System Response Quantity Research Articles

Computational Evaluation of Thermal Response of Open-Cell Foam With Circular Pore

Abstract The evaluation of effective material properties in heterogeneous materials (e.g., composites or multicomponent structures) is critically relevant to a wide spectrum of applications, including nuclear power, electronic packaging, flame retardants, hypersonics, and gas turbine power. The work described in this paper is centered around the numerical assessment of the thermal behavior of porous materials obtained from finite element thermal modeling and simulation. Two-dimensional, steady-state analyses were performed on unit cells with centered, circular pores using a second-order accurate Galerkin finite element method (FEM). The effective thermal conductivities of the porous systems were examined, encompassing a range of porosities from 4.9% to 60.1%. The geometries of the models were generated based on ordered circular pores for each modeled porosity level. The system response quantity (SRQ) under investigation was the dimensionless effective thermal conductivity across the unit cell. The dimensionless effective thermal conductivity was compared across all simulated cases, producing a trend between porosity and effective thermal conductivity. In the presented investigation, the method of manufactured solutions (MMS) was used to perform code verification, and the grid convergence index (GCI) was employed to estimate discretization uncertainty as solution verification. Code verification concluded an approximately second order accurate Galerkin FEM solver. It was found that the introduction of porosity to the unit cell material structure reduces effective thermal conductivity, as anticipated. Numerical results obtained in this study are compared to an analytical solution and to a sample of empirical data. This approach can be readily generalized to study a wide variety of porous solids from ranging from structures at the nanoscale—such as nanocarbon tubes—to structures at macrolevel scales—such as geological features.

Component based Finite Element Design of Seismically Qualified Joints

This paper describes the principles of Component Based Finite Element Modelling (CBFEM) and the system response quantity and application features for design of prequalified joints for seismic applications. The elements are analysed by geometrically and materially non-linear analysis with imperfections (GMNIA). The proper behaviour of components, e.g. of bolts, anchor bolts, welds etc., is treated by introducing components representing its behaviour in term of initial stiffness, ultimate resistance and deformation capacity. To show this process a contribution is prepared, which summarises the history of achievements of FEA application in structural connections. Contribution shows the currents trends in advanced modelling of connection components and differences of the research oriented and design-oriented models. Both have their roles in advanced analyses.

Multi‐Level Joints and Element Design

ABSTRACTThis paper describes the principles multi‐level joints and element design in steel structures. The system response quantity and application features of Component Based Finite Element Method (CBFEM) for design of eccentric gusset plate connection of a truss steel member. Research oriented finite element model (ROFEM) is validated on experiments. The models are analysed by geometrically and materially non‐linear analysis with imperfections (GMNIA). The ROFEM is compared with simplified CBFEM model which includes only the joint. The proper behaviour of components, e.g. of bolts, anchor bolts, welds etc., is treated by introducing components representing its behaviour in term of initial stiffness, ultimate resistance and deformation capacity. To show this process a contribution is prepared, which summarises the history of achievements of FEA application in structural connections. Contribution shows the current trends in advanced modelling of connection components and differences of the research oriented and design oriented FEA models. Both have their roles in advanced analyses. On the eccentric gusset plate connection of diagonal steel member is shown the coming models with coupling of element and its joint design.

Development of good practice guidance for quantification of thermal-hydraulic code model input uncertainty

Taking into account uncertainties is a key issue in nuclear power plant safety analysis using best estimate plus uncertainty methodologies. It involves two main types of treatment depending on the variables of interest: input parameters or system response quantity. The OECD/NEA PREMIUM project devoted to the first type of variables has shown that inverse methods for input uncertainty quantification can exhibit strong user-effect. One of the main reasons was the lack of a clear guidance to perform a reliable analysis. This work is precisely devoted to the development of a first good practice guidance document for quantification of thermal-hydraulic code model input uncertainty. The developments have been done in the framework of the OECD/NEA SAPIUM project (January 2017–September 2019). This paper provides a summary of the main project outcome. Recommendations and open issues for future developments are also given.

00.05: Validation and verification in design of structural steel connections

ABSTRACTThe only way to prove correctness of simulated results by Finite Element Analyse (FEA) is through a methodical System response quantity process. Without this approval are the results of FEA meaningless and cannot be used in design process for making any decisions. The System response quantity consist of validation, which compares the numerical solution with the experimental data, of verification, which compares computational solutions with highly accurate analytical or numerical solution, and of benchmark cases, the examples for check of the software and its user on approved and simplified input and output.In the eighties FEA of structural connection was treated by some researchers as a non‐scientific matter. Two decades later it was already a necessarily extension of experimental and analytical work. Today computational analysis, in particular computational mechanics and fluid dynamics, is commonly used as a catalyst of many research fields and an indispensable design tool. The recommendation for design by advanced modelling in structural steel is ready to be used in Chapter 5 and Annex C of EN 1993‐1‐5:2005 [1]. Development of modern general‐purpose software and decreasing cost of computational resources facilitate this trend. The FEA of structural connection is the coming step in structural steel design. As the computational tools become more readily available and easier to use even by relatively inexperienced engineers the proper procedure should be employed when judging the results of computational analysis.This paper describes the System response quantity for Component Based Finite Element Model (CBFEM) which is a multilevel FEA method to analyse and design connections of steel structures, see [2]. The steel plates in connection are analysed in CBFEM procedure by FEA. The proper behaviour of components is treated by introducing a components representing well its behaviour in term of initial stiffness, ultimate resistance and deformation capacity, of bolts, welds etc. To help with this process is prepared a contribution, which summarises the history of achievements of FEA application in structural connections. Contribution shows the currents trends in advanced modelling of connection components and differences of the research oriented design oriented models. The particular attention is dedicated to design models of generally loaded endplates.

A spectral stochastic element free Galerkin method for the problems with random material parameter

AbstractThis paper presents a spectral stochastic element free Galerkin method (SSEFGM) for the problems involving a random material property. The random material property and resulting system response quantity are represented by a probabilistic spectral expansion techniques (Karhunen–Loeve expansion and Polynomical Chaos series, respectively) and implemented into the element free Galerkin (EFG) analysis. Numerical solutions in 1D linear elastic problem with random elastic modulus are introduced, and compared with those of Monte Carlo simulation (MCS) so as to provide the validation of the proposed approach. The present SSEFGM approach can produce a probabilistic density distribution as well as a first‐ and second‐order statistical moments (mean and variance) of response quantity by a single calculation, which is distinguished from an iterative MCS. Moreover, the method is based on an element free analysis so that there is no need of nodal connectivities, which usually require more time and labourious task than main calculations. Thus the proposed SSEFGM approach can provide an alternative analysis tool for the problems contains a stochastic material property, and demands complex mesh structures. Copyright © 2004 John Wiley & Sons, Ltd.

Optimum Building Design for Forced‐Mode Compliance

A new dynamic system response quantity, referred to as forced‐mode compliance, is introduced for the forced steady‐state vibration of a shear building model subjected to a harmonic ground motion. An optimum design problem subject to the constraints on forced‐mode compliance, on fundamental natural frequency and on minimum stiffnesses is formulated and the necessary and sufficient conditions for global optimality are derived. It is shown theoretically and through numerical examples that the closed form optimal solution is useful not only for straightforward optimum design but also for controlling other significant dynamical characteristics.