Modified prediction approach of strength of high strength polyolefin fiber reinforced concrete corbels

This paper aims to investigate the effect of polyolefin fibers on high strength reinforced concrete corbels using twelve specimens with different quantities of fibers and shear span-to-span ratios, all corbels were only tested vertically. Due to the addition of polyolefin fibers, the ultimate load-carrying capacity of corbels was significantly improved, according to the findings of this study and other relevant data. The limitations and insufficiency of the three techniques were proven by a comparison of current test results and anticipated values by the ACI 318 Code -19 rules for the tested specimens, the Strut and Tie Model, and the proposed method. The ultimate shear load of polyolefin fiber reinforced high strength concrete corbels with was determined to be best predicted by applying the Strut and Tie Model technique to account for the fibers' contribution to strength

Structural behavior of high-strength concrete corbels involving steel fibers or closed stirrups

A comprehensive experimental evaluation of the shear behavior of corbels made by high-strength concrete (HSC) with steel fiber or with stirrups was investigated. Thirteen samples were prepared and tested, the main variables in this research were steel fiber type, steel fiber content (Vf %), and amount of horizontal closed stirrups (Ah). The constants in this investigation were the area of the main steel reinforcement (As), ratio of shear span to depth (a/d) and cube concrete strength (fcu). The obtained results clearly showed that, the presence of fibers or closed stirrups enhanced the strength and decreased the deformation of the explored specimens. It was concluded that the horizontal shear reinforcement can be substituted by supplementation of steel fibers to RHSC corbels. A comparison was performed between the test results and estimated shear capacity by ACI code and other adopted equations. Very conservative shear strength values were obtained from ACI 318–19 for corbels prepared with high-strength concrete because the strut and tie method were influenced by concrete strength and did not take the contribution of closed stirrups into account. However, the shear friction method depends only on the quantity of the main steel reinforcement and closed stirrups. Russo [2] proposed a model that adequately predicted the ultimate force of high-strength RC corbels incorporating closed stirrups, but this model did not take the effect of steel fibers into account. Campione [3] added the effect of steel fibers by means of the residual tensile strength expression

Torsional behavior of reinforced recycled aggregate flowing concrete hollow section beams

Fifteen reinforced concrete beams made with recycled aggregates and flowing concrete, which were tested under pure torsion to study the torsional behavior. The major parameters in this study were the percent of the recycled aggregates and the number of transverse reinforcements. The torsional response and crack behavior were investigated in this study. From the results, it can be noted that the increase of the recycled aggregate led to a decrease in the critical and ultimate torque of the beam, also, the increasing the number of transverse reinforcements led to the enhancement of the critical and ultimate torque. Numerical analysis by finite element method was conducted and gave a good indicator for agreement in the results of critical and ultimate load between the numerical and experimental study, as well as the angle of twisting of the beam. The second approach was Hsu᾽s softened truss model, the model proves it can predict the critical and ultimate torque for the beam and showed its ability to describe the behavior of the beams before and after cracks

Flexural Behavior of Normal and High Strength Self-Curing Self- Compacted Concrete Beams of Local Materials

In some construction industries, there are difficulties in achieving the required concrete compaction, Self-compaction is an alternative option. Working with self-compaction self-curing concrete requires a unique approach. This study aims to examine the possibility of producing self- compacting concrete with normal and high self-cure rates. This research observed how both the self- curing and self-compacting concrete behaved under normal and high-strength conditions. Two stages were prepared for this investigation. The first stage of this research studied the effect of a curing agent on the fundamental characteristics of both normal-strength and high-strength self-compacting concrete, with the aim of achieving self-curing self-compacting concrete. The primary variables of this study include the grade of concrete, the type of curing agent, the reinforcing bars, and the dosage of these variables. In the second stage, reinforced concrete beams were cast with one of the two proposed concrete types, and their behavior was studied. The findings were analyzed in terms of the beginning cracking loads, the ultimate loads, and the crack patterns of the testing beams. According to the results, both the normal-strength and the high-strength varieties of self-curing self-compacting concrete are effective in providing structural features, which are absent from the processes of curing and compacting. Curing chemicals are utilized to mitigate the process of water evaporation in self-compacting concrete, hence enhancing the water retention capabilities of self-compacting concretes that possess enough hardened concrete characteristics

EVALUATION OF EFFECTING FACTORS OF TRADITIONAL AND SUPER PLASTICIZER CONCRETE CORE STRENGTH

This paper deals with the investigation factors effecting core strength estimation by conducting an experimental study which included casting of six plain concrete beams. For each beam, 12 cubes were cast in addition to twenty-four core samples were extracted. The investigated factors involved the concrete compressive strength, concrete type, core extracting direction, core location, core depth in the beam, and the damage factor. It obtained results showed that the ratio of compressive strength in the vertical to horizontal cast direction is (1.075) and (1.080) for the traditional and superplasticizer concrete, respectively. Also, the depth factor of bottom to top zone strength in vertical cast direction is (1.110) and (1.066) for traditional concrete and the super plasticizer concrete respectively, while the location factor of center zone in vertical cast direction corresponding to (1.088) and (1.103). Finally, the damage factor is directly proportional with the concrete strength for both concrete types

Verification of a Torsional Behaviour Prediction Model for Reinforced Recycled Aggregate Concrete Beams

This study shows the torsional conduct of aggregate streaming beams of reinforced concrete recycling. Pure torsion was perceived for 15 reinforced concrete beams containing recycled concrete aggregates. The beams were grouped into five lengths and cross-sectional groups. The study’s principal parameters were the various percentages of longitudinal steel reinforcement and the proportions of recycled aggregates. The beams were purely twisted until failure and investigated for torsional and crack behaviour. The findings show that the beams with maximum steel enhancement and standard aggregate exhibited maximum cracking power and ultimate torsional strength. Recycled aggregates increased the presence of splitting and the ultimate strength, and the effects of steel strengthening in recycled beams were apparent. In a second analysis, the whole torsional reaction of the beams was analytically predicted. A soft truss model was used and matched with test results for standard beams. A strong compromise was generally reached