Papers by Keyword: Slab

Abstract: The aim of the work was to determine the possibility of not taking into account the orientation (vertical or horizontal) of the studied elements of steel-reinforced concrete slabs with a corrugated profile during their heating in a modular small-sized fire furnace. The work investigated the temperature distributions on the outer surface of the corrugated ceiling profile of a steel-reinforced concrete slab of horizontal orientation simulated in the fire furnace chamber. To create geometric models of the fire furnace chamber and the studied element, a CAD software complex was used. To solve the heat engineering problem, mathematical (numerical) methods were used, based on solving systems of differential equations of continuous media such as the Navier-Stokes equation and the Fourier heat conductivity equation. According to the results obtained, the temperature distribution on the outer surface of the steel profile of the reinforced concrete slab is uniform, the temperature deviation in different places on the surface does not exceed 7 %. The maximum temperature on the heating surface of the steel profile of the reinforced concrete slab in the last minute of computer simulation reached 921 °С and the average temperature at this time over the entire surface of the structure was 917 °С. To determine the appropriate orientation of the test sample during fire tests, a comparison of the obtained temperature distributions on the outer surface of the corrugated profile of a horizontally placed reinforced concrete slab with the temperature distributions on the outer surface of the corrugated profile of a vertically placed reinforced concrete slab, which were given in the previous work was made. Analysis of the average surface temperatures of the corrugated profile of a reinforced concrete slab of horizontal and vertical orientation showed that the temperature distribution over the surface of the profile was uniform in both cases and the results obtained show good reproducibility of the experiment during computer simulation. And the orientation of the tested elements does not affect the temperature distribution over the outer surface of the corrugated profile of a reinforced concrete slab in the simulated furnace.

Abstract: The paper examines three different ceiling slab concepts for garages, considering common column spacings (8 × 8 m, 5 × 11.2 m, and 5 × 16.2 m). It provides a comparison between reinforced and post-tensioned concrete slabs, highlighting the advantages of post-tensioned ceilings in terms of maximizing parking spaces and reducing material consumption (concrete and steel). Optimizing space and minimizing material usage are crucial in modern construction to lower CO2 emissions and enhance spatial flexibility.

Abstract: In this study, we investigated the effect of Si and Mo on the sigma-phase precipitation in S32750 super duplex stainless steel slab. The activity for Mo with increasing Si and Mo was calculated by the Wagner formula, and the equilibrium solidification phase diagrams of S32750 duplex stainless steels with different Si and Mo contents were calculated using the thermo-calc software. The sigma phase precipitated mainly at ferrite/austenite phase boundaries and grew up towards the interior of ferrite phase in S32750 SDSS slab. The area fraction and size of the sigma phases significantly increased with increasing Mo content and Si content. Also, the increment in Mo and Si content affected the Mo concentration in sigma phase. The sample（Mo:3.4%,Si：0.3%） had a lowest sigma-phase area fraction of 2.84% and had lowest Mo content in σ phase.The calculation results showed that the increase of Mo and Si content increased the initial precipitation temperature and maximum precipitation amount of σ phase in S32750 SDSS equilibrium phase diagram. The activity of Mo also increased with increasing Si content and Mo content. That is, Mo and Si elements promoted the precipitation of σ phase.

Abstract: Hydroxyapatite (HA) is a phosphate mineral with the chemical formula of Ca₁₀(PO₄)₆(OH)₂. The presence of pores in HA allows easy interaction with other compounds, so it can be used to detect the CO gas. Other than that, the hydroxyl group in hydroxyapatite allows the ion exchange process, a significant reaction in a gas sensor. The interaction of hydroxyapatite with CO gas has been studied using density functional theory. The HA adsorption potential energy surface was investigated using slab model with (001) expansion and 10 Å vacuum. CO gas kept fixed 1.0 Å above the HA surface and traced along the surface with grid 10×10. The result shows that the surface is divided into two main potentials that more likely and unlikely for CO to stay. The CO gas is most likely to stay between two oxygen from (PO₃) tetrahedral that pointing down.

Abstract: The paper compares the internal structure of two continuously cast slabs with a section of 300 × 2600 mm from a tube steel of the strength class K60, one of which is molded with a soft reduction, and the other is without external influence. A comparative analysis of the structure of two templates showed that the location of areas with an increased metal pickle ness in the axial part of the templates varies. On the template from a slab cast without reduction, this section is below the geometric center of the work-piece in thickness, at a distance of 49.2% from the underside, that is, the "lower" asymmetry of the slab structure is observed. On the template from the slab cast off with soft reduction, the area with an increased pickle-ness is located above the middle of the work-piece: at a distance of 51.7% of the side of the large radius, an "upper" asymmetry of the slab structure is formed. Consequently, as a result of the external action on the cast work-piece, the location of the axial sponginess, relative to the geometric centre of the slab, is changed by moving from the lower to the upper half of the work-piece. The metal of the axial part of the reduced slab has a denser structure, the degree of development of axial looseness in the metallographic evaluation is reduced by an average of 0.5 points. The work shows the change in the content of chemical elements along the thickness of slabs. In the reduced metal, the maximum value of the degree of zonal inhomogeneity of the most impurities is higher than in the metal without external influence. This is explained by the fact that, as a result of reduction, the zone of location of the axial chemical heterogeneity in the slab becomes smaller in width.

Abstract: This work deals with the need and possibility of building car parks in Bucharest above Dâmbovița River. They included analyses referring to the evolution of the number of existing vehicles in Bucharest, an analysis of the number of vehicles in Bucharest, as compared to other European capitals, and also certain elements leading to the possibility and profitability of building a car park above Dâmbovița River. As a result of impact studies and research on overland parking over the Dambovita river, it was concluded that the most popular solution of respondents would be a parking equipped with a smart boarding system, built on a round platform and metal frame. A photovoltaic-panel installation can be used in parallel to supply electricity with renewable energy(sunlight). The protection of the structures exposed to the risk of earthquake is based on the three fundamental operational modes: insulation, connection, dissipation of energy The parking is protected against earthquake using the method of design/consolidation by insulating the base.

Abstract: Nowadays finite element software is used for the design and analysis of reinforced concrete slabs. This paper intends to have a critical review based on a comparison study between the three design methods and to estimate the amount of reinforcement to be provided in each case. The three methods discussed are; the three-layer sandwich model (IRC 112-2011), Wood Armer method (EN1992-1-1:2004) and the conventional design method as per IS 456-2000. In the recently revised code for bridges IRC 112-2011, there is a recommendation to adopt three-layer sandwich model for the design of reinforced concrete slab. In this paper, a critical review of this method is done, and it is used for slabs subjected to uniformly distributed load. This method is illustrated by considering the design of rectangular slab subjected to uniformly distributed load. The results of this method are compared with the results obtained using Wood Armer method and using the moment coefficients suggested in IS 456-2000.

Abstract: In this paper the response of a reinforced concrete slab to a time variable load is presented. The time course of loading is in the first phase defined by a linearly increasing function and in the second phase by a constant function. The response is solved by a modified method of matrix functions.

Abstract: Degradation of reinforced concrete could occur in various forms including spalling of concrete cover as a result of reinforcement corrosion. The degradation would shorthen the service life of the reinforced concrete structure. Patch repair method may be employed to recover this type of degradation using a suitable patch repair material. The authors have developed a patch repair material made from unsaturated polyester resin (UPR)-mortar. In this paper, the mechanical properties of this material which includes compressive strength, elastic modulus, flexural strength and bond strength are highlighted. Comparisons are also made with the normal mortar to emphasize the superior properties of UPR-mortar. Based on these properties, the potential application of UPR-mortar for repairing damaged reinforced concrete slab is examined through finite element simulation. It is pointed out that the tensile stress intensity in the UPR-layer is reduced with a consequence of reducing a risk of cracking in the repair zone. In addition, the patching of damaged zone with UPR-mortar could minimize the deflection.

Abstract: The mathematical model for heat transfer during solidification of steel in the mould of slab caster was established in this paper. The temperature distribution of slab surface was described. Based on the work which was described above, the model of flux film state was developed in present paper. Lubrication function of mould flux and the effects of main factors on lubrication had been discussed. The simulation results provided theory foundation for appraising lubrication function of flux and optimizing casting production.