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To control the structural performance of reinforced concrete (RC) members, enough bonding between rebars and concrete should be provided. Different parameters affect the bond interaction between rebars and concrete. This investigation tends to assess the bonding resistance behaviour of high-strength steel (HSS) bars in concrete considering the effect of two types of concrete: high-performance concrete (HPC) and ultra-high-performance concrete (UHPC). In addition to the type of concrete, the effect of fibers incorporation is measured. For this aim, a total of thirty-six specimens were cast and evaluated. Two diameters (12 mm and 16 mm) and three embedded lengths (1, 2, and 3 times the diameter of rebars) were also used, and the impact of the rebar's diameter and embedded length on the load-bearing capacity, stress and slip of rebars were examined. To boost the bonding characteristics of reinforcements, three various polypropylene fibres (PF) contents were added: 0%, 0.5% and 1%. A pull-out test was carried out on samples. In addition, the obtained results and previous models proposed by literature have been employed to generate new models to predict the bond-slip characteristics of HSS bars in HPC and UHPC when different PF contents are incorporated. The results showed that the maximum peak of slip between the HSS bars and concrete deteriorated with the utilisation of PF, and this peak declined more for UHPC. Additionally, the load capability of specimens was significantly enhanced when PF were added. Finally, the model suggested in this paper may be used to forecast the ultimate stress and bond-slip characteristics of HSS bars in conventional and PF-reinforced HPC and UHPC, with a good level of correctness with the experimental results. [ABSTRACT FROM AUTHOR]

Material science advancements have resulted in the development of high-strength concrete and steel reinforcement, allowing more efficient and stable buildings against natural and manmade disasters. Increasing security concerns and the potential threat from terrorist activities have led to the safety and resilience of structures against blast loads in modern construction. The present study investigates the performance of reinforced concrete shear walls in mitigating blast-induced vibrations. The study examines four different reinforced concrete buildings based on their shapes, namely square, rectangular, C-shaped, and L-shaped, to understand the blast behaviours with and without shear walls. The study presents a methodology to protect the regular and irregular buildings equipped with shear walls against blast loads at varying standoff distances of 100 m, 200 m, 300 m, and 400 m, respectively. The study also compares the efficiency of passive control dampers and shear walls in enhancing the buildings' performance against blast vibrations. The best placement of the shear walls is also evaluated for all the selected buildings. The study also considers the effect of shear wall thickness in mitigating blast-induced vibrations in multi-storey buildings. The study also discusses the design guidelines and reinforcement detailing of shear walls to protect buildings against detrimental blast effects. [ABSTRACT FROM AUTHOR]

The structural performance of concrete structures requires swelling the bending and shear characteristics of reinforced concrete (RC) beams. The bending characteristics of RC beams consisting of waste granite aggregate (WGA), steel fibers (SF), polypropylene fibers (PF), and glass fibers (GF) are assessed in this research. Twenty-one 2,000 mm×200 mm×250 mm RC beams were cast and tested. WGA was sorted and utilized instead of natural coarse aggregates (NA), with three mass replacement fractions: 0%, 50%, and 100%. Besides, SF, PF, and GF were utilized separately at three fractions of 0%, 0.5%, and 1%. Beams were loaded under a four-point bending arrangement, and the ultimate bending resistance, deformability, stiffness and crack development were recorded and assessed. Also, an evaluation of experimental results and existing design standards in terms of maximum crack width has been carried out. Moreover, a cost-sensitivity examination has been made to analyze the effectiveness of using various fibers in terms of cost. Experiments revealed that the impact of PF on enhancing the load-bearing capability of beams with WGA was greater than that of strengthened with SF and GF. However, the impact of GF on the ultimate deformability of WGA RC beam samples was superior to that of PF and SF. PF has a greater influence on enhancing the flexural capacity of RC beams than SF; nevertheless, SF has a greater influence on deformation. The ductility and deformability of RC beams were substantially enhanced when GF was introduced in specimens made with WGA. [ABSTRACT FROM AUTHOR]

Nowadays, reducing the waste and recycled material resources in nature and environmental protection, as well as reducing the use of natural resources, has gained the attention of engineers and researchers. One of the ways to reach this goal is to use waste and recycled materials in new concrete members' construction. Additionally, using glass fiber‐reinforced polymer (GFRP) rebars has gained high consideration owing to their advantages such as high tensile strength and corrosion resistance. Therefore, this study aims to measure the influence of recycled coarse aggregates (RCA) on the structural performance of reinforced concrete (RC) columns reinforced by GFRP rebars under concentric and eccentric loading conditions. A total of 24 RC columns were cast and subjected to concentric and eccentric loads with different eccentricity ratios (e/h):0 (no eccentricity), 0.25 (moderate eccentricity), and e/h = 0.5 (high eccentricity). A total of 18 columns were strengthened with longitudinal GFRP rebars, and six specimens were considered control samples reinforced by steel rebars. RCA was used at two contents of 0% and 100% in terms of weight as a substitute for natural coarse aggregates (NCA). In addition, to measure the influence of transverse reinforcement, three different spacings were considered: 60, 120, and 180 mm. Evaluation of axial behavior, the strain of rebars and concrete, and the ductility were the main aims of this study. Moreover, a comparison between the experimental results and existing standards was carried out. Findings revealed the adequate axial resistance of specimens when RCA was used. Therefore, RCA incorporation improved the axial resistance of GFRP‐RC columns by about 25% and 35% when the stirrup spacing declined by 60 and 120 mm, respectively in comparison with the same specimens made with NCA. However, the influence of RCA on the RC columns' axial behavior was declined by raising the eccentricity distance. [ABSTRACT FROM AUTHOR]

In this research, the consequence of using rubber tire aggregates (RTA) on the durability and mechanical characteristics of polypropylene fibers (PF) reinforced concrete is evaluated. Fifteen concrete mixtures were produced and tested in the laboratory. RTA was utilized instead of fine natural aggregates (FNA) to the concrete at concentrations of 0%, 5%, 10%, 15%, and 20% by a volumetric fraction; also, the contents of PF in the concrete mixtures were 0%, 1%, and 2% by weight fraction. Finally, the following parameters were tested for all the mixtures: compressive and tensile resistances, fracture, changes in drying shrinkage, bulk electrical resistivity, elastic moduli, and resonance occurrences. The control sample was the one without RTA and PF. According to the results, by adding RTA to the mixtures, the shrinkage deformation amplified, but the PF addition caused a decrease in the shrinkage deformation. Furthermore, adding 0%, 5%, 10%, and 15% RTA, with 2% PF leads to an upsurge in the flexural resistance by 34%, 24%, 16%, and 6%, respectively, relative to the control sample without PF and RTA. Moreover, the fracture energy of mixtures increased by utilizing PF and RTA simultaneously. [ABSTRACT FROM AUTHOR]

The effects of earthquake incidence angle on the seismic fragility of highway bridges of unequal pier heights are investigated. A variety of configurations from regular to so-called highly irregular models are considered. In order to accurately quantify the uncertainties in the modeling process, the most influential sources related to the material properties, earthquake characteristics and structural geometries are considered in the nonlinear simulation. Several three-dimensional bridge models are simulated in OpenSees platform, and a set of strong ground motion records are employed in a series of nonlinear time history analyses of the bridge models. Different incidence angle of the records have been used to investigate the response of the models and to extract the most critical engineering demand parameters. The system and component fragility parameters are developed and compared for different values of the excitation angles for all the bridge models. Given the wide range of variables used here, a conversion coefficient is proposed to convert the bridge response for different incidence angles to critical response. [ABSTRACT FROM AUTHOR]