Examinando por Materia "Closed-form solution"

Mostrando 1 - 4 de 4
  • No hay miniatura disponible
    Publicación
    Closed-form Solution of Timoshenko Frames on Elastic Winkler Foundation Using the Green's Function Stiffness Method
    (Universidad EAFIT, 2024) Posso Sabogal, Cristian Daniel; Molina Villegas, Juan Camilo; Ballesteros Ortega, Jorge Eliecer; Molina Villegas, Juan Camilo
    This paper presents a method to obtain the exact closed-form solution for the static analysis of Timoshenko beams and frames on elastic Winkler foundation, subjected to arbitrary external loads and bending moments. The solution is derived using the Green’s Functions Stiffness Method (GFSM), a novel mesh reduction method that combines the strengths of the Stiffness Method (SM) and Green’s Functions (GFs). By incorporating the core concepts of the SM, the GFSM exhibits similarities to the Finite Element Method (FEM), including the use of shape functions, stiffness matrices, and fixed-end forces. The application of GFs facilitates the derivation of analytical expressions for displacement and internal force fields for arbitrary external loads and bending moments. Three examples are presented: a single-span beam, a two-span beam, and a one-bay, one-story plane frame on elastic Winkler foundations; which demonstrate applicability and efficacy of the method.
  • No hay miniatura disponible
    Publicación
    Closed-form solution of Timoshenko frames on elastic Winkler foundation using the Green’s function stiffness method
    (Elsevier, 2024-10-01) Posso, Cristian; Molina-Villegas, Juan Camilo; Ballesteros Ortega, Jorge Eliecer; Universidad EAFIT; University of Central Florida; Mecánica Aplicada
    This paper presents a method to obtain the exact closed-form solution for the static analysis of Timoshenko beams and frames on elastic Winkler foundation, subjected to arbitrary external loads and bending moments. The solution is derived using the Green’s Functions Stiffness Method (GFSM), a novel mesh reduction method that combines the strengths of the Stiffness Method (SM) and Green’s Functions (GFs). By incorporating the core concepts of the SM, the GFSM exhibits similarities to the Finite Element Method (FEM), including the use of shape functions, stiffness matrices, and fixed-end forces. The application of GFs facilitates the derivation of analytical expressions for displacement and internal force fields for arbitrary external loads and bending moments. Three examples are presented: a single-span beam, a two-span beam, and a one-bay, one-story plane frame on elastic Winkler foundations; which demonstrate applicability and efficacy of the method.
  • No hay miniatura disponible
    Publicación
    Closed-form solutions for axially non-uniform Timoshenko beams and frames under static loading
    (Elsevier, 2024-03-23) Molina-Villegas, Juan Camilo; Ballesteros Ortega, Jorge Eliecer; Benítez Soto, Simón; Universidad EAFIT; University of Central Florida; Mecánica Aplicada
    This paper presents the Green’s Functions Stiffness Method (GFSM) for solving linear elastic static problems in arbitrary axially non-uniform Timoshenko beams and frames subjected to general external loads and bending moments. The GFSM is a mesh reduction method that seamlessly integrates elements from the Stiffness Method (SM), Finite Element Method (FEM), and Green’s Functions (GFs), resulting in a highly versatile methodology for structural analysis. It incorporates fundamental concepts such as stiffness matrices, shape functions, and fixed-end forces, in line with SM and FEM frameworks. Leveraging the capabilities of GFs, the method facilitates the derivation of closed-form solutions, addressing a gap in existing methods for analyzing non-uniform reticular structures which are typically limited to simple cases like single-span beams with specific axial variations and loading scenarios. The effectiveness of the GFSM is demonstrated through three practical examples, showcasing its applicability in analyzing non-uniform beams and plane frames, thereby broadening the scope of closed-form solutions for axially non-uniform Timoshenko structures.
  • No hay miniatura disponible
    Publicación
    Prediction of in-vivo iontophoretic drug release data from in-vitro experiments-insights from modeling
    (ELSEVIER SCIENCE INC, 2015-12-01) Simon, L.; Ospina, J.; Ita, K.; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
    A strategy was developed to predict in-vivo plasma drug levels from data collected during in-vitro transdermal iontophoretic delivery experiments. The method used the principle of mass conservation and the Nernst-Planck flux equation to describe molecular transport across the skin. Distribution and elimination of the drug in the body followed a one- or two-compartment open model. Analytical expressions for the relaxation constant and plasma drug concentration were developed using Laplace transforms. The steady-state dermal flux was appropriate for predicting drug absorption under in-vivo conditions only when the time constant in the skin was far greater than its value in the blood compartment. A simulation study was conducted to fully assess the performance of estimations based on the equilibrium flux approximation. The findings showed that the normalized integral of squared error decreased exponentially as the ratio of the two time constants (blood/skin) increased. In the case of a single compartment, the error was reduced from 0.15 to 0.016 when the ratio increased from 10 to 100. The methodology was tested using plasma concentrations of a growth-hormone releasing factor in guinea pigs and naloxone in rats. © 2015 Elsevier Inc. All rights reserved.