Applied Mechanics and Materials Vol. 749

Abstract: The present work contains information on control processes of interaction in the system "organic binder - mineral filler" by mechano-chemical water-repellency treatment of the latter with the purpose of expansion of a raw-material base in the production of road-building composites from man-made materials.

Abstract: This work carries an experimental study on the composition and the characterization of the self-compacting concretes made starting from waste of construction with comparisons which were made by contribution with the vibrated concrete. Studies on the workability and the compactness of material were made and this in a fresh state and a hardened state. Five different mechanical tests were performed: compression, direct tensile, splitting tensile, 3 points binding and failure to the shear force. Confrontations of the test results compared to formulas for calculating the shear force were realized. All the test results showed an increase in terms of resistance for SCC contribution to the VC, except the direct tensile test which gave values slightly lower. The SCC improves the failure load notably and gives better mechanical performances.

Abstract: In order to improve indoor air quality, the interest in and the use of sorptive building materials that decrease the concentration of an indoor air pollutant have increased. The use of sorptive building materials is one way to decrease the concentration of an indoor pollutant that can adversely affect human health. In this study, we evaluated the effects of sorptive building materials applied to a wall on the decrease in the concentration of toluene emitted from the flooring. We also examined how the air exchange rate of the room, the loading factor of the sorptive materials, and the mass transfer coefficient influenced the sorptive performance; these effects were well reproduced experimentally with computational fluid dynamics (CFD) simulations. The results show that sorptive building materials have a fairly strong effect on the decrease in toluene concentrations in rooms and that this effect can be expected in real-world scenarios.

Abstract: The effect of a-SiO₂ of various origin on the properties of cement paste with incorporated different silica containing materials is experimentally studied in the paper. For the applied a-SiO₂ materials, basic physical and chemical properties are accessed, together with their chemical composition. Amount of amorphous phase of SiO₂ in particular siliceous materials is determined using XRD analysis. Matrix density, bulk density, total open porosity, compressive and bending strength are measured for all developed pastes with incorporated a-SiO₂ containing materials, together with initial and final setting time of fresh mixtures. The obtained data give evidence on a high and fast reaction activity of tested siliceous materials which results in a significant improvement of porosity and mechanical strength of a-SiO₂ modified cement pastes.

Abstract: The subject of this paper is an universal software for reinforced concrete annular and circular slabs reinforced in the radial and tangential direction. Such slabs are used for roof and ceiling structures of buildings. The software can be used for design and assessment of rotationally symmetrically loaded annular and circular reinforced concrete slabs with arbitrary supports and span. Based on user's choice, the software proposes solutions to not only meet all the design principles, but especially ultimate limit state and serviceability limit state.

Abstract: SCBFs (Special Concentrically Braced Frames) have been praised for considerable strength, high lateral stiffness, economic feasibility and good performance of seismic loads, which make engineers widely use SCBF as lateral-load resisting systems in buildings and have researchers develop design requirements. Compared to the extensive research of SCBF, comparatively little information is currently available on the performance of SCBFs designed and constructed before the early 1990’s. Before the early 1990’s, CBFs (Concentrically Braced Frames) design requirements were substantially less restrictive. As a result, many existing structures designed to these requirements may not exhibit desirable behavior in a seismic event. Existing CBFs that do not meet modern SCBF criteria shall be referred to herein as NCBFs (Non-Seismic Concentrically Braced Frames). In this study, FE (Finite Element) analysis was carried out. The detailed inelastic FE models were verified, which are based on the preceding research. Finally, these models were compared to evaluate the seismic performance of NCBFs.

Abstract: In this paper, we present an analytical model to analyze reinforced and prestressed concrete beams loaded in combined bending, axial load and shear, in the frame of non linear elasticity. In this model, the equilibrium of the beam is expressed by solving a system of equations, governing beams equilibrium, based on the stiffness matrix of the beam, which connects the load vector to the node displacements vector of the beam. It is built from the stiffness matrix of the section which takes into account a variation of the shearing modulus (depending on the shear variation) instead of assuming a constant shearing modulus as in linear elasticity. For the internal tendons, the stiffness matrix is completed by the terms due to the prestress effect in flexural equilibrium and by the balancing of one part of the shear by the transverse component of the force in the inclined cables.

Abstract: The damage mechanics allows a detailed modeling of reinforced concrete’s degradation phenomenon. The theory of isotropic damage leads to quite satisfactory results in the description of both in the local and the global behavior. It is within the scope of this work to provide a model of damage based on the non-linear mechanical behavior of fiber concrete. This model takes into account the ductile nature of the observed during testing of material and direct tension after cracking. The modeling will be done while checking the principles of damage mechanics using the fundamentals of continuous mechanics of materials to propose a law of damage variation in unidirectional compression and tension. Confrontations with experimental test results are established.

Abstract: A new model is introduced, for predicting the nonlinear behavior of the concrete until the rupture. The non-linear behavior of the concrete is taken into account under monotonic load verifying the principles of the mechanics damage [1] and the concepts of the mechanics of the fracture, using the foundations of the continuum mechanics of materials [2]. The nonlinear mechanical behavior of the concrete in unidirectional is described by two laws (Sargin [3] for the compression and Grelat [4] on the tension). By introducing two variables of damage applied in unidirectional respectively in tension and in compression (Y. Bouafia , R. Smahi, and al., (2014)) [5]. Their combination with the laws of the continuum mechanics of materials (Hooke’s low generalized) [2], and the theory of the mechanics damage (theory of the isotropy of the damage, and principle of the equivalent deformation), brings us to a law of variation of the damage in three-directional applied in bidirectional. In addition, if the variation of the Poisson’s ratio of concrete in unidirectional compression has attracted the interest of several researchers we can cites: (Sami, A., Klink, 1975 [6], Murray D.W. 1979 [7], Niels Saabye ottosen, (1980) [8], Atheel E. Allos., L.H.Martin, (1981) [9], Ramtani.S, Y. Berthaud , J. Mazars, (1992) [10] and Ferretti, E., (2004) [11]. For the three-dimensional, we can mention: Chen 1982 [12], Guo 1997 [13], Zhu 1998 [14], Hyuk-Chun Noh, Hyo-Gyoung Kwak 2006 [15] and Ding Faxing Yu Zhiwu 2006 [16]. Confrontations of the calculations with experimental results (behavior of the concrete in biaxial compression and tension) have allowed to describe and to follow the real behavior of the concrete.

Abstract: Contribution deals with laboratory measurements of deformations in the place exposed to local load caused by additional pre-stressing and its comparison with numerical simulation. The measurements are made at the masonry brick corner built in the laboratory equipment. The laboratory equipment was designed at Faculty of Civil Engineering VŠB – TU Ostrava for measurement tri-axial stress-strain conditions in masonry. The masonry structure of the brick corner is imposed on the vertical load and pre-stress is applied through two bars. The values of deformation from pre-stressing are sensed by potentiometer sensors. Numerical simulation of the brick corner is based on the finite element method using appropriate software and then the results are compared with those of experimental testing. For numerical simulation were used material linearity and material non-linearity of model. On the basis of these results it should be possible to improve the models and come closer to achieving an accurate and at the same time, simple procedure for the design of pre-stressed masonry.