Elastic Constitutive Laws and Stability Analyses

In this paper, the influence of several elastic constitutive laws upon the stability analyses of plane trusses is discussed. The chosen laws are connected to the engineering strain, Green’s strain and logarithmic strain concepts. A geometrically exact nonlinear formulation for a truss bar element is developed for each of them and the correspondent tangent stiffness matrices are obtained. The stability analyses of some sample plane trusses are performed by finding the conditions when the determinant of their respective global tangent stiffness matrices is found to be zero. The first example is a symmetric two-bar structure and both limit loads and buckling loads are plotted for the full range of possible initial inclination angles of the bars for the three chosen constitutive laws. A similar truss with an extra vertical bar is studied to discuss possible material instability if Green’s strain concept is adopted

STRONG MOTION TIME-HISTORY FOR STORAGE TANKS BY USING SEVEN DIFFERENT EARTHQUAKE ACCELEROGRAMS

This paper aims to describe the seismic performance of circular oil storage tanks by calculating the total base shear induced from each seismic horizontal acceleration: magnitude varies between 6 and 8, and depth from 0 km to 35 km. Time-history analysis has been made considering that the stresses are not excited at the same time. The equations used are in accordance to Eurocode 8 and for the response spectra seven different accelerograms of seven different stations have been considered. The main objective is to provide an approach that describes many important seismic actions in tanks as well as their implications for the dynamic analysis of structural instability. Despite the area of oil being considerably discussed, there are few studies on this topic in Brazil. The results of the analysis show the importance to study the dynamic action and its effects. Keywords: Response time-history, Seismic action, Oil storage tanks, Structural engineerin

Analytical and Mathematical Analysis of the Vibration of Structural Systems Considering Geometric Stiffness and Viscoelasticity

For a complete analysis of vibration, the stiffness of a structure must have two characteristics: one corresponding to conventional stiffness and the other to the geometric stiffness. Thus, the total stiffness takes form where the model to be used to represent any behavior of the material is introduced to the first part via the modulus of elasticity. The second is the geometric stiffness, through which it is possible to linearize a geometric nonlinear problem. To consider both aspects, a mathematical model based on the Rayleigh method has been elaborated. Two systems were numerically studied. First, the occurrence of resonance in the vibration of a prestressed reinforced concrete beam has been investigated. The results indicated resonant and non-resonant schemes between the natural frequency of the beam and the frequency of the engine. To the second system, the first natural frequency of a slender, 40-m-high concrete mobile phone mast, was calculated, and an evaluation of the structural collapse was performed. To the both systems, the cross section of reinforced concrete was treated by the theory for the homogenized section in order to consider the presence of the steel, and the viscoelasticity of the concrete was taken into account through a three-parameter rheological model

MODELING A ROCKET ELASTIC STRUCTURE AS A BECK’S COLUMN UNDER FOLLOWER FORCE

It is intended, in this paper, to develop a mathematical model of an elastic space rocket structure as a Beck’s column excited by a follower (or circulatory) force. This force represents the rocket motor thrust that should be always in the direction of the tangent to the structure deformed axis at the base of the vehicle. We present a simplified two degree of freedom rigid bars discrete model. Its system of two second order nonlinear ordinary differential equations of motion are derived via Lagrange’s energy method, allowing for a general understanding of the main characteristics of the problem. The proposed equations consider up to third order (cubic) inertia, stiffness andforcing terms. Among other rich nonlinear dynamic behavior of this model, depending on parameters and initial conditions choices, either stable or unstable limit cycle solutions are possible. The unstable solution is, of course, an interesting simple example of flutter instability. Keywords: Beck’s column, follower force, nonlinear dynamics, flutter

Effects of an aquagym training in postmepausal women

Los cambios en la composición corporal de mujeres posmenopáusicas, principalmente, el aumento del tejido adiposo visceral y abdominal, son indicadores de enfermedades metabólicas y cardiovasculares. Veintiuna mujeres posmenopáusicas participaron en un programa de 16 semanas de clases de Aquagym. Las variables analizadas fueron la circunferencia de cintura (CCi), la circunferencia de cadera (CCa), el índice cintura-cadera (ICC), el diámetro sagital abdominal (DAS) y el tejido adiposo visceral (TAV). El tratamiento estadístico empleado fue una prueba t para comparar entre los grupos y el test de Goodman para analizar las alteraciones en la clasificación cualitativa del ICC. Se han obtenido reducciones significativas (p≤0,05) para todas las variables medidas después de la intervención de ejercicio. El programa de Aquagym fue capaz de reducir el tejido adiposo visceral y abdominal, además de disminuir el riego para el desarrollo de enfermedades de enfermedades metabólicas y cardiovasculares, constituyendo una estrategia eficaz para tratar la obesidad central.Changes in body composition in postmenopausal women and increased abdominal visceral adipose tissue are markers of metabolic and cardiovascular diseases. Twenty-one postmenopausal women participated in Aquagym's classes during 16 weeks. The analyzed variables included measures of waist circumference (WC), hip circumference (HC), waist-hip ratio (ICC), abdominal sagittal diameter (ASD) and intra-abdominal adipose tissue (IAAT). Statistical treatment was used as the paired t test for comparisons between the groups before and after Aquagym practice and Goodman`s test to analyze the changes in the qualitative classification of the ICC. Significant reductions (p≤0.05) have been found for all measured variables. Aquagym program was able to reduce the abdominal visceral adipose tissue, thus decreasing the risk of developing metabolic and cardiovascular diseases, constituting an effective strategy to deal with central obesity

Alternativas tecnológicas para o aproveitamento de resíduos gerados durante o processo de produção de ferro gusa voltadas para utilização agroflorestal: estudo de viabilidade técnica e econômica.

Estudo de viabilidade técnica dos resíduos; Caracterização química dos resíduos; Testes exploratórios com os resíduos; Resultados alcançados; Escória de siderurgia; Pó de balão; Estudo de viabilidade econômica e comercial dos resíduos siderúrgicos; Caracterização dos produtos; Estimativa das quantidades produzidas e demanda potencial dos resíduos; Análise de custo dos insumos; Análise comparativa dos custos da escória em relação ao calcário; Análise comparativa dos custos do pó de balão em relação a adubos orgânicos; Potencialidades de mercado.bitstream/item/27645/1/Doc333.pdfDisponível também on-line

Controle genético do teor proteico nos grãos e de caracteres agronômicos em milho cultivado com diferentes níveis de adubação nitrogenada.

O objetivo deste trabalho foi determinar o controle genético do teor de proteína em grãos e de caracteres agronômicos de milho (Zea mays) cultivado com diferentes níveis de adubação nitrogenada