Shape optimization of structures under earthquake loadings (original) (raw)
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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.
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...
All loads in the real world act dynamically on structures. Since dynamic loads are extremely dicult to handle in analysis and design, static loads are utilized with dynamic factors. The dynamic factors are generally determined from design codes or experience. Therefore, static loads may not give accurate solutions in analysis and design. An analytical method based on modal analysis in ®nite element analysis is proposed for the transformation of dynamic loads into equivalent static load sets. Equivalent static load sets are calculated to generate an identical displacement ®eld in a structure with that from dynamic loads at a certain time. The process is derived mathematically and evaluated. The method is veri®ed through numerical tests. Various characteristics are identi®ed to match the dynamic and static behaviors. For example, the opposite direction of a dynamic load should be considered due to the vibrational response. A dynamic load is transformed into multiple equivalent static load sets according to the number of critical times. The places of the equivalent static loads can be dierent from those of the dynamic loads. An optimization method is de®ned to use the equivalent static loads. The developed optimization process has the same eect as dynamic optimization which uses the dynamic loads directly. Standard examples are solved and the results are discussed.
Dynamic Optimization of Structures Subjected to Earthquake
International Journal of Engineering and Technology, 2016
To reduce the overall time of structural optimization for earthquake loads two strategies are adopted. In the first strategy, a neural system consisting self-organizing map and radial basis function neural networks, is utilized to predict the time history responses. In this case, the input space is classified by employing a self-organizing map neural network. Then a distinct RBF neural network is trained in each class. In the second strategy, an improved genetic algorithm is employed to find the optimum design. A 72-bar space truss is designed for optimal weight using exact and approximate analysis for the El Centro (S-E 1940) earthquake loading. The numerical results demonstrate the computational advantages and effectiveness of the proposed method.
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
Large scale structural optimization: Computational methods and optimization algorithms
Archives of Computational Methods in Engineering, 2001
The objective of this paper is to investigate the efficiency of various optimization methods based on mathematical programming and evolutionary algorithms for solving structural optimization problems under static and seismic loading conditions. Particular emphasis is given on modified versions of the basic evolutionary algorithms aiming at improving the performance of the optimization procedure. Modified versions of both genetic algorithms and evolution strategies combined with mathematical programming methods to form hybrid methodologies are also tested and compared and proved particularly promising. Furthermore, the structural analysis phase is replaced by a neural network prediction for the computation of the necessary data required by the evolutionary algorithms. Advanced domain decomposition techniques particularly tailored for parallel solution of large-scale sensitivity analysis problems are also implemented. The efficiency of a rigorous approach for treating seismic loading is investigated and compared with a simplified dynamic analysis adopted by seismic codes 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. The numerical tests presented demonstrate the computational advantages of the discussed methods, which become more pronounced in large-scale optimization problems. c 2001 by CIMNE, Barcelona (Spain).
A New Energy-Based Structural Design Optimization Concept under Seismic Actions
Frontiers in Built Environment
A new optimization concept is introduced which involves the optimization of non-linear planar shear buildings by using gradients based on equivalent linear structures, instead of the traditional practice of calculating the gradients from the non-linear objective function. The optimization problem is formulated as an equivalent linear system of equations in which a target fundamental eigenfrequency and equal dissipated energy distribution within the storeys of the building are the components of the objective function. The concept is applied in a modified Newton-Raphson algorithm in order to find the optimum stiffness distribution of two representative linear or non-linear MDOF shear buildings, so that the distribution of viscously damped and hysteretically dissipated energy, respectively, over the structural height is uniform. A number of optimization results are presented in which the effect of the earthquake excitation, the critical modal damping ratio, and the normalized yield inter-storey drift limit on the optimum stiffness distributions is studied. Structural design based on the proposed approach is more rational and technically feasible compared to other optimization strategies (e.g., uniform ductility concept), whereas it is expected to provide increased protection against global collapse and loss of life during strong earthquake events. Finally, it is proven that the new optimization concept not only reduces running times by as much as 91% compared to the classical optimization algorithms but also can be applied in other optimization algorithms which use gradient information to proceed to the optimum point.
Structural optimization: A tool for evaluating seismic design procedures
Engineering Structures, 2006
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 linear and nonlinear time-history analysis are adopted. In order to simulate seismic actions realistically, suites of both natural and artificial ground motion records are used. Furthermore, it is shown that structural optimization is a very efficient design tool that can be applied on realistic buildings. For the solution of the optimization problem, a highly efficient evolutionary algorithm is adopted. The results obtained demonstrate the advantages of using more elaborate seismic design procedures, based on a detailed simulation of the structural behaviour and the applied seismic loading, as opposed to the commonly used simplified design approaches. Designs with less material cost combined with better seismic performance are obtained when nonlinear time-history analysis is performed.
Topology optimization for the seismic design of truss-like structures
Computers & Structures, 2011
A practical optimization method is applied to design nonlinear truss-like structures subjected to seismic excitation. To achieve minimum weight design, inefficient material is gradually shifted from strong parts to weak parts of a structure until a state of uniform deformation prevails. By considering different truss structures, effects of seismic excitation, target ductility and buckling of the compression members on optimum topology are investigated. It is shown that the proposed method could lead to 60% less structural weight compared to optimization methods based on elastic behaviour and equivalent static loads, and is efficient at controlling performance parameters under a design earthquake.