Experimental and Numerical Investigations on Load Capacity of SRC Beams with Various Sections

The passivation behavior of steel reinforcements in concrete is significantly influenced by the environment, concrete pore solution, and the passive film formed on the steel surface. The present study used electrochemical methods to successfully characterize the passivation process of steel reinforcements in concrete. The passivation behavior of commonly used HRB400 steel reinforcement material in concrete was studied using various electrochemical parameters quantitatively. As the soaking test time increased, the OCP gradually increased and stabilized after 5 days, indicating that the steel electrode transitioned from an active state to a passive state in the simulated liquid environment of concrete. The steel reinforcement developed a protective passive film that reduced its tendency to corrode. According to EIS, after soaking for one day, the steel electrode showed significant early passivation, indicated by an increase in its arc diameter. The WE arc gradually increased in the first 5 days of immersion, suggesting dynamic passive film formation and development. Beyond 5 days, the passive film stabilized with minimal further changes in its impedance spectrum, indicating carbon steel electrode passivation. The working electrode’s impedance increased significantly on the fifth day, and gradually increased slightly after 10 days, indicating comprehensive coverage by the oxide film. Attributed to the growth and development of the oxide film, the electrode resistance reached a relatively stable state after the fifth day. The shift in corrosion potential offers an indication of the level of passivation of the steel reinforcements. The decrease in the anode Tafel slope and increase in the corrosion potential indicate the formation and stabilization of an oxide film on the steel surface, which is beneficial for its long-term durability in concrete structures. By analyzing the OCP, EIS, and dynamic potential polarization curve method data, it is possible to gain insights into the passivation behavior of steel reinforcements in concrete structures. This study aims to provide a basis for optimizing the corrosion protection of steel reinforcements in concrete structures. The significance of this study lies in a deep understanding of the passivation behavior of steel bars in concrete, providing a theoretical basis for improving the durability and lifespan of steel bars in concrete structures.

This paper presents an experimental study on the flexural behavior of composite Reinforced Concrete (RC) beams having a monolithic Engineered Cementitious Composites (ECC) layer at the tension face. Due to the brittle nature of normal concrete, clear cover on the tension side of beam cracks results in spalling and corrosion of reinforcement. The proposed technique overcomes the inherent brittle behavior of normal concrete with the incorporation of ECC on the tension face. This also helps in reducing bond-splitting, cover-spalling, and buckling of reinforcement in RC flexural members. For testing purposes, six full-scale beam specimens (225 mm x 300 mm x 2400 mm) with the same reinforcement were cast and tested. Out of six, two specimens were made of conventional concrete, whereas the remaining four (two each) had an ECC layer of 75mm and 100mm thick at the tension face respectively. Each specimen was installed with three strain gauges (one each at the midspan top & bottom surface of concrete and one midspan rebar on the tension face) and one LVDT at midspan. The samples were then subjected to simple monotonic loading under a third-point bending test as per ASTM C78. The load-displacement, stress-strain and moment-curvature curves were obtained for all the tested specimens. It was found that ECC-strengthened beam samples displayed an increased flexural performance at first crack, yield, and ultimate load-carrying capacity as compared to conventional RC specimens. Whereas a better crack arrest with even distribution of cracks and improvement in ductility was observed for the ECC-strengthened composite beams.

This paper examines the impact of transverse reinforcement and shear span on the shear capacity of reinforced concrete (RC) cantilever beams through both experimental and numerical investigations. The experimental program included testing nine RC beams, each with dimensions of 200 × 300 × 1200 mm. The experimental results were compared with analytical predictions derived from empirical models based on the ACI 318-19 and British Standards (BS) codes.The findings reveal that stirrups significantly enhance shear strength, resulting in an increase in load-carrying capacity ranging from 16.6% to 32.7%, while ductility, as evidenced by increased rotation and curvature, improved by up to 260%. The stirrup spacings employed in the specimens were 75, 100, and 150 mm, with both reinforced and unreinforced specimens exhibiting shear failure.Increasing the shear span-to-depth ratio (a/d) from 2.44 to 3, while keeping the stirrup spacing at 75 mm, resulted in a 12.9% reduction in ultimate load capacity. When the stirrup spacing was increased to 100 mm, the ultimate load capacity experienced a further decline of 23.9%. All beams were analysed using the finite element software ABAQUS, with the finite element analysis (FEA) results closely aligning with the experimental outcomes, particularly in the load-deflection relationship and maximum load capacity. On average, the predicted ultimate load capacity from ABAQUS was 2.7% lower than the experimental results, while the average difference in deflection at ultimate loads between the experimental and numerical results was 7.54%.

Structural strengthening is essential in civil engineering to ensure the integrity, safety, and longevity of various types of structures. Effective strengthening is required to solve these issues and lengthen the service life of structures as they naturally deteriorate with time. Hence, the use of various strengthening techniques to enhance the structural integrity of existing structures and infrastructure has gained prominence in recent years. This study demonstrates how Reinforced Concrete (RC) structures may benefit from Near-Surface Mounted (NSM) technology. The demonstration involves the experimental study on the performance of three different types of RC beams; unstrengthened RC beam, RC beam strengthened with NSM procedure using a conventional steel ribbed bar, and RC beam strengthened with NSM procedure using an iron-based smart memory alloy (Fe-SMA) ribbed bar. Consequently, three RC beams were evaluated at room temperature throughout the experimental testing, while the remaining three RC beams were examined after being exposed to a 200°C temperature exposure. The load-deflection, strain deformation and crack propagation were demonstrated to determine the behaviour of the RC beam. The experimental findings suggested that the performance of RC beams strengthened using NSM techniques was superior to that of RC beams that had not been strengthened. Although the results generally indicated a decrease in ultimate load obtained in the RC beams exposed to elevated temperature compared to RC beams tested at room temperature. It is shown that Fe-SMA RC beams performance better compared to steel strengthened RC beams. The RC beams strengthened with an Iron-based smart memory alloy ribbed bar recorded an increase in load-carrying capacity. These results demonstrate the substantial variations in load-bearing capacities among the beams and emphasise the efficiency of the strengthening application for RC beams in the constructions industry, particularly the use of iron-based smart memory alloy ribbed bars as strengthening materials.

Study on collapse of steel-reinforced concrete structure caused by self-weight during construction

Objectives: The primary objective of this current research is to determine the ideal horizontal spacing for hexagonal web openings and their maximum load-bearing capacity through Finite Element Analysis (FEA). Methods: The ISMB150 was implemented as a cross-sectional profile to fabricate distinct models of castellated beams with heights of 225 mm. The height of the web openings remained constant at 150 mm for the castellated beam model. The entire analysis is being done on ANSYS 19.2. Findings: The analysis has revealed that, for castellated beams with shallower depths, an optimal horizontal spacing of 44.9 mm for the web openings yields an ultimate load-bearing capacity of 144.26 KN. The results of castellated beams are measured in terms of ultimate load-carrying capacity, span-to-deflection ratio, load density, failure location, span-to-beam depth ratio, and the ratio of horizontal distance of opening-to-opening depth. Novelty: This research contributes analytical findings for the ideal horizontal distance of hexagonal web opening through maximum load-bearing capacity. Castellated beams have gained immense popularity within the structural engineering community today due to their visually appealing design featuring a variety of web-opening shapes. The primary objective of this current research is to determine the ideal horizontal spacing for hexagonal web openings and their maximum load-bearing capacity through Finite Element Analysis (FEA). The ISMB150 was implemented as a cross-sectional profile to fabricate distinct models of castellated beams with heights of 225 mm. The height of the web openings remained constant at 150 mm for the castellated beam model. The analysis has revealed that, for castellated beams with shallower depths, an optimal horizontal spacing of 44.9 mm for the web openings yields an ultimate load-bearing capacity of 144.26 KN. The results of castellated beams are measured in terms of ultimate load-carrying capacity, span-to-deflection ratio, load density, failure location, span-to-beam depth ratio, and the ratio of horizontal distance of opening-to-opening depth. This research contributes valuable insights into optimizing the design of castellated beams for enhanced structural performance. Further exploration and validation could provide additional refinements and applications in structural engineering. Keywords: Horizontal distance of web opening, Number of openings, Ultimate load carrying capacity, Failure modes, ANSYS, Castellated beams

This paper investigates numerically and experimentally the performance of reinforced concrete (RC) beam with unequal depths subjected to combined bending and shear. Such beams can geometrically be considered for unleveled reinforced concrete (RC) floor slab-beam system. However, it may generate critical disturbances in stress flow at the re-entrant corner (i.e. location of drop in beam depth). This research investigates the use of shear reinforcement and geometric properties to enhance cracking characteristics, yielding, ultimate load-carrying capacity, and exhibiting ductile failure mode. Ten reinforced concrete (RC) beams were constructed and tested experimentally considering the following key parameters: recess length, depth of smaller beam nib, and amount and layout of shear reinforcement at re-entrant corner. Finite element analysis (FEA) with material non-linearity was conducted in two RC beams that were tested experimentally to validate the computer modelling. The FEA models were then extended to conduct a parametric study to investigate the influence of geometric parameters (beam shape and width) and amount and arrangement of shear reinforcement on the structural response. Results confirmed that geometric properties and ratio of shear reinforcement at the re-entrant region significantly affect the behavior of reinforced concrete beam with unequal depths in terms of first cracking, yielding level, ultimate load carrying capacity and mode of failure.

<p>This paper investigates numerically and experimentally the performance of reinforced concrete (RC) beam with unequal depths subjected to combined bending and shear. Such beams can geometrically be considered for unleveled reinforced concrete (RC) floor slab-beam system. However, it may generate critical disturbances in stress flow at the re-entrant corner (i.e. location of drop in beam depth). This research investigates the use of shear reinforcement and geometric properties to enhance cracking characteristics, yielding, ultimate load-carrying capacity, and exhibiting ductile failure mode. Ten reinforced concrete (RC) beams were constructed and tested experimentally considering the following key parameters: recess length, depth of smaller beam nib, and amount and layout of shear reinforcement at re-entrant corner. Finite element analysis (FEA) with material non-linearity was conducted in two RC beams that were tested experimentally to validate the computer modelling. The FEA models were then extended to conduct a parametric study to investigate the influence of geometric parameters (beam shape and width) and amount and arrangement of shear reinforcement on the structural response. Results confirmed that geometric properties and ratio of shear reinforcement at the re-entrant region significantly affect the behavior of reinforced concrete beam with unequal depths in terms of first cracking, yielding level, ultimate load carrying capacity and mode of failure.</p>

<p>This paper investigates numerically and experimentally the performance of reinforced concrete (RC) beam with unequal depths subjected to combined bending and shear. Such beams can geometrically be considered for unleveled reinforced concrete (RC) floor slab-beam system. However, it may generate critical disturbances in stress flow at the re-entrant corner (i.e. location of drop in beam depth). This research investigates the use of shear reinforcement and geometric properties to enhance cracking characteristics, yielding, ultimate load-carrying capacity, and exhibiting ductile failure mode. Ten reinforced concrete (RC) beams were constructed and tested experimentally considering the following key parameters: recess length, depth of smaller beam nib, and amount and layout of shear reinforcement at re-entrant corner. Finite element analysis (FEA) with material non-linearity was conducted in two RC beams that were tested experimentally to validate the computer modelling. The FEA models were then extended to conduct a parametric study to investigate the influence of geometric parameters (beam shape and width) and amount and arrangement of shear reinforcement on the structural response. Results confirmed that geometric properties and ratio of shear reinforcement at the re-entrant region significantly affect the behavior of reinforced concrete beam with unequal depths in terms of first cracking, yielding level, ultimate load carrying capacity and mode of failure.</p>

Concrete is one of the most common building materials and is used for constructing buildings, bridges and other heavy structures. Strengthening structures via external bonding of advanced fibre reinforced polymer (FRP) composites is becoming very popular worldwide during the past few decades, because it provides a more economical and technically superior alternative to the traditional techniques in many situations, as it offers high strength, low weight, corrosion resistance, high fatigue resistance, easy and rapid installation and minimal change in structural geometry. It is important to understand the behaviour of a strengthened structure well and realize what parameters affect the failure mode and load-bearing capacity. The aim of this study is to investigate and improve the understanding of the behaviour of reinforced concrete (RC) beams strengthened with fibre composite. In the present study, a numerical investigation is carried out to study the behaviour of RC beams under static three-point loading. Concrete beam specimens with dimensions of 130 mm width, 200 mm height, and 2,500 mm length were modelled. The beams were strengthened with externally bonded glass fibre reinforced polymer (GFRP) sheets and carbon fibre reinforced polymer (CFRP) sheets. The present study examines the responses of the RC beams with GFRP and CFRP sheets by increasing number of layers using finite element simulation in ABAQUS, in terms of failure modes, enhancement of load carrying capacity, load-deflection behaviour and flexural behaviour.

Prestressed Steel Reinforced Concrete (PSRC) Structure is a new system by combining PC technology and steel reinforced concrete (SRC) structure, and is a technical innovation to the conventional structures, such as concrete structures, PC structures and SRC structures. Because having much virtue, for instance high bearing capacity, fine serviceable performance, covering and over loading capability, it will have expansive application. The serviceable performance can be observably improved by putting PC technology on the SRC beams, such as rigidity and crack resistibility degree. Based on static loading experiments of seven PSRC beams with different designing coefficients, the experimental phenomena as loading process, failure pattern are studied, and the primarily influencing factors on flexural performance have been contrasted to educe conclusion for future design.

Preventing corrosion in the steel reinforcement of concrete structures is crucial for maintaining structural integrity and load-bearing capacity as it directly impacts the safety and lifespan of concrete structures. By preventing rebar corrosion, the durability and seismic performance of the structures can be significantly enhanced. This study investigates the hysteresis behavior of both corroded and non-corroded engineered cementitious composite (ECC)-glass-fiber-reinforced polymer (GFRP) spiral-confined reinforced-concrete (RC) columns. Employing experimental methods and finite element analysis, this research explores key seismic parameters such as crack patterns, failure modes, hysteretic responses, load-bearing capacities, ductility, stiffness degradation, and energy dissipation. The results demonstrate that ECC-GFRP spiral-confined RC columns, compared to traditional RC columns, show reduced corrosion rates, smaller crack widths, and fewer corrosion products, indicating superior crack control and corrosion resistance. Hysteresis tests revealed that ECC-GFRP columns, at a 20% target corrosion rate, exhibit an enhanced load-bearing capacity, ductility, and energy dissipation, suggesting improved durability and seismic resilience. Parametric and sensitivity analyses confirm the finite element model's accuracy and highlight the significant influence of concrete compressive strength on load-bearing capacity. The findings suggest that ECC-GFRP spiral-confined RC columns offer promising applications in coastal and seismic-prone regions, enhancing corrosion resistance and mechanical properties, thus potentially reducing formwork costs and improving construction quality and efficiency.

Probabilistic models for characteristic bond stresses of steel-concrete in steel reinforced concrete structures

Deterioration of infrastructure is a major challenge in the civil engineering industry. One of the methods that has been deemed effective in upgrading reinforced concrete (RC) structures is using externally bonded fiber-reinforced polymer (FRP) composites. However, the efficacy of this retrofitting technique is limited by the premature debonding failure of the FRP at the concrete-FRP interface; thus, the full capacity of the FRP is rarely utilized. Anchorage systems were proposed as a feasible solution to suppress or delay debonding failure. This paper presents an experimental investigation on the use of end U-wraps and carbon FRP (CFRP) spike anchors to anchor CFRP plates bonded to flexure-deficient RC beams. The experimental program consisted of seven RC beams with the length of the CFRP plate, type of anchorage, and the number of anchors as experimental variables. Test results indicated a remarkable enhancement in the ultimate load-carrying capacity when longer CFRP plates were used to strengthen the beams. In addition, anchoring the plates enhanced the strength of the CFRP-plated beams by 16–35% compared to the unanchored specimen, depending on the anchorage type and scheme. Finally, fib Bulletin 90 (2019) provisions provided the most accurate predictions of the moment capacity of the strengthened specimens.

Effect of corrosion on bond slipping between steel and concrete in SRC structures