Aspekt promene geometrije pri dejstvu koncentrisane sile u projektovanju montažnih membranskih konstrukcija

Point loads can act on membrane structures; nevertheless, they are rarely checked in the structural analysis. This is a consequence of the fact that there are no precise instructions that would oblige and direct membrane structures designers how to conduct this analysis. The work to create Eurocode for the Structural Design of Tensile Membrane Structures is underway. When this standard comes into force, it will require following Eurocode 1 with regard to actions on membrane structures. This means that point loads will be included in this structural analysis. However, the consequences of point load actions have yet to be investigated. The subject of this doctoral dissertation research is the change of geometry of membrane structures under point load action. The research for this doctoral dissertation is conducted by testing numerical models of membrane structures in software package Sofistik 2016. Parametric analysis is used to find out how much and in which way varying the values of selected parameters changes the geometry of membrane structures under point load action. Nine parameters divided into groups of those which are related to load, membrane material and the supports have been analyzed. A large number of models differing by parameter values has been created. The goal of the research is to find out how the change of values of analyzed parameters affects the changes of geometry, how big is the influence of these parameters, and what is the importance of point loads for changes of geometry of membrane structures. Based on the obtained results, the dependence of changes of geometry under point load on the analized parameters is determined. The results of the research show that the point load can cause larger changes of geometry compared to the area load whose value is taken to be the usual snow load. Since the point load actions are currently almost completely neglected, this result was not expected. Based on this, it can be concluded that the point load actions are very significant, and that it is necessary to further continue the research of point load action on membrane structures

Endonuclease heteroduplex mismatch cleavage for detecting mutation genetic variation of trypsin inhibitors in soybean

The objective of this work was to evaluate the genetic variation of trypsin inhibitor in cultivated (Glycine max L.) and wild (Glycine sofa Siebold & Zucc.) soybean varieties. Genetic variations of the Kunitz trypsin inhibitor, represented by a 21-kD protein (KTI), and of the Bowman-Birk trypsin chymotrypsin inhibitor (BBI) were evaluated in cultivated (G. max) and wild (G. sofa) soybean varieties. Endonuclease heteroduplex mismatch cleavage assays were performed to detect mutations in the KTI gene, with a single-stranded specific nuclease obtained from celery extracts (CEL I). The investigated soybean varieties showed low level of genetic variation in KTI and BBI. PCR-RFLP analysis divided the BBI-A type into subtypes A1 and A2, and showed that Tib type of KTI is the dominant type. Digestion with restriction enzymes was not able to detect differences between ti-null and other types of Ti alleles, while the endonuclease heteroduplex mismatch cleavage assay with CEL I could detect ti-null type. The digestion method with CEL I provides a simple and useful genetic tool for SNP analysis. The presented method can be used as a tool for fast and useful screening of desired genotypes in future breeding programs of soybean

Comparison of Point and Snow Load Deflections in Design and Analysis of Tensile Membrane Structures

Tensile membrane structures are often used as protective structures in order to provide cover from snow, rain, and direct sunlight. They are widely popular because of their advanced structural and architectural properties. Currently, their application is common at sport stadia and public spaces. There are several types of loads acting on tensile membrane structures, most importantly prestress, snow load, and wind load. However, concentrated loads also act on these structures, but they are frequently neglected during the structural analysis. There is yet no European standard on designing tensile membrane structures that would give guidance on structural analysis and incorporation of point load actions in the analysis. In addition, there is little scientific knowledge on how point loads affect tensile membrane structures. This research aims at revealing whether point loads can produce significant membrane deflections and in such way cause damage to the structure or to the objects underneath the membrane. In order to evaluate their importance, point load deflections are compared to deflections induced by snow load. This was done on a large number of numerical models differing in several parameters. Models represent typical geometries of hypar membrane structures on a square base. Obtained results show that, in many cases, point loads can produce larger membrane deflections compared to the snow load. This finding will have an impact on including the point load actions into standardization of design and analysis procedures of tensile membrane structures in Europe