Papers by Keyword: Slabs

Abstract: Conducting surveys of multi-storey buildings is a laborious task, because large volumes of visual and instrumental research should be carried out. Reduction of labor costs with an increase in the reliability of information about the state of damage and technical condition is an actual scientific and practical task. One of the ways to solve it is to use non-destructive vibration diagnostic methods. The purpose of carrying out diagnostics with the use of vibration based damage detection methods is to search for damages in structural elements that can cause the deviation of the dynamic parameters of a structure from calculated ones. Determination of the dynamic parameters of the structure, in particular natural frequencies and mode shapes of mechanical systems, is one of the most important tasks that allows obtaining integral information about the state of a structure. This article presents the results of calculations for the localization of slabs defects in a multi-storey building with a transverse crack, span L = 4.5 (m), height H = 0.2 (m), with prestressed reinforcement d = 0.05 (m). Vibration based Damage Index method was used to localize the defect. During the study, reliable localization values of the defect area of the slab were obtained, this indicates that the vibration method for determining the damage index with a sufficient degree of accuracy allowed predicting the site of damage to the structure.

Abstract: The paper discusses one of possible approaches for speedup of computational analysis of reinforced concrete slabs on foundation. The parallel processing is utilised to accomplish this task. The studied structure is divided to several parts are processed in parallel. A solution of real problems which can include iterative procedures and different levels of interaction between them, however it requires refinement and adaptation of such procedures.The main aim of the paper is to discuss these challenges and to propose solution of them for the particular case of the concrete and reinforced concrete slabs on a foundation.

Abstract: The addition of fibers in order to obtain better performance of mechanical characteristics of concrete has been common place in the last fifteen years in Brazil. Following a request from the Faculty of Architecture at the Federal University of Bahia to replace the Eternit Wall panels with structural deterioration used in its mezzanine floor, this research was developed to analyze the flexural behavior of reinforced concrete slabs with the addition of PET (polyethylene terephthalate) fibers obtained from soda bottles. Selection of this material was based on sustainability since PET wastes represent a serious environmental issue although it can be recycled at a low cost. The importance of this work is based on verifying some of the characteristics of PET fibers reinforced concrete aiming sustainability of civil construction. After laboratory analysis of materials used for slabs, specimens and concrete slabs were shaped with and without PET fibers, being respectively submitted to standard axial compression and flexural tests. Despite the averages of compressive and flexural strengths of slabs with fiber being similar to those without fiber, the firsts presented a better result in terms of cracking, deformation and a less abrupt rupture.

Abstract: Hydrogen is harmful in steel which makes it important to reduce the hydrogen content. Piling slabs after casting gives a slow cooling which increases the diffusion out of the steel. Finite element modeling has been used to simulate this process where hydrogen solubility and phase dependent diffusivity can be taken into account. The hydrogen diffusion model is using STEELTEMP^® 2D for the thermal analysis. Measurements of temperature and hydrogen content in piled slabs have been done and the calculations are in good agreement.

Abstract: The use of lightweight and energy saving materials is the main trend of modern building and construction technology. All-lightweight aggregate concrete, which is a new type of lightweight aggregate concrete, not only has all the advantages of light weight concrete but also a lower apparent density of 600kg/m³. At present, the commonly-used energy-saving organic insulation materials include the EPS insulation and polyurethane insulation. The paper presents a new type of all-lightweight inorganic aggregate concrete by replacing organic material, in order to obtain a lightweight, energy-efficient building structure which synthesizes the load-bearing capacity, lightweight and energy-saving. Tests on the flexural behaviors of 11 all-lightweight aggregate concrete beams and 6 slabs were conducted. The effects of steel reinforcement ratio and loading distribution on the flexural and shear behaviors and method to calculate the load carrying capacity were carried out. The feasibility of application of all-lightweight aggregate concrete on multi-story buildings and to replace common reinforced concrete members in bending was discussed. The experimental study in the paper can provide a basis of the lightweight and energy-saving multi-story structure.

Abstract: Experimental tests were recently performed to evaluate resistance and deformability of nine concrete slabs reinforced with Fiber Reinforced Polymer (FRP) bars in fire situation by varying (a) external loads in the range of the service loads, (b) concrete cover in the range of usual values (30-50mm), (c) bar end shape (straight or bent) and its length at the end of the concrete members, namely in the zone not directly exposed to fire (250-500mm). Experimental results showed the importance of concrete cover in the zone directly exposed to fire for the protection provided to FRP bars, due to its low thermal conductivity. Moreover, the length of the FRP bars in the zone of slab not directly exposed to fire and its shape at the end of the members was crucial to ensures slab resistance once the resin softening reduced the adhesion at the FRP-concrete interface in the fire exposed zone of slab. In particular the anchorage obtained simply by bending bars at the end of member in a short zone (250mm) allowed attaining a good structural behavior in case of fire equivalent to that showed by slabs characterized by a large anchoring length (500mm). Tests results are briefly compared and discussed in this paper, whereas the behavior of the bar anchorage is carefully examined based on both the results of numerical thermal analysis and the predictions of a bond theoretical model adjusted for fire situation.