scholarly journals Optimal Fire Design of Steel Tapered Portal Frames

2017 ◽  
Author(s):  
Tamás Balogh ◽  
Gergely László Vigh
Keyword(s):  
Structural Optimization ◽  
Conceptual Design ◽  
Structural Safety ◽  
First Order ◽  
Design Concepts ◽  
Optimization Framework ◽  
Reliability Method ◽  
Discrete Nature ◽  
Optimal Configurations ◽  
Fire Design

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.

scholarly journals RESISTANCE FACTOR CALIBRATION FOR PERFORATED COLD-FORMED STEEL COMPRESSION MEMBERS

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Roberta Layra Faragó Jardim ◽  
◽  
Marcilio Sousa da Rocha Freitas ◽  
André Luís Riqueira Brandão ◽  
◽  
...  
Keyword(s):  
Resistance Factor ◽  
Structural Safety ◽  
Security Level ◽  
Limit States ◽  
Safety Level ◽  
Resistance Factors ◽  
First Order ◽  
Reliability Method ◽  
First Order Second Moment ◽  
Cold Formed Steel

Cold-formed Steel profiles are structural profiles widely used in civil construction. They are often manufactured with perforations. The designing can be performed using the direct resistance method. Formulations were adapted by Moen and Schafer (2008) to consider the presence of perforations in these profiles. The objective of this study is to investigate the structural safety of columns with web perforations. The calculation of the resistance capacity was performed using the formulations proposed by the authors. The reliability indexes were determined using the First Order Reliability Method (FORM), First Order Second Moment (FOSM) and Monte Carlo Method (MCM), which are reliability methods for the Load and Resistance Factor Design (LRFD) and Limit States Design (LSD) philosophies. Following the same criteria performed by AISI S100, the resistance factors were obtained from the FOSM method. Based on the results, it was found that the desired security level for the LSD philosophy was not achieved. The calculated resistance factors are predominantly lower than the target. However, for the LRFD philosophy, the safety level was achieved, and the resistance factors were higher than the target.

scholarly journals Metrics for Measuring Sustainable Product Design Concepts

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3469
Author(s):  
Ji Han ◽  
Pingfei Jiang ◽  
Peter R. N. Childs
Keyword(s):  
Product Design ◽  
End Of Life ◽  
Environmental Impacts ◽  
Conceptual Design ◽  
Design Stage ◽  
Sustainable Product Design ◽  
Early Design ◽  
Design Concepts ◽  
Concept Evaluation ◽  
Sustainable Product

Although products can contribute to ecosystems positively, they can cause negative environmental impacts throughout their life cycles, from obtaining raw material, production, and use, to end of life. It is reported that most negative environmental impacts are decided at early design phases, which suggests that the determination of product sustainability should be considered as early as possible, such as during the conceptual design stage, when it is still possible to modify the design concept. However, most of the existing concept evaluation methods or tools are focused on assessing the feasibility or creativity of the concepts generated, lacking the measurements of sustainability of concepts. The paper explores key factors related to sustainable design with regard to environmental impacts, and describes a set of objective measures of sustainable product design concept evaluation, namely, material, production, use, and end of life. The rationales of the four metrics are discussed, with corresponding measurements. A case study is conducted to demonstrate the use and effectiveness of the metrics for evaluating product design concepts. The paper is the first study to explore the measurement of product design sustainability focusing on the conceptual design stage. It can be used as a guideline to measure the level of sustainability of product design concepts to support designers in developing sustainable products. Most significantly, it urges the considerations of sustainability design aspects at early design phases, and also provides a new research direction in concept evaluation regarding sustainability.

Some Important Issues on First-Order Reliability Analysis With Nonprobabilistic Convex Models

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
C. Jiang ◽  
G. Y. Lu ◽  
X. Han ◽  
R. G. Bi
Keyword(s):  
Reliability Analysis ◽  
Reliability Index ◽  
Probability Model ◽  
Mean Value ◽  
Convex Model ◽  
First Order ◽  
Reliability Method ◽  
Complex Engineering ◽  
Mean Value Method ◽  
Form Type

Compared with the probability model, the convex model approach only requires the bound information on the uncertainty, and can make it possible to conduct the reliability analysis for many complex engineering problems with limited samples. Presently, by introducing the well-established techniques in probability-based reliability analysis, some methods have been successfully developed for convex model reliability. This paper aims to reveal some different phenomena and furthermore some severe paradoxes when extending the widely used first-order reliability method (FORM) into the convex model problems, and whereby provide some useful suggestions and guidelines for convex-model-based reliability analysis. Two FORM-type approximations, namely, the mean-value method and the design-point method, are formulated to efficiently compute the nonprobabilistic reliability index. A comparison is then conducted between these two methods, and some important phenomena different from the traditional FORMs are summarized. The nonprobabilistic reliability index is also extended to treat the system reliability, and some unexpected paradoxes are found through two numerical examples.

Reliability approach for the side resistance of piles by means of the total stress analysis (α Method)

2007 ◽  
Vol 44 (11) ◽  
pp. 1378-1390 ◽  
Author(s):  
C. Cherubini ◽  
G. Vessia
Keyword(s):  
Stress Analysis ◽  
Undrained Shear Strength ◽  
Clayey Soils ◽  
Total Stress ◽  
First Order ◽  
Side Resistance ◽  
Reliability Method ◽  
Real Size ◽  
Bored Piles ◽  
Adhesion Factor

The evaluation of the pile–soil adhesion plays a fundamental role in the estimation of the side resistance for total stress analysis. Over the years, researchers have presented proposals for adhesion factor formulations even though only a few of them have shown a certain agreement in numerical and (or) methodological terms. Hence, several real-size experimental analyses have improved the understanding of the pile–soil adhesion phenomenon and mechanism. Nevertheless, the undrained shear strength (cu) values depend on the experimental technique employed. Such results force engineers to make a difficult choice among various formulations. A reliability analysis is performed in this paper to take into consideration the variations in formulations and values of the side resistance of bored piles in clayey soils. This study involves piles having different lengths and diameters, which are supposed to be bored in Matera clays. Such soil is characterized by means of laboratory investigation campaign, and its mechanical and stochastic main features are reported here. Values of reliability index β are calculated by means of the first-order reliability method.

An accuracy analysis method for first-order reliability method

2018 ◽  
Vol 233 (12) ◽  
pp. 4319-4327 ◽  
Author(s):  
Zhenzhong Chen ◽  
Zihao Wu ◽  
Xiaoke Li ◽  
Ge Chen ◽  
Guangfeng Chen ◽  
...  
Keyword(s):  
Structural Reliability ◽  
Nonlinear Problems ◽  
Accuracy Analysis ◽  
Analysis Method ◽  
First Order Reliability Method ◽  
First Order ◽  
Reliability Level ◽  
Reliability Method ◽  
Value Range ◽  
Crashworthiness Design

The first-order reliability method is widely used for structural reliability analysis; however, its accuracy would become worse for nonlinear problems. This paper proposes the accuracy analysis method of the first-order reliability method, which considers the worst cases when using the first-order reliability method and gives the possible value range of the probability of safety. The accuracy analysis method can evaluate the reliability level of the first-order reliability method when the failure surfaces are nonlinear. The calculation formula for the possible value range of the probability of safety is proposed, and its trend as the dimensions and reliability rise is also discussed in this paper. A numerical example and a honeycomb crashworthiness design are presented to validate the accuracy of the first-order reliability method, and the results show that they are located within the possible value range proposed in this paper.

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