Pareto-based optimum seismic design of steel frames (original) (raw)
Related papers
Seismic Optimum Design of Steel Structures Using Gradient- Based and Genetic Algorithm Methods
Optimum design of structures under time-variable loadings is a difficult task. Time-dependent behavior of constraints and cost of gradients calculations could be mentioned when applying time history loadings in the optimization problems. To overcome these difficulties, the response spectra as a seismic demand are used instead of using time history acceleration in the structural modeling. In this paper, the P-Delta effects are considered in the finite-element modeling of the frames. Furthermore, many practical constraints are included in the optimization formulation according to the Iranian national building code (Standard N. 2800). The developed MATLAB-based computer program is utilized for optimization of the low, intermediate-and relatively high-rise braced and un-braced steel frames. The obtained results of sequential quadratic programing (SQP) method are compared with the results of genetic algorithm (GA) technique for guarantying the global optimal designs. Because of the inexpensive costs of SQP method in comparison with genetic algorithm technique , SQP method could be confidently applied for obtaining the global optimum designs of the steel frames. Keywords Seismic optimum design Á Steel frames Á Response spectrum analysis Á Sequential quadratic programming (SQP) Á Genetic algorithm (GA)
Scientia Iranica
The main problem in performance-based structures is the extremely high computational demand of time-history analyses. In this paper, an e�cient framework is developed for solving the performance-based multi-objective optimal design problem considering the initial cost and the seismic damage cost of steel moment-frame structures. The Non-dominated Sorting Genetic Algorithm (NSGA-II) is employed as the optimization algorithm to search the Pareto optimal solutions. For improving the time e�ciency of the solution algorithm, the Generalized Regression Neural Network (GRNN) is utilized as the meta-model for �tness approximation, and a speci�c evolution control scheme is developed. In this scheme, in order to determine which individuals should be evaluated using the original �tness function and which by the meta-model, the Fuzzy C-Mean (FCM) clustering algorithm is used to choose the competent individuals rather than choosing the individuals randomly. Moreover, the computational burden of ...
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.
Structural optimization procedures under seismic loading
The purpose of this work is twofold. The first objective is to present robust and efficient methodologies for performing structural optimum design of steel frames under seismic loading with deterministic and/or probabilistic constraints. The second objective is to consider the impact of future earthquakes on the design adopted using an estimation of the life cycle cost of the structure.
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...
Ant colony algorithm is employed to find the optimum design of steel type, Ordinary Moment Resisting Frames (OMRF), under dead loads and earthquake forces calculated from modal spectral analysis. Due to the proportionality of structural Eigenperiod with the resultant seismic loads, multi-objective weight minimization and Eigenperiod maximization are processed. The structure is under strength and serviceability constraints. All design requirements are corresponding to Uniform Building Code (UBC) and Allowable Stress Design (ASD) codes of practice of American Institute of Steel Construction (AISC). Multi-Objective Ant Colony Optimization (MOACO) was applied to obtain a pareto-based optimization solution. Also the Genetic Algorithm (GA) was employed for means of comparison.
Optimal seismic-resistant design of a planar steel frame
Earthquake Engineering & Structural Dynamics, 1983
This paper illustrates the design of a four-storey, three-bay, moment-resisting, planar steel frame. Non-linear step-by-step integration is used as the analysis technique within the design process itself rather than as a check at the end of the design process.
OPTIMUM DESIGN OF SPACE FRAMES UNDER SEISMIC LOADING
International Journal of Structural Stability and Dynamics, 2001
The objective of this paper is to perform structural optimization under seismic loading. Combinatorial optimization methods and in particular algorithms based on Evolution Strategies are implemented for the solution of large-scale structural optimization problems under seismic loading. In this work the efficiency of a rigorous approach in treating dynamic loading is investigated and compared with a simplified dynamic analysis in the framework of finding the optimum design of structures with minimum weight. In this context a number of accelerograms are produced from the elastic design response spectrum of the region. These accelerograms constitute the multiple loading conditions under which the structures are optimally designed.
Seismic Design Procedures in the Framework of Evolutionary Based Structural Optimization
Since the early seventies structural optimization has been the subject of intensive research and several different approaches have been advocated for the optimal design of structures in terms of optimization methods or problem formulation. Most of the attention of the engineering community has been directed towards the optimum design of structures under static loading conditions with the assumption of linear elastic structural behaviour. For a large number of real-life structural problems assuming linear response and ignoring the dynamic characteristics of the seismic action during the design phase may lead to structural configurations highly vulnerable to future earthquakes. Furthermore, seismic design codes suggest that under severe earthquake events the structures should be designed to deform inelastically due to the large intensity inertia loads imposed. The objective of this work is to evaluate various design procedures adopted by seismic codes and their influence on the performance of real-scale structures under an objective framework provided by structural optimization. Several studies have appeared in the literature where seismic design procedures based on non-linear response (e.g. [1,2]) are presented and compared. However, this task can be accomplished in a complete and elaborate manner only in the framework of structural optimization, where the designs obtained with different procedures can be directly evaluated by comparing the value of the objective function of the optimization problem and the seismic performance of the optimum solution achieved. In this work evolutionary methods are implemented [3–5] to address the optimization problem and replace the conventional trial and trial and adjustmentbased procedures