The research on population shows that the count of overweight people has been constantly growing. Therefore, designing and modifying utility items, e.g., furniture should be brought into focus. Indeed, furniture function and safety is associated with the weight of a user. Current processes and standards dealing with the design of seating furniture do not meet the requirements of overweight users. The research is aimed at designing flexible chairs consisting of lamellae using the finite element method (FEM). Three types of glued lamellae based on wood with different number of layers and thickness were made and subsequently, their mechanical properties were tested. Values for modulus of elasticity and modulus of rupture were used to determine stress and deformation applying the FEM method for modelling flexible chairs. In this research, the methodology for evaluating the ultimate state of flexible chairs used to analyse deformation and stability was defined. The analysis confirms that several designed constructions meet the requirements of actual standards (valid for the weight of a user up to 110 kg) but fail to meet the requirements for weight gain of a population.
Good quality sleep is a prerequisite for regenerating the human body, hence, beds should be optimized for specific group of users, taking into consideration their size or age. Current research studies show similar trends in adult populations around the world, where increases in height as well as in weight can be observed. Not only the ergonomics but also the safety of beds, which is determined by the quality and dimensions of structural elements, must be taken into account in bed design. Designing the structural elements for users with a high body weight is presented in the paper. The properties of a bed’s structural elements, which ensure comfort as well as the safety of a bed are affected by the excess weight of users. New requirements for cross sections, suitable materials and construction of structural elements were set in accordance with the standard EN 1725:1998 [1]. Also, an analysis of stresses was done using the finite element method (FEM) and the calculation of allowable stresses related to a user weighing 150 kg. The results of our research provide complete standards and regulations associated with the safety requirements of bedroom furniture for users with a weight more than 110 kg to ensure that the manusfacture of quality products in Slovakia.
The presented study is focused on the evaluation of the changes in weight and height of the adult population in Slovakia to provide updated information on the secular growth trend. The main objective was to identify and quantify the pace of gradual changes in the dimensions of the Slovak adult population, which is key ergonomic information for multiple disciplines. The measurements of weights, heights and body mass indices of the current adult population of Slovakia ranging from 26 to 94 years of age that were obtained in period 1993–2017 were compared with a sample of students studying at four Slovak universities during the same years (aged 18 to 25). The increase of mean heights was app. 0.104–0.203 cm per one year (or app. 1–2 cm per decade) for males and app. 0.031–0.178 cm per one year (or app. 0.3–1.8 cm per decade) for females was statistically confirmed at different age classes covering the age structure of the whole adult population. The positive secular height trends were manifested in weight and BMI increases too. The changes in means and variation of distributions of selected variables also cause changes in quantile values. For example, the 95% quantiles of heights derived for the period 1993–2003 only cover 92–93% of the heights in the current population. This fact could have a major impact on proposals for optimal and safe arrangement of work, residential and non-residential space, including the furniture production.
The effect of moisture content on mechanical properties of corner furniture joints was evaluated for when different joining methods and materials were used. Results included statistical processing of the measured and calculated data and evaluation of the effect of selected factors on mechanical properties of joints caused by using mechanical fasteners and glue. The load-carrying capacity and stiffness of corner joints were investigated in two environments, humid and dry, with standard conditions for temperature and pressure, i.e., dry environment had a temperature of 23 °C ± 2 °C and relative humidity of 45% ± 5%, and the humid environment had a temperature of 23 °C ± 2 °C and relative humidity of 90% ± 5%. The two types of materials used were particleboard (PB) with a thickness of 12 mm and artificial stone (plastic) with a thickness of 12 mm. Both materials were tested individually as well as their combination. Epoxy and polyurethane (PUR) adhesives were used for the glued dowel joints. When the same materials were bonded, maximum load carrying capacity was achieved with PUR adhesive, material combination of plastic-plastic, and moisture content of 90%. The epoxy adhesive was most suitable for bonding materials with different properties.
Market globalization, with its accompanying higher living standards, food availability, and sedentary jobs noticeably affects the eating habits and lifestyles of people. Therefore, the body weight of populations is increasing globally. These changes must be taken into account when various everyday items (furniture, clothes, and shoes) are designed. Population-based studies dealing with measuring the height and body weight of adult male populations were analyzed (body mass index categories: 25 kg/m2 to < 30 kg/m2 (overweight), > 30 kg/m2 (obese), > 35 kg/m2 (severely obese)). Because of the analysis of anthropometric parameters in Central Europe, especially Slovakia, it is necessary to produce chairs with two weight categories for the common population (normal weight up to 110 kg) and a population with a higher weight. The aim of this research was to investigate the effect of the body weight of users on the load capacity and dimensions of structural elements of chairs. Following the static analysis of the load-carrying capacity of several chair types, it was calculated that the only suitable construction type for users with a higher weight is the construction with stretchers. The cross-section of the leg space and side rail increased by 20% and 25%, respectively, in the case of a 150-kg user and tenon dimensions of 10 mm × 60 mm × 30 mm.
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