogenic influences on the Patía River drainage basin have altered the deltaic environment and beyond significantly. © 2011 Elsevier B.V.
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    Influence of the uncertainty in the soil-rock spectral ratios in the definition of uniform hazard spectra at surface level
    (IMPERIAL COLLEGE PRESS, 2006-07-01) Jaramillo, Juan Diego; Mecánica Aplicada
    Based on traditionally accepted hypothesis and verified by existing data, an expression is derived to calculate response spectrum at the ground surface if the response spectrum at the basement rock is known. The fundamental assumptions are with regards to the form of variation of the exceedance rates of spectral accelerations in the basement rock, and based also on the usual (lognormal) distribution forms of the uncertainties associated with the spectral amplification function. The resulting approach multiplies the mean of the amplification function in order to consider in a rigorous way its uncertainty. © Imperial College Press.
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    Modeling added spatial variability due to soil improvement: Coupling FEM with binary random fields for seismic risk analysis
    (Elsevier Ltd, 2018-01-01) Montoya-Noguera, Silvana; Lopez-Caballero, Fernando; Mecánica Aplicada
    A binary mixture homogenization model is proposed for predicting the effects on liquefaction-induced settlement after soil improvement based on the consideration of the added spatial variability between the natural and the treated soil. A 2D finite element model of an inelastic structure founded on a shallow foundation was coupled with a binary random field. Nonlinear soil behavior is used and the model is tested for different mesh size, model parameters and input motions. Historical evidence as well as physical and numerical modeling indicate that improved sites present less liquefaction and ground deformation. In most cases this improvement is modeled as homogeneous; however, in-situ measurements evidence the high level of heterogeneity in the deposit. Inherent spatial variability in the soil and the application of some soil improvement techniques such as biogrouting and Bentonite permeations will necessary introduce heterogeneity in the soil deposit shown as clusters of the treated material in the natural soil. Hence, in this study, improvement zones are regarded as a two-phase mixture that will present a nonlinear relation due to the level of complexity of seismic liquefaction and the consequent settlement in a structure. This relation is greatly affected by the mechanical behavior of the soils used and the input motion. The effect on the latter can be efficiently related to the equivalent wave period as the proposed homogenization model depends on the stiffness demand of the input motion. © 2017 Elsevier Ltd
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    Prediction of landslide occurrence in urban areas located on volcanic ash soils in Pereira, Colombia
    (Springer Verlag, 2004-01-01) Rios, D.A.; Hermelin, M.; Rios, D.A.; Hermelin, M.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y Tectónica
    As a result of the 25 January 1999 Armenia earthquake, the city of Pereira (400,000 inhabitants), located on a volcanic ash-covered alluvial fan in the western limit of the Central Cordillera (Colombia), suffered 250 slope movements. After a complete inventory, a monitoring process of unstable areas was designed, based on repeated topographic surveys, soil pore saturation levels and visual inspections. The participation of the communities was crucial and permitted the prediction of slope movements between 2 weeks and 3 months in advance and the evacuation of the inhabitants. Three specific examples are discussed. The method could be improved by excavating observation trenches and observing in detail local rainfall. In all cases, the strong involvement of the community was considered indispensable for the success of the process. © Springer-Verlag 2004.
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    Prenolin: International benchmark on 1D nonlinear: Site-response analysis—validation phase exercise
    (Seismological Society of America, 2018-04-01) Régnier J.; Bonilla L.-F.; Bard P.-Y.; Bertrand E.; Hollender F.; Kawase H.; Sicilia D.; Arduino P.; Amorosi A.; Asimaki D.; Boldini D.; Chen L.; Chiaradonna A.; Demartin F.; Elgamal A.; Falcone G.; Foerster E.; Foti S.; Garini E.; Gazetas G.; Gélis C.; Ghofrani A.; Giannakou A.; Gingery J.; Glinsky N.; Harmon J.; Hashash Y.; Iai S.; Kramer S.; Kontoe S.; Kristek J.; Lanzo G.; Lernia A.D.; Lopez-Caballero F.; Marot M.; McAllister G.; Mercerat E.D.; Moczo P.; Montoya-Noguera S.; Musgrove M.; Nieto-Ferro A.; Pagliaroli A.; Passeri F.; Richterova A.; Sajana S.; Santisi D’Avila M.P.; Shi J.; Silvestri F.; Taiebat M.; Tropeano G.; Vandeputte D.; Verrucci L.; Mecánica Aplicada
    This article presents the main results of the validation phase of the PRENOLIN project. PRENOLIN is an international benchmark on 1D nonlinear (NL) site-response analysis. This project involved 19 teams with 23 different codes tested. It was divided into two phases; with the first phase verifying the numerical solution of these codes on idealized soil profiles using simple signals and real seismic records. The second phase described in this article referred to code validation for the analysis of real instrumented sites. This validation phase was performed on two sites (KSRH10 and Sendai) of the Japanese strong-motion networks KiK-net and Port and Airport Research Institute (PARI), respectively, with a pair of accelerometers at surface and depth. Extensive additional site characterizations were performed at both sites involving in situ and laboratory measurements of the soil properties. At each site, sets of input motions were selected to represent different peak ground acceleration (PGA) and frequency content. It was found that the code-to-code variability given by the standard deviation of the computed surface-response spectra is around 0.1 (in log10 scale) regardless of the site and input motions. This indicates a quite large influence of the numerical methods on site-effect assessment and more generally on seismic hazard. Besides, it was observed that sitespecific measurements are of primary importance for defining the input data in siteresponse analysis. The NL parameters obtained from the laboratory measurements should be compared with curves coming from the literature. Finally, the lessons learned from this exercise are synthesized, resulting also in a few recommendations for future benchmarking studies, and the use of 1D NL, total stress site-response analysis. © 2018, Seismological Society of America. All rights reserved.
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    Scale-up from shake flasks to pilot-scale production of the plant growth-promoting bacterium Azospirillum brasilense for preparing a liquid inoculant formulation
    (SPRINGER, 2013-11-01) Trujillo-Roldan, Mauricio A.; Valdez-Cruz, Norma A.; Gonzalez-Monterrubio, Cesar F.; Acevedo-Sanchez, Eduardo V.; Martinez-Salinas, Carlos; Garcia-Cabrera, Ramses I.; Gamboa-Suasnavart, Ramses A.; Marin-Palacio, Luz D.; Villegas, Jesus; Blancas-Cabrera, Abel; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)
    Azospirillum brasilense has industrial significance as a growth promoter in plants of commercial interest. However, there is no report in the literature disclosing a liquid product produced in pilot-scale bioreactors and is able to be stored at room temperature for more than 2 years. The aim of this work was to scale up a process from a shake flask to a 10-L lab-scale and 1,000-L pilot-scale bioreactor for the production of plant growth-promoting bacterium A. brasilense for a liquid inoculant formulation. Furthermore, this work aimed to determine the shelf life of the liquid formulation stored at room temperature and to increase maize crops yield in greenhouses. Under a constant oxygen mass transfer coefficient (K L a), a fermentation process was successfully scaled up from shake flasks to 10- and 1,000-L bioreactors. A concentration ranging from 3.5 to 7.5 × 108 CFU/mL was obtained in shake flasks and bioreactors, and after 2 years stored at room temperature, the liquid formulation showed one order of magnitude decrease. Applications of the cultured bacteria in maize yields resulted in increases of up to 95 % in corncobs and 70 % in aboveground biomass. © 2013 Springer-Verlag Berlin Heidelberg.
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    Scale-up from shake flasks to pilot-scale production of the plant growth-promoting bacterium Azospirillum brasilense for preparing a liquid inoculant formulation
    (SPRINGER, 2013-11-01) Trujillo-Roldan, Mauricio A.; Valdez-Cruz, Norma A.; Gonzalez-Monterrubio, Cesar F.; Acevedo-Sanchez, Eduardo V.; Martinez-Salinas, Carlos; Garcia-Cabrera, Ramses I.; Gamboa-Suasnavart, Ramses A.; Marin-Palacio, Luz D.; Villegas, Jesus; Blancas-Cabrera, Abel; Trujillo-Roldan, Mauricio A.; Valdez-Cruz, Norma A.; Gonzalez-Monterrubio, Cesar F.; Acevedo-Sanchez, Eduardo V.; Martinez-Salinas, Carlos; Garcia-Cabrera, Ramses I.; Gamboa-Suasnavart, Ramses A.; Marin-Palacio, Luz D.; Villegas, Jesus; Blancas-Cabrera, Abel; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)
    Azospirillum brasilense has industrial significance as a growth promoter in plants of commercial interest. However, there is no report in the literature disclosing a liquid product produced in pilot-scale bioreactors and is able to be stored at room temperature for more than 2 years. The aim of this work was to scale up a process from a shake flask to a 10-L lab-scale and 1,000-L pilot-scale bioreactor for the production of plant growth-promoting bacterium A. brasilense for a liquid inoculant formulation. Furthermore, this work aimed to determine the shelf life of the liquid formulation stored at room temperature and to increase maize crops yield in greenhouses. Under a constant oxygen mass transfer coefficient (K L a), a fermentation process was successfully scaled up from shake flasks to 10- and 1,000-L bioreactors. A concentration ranging from 3.5 to 7.5 × 108 CFU/mL was obtained in shake flasks and bioreactors, and after 2 years stored at room temperature, the liquid formulation showed one order of magnitude decrease. Applications of the cultured bacteria in maize yields resulted in increases of up to 95 % in corncobs and 70 % in aboveground biomass. © 2013 Springer-Verlag Berlin Heidelberg.
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