Failure Analysis of Steel Fiber-Reinforced Concrete T-Beams without Shear Stirrups

The shear failure of a reinforced concrete member is a sudden diagonal tension failure; flexible failure is gradual, associated with significant cracks, and leads to extensive sagging. Therefore, reinforced shear rebars are commonly used to ensure that flexible failure occurs before shear failure under extreme conditions. Extensive efforts are underway to replace conventional shear reinforcements with steel fibers. Here, a nonlinear analysis of a steel fiber-reinforced concrete T-beam was performed in order to estimate the maximum shear capacity with the aid of experimental test data. A continuum-damaged plasticity model and modified compression field theory were used for nonlinear analysis. Three 360 × 360-mm web elements were selected between the shear span; changes in the principal axis caused by crack development and propagation were traced. Changes in the crack angle according to the average strain of the bottom longitudinal reinforcement and the vertical strain of the web element were also determined. For verification, a strut-tie model was used to predict shear capacity. The experimental results and the finite element analyses were in good agreement.

The shear resistance of a member without shear reinforcement according to Eurocode 2; the error of the calculated value and the mechanical explanation of the problem

In this paper the shear resistance of a member without shear reinforcement according to Eurocode 2 is investigated. This expression, as most expressions of design codes typically used to estimate the nominal shear resistance, has been created based on experimental investigations. It will be verified that in case of non-prestressed reinforced concrete member without stirrups, the shear resistance is carried by the shear resistance of the compressive zone; and the shear resistance given by the empirical expression of Eurocode 2 is actually the shear resistance of the compressive zone.Knowing the mechanical background of the empirical expressions of Eurocode 2, the limits of its applicability can be shown, thus its error can be predicted. Using the reports of experimental investigations, it is easy to find cases to prove the correctness of the error-prediction. In this paper simple modifications will be suggested to Eurocode 2 shear design procedures, by which a more consistent level of safety can be ensured.

Digital Image Correlation Analysis of Corrosion Crack Behavior in a Reinforced Concrete Member

The corrosion of the internal steel bars of reinforced concrete structures is still a maintenance problem. This study aims to detect corrosion cracks in covered concrete by DIC. We proposed a new test specimen and method of electrolytic corrosion testing suitable for tracking corrosion cracks by DIC (Digital Image Correlation Analysis), and succeeded in understanding the crack initiation behavior of single and double bar specimens.

Analytical modeling of the contact pressure at the steel-concrete interface

This research studies the effect of corrosion on bond strength at the steel-concrete interface in a reinforced concrete member. Bond stress, which can be defined as the shear stress which develops along the lateral surface of the bar, is expressed as a function of contact pressure at the steel-concrete interface. An analytical model of bond which describes the contact pressure between the reinforcing bar and concrete in a reinforced concrete member is developed. The expression for the reduction in contact pressure due to the accumulation of corrosion products is then developed using the model developed for the uncorroded reinforcing steel bar. The developed analytical model was implemented in a finite element analysis, which was conducted using ABAQUS, of pull-out specimens conducted by Amleh (2000). A reasonable good agreement between the experimental and finite element analysis results was obtained.

Analytical modeling of the contact pressure at the steel-concrete interface

This research studies the effect of corrosion on bond strength at the steel-concrete interface in a reinforced concrete member. Bond stress, which can be defined as the shear stress which develops along the lateral surface of the bar, is expressed as a function of contact pressure at the steel-concrete interface. An analytical model of bond which describes the contact pressure between the reinforcing bar and concrete in a reinforced concrete member is developed. The expression for the reduction in contact pressure due to the accumulation of corrosion products is then developed using the model developed for the uncorroded reinforcing steel bar. The developed analytical model was implemented in a finite element analysis, which was conducted using ABAQUS, of pull-out specimens conducted by Amleh (2000). A reasonable good agreement between the experimental and finite element analysis results was obtained.

Retrofitting of RC Beam Structure Member by using CFRP

The research has been lead relating the use of carbon fibre-reinforced polymer (CFRP) sheets in retrofitting and strengthening of the reinforced concrete member. The present research was conducted by using the epoxy to reinforced concrete beams retrofitted and strengthened for flexural strength by using CFRP sheet. The selected cross-section of the beam having 2400 mm length with 150 mm width and 225 mm height and the beam tension reinforcement on the bottom was set on 2#[email protected]" with the 38.1 mm clear cover was set to the main flexural reinforcement. The studied beam was focused on flexural behaviour. The experimental study has shown that while the using of CFRP with epoxy will improve the rigidity and durability of the concrete beam. Their great deformability greatly improves the seismic properties of the beam structures. Under the reinforced RC beams showed a very large deflection by control beam before their failure. By using CFRP externally the rigidity of retrofitted and strengthened beams can be improved.