Novi končni elementi so potrebni na raziskovalnem področju in industriji za razvoj novih metod napovedovanja naravnih procesov. Razvoj novih končnih elementov je časovno potratno delo, še posebej za nelinearne formulacije. Avtomatizacija tega procesa lahko pospeši tak proces za več velikostnih razredov. Monografija podaja bralcu potrebna znanja za uporabo orodij za avtomatizacijo kot je AceGen na področju mehanike trdnin. Monografija pokriva tako teoretično ozadje uporabljenih metod, njihovo algoritmično implementacijo in aplikacijo na praktične probleme mehanike trdnin. Knjiga je namenjena študentom tehničnih študijev na višjih stopnjah ter raziskovalcem v akademskem in okolju in industriji.
COBISS.SI-ID: 7504993
Quality of indoor environment as well as energy consumption in buildings are a growing concern in the context of overheating of buildings, as the EU legislation is primarily focused on heating season. The statistical data of EU have shown that there is already a large amount of buildings not comfortably cool during summer and the trend is increasing. Therefore, the main goal of this paper is to evaluate the influence of high intensity passive cooling as one of the passive solutions for overheating of buildings on the overall thermal response of building envelope systems. Specifically, a variety of multi-layer external walls during realistic summer time conditions of Central European climate were considered. For this purpose, a finite element method was used to simulate the non-stationary thermal response of several heavy weight and light weight external wall constructions. The results have shown that indoor air change intensity as well as internal heat gains have a significant impact on heat flow through the building envelope. Clear difference in thermal behaviour was detected between light weight and heavy weight envelope systems, as a consequence of different thermal mass and thermal insulation position. While the results of the conducted study represent guidelines to architects, designers, investors and other stakeholders in building industry, the growing popularity of light weight constructions, especially in residential buildings, dictates further research of building envelope configurations and passive cooling system impact on the thermal response of constructions.
COBISS.SI-ID: 7505505
This paper presents a phenomenological criterion for crack initiation based failure prediction of steel structural components exposed to low-cycle fatigue loading. The criterion was established on the basis of available effective damage concept and associated two-parameter criterion. First, experimental cyclic test results on rib stiffened and cover plate stiffened beam-to-column joints are presented, which were used subsequently to verify the numerical model employed for the development of the proposed crack initiation criterion. The two-parameter criterion in which total accumulated plastic strain and stress triaxiality h were adopted as mechanical parameters that control the LCF cracking was applied to define a new damage curve. Several validation examples are presented to demonstrate the capability and accuracy of the proposed methodology for low-cycle fatigue life prediction. The applicability aspect of the proposed cracking criterion is further presented in terms of systematically defined complementary numerical analysis on welded stiffened beam-to-column joints focused on exploring any potential adverse beam member type and size effects on the cyclic response of the full-strength joint configurations. To this aim a set of eight practically applicable I and H European beam profiles was considered for the joints. All the analysed stiffened joints subjected to cyclic loading simulations possessed sufficient degree of overstrength to allow for the development of the full beam plastic rotation capacity. However, from the subsequent analysis important difference in fatigue behaviour between RS and CP joints was found.
COBISS.SI-ID: 7331169
The paper presents new approach to the evaluation of matrix functions operating over tensors that are essential part of formulation of complex nonlinear material models in mechanics of solids. A method is presented how to automatically derive numerically efficient closed-form representation of an arbitrary matrix function and its first and second derivatives for 3*3 matrices with real eigenvalues. The method offers an unique solution to the standard problem of ill-conditioning in the vicinity of multiple equal eigenvalues which is characteristic for all closed-form representations. A compiled library of subroutines with derived closed-form representation of most commonly used matrix functions along with their first and second derivatives has been created and is available for the use in general finite element environments. Consequently, the matrix functions can become as accurate, efficient and commonly available as their scalar counterparts, resulting in more common use of advanced strain and stress measures, such as Hencky strain measure which have so far been considered difficult for implementation. Accuracy and efficiency of the derived closed-form representations was compared with corresponding truncated series expansion and a speed up between 20 and 80 times has been observed depending on the matrix. The proposed methodology was tested on a set of selected nonlinear material models where matrix functions play an essential part in nonlinear finite element formulation.
COBISS.SI-ID: 7327329
The laboratory investigation on the autogenous and total shrinkage of high strength concrete, and the ways of its reduction, are presented. Such concretes demonstrate significant autogenous shrinkage, which should, however, be limited in the early stages of its development in order to prevent the occurrence of cracks. The following ways for reducing concrete shrinkage were investigated and analysed: the use of low-heat cement, steel fibres, pre-moistened polypropylene fibres, and pre-soaked lightweight aggregate. In the case of the use of pre-soaked natural lightweight aggregate, with a fraction from 2 to 4 mm, the shrinkage of 28-days old high strength concrete decreased by about 48%, with no change to the concrete's compressive strength in comparison with that of the reference concrete.
COBISS.SI-ID: 7947105