Analytical Prediction of Steel Grid-Shell Stability and Dynamic Behaviors Using Neural Networks – Part 1

<p>Artificial Intelligence is a cutting-edge technology expanding very quickly into every industry. It has made its way into structural engineering and it has shown its benefits in predicting structural performance as well as saving modelling and experimenting time. This paper is the first one (out of three) of a broader research where artificial intelligence was applied to the stability and dynamic analyzes of steel grid-shells. In that study, three Artificial Neural Networks (ANN) with 8 inputs were independently designed for the prediction of a single target variable, namely: (i) the critical buckling factor for uniform loading (i.e. over the entire roof), (ii) the critical buckling factor for uniform loading over half of the roof, and (iii) the fundamental frequency of the structure. This paper addresses target variable (i). The ANN simulations were based on 1098-point datasets obtained via thorough finite element analyzes.</p> <p>The proposed ANN for the prediction of the critical buckling factor in steel grid-shells under uniform loading yields mean and maximum errors of 1.1% and 16.3%, respectively, for all 1098 data points. Only in 10.6% of those examples (points), the prediction error exceeds 3%. </p>

The list algorithms accuracy characteristics improvement based on Krohn’s algorithm and its modifications

The research of algorithms for uniform loading of devices for homogeneous information processing systems is a very important science-intensive task. An experimental approach was chosen for the research. This is primarily due to the fact that the analytical solution of the distribution problem gives solutions that are far from reality, since it is unable to take into account many factors that affect the computing machine during its operation. The aim of this research is to improve the accuracy characteristics of the list algorithms through the use of heuristic algorithms, such as Krohn’s algorithm and its modifications. This made it possible to obtain a more even distribution of tasks among executive devices, which can be networked workstations, processors or processor cores. The work uses list algorithms, such as the Critical Path algorithm and Pashkeev’s algorithm, as well as heuristic algorithms - Krohn’s algorithm and its modifications. The main idea of the research is to obtain the best suboptimal solution by improving the quality of the resulting distribution. In this case, with the help of the list algorithms, the initial distribution is formed, and its refinement is carried out through the application of the Krohn’s algorithm and its modifications. In fact, in the work, a number of symbiotic algorithms are examined and analyzed. For this, many computational experiments were carried out and a large amount of output data were collected, on the basis of which conclusions were drawn about the effectiveness of the solution obtained for each symbiotic group and for all groups as a whole.

Descriptions of Attack Angle and Ideal Lift Coefficient for Various Airfoil Profiles in Wind Turbine Blade

The angle of attack is highly sensitive to pitch point in the airfoil shape and the decline of pitch point value induces smaller angle of attack, which implies that airfoil profile possessing closer pitch point to the airfoil tip reacts more sensitively to upcoming wind. The method of conformal transformation functions is employed for airfoil profiles and airfoil surfaces are expressed with a trigonometric series form. Attack angle and ideal lift coefficient distributions are investigated for various airfoil profiles in wind turbine blade regarding conformal transformation and pitch point. The conformed angle function representing the surface angle of airfoil shape generate various attack angle distributions depending on the choice of surface angle function. Moreover, ideal attack angle and ideal lift coefficient are susceptible to the choice of airfoil profiles and uniform loading area. High ideal attack angle signifies high pliability to upcoming wind, and high ideal lift coefficient involves high possibility to generate larger electric energy. According to results obtained pitch point, airfoil shape, uniform loading area, and the conformed airfoil surface angle function are crucial factors in the determination of angle of attack.

Parametric study on application of Voronoi patterns in design of 2-D beams

The trend of engineering has been towards modern innovation in designs by maintaining not only the esthetic point of view but also stability and efficiency. In this regard, in this study, one of the nature-inspired structures, Voronoi tessellation, is introduced and applied as a structural configuration in the design of beams. Thus, various models of beams built with Voronoi diagrams are considered. To this end, first, the rules and regulations which govern the structure of Voronoi tessellation will be presented. Then various stages of generating the geometry of Voronoi beams will be described in detail. Considering the logical architectural requirements, the presented models are prepared as 2D-beams with different degrees of uniformity comprising the minimum and maximum Voronoi cells, which will be designed according to guidelines. In the next step, uniform loading under different boundary conditions will be applied to all Voronoi beams, and the results including structural weight, maximum displacement, and load-bearing capacity will be presented. The results of beams designed with Voronoi structures reveal that increasing the size of minimum cell will result in the rise of the maximum displacements as well as load-to-weight ratios and considerably reduce the weight of Voronoi beams but demonstrate sufficient load-bearing capacity. It also proves that as the non-uniformity of cells increases, displacements will grow. In addition, although the weight of samples will reduce, the load-to-weight ratios of the archetypes remain almost constant. Placing more supports for these structures will lead to an improvement in all aspects of design, especially on the response of beams with large spans.

Global Stability Behaviour og Single-Layer Reticulated Domes Created Using a New Nomenclature

The primary objective of the paper is to investigate the post buckled behaviour of the single-layered Kite geometry dome developed using a novel crystallographic parameterisation principle. Both triangulated and non-triangulated domes are evolved based on the crystallographic parameterisation principles. It brings in a unique nomenclature for identifying different tessellations in reticulated single-layer dome configurations. This nomenclature brings in a physical meaning to dome tessellations instead of being called by the inventors such as Schwedler dome etc. In this paper, the effect of surface pattern on the load capacity of dome configuration is demonstrated with the comparison of domes having different surface patterns. The comparison of post-buckling behaviour of two different single-layer dome configurations - Kiewitt dome and Kite dome is presented. Despite having rigid nodal joints, the load capacity of the dome is significantly reduced when subjected to unsymmetrical and collateral loads due to the localised effect of these loads and the increased chance of snap-through compared to symmetrical uniform loading acting all over the structure. The Kite geometry have higher performance under uniform gravity loading with a low rise to span ratio.

INFLUENCE OF EXTERNAL FORCE FACTORS ON THE STRENGTH OF UNIFORMLY LOADED CONSOLE-FIXED PARTS SUBJECT TO ABRASIVE WEAR

The intensity of wear observed in the working parts of machines operating in an abrasive environment largely determines their service life. However, in a number of cases, the downtime of equipment is associated with fractures of the operating elements casued by their abrasion. In this case, the operational state of the product is determined by the tolerable stresses. Theoretical studies on fi nding the mathematical relationships connecting wear and tolerable stresses are thus relevant. In addition, they are general and can be applied to various materials: metal, polymer, and composite ones. The goal of the present research is to make a theoretical study of the infl uence of external force factors on the strength of cantilever-fi xed parts of various geometric shapes in the process of their abrasive wear during the period of operation under uniform loading. In other words, the authors seek to determine the theoretical value of the limiting wear of a part according to the tolerable stresses. As a result of the study, a mathematical expression was obtained to establish the relationship between the maximum tolarable stresses and the value of the limiting wear of a cantilever-fi xed part under uniform loading. This relationship is necessary to analyse the values of the maximum tensile stresses in its sections. It has been established that the maximum tensile stresses are characteristic of the pinch point of the beam, regardless of its shape.