Feszített kötél- és ponyvaszerkezetek optimalizálása = Optimization of prestressed cable-net and membrane structures

Az ívtartókra feszített kötél- és ponyvaszerkezetek gazdaságos megoldást kínálnak nagy területű létesítmények belső alátámasztás nélküli lefedésére. Egy szabadalom, a csigasoros függesztőrendszer ezeket a szerkezeteket még hatékonyabbá teszi és megnöveli a statikailag lehetséges fesztávot az ívtartókban fellépő hajlítónyomaték minimalizálásával. A kutatás során ki kellett dolgozni egy numerikust eljárást a csigasorok számítására és az új csigasor elemet be kellett illeszteni a teljes szerkezet számítását végző, dinamikus ellazításon alapuló nemlineáris eljárásba. A kidolgozott program segítségével különböző ívtartókra feszített függőtetőket vizsgáltunk. A csigáknál fellépő súrlódás, az ívtartók számának, fesztávjának, görbületének hatását elemeztük a szerkezetek statikai viselkedésére. Az ívtartókban fellépő igénybevételek, a függőtetőben fellépő erők és a függőtető elmozdulásai kerültek összehasonlításra a különböző geometriájú és topológiájú szerkezetek esetén. A legfontosabb eredmény az, hogy a numerikus vizsgálatok igazolták, hogy csigasoros függesztés segítségével jelentősen csökkenthető az ívtartókban fellépő nyomaték. | Arch-supported tensile structures provide a very efficient way to cover large areas without inner support. An invention, the block and tackle suspension system can make this type of structures even more efficient and increase the possible span of the supporting arches as well by minimizing the bending moment of the supporting arches. A numerical procedure has been developed for the numerical analysis of the block and tackle and it has been integrated into the large displacement analysis of the whole tensile structure. The procedure is based on the dynamic relaxation method. By the help of the developed numerical procedure arch supported tensile roofs have been analysed. The effect of the coefficient of friction between the pulley and its shaft, the number, the free span and the curvature of the supporting arches on the static behaviour of the structure have been analysed. The internal forces of the supporting arches, the forces in the tensile roof and the displacements of the roof have been compared in the case of structures with different geometry and different topology. The results show that the block and tackle suspension system can reduce the bending moments in the supporting arches significantly

Stress analysis of inflated polyhedra for the 32-panel soccer ball

This paper presents a stress analysis of a membrane modelling the 32-panel soccer ball. The most popular soccer ball type and three variations are considered. The discretized mesh of the stress-free polyhedron-shaped membrane is subjected to internal pressure and the sphericity and the stress distribution of the models are compared

STRESS ANALYSIS OF INFLATED POLYHEDRA FOR THE 32-PANEL SOCCER BALL

This paper presents a stress analysis of a membrane modelling the 32-panel soccer ball. The most popular soccer ball type and three variations are considered. The discretized mesh of the stress-free polyhedron-shaped membrane is subjected to internal pressure and the sphericity and the stress distribution of the models are compared

PARTIAL COVERING OF A CIRCLE BY EQUAL CIRCLES. PART I: THE MECHANICAL MODELS

How must n equal circles of given radius be placed so that they cover as great a part of the area of the unit circle as possible? To analyse this mathematical problem, mechanical models are introduced. A generalized tensegrity structure is associated with a maximum area configuration of the n circles, whose equilibrium configuration is determined numerically with the method of dynamic relaxation, and the stability of equilibrium is investigated by means of the stiffness matrix of the tensegrity structure. In this Part I, the principles of the models are presented, while an application will be shown in the forthcoming Part II

Computational Wind Engineering of a Mast-supported Tensile Structure

The Computational Fluid Dynamics (CFD) analysis of wind actions on a cube and on the hyperbolic surface of a mast-supported tensile structure is presented. As standard in Computational Wind Engineering (CWE) the models were analyzed in incompressible fluid flow. For the CWE study, the Reynolds-Averaged Navier-Stokes (RANS) equations were solved with two of the most widely used turbulence models, Realizable k−ε and SST k−ω. The validation of the CWE models included the comparison of the numerically determined pressure coefficient fields with existing Wind Tunnel test (WT) results. The membrane forces and the displacements of the membrane roof were calculated by the Dynamic Relaxation Method (DRM), corresponding to the different (CWE and WT) pressure coefficient fields of the tensile roof. In addition to the pressure coefficients, the membrane force and the displacement fields and their significant values were also compared. It is presented that both turbulence models provide a suitable solution; the pressure coefficients and the membrane forces are also acceptable approaches to the experimental results

Feszített ponyvaszerkezetek szabásmintáinak összehasonlító elemzése

Cutting patterns of a simple form of a tent, so called 'Chinese hat', were analyzed in the paper. Stress distributions in prestressed membrane structures, according to cutting patterns prepared by the help of various numerical methods, were compared. A recently developed computer program, based on the dynamic relaxation method was used for the numerical analysis. The close connection between the shrinking of the cutting pattern and the stressing process of the tent was shown. Shrinking of the cutting pattern means that the stress free size of the tent is smaller than the boundaries of the theoretical shape, the tent structure achieves its shape and prestress during stressing on the original edges. The shrinking can be uniform or proportional to the stresses in the theoretical shape. The cutting pattern prepared without shrinking, produces tent surface that fits to the original boundaries without any strain and stress. To get prestress in the structure, the boundary conditions have to be changed.  Cutting patterns prepared by the help of different methods and based on various models, without shrinking and with different shrinking, were analyzed. After the short demonstration of the different methods, the stresses in warp and weft directions were compared in the different construction shapes