Robert Studziński

Optimal Support System of Sandwich Panels

AbstractThis paper discusses self-supporting sandwich panels, which are used as wall and roof cladding. They consist of two external thin and flat facings and a thick soft core. The panels are subjected to mechanical and temperature actions. The aim of this paper was to find the optimal solution for supports of a multispan sandwich structure. The following support models were considered: rigid support and linear-elastic support, with or without an imposed limit of elastic deflection. The problem was formulated as a two-criterion optimization (i.e., the maximization of the load multiplier and the maximization of the allowable length of the span). The criteria were in mutual exclusion (i.e., the results of the optimization comprise a set of nondominated optimal solutions). It shows that the optimal choice of supporting conditions remarkably improves the capacity of thermally loaded sandwich panels used in civil engineering.

Experimental and numerical analysis of sandwich panels with hybrid core

The paper presents the experimental and numerical studies of sandwich panels with a hybrid core. The sandwich panel consists of external steel facings and a core, which is made of polyurethane foam or mineral wool or a combination of those two materials. The polyurethane foam material has a low weight and high thermal insulation properties, while the mineral wool material can provide high acoustic insulation and excellent fire resistance. Various proportions of the core materials are taken into account. It is assumed that a proper combination can provide the benefits of both materials. The structural behavior of a sandwich structure with a hybrid core is observed during laboratory tests. The failure mechanism is investigated in a four-point bending test. The material parameters of the core and facings are determined in standardized tests. The obtained parameters are used for FE simulations of the four-point bending tests. The criteria of damage initiation and propagation are defined in the interface layer of the numerical model. A satisfactory correlation between laboratory tests and numerical results is reported. Additionally, the sensitivity analysis of the numerical model response to the variation of the parameters of the interface is presented.

Optimal design of sandwich panels with hybrid core

The main aim of the paper is to find optimal solutions of sandwich panels with flat steel facings and a hybrid core made of aerogel and polyisocyanurate (PIR) foam. The optimal solutions have to satisfy conflicting criteria, i.e. a maximum range of applications and minimum weight, while at the same time respecting both the principles of sustainable development in the construction industry and the limit states (ultimate and serviceability) conditions. The design vector consists of the geometrical parameters of the sandwich panel including its span length and the parameter which describes the proportion of aerogel thickness to the total thickness of the core. The mechanical properties of the hybrid core are described by mathematical functions which were obtained in laboratory tests. In optimization, an evolutionary algorithm was used. The Pareto results were obtained while respecting the inequality constraints introduced in the optimization procedure directly (box conditions) and by means of the external penalty function. The presented optimization of a sandwich panel extends the class of problems discussed in the literature by considering both the hybrid core and the thermal conductivity aspect.

Connection stiffness between thin-walled beam and sandwich panel

In this paper, the connection stiffness between a thin-walled Z-beam and a sandwich panel is investigated by means of laboratory experiment, analytical approach, and numerical simulation. The scheme of the conducted experiment refers to a double lap shear test. The two thicknesses of the sandwich panel (100 mm and 60 mm) and two groups of fasteners (four and three) were investigated. The laboratory tests allowed for the determination of the failure mechanisms and the prediction of the reliability of the restraint of the thin-walled beam, provided by sandwich panels. The assumed finite element model created in Abaqus/CAE consisted of solid finite elements (core layer of the sandwich panel, roller support) and shell finite elements (thin-walled beam, facings of the sandwich panel). The fasteners were modeled implicitly, i.e. using spring connectors. The stiffness of the spring connector was determined on the basis of the derived analytical expression and the laboratory test results. The kinematical response of the adopted finite element model was in agreement with the laboratory results. Such a model can be used to verify more complex finite element models with explicitly introduced fasteners.

Wyznaczenie sprężystego momentu krytycznego dla dowolnych przekrojów otwartych i zamkniętych

P ryzmatyczne belki stalowe to podstawowe elementy wielu nowoczesnych konstrukcji szkieletowych. Charakteryzują się dużą nośnością w stosunku do ich masy, wykazując jednocześnie dużą wrażliwość na lokalną i/lub globalną utratę stateczności związaną z osiągnięciem przez analizowany element obciążeń i stanów krytycznych, z którymi związane są gwałtowne zmiany postaci deformacji [1, 2]. Kinematyka tego zjawiska, w przypadku obciążonej równomiernie belki dwuteowej i ceowej podpartej widełkowo, została przedstawiona na rysunku 1. W artykule omówiono problemy utraty stateczności (zwichrzenia) otwartych i zamkniętych przekrojów stalowych poddanych jednokierunkowemu zginaniu. Rozważano elementy nieusztywnione i usztywnione z płaszczyzny zginania.