Structural optimization procedures under seismic loading (original) (raw)
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Robust seismic design optimization of steel structures
Structural and Multidisciplinary Optimization, 2007
Stochastic performance measures can be taken into account, in structural optimization, using two distinct formulations: robust design optimization (RDO) and reliability-based design optimization (RBDO). According to a RDO formulation, it is desired to obtain solutions insensitive to the uncontrollable parameter variation. In the present study, the solution of a structural robust design problem formulated as a two-objective optimization problem is addressed, where cross-sectional dimensions, material properties and earthquake loading are considered as random variables. Additionally, a two-objective deterministic-based optimization (DBO) problem is also considered. In particular, the DBO and RDO formulations are employed for assessing the Greek national seismic design code for steel structural buildings with respect to the behavioral factor considered. The limit-state-dependent cost is used as a measure of assessment. The stochastic finite element problem is solved using the Monte Carlo Simulation method, while a modified NSGA-II algorithm is employed for solving the two-objective optimization problem.
Seismic Design of Steel Moment-Resisting Frame Structures Using Multiobjective Optimization
Earthquake Spectra, 2005
Design of seismic-resistant civil structural systems necessitates a balanced minimization of two general conflicting objective functions: the short-term construction investment and the long-term seismic risk. Many of the existing seismic design optimization procedures use single objectives of either the traditional minimum material usage (weight or cost) or the recent minimum expected life-cycle cost, while imposing constraints from relevant code specifications as well as additional seismic performance requirements. The resulting single optimized structural design may not always perform satisfactorily in terms of other important but competing merit objectives; the designer's individual risk-taking preference is not explicitly integrated into the design process. This paper presents a practical and general framework for design optimization of code-compliant seismic-resistant structures. Multiple objective functions, which reflect material usage, initial construction expenses, degr...
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Structural Optimization For Seismic Design
2002
Structural Optimization For Seismic Design Structural Seismic Design Optimization and Earthquake Engineering: Formulations and Applications focuses on the research around earthquake engineering, in particular, the field of implementation of optimization algorithms in earthquake engineering problems. Structural Seismic Design Optimization and Earthquake ... Their topics include discrete variable structural optimization of systems under stochastic earthquake excitation, assessing the damage in inelastic structures under simulated critical earthquakes, and overall conceptual seismic design and local seismic capacity design for bridges..." -Book News Inc., Research Book News, 2012 Structural Seismic Design Optimization and Earthquake ... The objective of this paper is to evaluate seismic design procedures for three-dimensional (3D) frame structures using structural optimization methodologies. The evaluation is based on European seismic design code, where procedures based on both li...
An overview to structural seismic design optimisation frameworks
Computers & Structures, 2011
The application of the performance-based seismic design concept using alternative problem formulations is presented in this work. The formulations discussed, are implemented within an automated structural design framework using a metaheuristic optimisation algorithm. Such frameworks are able to accommodate any advanced -linear or nonlinear, static or dynamic-analysis procedure and thus replace, the conventional trial-and-error process. The formulations presented treat the seismic design problem in a deterministic or a probabilistic manner, with one or more objectives that represent the initial cost or the cost of future earthquake losses that may occur during the lifetime of a structural system. The implementations presented are all consistent with the performance-based design concept and take into consideration the structural response at a number of limit-states, from serviceability to collapse.
Computers & Structures, 1991
The objective of this paper is to develop a probabilistic multi-objective optimal design method for concentrically braced steel frames, including the design earthquake via a dynamic ARMA (Auto-Regressive Moving Average) model. The features of this design method are: (i) to make it possible to incorporate inherent uncertain features of design earthquakes into the design process itself through the dynamic ARMA model, (ii) to provide a simplified design formula for a preliminary design of concentrically braced steel frames based upon the concept of decomposed stiffness design, and (iii) to facilitate the formulation of a new probabilistic multi-objective optimal design problem aimed at finding the design with the minimum level of designer's dissatisfaction. In this optimal design problem, constraints and objectives are handled in a unit&i manner after a feasible design is obtained. Two design examples are presented to demonstrate the validity of this design method. Finally, the generality and practicality of the design method are assessed.
Recent advances in reliability-based structural optimization under earthquake loading
2005
In this paper a robust and efficient methodology is presented for treating large-scale reliability-based, structural optimization problems under seismic loads using the pushover analysis method. The optimization problem is solved with the Evolution Strategies method, while the reliability analysis is carried out with the Monte Carlo simulation method. In order to reduce the excessive computational cost of the reliability-based optimization process the repeated structural analyses that are required during the Monte Carlo simulations are replaced by an efficient artificial neural network approximation scheme. 2. Keywords: structural optimization, reliability analysis, Monte Carlo, evolutionary computation, artificial neural networks.
Optimal design of steel frames subject to gravity and seismic codes' prescribed lateral forces
Structural Optimization
Allowable stress design of two-dimensional braced and unbraced steel frames based on AISC specifications subject to gravity and seismic lateral forces is formulated as a structural optimization problem. The nonlinear constrained minimization algorithm employed is the feasible directions method. The objective function is the weight of the structure, and behaviour constraints include combined bending and axial stress, shear stress, buckling, slenderness, and drift. Cross-sectional areas are used as design variables. The anylsis is performed using stiffness formulation of the finite element analysis method. Equivalent static force and response spectrum analysis methods of seismic codes are considered. Based on the suggested methodology, the computer program OPTEQ has been developed. Examples are presented to illustrate the capability of the optimal design approach in comparative study of various types of frames subjected to gravity loads and seismic forces according to a typical code.
Pareto-based optimum seismic design of steel frames
The primary objective of this work is to introduce the idea of using Pareto optimal solutions (POS) for the computation of relationships among the factors involved in seismic design of skeletal steel frames. To verify the capability of this concept, multi-objective optimisation is applied and the relations among total skeletal weight, resultant seismic base shear, maximum lateral displacement and first eigen period of the structure are investigated. Due to the importance of structural safety and for economical reasons, due to its intrinsic conflicting manner, investigation of POS for minimisation of skeletal weight against minimisation of maximum lateral displacement of the structure is also considered. For this purpose, the fast non-dominated sorting genetic algorithm is applied to compute POS. After computing related Pareto designs, they are used to determine relationships among design factors. The design of an ordinary moment-resisting frame is considered under gravitational dead loads and seismic loads in which lateral earthquake forces are calculated from modal spectral analysis. The structures are under strength and serviceability constraints. All design requirements correspond to the uniform building code and to allowable stress design code of practice of the American Institute of Steel Construction. The effectiveness of the proposed method is verified using some examples.