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New optimum distribution of lateral strength of shear-type buildings for uniform damage
Jesús Donaire-Á vila,Andrea Lucchini,Amadeo Benavent-Climent,Fabrizio Mollaioli 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.3
The seismic design of conventional frame structures is meant to enhance plastic deformations at beam ends and prevent yielding in columns. To this end, columns are made stronger than beams. Yet yielding in columns cannot be avoided with the column-to-beam strength ratios (about 1.3) prescribed by seismic codes. Preventing plastic deformations in columns calls for ratios close to 4, which is not feasible for economic reasons. Furthermore, material properties and the rearrangement of geometric shapes inevitably make the distribution of damage among stories uneven. Damage in the i-th story can be characterized as the accumulated plastic strain energy (Wpi) normalized by the product of the story shear force (Qyi) and drift (yi) at yielding. Past studies showed that the distribution of the plastic strain energy dissipation demand, Wpi /Wpj, can be evaluated from the deviation of Qyi with respect to an “optimum value” that would make the ratio Wpi/(Qyiyi) —i.e. the damage— equal in all stories. This paper investigates how the soil type and ductility demand affect the optimum lateral strength distribution. New optimum lateral strength distributions are put forth and compared with others proposed in the literature.
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E. ALCALÁ,F. BADEA,Á. MARTIN,F. APARICIO 한국자동차공학회 2013 International journal of automotive technology Vol.14 No.5
The analysis of structures with finite elements methods (FEM) represents a widely spread technique. For large tubular structures similar to the buses and coaches upper structures, beam type elements are utilized due to the fact that these elements provide satisfactory results at relatively reduced computational performances. However the beam type elements have a main disadvantage determined by the fact that the modeled joints have an infinite rigid behavior. This shortcoming determines a stiffer behavior of the modeled structures which translates into an error source for the structural simulations (up to 45%). To overcome this problem, a simple methodology was conceived and an alternative optimized equivalent beam model obtained. The methodology studies the behavioral characteristics of beam modeled T-junctions determining their limitations and comparing them to equivalent T-junctions modeled with shell and volume elements. This way an improved Tjunction has been obtained, in which the behavioral error was reduced to less than 5%. Furthermore the FEM obtained results were validated with real T-junctions.
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D. Santillán,E. Salete,M.Á. Toled,A. Granados 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.1
Thermal effects are significant loads for assessing concrete dam behaviour during operation. A new methodology to estimate thermal loads on concrete dams taking into account processes which were previously unconsidered, such as: the evaporative cooling, the night radiating cooling or the shades, has been recently reported. The application of this novel approach in combination with a three-dimensional finite element method to solve the heat diffusion equation led to a precise characterization of the thermal field inside the dam. However, that approach may be computationally expensive. This paper proposes the use of a new one-dimensional model based on an explicit finite difference scheme which is improved by means of the reported methodology for computing the heat fluxes through the dam faces. The improved model has been applied to a case study where observations from 21 concrete thermometers and data of climatic variables were available. The results are compared with those from: (a) the original one-dimensional finite difference model, (b) the Stucky-Derron classical one-dimensional analytical solution, and (c) a three-dimensional finite element method. The results of the improved model match well with the observed temperatures, in addition they are similar to those obtained with (c) except in the vicinity of the abutments, although this later is a considerably more complex methodology. The improved model have a better performance than the models (a) and (b), whose results present larger error and bias when compared with the recorded data.
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CFD practical application in conceptual design of a 425 m cable-stayed bridge
F. Nieto,S. Hernández,J.Á. Jurado,A. Baldomir 한국풍공학회 2010 Wind and Structures, An International Journal (WAS Vol.13 No.4
CFD techniques try to find their way in the bridge engineering realm nowadays. However, there are certain fields where they offer superior performance such as conceptual bridge design and bidding design. The CFD studies carried out for the conceptual design of a 425 m length cable-stayed bridge are presented. A CFD commercial package has been employed to obtain for a set of cross-sections the aerodynamic coefficients considering 2D steady state. Additionally, for those cross-sections which showed adequate force coefficients, unsteady 2D simulations were carried out to detect the risk of vortex shedding. Based upon these computations the effect on the aerodynamic behavior of the deck cross-section caused by a number of modifications has been evaluated. As a consequence, a new more feasible cross-section design has been proposed. Nevertheless, if the design process proceeds to a more detailed step a comprehensive set of studies, comprising extensive wind tunnel tests, are required to better find out the aerodynamic bridge behavior.
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