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This thesis is dedicated to the structured sheet metals topic. Structured sheet metals are semi-finished products with the honeycomb (cell) shape, made by cold forming of the flat sheets. They represent an innovative technology in the field of lightweight construction. In recent years, this technology has undergone dynamic development what gives to researchers possibilities to improve the level of knowledge about structured sheets metals properties and explore new application fields for them.
The structuring improves basic properties, such as stiffness, compared to the flat sheet material. Due to these advantages, the use of structured sheet metals offers enormous innovation potential for efficient lightweight construction in many industrial sectors such as aerospace, rail transport technology, architectural products. Structured sheets have already been implementing in lighting technology, in the manufacture of household appliances and even in automotive industry. So that, the question arises if it possible to apply this kind of material successfully in other areas such as building industry.
This work contains an overview of the lightweight constructions historical development and stiffening elements in the steel industry, also the creation process of structured sheet metals, manufacturing investigated specimens, further bending tests, numerical simulations, analysis and comparison of resulting data and possible further use of lightweight beams with structured sheet elements as a building construction.
In this work beams compound of structured and flat plates are investigated. Steps of structured plates manufacturing process are described: hydroforming, point- and laser welding and bending. As a result, lightweight beams of two main shapes are manufactured: C- and square sectioned. There are four types of beams for each of the shapes are investigated. Every type has same geometrical dimensions, but thicknesses vary.
The series of laboratory tests with created beams under load is made. Three- and four-points bending tests are chosen for that.
This work also presents numerical analysis based on conducted experiments: buckling and global non-linear behavior of specimens by use of the software package ABAQUS/CAE are obtained. The behavior of the beams with structured and flat sheets under load is analyzed and the comparison of parameters such as load bearing capacity and stiffnesses is made.
Finally, in addition to laboratory and simulations, parametric modelling is done. Also, based on parametric calculations, the proposal for calculation the beams stiffness for with higher thicknesses is given. It allows to predict the behavior of beams with structured sheets with different thicknesses without manufacturing and conducting the expensive and time-taking laboratory experiments.
In conclusion, the recommendations for the simplifying of manufacturing process and for the improving of the beams stiffnesses are given.
Steel cladding structures such as sandwich panels can replace bracing systems to provide further stability to individual structural members such as beams and columns. Previous researches studied the stabilizing effects of sandwich panels on the whole structure at ambient temperatures. It was shown that considerable savings could be achieved in the case of using steel cladding systems. In the STABFI (Steel Cladding Systems for Stabilisation of Steel Buildings in Fire) project, the primary objective was to study the stabilizing behavior of cladding systems in the fire. The current thesis is a part of the STABFI project focusing on the bending and translational stiffness of sandwich panels at ambient and elevated temperatures.
The thesis consists of two separate parts, the bending and translational performance of sandwich panels at ambient and elevated temperatures. Sandwich panels are typically composites of two thin steel sheets and a core of higher thickness and lower density. They are valued for their excellent thermal properties. This research employs two different materials, including mineral wool (MW) and Polyisocyanurate (PIR), as a core.
In the first part of the thesis, the bending tests carried out in Prague are described. The experimental results are presented in the first phase of this part. A finite element (FE) model is developed to validate simulations with experimental results, and then a comprehensive parametric study is carried out. During the parametric study, different factors such as panel thickness, width, span, the thickness of steel sheets, and the fire's influence on panels' mechanical behavior are investigated. Moreover, the analytical solutions obtained from Eurocodes (EN 14509, 2013) at ambient temperature are employed to predict the bending stiffness values. The analytical solutions are then developed to apply at elevated temperatures by incorporating the reduction factors into the equations. Eventually, the accuracy of suggested analytical equations is compared with numerical results.
In the second part of the thesis, after presenting the translational tests which also conducted in Prague and validation of FE models, an extensive parametric study on the decisive factors such as the steel sheet thicknesses, screw diameters and temperature effects on the sandwich panel connections behavior is performed. The parametric study shows how each parameter affects the shear resistance and stiffness of sandwich panel connections. Furthermore, the deterioration of shear performance at elevated temperatures is evaluated. The analytical solutions achieved from the ECCS manual are used to estimate the shear stiffness and resistance of connections at ambient temperatures. At elevated temperatures, the equations are developed to anticipate the abovementioned values in the fire case. Finally, the safety and accuracy of proposed analytical solutions are assessed.