Shear Strength Of Reinforced Concrete Members Research Articles

Performance of Reinforced Concrete Beams Strengthened by Bidirectional Carbon-Fiber-Reinforced Polymers Based on Numerical Models.

The use of carbon-fiber-reinforced polymers (CFRPs) for the repair and rehabilitation of reinforced concrete (RC) structures has been receiving a lot of attention. Specifically, the shear strengthening of RC members based on CFRP materials has been treated as an effective and efficient strengthening method. Previous research projects focused on the shear strengthening of RC members with unidirectional CFRP strips. Although the effectiveness of a bidirectional CFRP layout compared to a unidirectional CFRP layout was discussed in several studies, these studies only investigated the issue based on experiments. Morever, the parameters of the bidirectional CFRP layout were not clearly defined. This study investigates the performance of RC beams strengthened by bidirectional CFRP based on numerical models. A numerical model based on finite element analysis is designed. Using the numerical model, the parameters of the horizontal CFRP strips, such as the layouts of horizontal CFRP strips and the number of horizontal CFRP strips, are studied. The results show that the effect of horizontal CFRP strips is maximized if the strips are distributed along the depth. In contrast, the number of horizontal CFRP strips does not significantly affect the shear strength of RC members.

Predicting Shear Strength of RC Columns Using Artificial Neural Networks

A primary objective in the seismic design of structures is to ensure that the capacity of individual members of a structure exceeds the associated demands. For reinforced concrete (RC) columns, several parameters involving steel and concrete material properties control behavior and strength. Furthermore, it is unrealistic to simply consider the shear strength calculation as the sum of concrete and steel contributions while accounting for axial force when, in fact, all those parameters are interacting. Consequently, it is challenging to reasonably estimate the shear capacity of a column while accounting for all the factors. This study investigates the viability of using artificial neural networks (ANN) to estimate the shear capacity of RC columns. Results from ANN are compared with both experimental values and calculated values, using semi-empirical and empirical formulas from the literature. Results show that ANNs are significantly accurate in predicting shear strength when trained with accurate experimental results, and meet or exceed the performance of existing empirical formulas. Accordingly, ANNs could be used in the future for analytical predictions of shear strength of RC members.

Effect of Recycled Aggregate Quality on the Bond Behavior and Shear Strength of RC Members

During the aggregate crushing process, natural aggregate and clinging mortar from existing concrete will inevitably produce small cracks and weak bonds between the aggregate and the existing cement mortar. The weaknesses of the existing cement mortar, adhered to a natural aggregate, negatively affect the properties of a recycled aggregate concrete, which prevents its application in reinforced concrete (RC) structures. Recycled aggregate can be classified into several categories, according to its physical and mechanical properties. The properties of concrete incorporated with the recycled aggregate of various qualities can be controlled, and the variability in its strength can also be reduced. This study aims to promote the application of recycled aggregate by investigating the effects of recycled aggregate quality (i.e., water absorption and the number of fine particles) classified by the Japanese Industrial Standards (JIS) on material properties, mechanical properties, and shear behavior of RC beams with recycled aggregate.

Design‐oriented approach to predict shear strength of reinforced concrete beams

There are different approaches to predict the shear strength of reinforced concrete (RC) beams, but their predictive performance is still relatively low due to several and complex resisting mechanisms involved in shear. In addition, most of design approaches ignore the influence of the flange of T cross section beams on the ultimate shear capacity. This paper aims to present a design‐oriented approach to predict the load carrying capacity of RC beams failing in shear. This approach is based on the simplified modified compression field theory (SMCFT). A sensitivity analysis is carried out to assess the importance of the input parameters that mostly affect the shear strength of RC members. Taking into account the results of the sensitivity analysis, two simple equations are proposed for obtaining the: (a) tensile stress factor in the cracked concrete (β) and (b) inclination of the diagonal compressive stress in the web of the section (θ). The obtained equations eliminate the iterative process required by the SMCFT and provide a straightforward design methodology to find β and θ with suitable accuracy for design purposes. In addition, a coefficient is presented to take into account the effect of the flange on the shear capacity of T shaped cross section beams. To appraise the predictive performance of the new approach, a database is set. By evaluating the ratio between the experimental results and the analytical predictions, an average value of 1.24 with a coefficient of variation of 20.9% is obtained.

Influence of Displacement Ductility on Concrete Contribution to Shear Strength

Shear strength of reinforced concrete (RC) members is composed of the contributions of the nominal shear strength provided by transverse reinforcement and concrete. The shear strength of RC members under cyclic lateral loading degrades much faster than the flexural strength. Based on this state, Seismic Codes tend to be excessively conservative and do not take into account the contribution of concrete in certain cases. The aim of this study is to investigate the influence of displacement ductility on concrete contribution to shear strength using finite element analyses (FEA). Based on the agreement between the FEA and experimental results selected from literature, a simple relation is proposed for the prediction of the concrete contribution to shear strength of RC beams. The relation proposed takes into account a reduction of the normalized concrete contribution for increasing inelastic displacement demands, with a small residual strength at large ductility levels.

Minimum shear reinforcement ratio of steel plate concrete beams

Steel plate Concrete (SC) has been used for the shield building in nuclear power plant AP1000 recently. However, the minimum shear reinforcement ratio for SC beams is unknown. This paper reports that six steel plate concrete beams were tested to determine the minimum shear reinforcement ratio $$(\rho_{t,\hbox{min} } )$$ to ensure a certain shear ductility. The main parameters of the experimental program include shear reinforcement ratio $$(\rho_{{t,{\text{test}}}} )$$ and shear span-to-depth ratio (a/d). Currently no minimum shear reinforcement ratio of SC beams is proposed in any technical document. Designers quite often use the provision of reinforced concrete (RC) structures specified by ACI 349 code (2006) for SC structure design. Based on the test results, a minimum shear reinforcement ratio of SC beams is proposed, which is greater than a minimum shear reinforcement ratio specified by ACI 349 code. Existing approaches to predict shear strength of RC members, ACI method (2006) and Kuo et al. method (2014), were evaluated and were found to overestimate the shear strength of SC beams because bond slip between steel plate and concrete weakens the shear capacity. In addition, the Model Code (2010) was compared with the test results and was found very conservative. A method is recommended to estimate shear strength of SC beams with a reasonable accuracy.