Deformation Of Concrete Beams Research Articles

Nondestructive Testing for Defects and Damage to Structures in Reinforced Concrete Foundations Using Standard G.652 Optical Fibers

The relevance of this work is due to the importance of identifying latent defects in building structures of reinforced concrete foundations. The results of the study of defects and damage to reinforced concrete structures are provided. It is proposed to use a telecommunication optical fiber of the G.652 standard as a sensor for identifying mechanical influences for long-haul objects. The optical fiber is placed directly inside a reinforced concrete foundation. As a result, we revealed dependences of the increase in the amount of additional optical losses arising in the fiber located in the concrete beam under varying mechanical stresses and deformations with increasing load. Based on the data obtained, two schemes have been proposed that make it possible to locate local latent defects in the structures of reinforced concrete foundations. New results of measuring the values of mechanical damage and deformation of concrete beams in real time when varying the properties of light passing through an optical fiber of the G.652 standard are obtained.

Research on Deforming Law of Beam Structure

The equations of damage evolution of cross-section and the deflection deformation of concrete beam were established. Through the plain concrete beam bending test, the formula for calculating the deflection was verified. It is proved that the formula established in this paper is more accurate than the equation that doesn’t consider the damage effect. The concrete beam was modelled and analyzed by means of finite element analysis software, and comparison was carried out between the numerical simulation result and the experimental data. On the basis, new methods and ideas about concrete-damage were proposed.

Application Research on Transformed Section Method in Stress Redistribution Deduced by Creep in Concrete Beam Reinforced with FRP

For un-cracked reinforced concrete beam with FRP, the adjusted effective modulus theory (AEMM theory) is applied and the calculation method of internal force and stress redistribution of various materials under creep is given with the transformed section method. A comparative analysis is carried out from height change of the concrete beams, reinforcement ratio, FRP layers and the initial stress. The stress of the bars and FRP will increase over time and the degree of increase will be more obvious with the height of the beam and the reinforcement increased, but the concrete stress will be reduced accordingly. The conclusion plays an important role for the performance evaluation of the long-term stress and deformation of concrete beam reinforced with FRP.

Chloride penetration into concrete using various cement types under flexural cyclical load and tidal environment

Presented herein is a model to simulate the chloride ingress into plain concrete, using four common cement types, under flexural cyclical load and tidal environment. Flexural cyclic load was applied from 50 to 80% ultimate bending load, stress ratio (SR) = 0.5; 0.6; 0.7 and 0.8. Fictitious crack model was adopted to predict fatigue deformation of concrete beam under flexural fatigue. The four cement types used were Ordinary Portland cement (OPC), modified cement (MC), rapid hardening cement (RHC) and low heat cement (LHC). The proposed model and experimental results showed that the flexural cyclical load, in terms of the number of cycles, N, and the load level, SR, accelerated chloride penetration into concrete, especially with SR of 0.7 and 0.8. Of four common cement types, OPC is the best cement to retard the chloride penetration into concretes. The model predictions fitted well with experimental results when the crack density parameter, μ, and the tortuosity parameter, τ, were introduced.

Deformability of concrete beams with unbonded FRP tendons

As fibre-reinforced polymer (FRP) behaves linearly until it ruptures without any yielding, the ductility and deformability of prestressed concrete beams with FRP tendons are of prime concern. This paper describes a comparative study of five existing deformability indices for unbonded partially prestressed concrete (UPPC) beams with FRP tendons. A numerical method has been developed to predict the full-range response of prestressed concrete beams with bonded and/or unbonded FRP tendons under loading, and the results agree well with experimental results reported in the technical literature. The results show that the deformability index defined as the ratio of the product of moment and deflection at ultimate to the corresponding value at cracking is consistently decreasing with the increase of combined reinforcement ratio. In addition, this index is sensitive to changes of factors that may influence the deformability of UPPC beams with FRP tendons. The present investigation also indicates that, when the ratio of neutral axis depth to the depth to FRP tendons at the critical section at ultimate is greater than 0.3, the beam would fail by crushing of concrete, which is the more favourable failure mode compared to the rupture of tendons.

Deformation adjustment of concrete beams laminated with carbon fiber mats

A carbon fiber mat is a sheet composed of intercrossing short carbon fibers, which has more stable and lower electrical resistivity compared with dispersed short carbon fiber mixed in cement. Thereby carbon fiber mats can be used in cement and then make cement structures exhibit obvious electro-thermal effect. In this paper, Electro-thermal properties of carbon fiber mats and an elementary strengthening experiments against deformation of carbon fiber mat cement laminated beams were researched. Firstly, electro-thermal properties of carbon fiber mats were studied. Secondly, carbon fiber mat laminated beams are designed and experiments were conducted to get temperature and deformation responses driven by the electro–thermal effects of the carbon fiber mat cement laminated beams. Finally, some experiments of deformation adjustment were done according to the above experimental results. The results show that deformation of concrete beams upon loads can be reduced even removed, and the beams can be strengthened against deformation.

Adjustment for Temperature and Deformation of Concrete Beams

Cement structures such as bridges and dams often come into being distortion or exhibit excessive thermal stresses due to the sun radiation or freeze-thaw cycle. Therefore, temperature especially inner temperature difference or deformation of structures must be controlled or regulated sometimes in order to reduce thermal stresses or excessive deformation and to extend the life-span of structures. In this paper, the electro-thermal effects of smart cement are used to adjust temperature difference or deformation of concrete beams without the need of peripheral non-structural materials. Concrete beams for temperature and deformation adjustment were fabricated, and some experimental results as well as the related conclusions about temperature difference and deformation were produced. Based on these results, experiments of temperature difference or deflection adjustment are further conducted successfully. The research results in this paper are the bases of temperature and deformation adjustment for mass concrete structures. A new path will be broken to adjust temperature or deformation easily for some structures.