摘要: Timber elements with an I-shaped cross-section are used as supporting elements in wall, ceiling and roof panels of light timber frames. The reinforcement of the panel (I-stud) is provided by means of glued timber composite I-shaped element consisting of a web made of a wood-based desk embedded into flanges of solid or glued laminated timber. The stability of the wall panels is usually ensured by sided board sheathing, which prevents buckling of studs in the plane of the wall or their twist. Walls with one-side board sheathing are used for some types of modern timber structures and their load bearing capacity is determined for situation when one-side sheathing burns down during fire or sheathing is not made of a load-bearing material.
摘要: This paper deals with the use of waste materials from processing of stone in the construction industry. The tested mixtures consisted of Portland cement CEM I 42.5 R, micronized waste marble powder and crushed waste limestone. The article examines the effect of varying the amount of waste on the mechanical properties of the cement composite. At first, samples were tested non-destructively for determine the dynamic modulus of elasticity and then were tested destructively for determine tensile bending and compressive strength.
摘要: The early stage development of the cement microstructure is a crucial aspect affecting the overall performance of cementitious materials. The formation of hydration products depends on the presence of water and carbon dioxide, as well as on the distribution and re-crystallization of the cement particles. In this paper we evaluate the micromechanical properties evolution of cement phases over first 28 days after casting by the electron microscopy and static areal indentation.
摘要: This article deals with the usage of recycled concrete, which arises from the demolition of concrete structures. The work is focused on the development of mechanical properties (Young's modulus) depending on the microstructure of composite cement based materials with different percentage of fine ground recycled concrete as a partial substitute of the filler in the cement mixture, which under certain circumstances also functions as a binder component. To assess of the microstructure there were used images from the optical and scanning electron microscopy. There were used four mixtures of the cement pastes containing 0, 33, 50 and 67 wt. % of finely ground recycled concrete. Development of Young's modulus was measured by nondestructive method. The results showed that of the captured images of surfaces of individual mixtures with increasing amounts of fine ground recycled concrete is seen an increasing amount of pores, which results in a loss of cohesion of the cement matrix and decrease of the Young's modulus.
摘要: This paper is concerned with the selected aspects, which are discovered during a design stage of cable and membrane structures, known as “form-finding” process. The aim of this paper is the understanding of the basic principles of the form-finding process and their explanation of the very simple examples. The use of the finding a shape of a tension membrane that is in static equilibrium as an analogy with the search condition of minimal surfaces is explained. The basic principles are demonstrated on simple 2D example, in which the finding a stable minimal surface passes in the finding a stable minimal length.
摘要: Numerical analysis of masonry structures is a complex task requiring deep knowledges about the problematics. This paper deals with concentrically compressed brick masonry column reinforced by fiber reinforced polymer (FRP) wrapping. The experimental research across the world has proved that FRP external sheets are an efficient tool for stabilization or strengthening of masonry structures. A combination of several types of column’s failure were observed during the experimental testing – failure in masonry, rupture of FRP sheet or failure at interface between reinforcement and masonry support. The rupture of sheet occurs close to sharp corners under the assumption of sheets’ perfect overlap. The rounded corners result in an enlargement of the FRP-masonry contact and reduction of the stress concentration. The increasing of an effective area causes a greater influence of FRP wrapping. For all 3D simulations the commercial software package ABAQUS was used and the obtained results are discussed.
摘要: This paper is focused on testing in mode II. In this article there is presented the double-edge notched specimen based on the theory of the infinite plate to determine the critical factor KII. There are three approaches to this testing here. Firstly, the real test documented by photos and measured data to determine the value of the critical stress intensity was carried out. Secondly, the real test evaluated by the digital image correlation and finally the numerical model in Adina was made. The success of the testing was lower than has been expected (only 24 %). All three prescriptions were used for all 55 specimens. The highest value of KII is reached with the prescription without fly ash.
摘要: Clay is a traditional construction material which has got to background with introduction of modern materials to building practice. There is not proper material available for clay constructions design due to a lack of proper examination of its mechanical properties. This article focuses on tensile bending strength of rammed earth. The mechanical properties depend on the amount of mixture water and on the amount and type of clay minerals. The clay minerals play role of the binder similarly like a cement in concrete. This paper is focused on the tensile bending strength and its dependence on the composition and quantity of clay mineral and its dependence on the amount of mixture water. Five earth mixtures were tested. Mechanical properties were examined on small test bodies made of these mixtures. The mechanical properties of the five mixtures are compared at the end of the paper.
摘要: This article was focused on the influence of the micronized waste marble powder on mechanical properties of cement pastes. Resulting blended cement was composed of Portland cement CEM I 42.5 R and micronized marble powder with different percentage amounts (0 wt. %, 5 wt. %, 10 wt. % and 15 wt. %). Testing was carried at prismatic samples of dimension 40 × 40 × 160 mm. The investigated mechanical properties were dynamic modulus of elasticity, dynamic shear modulus, flexural strength and compressive strength for the 28 days old samples. The results obtained from these materials were compared with reference material.