Discrete Optimum Design of Planar Steel Curved Roof and Pitched Roof Portal Frames Using Metaheuristic Algorithms

Portal frames are single-story frame buildings including columns and rafters, and their rafters can be either curved or pitched. These are used widely in the construction of industrial buildings, warehouses, gyms, fire stations, agricultural buildings, hangars, etc. The construction cost of these frames considerably depends on their weight. In the present research, the discrete optimum design of two types of portal frames including planar steel Curved Roof Frame (CRF) and Pitched Roof Frame (PRF) with tapered I-section members are presented. The optimal design aims to minimize the weight of these frame structures while satisfying some design constraints based on the requirements of ANSI/AISC 360-16 and ASCE 7-10. Four population-based metaheuristic optimization algorithms are applied to the optimal design of these frames. These algorithms consist of Teaching-Learning-Based Optimization (TLBO), Enhanced Colliding Bodies Optimization (ECBO), Shuffled Shepherd Optimization Algorithm (SSOA), and Water Strider Algorithm (WSA). Two main objectives are followed in this paper. The first one deals with comparing the optimized weight of the CRF and PRF structures with the same dimensions for height and span in two different span lengths (16.0 m and 32.0 m), and the second one is related to comparing the performance of the considered metaheuristics in the optimum design of these portal frames. The obtained results reveal that CRF is more economical than PRF in the fair comparison. Moreover, comparing the results acquired by SSOA with those of other considered metaheuristics reveals that SSOA has better performance for the optimal design of these portal frames

Design optimization of steel building using MINLP

The paper presents the design optimization of the steel building. The structure consists of the main portal frames, which are mutually connected with the purlins. It is proposed that all structural elements are constructed from standard hot rolled IPE sections. The structural optimization is calculated by the mixed-integer non-linear programming approach, MINLP. The dimensioning of steel members is carried out in accordance with the design specifications of Eurocode 3. The Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm, a three-phase MINLP strategy and a special prescreening procedure of discrete alternatives are used for the optimization. In addition to the optimal structural mass, the optimal cross-section sizes of the structural elements, the optimal intermediate distances between the steel frames and the optimal intermediate distances between the purlins and rails were determined. An example of structural optimization is presented at the end of the paper

Optimal fire design of steel tapered portal frames

The development of new and valuable conceptual design concepts based on structural optimization results is the global aim of the presented research in order to assist the industry in economical fire design of steel tapered portal frames. In order to find optimal configurations regarding the life cycle of the structure, a complex, reliability based structural optimization framework has been developed for tapered portal frame structures. Due to the high nonlinearity and discrete nature of the optimality problem, Genetic Algorithm is invoked to find optimal solutions according to the objective function in with the probability of failure is evaluated using First Order Reliability Method. The applied heuristic algorithm ensures that a number of possible alternatives are analysed during the design process. Based on evaluation of the results of a parametric study, new conceptual design concepts and recommendations are developed and presented for steel tapered portal frames used as storage hall related to optimal structural safety, common design practice and optimal structural fire design

Design and optimization of steel portal frames according to Eurocode using genetic algorithm

One of the essential engineer’s jobs is to achieve the most economical technical solutions. Weight optimization is important since it provides a structure that can carry the applied loads in addition to fulfilling the structural requirements. In this project, a Matlab-algorithm has been developed to find the optimum design of steel portal frames according to “Eurocode 3: Design of steel structures” with regard to the weight. To get the final design of the frame, some inputs have to be specified by the user such as the material, the coordinates, the loads and the distribution pattern of the bracings. The algorithm goes through three essential steps before getting the optimal frame: - Analyzing the frame with help of CALFEM-toolbox: In this step, the frame is geometric nonlinearly analyzed due to certain load combination according to the Ultimate Limit State (ULS) and Serviceability Limit State (SLS) criterion. The internal forces and the displacement established and the axial force diagram, shear force diagram, bending moment diagram and the deformed shape of the frame to be calculated and plotted. - Checking the capacity of the frame according to Eurocode: Some constraints with regard to EC should not be violated. These checks may refer to the frame capacity, checking the capacity against the risk of buckling and the deformations which should not be exceed the Serviceability Limit State (SLS) limitations. - Finding the optimal design of the frame using Genetic Algorithm optimization method: Genetic Algorithm (GA) is an iterative searching method based on the evolution of species’ principle. The algorithm repeat the two steps above every iteration cycle trying to find the best design that has the minimum weight without violating the limitations. Since it is an iterative process, the time required to find the optimum design depends on some factors such as the speed of the computer, the number of variables the size of frame mesh etc. The project ends with some testing examples in which a frame with width span of 20 m, and a height of 6.5 m and uniformly distributed loads as snow loads are acting on the roof of the frame. In these examples, the algorithm has been tested to compare the design that have been got in case of fully braced frame, unbraced and by letting the algorithm to find the optimal number and position of the bracings along the frame. Another comparison has been done to see the difference of the design in case of absence /existing of the deformation limitations

Optimization of steel portal frames using meta-heuristic algorithms

Este trabalho propõe e avalia uma metodologia que integra ferramentas de análise e dimensionamento estrutural a algoritmos meta‐heurísticos para o projeto ótimo de pórticos de aço comumente encontrados em edifícios industriais. As seções transversais de pórticos planos de vão único, simétricos e com cobertura inclinada, formados por perfis I soldados, são otimizadas para minimizar o consumo de aço. O dimensionamento é formulado como um problema de otimização não linear com variáveis mistas e incluindo restrições definidas por estados limites últimos e de serviço. O algoritmo de busca harmônica foi superior aos algoritmos genéticos e de enxame de partículas nos experimentos numéricos realizados. A metodologia também foi aplicada com sucesso em estudos paramétricos com diferentes condições de projeto.This work introduces and evaluates a methodology that integrates structural analysis and design tools with meta‐heuristic algorithms for the optimal design of steel portal frames. The cross‐sections of single‐span pitched roof symmetric portal frames, formed by welded I‐shaped members, are optimized for the minimization of steel consumption. The design is formulated as a nonlinear optimization problem with mixed variables and includes constraints defined by ultimate and serviceability limit states. The harmony search algorithm was superior to the genetic algorithm and the particle swarm optimization in the numerical experiments performed. The methodology was also successfully applied in parametric studies with different design conditions

Effect of serviceability limits on optimal design of steel portal frames

The design of hot-rolled steel portal frames can be sensitive to serviceability deflection limits. In such cases, in order to reduce frame deflections, practitioners increase the size of the eaves haunch and / or the sizes of the steel sections used for the column and rafter members of the frame. This paper investigates the effect of such deflection limits using a real-coded niching genetic algorithm (RC-NGA) that optimizes frame weight, taking into account both ultimate as well as serviceability limit states. The results show that the proposed GA is efficient and reliable. Two different sets of serviceability deflection limits are then considered: deflection limits recommended by the Steel Construction Institute (SCI), which is based on control of differential deflections, and other deflection limits based on suggestions by industry. Parametric studies are carried out on frames with spans ranging between 15 m to 50 m and column heights between 5 m to 10 m. It is demonstrated that for a 50 m span frame, use of the SCI recommended deflection limits can lead to frame weights that are around twice as heavy as compared to designs without these limits

Efficient optimum seismic design of reinforced concrete frames with nonlinear structural analysis procedures

Performance - based seismic design offers enhanced control of structural damage for different levels of earthquake hazard. Nevertheless, the number of studies dealing with the optimum performance - based seismic design of reinforced concrete frames is rather limited. This observation can be attributed to the need for nonlinear structural analysis procedures to calculate seismic demands. Nonlinear analysis of reinforced concrete frames is accompanied by high computational costs and require s a priori knowledge of steel reinforcement. To address this issue, previous studies on optimum performance-based seismic design of reinforced concrete frames use independent design variables to represent steel reinforcement in the optimization problem. This approach drives to a great number of design variables , which magnifies exponentially the search space undermining the ability of the optimization algorithms to reach the optimum solutions. This study presents a computationally efficient procedu re tailored to the optimum performance-based seismic design of reinforced concrete frames. The novel feature of the proposed approach is that it employs a deformation-based, iterative procedure for the design of steel reinforcement of reinforced concrete frames to meet their performance objectives given the cross-sectional dimensions of the structural me mbers. In this manner, only the cross-sectional dimensions of structural members need to be addressed by the optimization algorithms as independent design variables. The developed solution strategy is applied to the optimum seismic design of reinforced concrete frames using pushover and nonlinear response-history analysis and it is found that it outperforms previous solution approaches

Impacto de la rigidez de las uniones en el coste global de pórticos a dos aguas de acero

This paper studies the influence of joint stiffness value combinations in gabled steel frames. Twelve different joint stiffness values were combined for the column base, knee joint and ridge joint. Ten different geometries were combined for gabled steel frames (8-20 m span, 3.5-10 m column height and 10-20% roof slope). Finally, three different load levels for snow and wind were considered, with constant values of permanent and maintenance loads. A total of 46656 cases were analyzed using specific software for steel structure design, obtaining in each case the total cost. Graphical cost representation was obtained for each joint stiffness value combination. Joints represent an average of 17% of the total cost of gabled steel frame structures. In general, lower cost structures were obtained with low joint rigidity values. It is possible to reduce the total cost by around 18% on average, with appropriate selection of joint stiffness combinations.En este artículo se presenta un estudio sobre la influencia de la rigidez de las uniones en pórticos a dos aguas de acero. Se combinan doce valores diferentes de rigidez de placa de anclaje, hombro y cumbrera. Se combinan diez geometrías (8- 20 m de luz, 3.5-10 m de altura de pilares y 10-20% de pendiente de cubierta). Se consideran tres niveles de carga de nieve y viento con valores constantes de carga de mantenimiento. Se analizan un total de 46656 supuestos utilizando un programa informático de cálculo de estructuras para obtener en cada caso su coste total. Se obtiene la representación gráfica del coste para cada combinación de rigideces. En general, los costes más bajos de las estructuras se corresponden con valores bajos de rigidez. Es posible reducir el coste total un 18% de media, con la selección apropiada de la combinación de valores de rigidez de las uniones