The paper investigates the problem of numerical stability of the Karhunen–Loève expansion for the simulation of Gaussian stochastic fields using Galerkin scheme. The instability is expressed as loss of positive definiteness of covariance matrix and is the result of modifications of standard exponential covariance functions that are commonly applied to increase the sparsity of the covariance matrix. The loss of positive definiteness of covariance matrix limits the use of efficient eigenvalue solvers that are needed for the solution of the resulting generalized eigenvalue problem. Two modifications of the shape of covariance function to avoid instability problems and at the same time to raise the numerical efficiency of Karhunen–Loève expansion by increasing the sparsity of the covariance matrix are proposed.
COBISS.SI-ID: 6653793
In recent years implementation of sustainable building design in the EU has become one of the key issues in reducing energy dependence. In this context efficient use of solar potential incident on building envelope is essential. The goal of the study is to evaluate the influence of interventions required by the new Slovenian legislation and to propose general site planning guidelines. Special emphasis is devoted to the existing building stock, which is due for refurbishment. The study is carried out on the basis of seven typical urban layouts, which are assessed according to the shape of layout, density, building orientation and design. The calculations are carried out with the program SHADING. The study showed that the existing layouts are not as problematic as had been expected and that form and orientation of buildings present a major challenge. Nevertheless, the quality and the duration of insolation are highly dependent on the specifics of each case. The study showed that by respecting the basic rules of good practice in conjunction with the existing requirements no major changes in the existing design principles are needed.
COBISS.SI-ID: 6496609
The purpose of the paper is to test a Low Exergy heating and cooling system (LowEx system) that enables the creation of healing and comfort conditions for individual user with minimal possible energy use. The LowEx system was tested in a model room for burn patient and compared with the conventional one. Thermal comfort conditions were simulated for three individual users (burn patient, healthcare worker and visitor) energy use was measured. In a simulation, users were exposed to the required conditions for burn patient created with both systems. The LowEx system creates optimal conditions for burn patient with lower human body exergy consumption (hbExC) rate valid for thermoregulation, minimal evaporation, radiation and convection. For healthcare worker and visitor, the LowEx system creates individual thermal comfort zones. For the LowEx system, the measured energy use for heating was 11-27% lower and for cooling 32-73% lower than for the conventional system.
COBISS.SI-ID: 6529121
The paper presents experiments on connections with one and two bolts made of mild steel grade S235. The results are compared with the tests on connections made of high strength steel. The test results are substantiated with numerical parametric analysis. The effect of bolt bearing is thoroughly analysed. The bearing strength at bolt holes according to standard EN 199318 is critically evaluated and a modified design check is proposed. The modified check is conceptually the same as the current one, but it is simpler, less conservative and it is in better correlation to the test results. The block shear strength and net crosssection strength are also discussed and modifications to the EN 1993 design rules are given.
COBISS.SI-ID: 6514785
The market offers new large steel angle profiles, the largest being L300/35. To check their buckling resistance, the investigation of the residual stress field is presented in this paper. Since the buckling behaviour of steel angles is significantly affected by the residual stresses, the stresses were measured on six hot rolled and two welded equal angles by sectioning method. The traditional sectioning method was improved by introducing the water jet cutting. The released deformations were measured by the strain gauges. On the basis of the statistical evaluation of the test results, the most appropriate residual stress distribution models were considered in the numerical analysis. The results of the geometrical and material nonlinear numerical analysis were equal angle buckling curves.
COBISS.SI-ID: 6545249