Reinforced Concrete Structures Research Articles

A Reliability-Based Design Approach for the Flexural Resistance of Compression Yielded Fibre-Reinforced Polymer (FRP)-Reinforced Concrete Beams

Fibre-reinforced polymer (FRP) reinforcement has been employed as an alternative to conventional steel reinforcement in concrete structures, which is attributed to its excellent strength and corrosion resistance. However, one drawback is that FRP reinforcements are brittle and affect the ductility of concrete structures. One of the recent effective techniques proposed to overcome ductility issues is the compression yielding (CY) concept. The CY mechanism allows the structure to fail differently than the conventional FRP-reinforced concrete structure. Thus, the existing design recommendations as per the current codes for FRP-reinforced concrete structures are not appropriate. Hence, reliability studies are crucial for the development of a functional CY beam design in order to emphasise the structure’s lifetime performance and to guarantee safety requirements. In this study, a reliability-based design approach is developed for a compression-yielded FRP-reinforced concrete beam (CY beam) using load and resistance factor design (LRFD). Firstly, the flexural failure modes of CY beams are discussed. The uncertainties involved in the development of the probabilistic model for the CY beam are defined. A case study is consequently conducted for a CY beam with random variables that are associated with the statistical characteristics of material properties and load. The reliability analysis method employed in this research is the Hasofer–Lind method. The results suggest the importance of choosing appropriate design variables and stochastic parameters for CY blocks that contribute to a higher level of reliability. The reliability index and resistance factors of a CY beam are then evaluated using the Monte Carlo Simulation computational method. The reliability index value of 3.336 is obtained from the simulation, which indicates that the CY beam demonstrates ductile behaviour. The results not only demonstrate ductile behaviour but also contribute to a possible reduction in material costs and a substantial safety margin. When compared to conventional FRP-reinforced concrete beams, for different load ratios, CY beams showed higher resistance and better reliability levels.

Durability Concerns for Different Clear Covers Provided to Reinforcement in Concrete Structures When Considering Different Chloride Exposure Conditions for External and Internal Faces of Members

Durability Concerns for Different Clear Covers Provided to Reinforcement in Concrete Structures When Considering Different Chloride Exposure Conditions for External and Internal Faces of Members

Early Detection and Monitoring of Corrosion in Reinforced Concrete Structures Using Coupled Time-Frequency Analysis

Early Detection and Monitoring of Corrosion in Reinforced Concrete Structures Using Coupled Time-Frequency Analysis

Life-Cycle Cost Assessment of the Base-Isolated Reinforced Concrete Structure

Life-Cycle Cost Assessment of the Base-Isolated Reinforced Concrete Structure

Multiscale insights on compression cast sea sand and seawater concrete

Reinforced concrete (RC) structures in coastal and marine regions face two primary challenges, the shortage of raw materials and severe service environments. Concrete made from sea sand and seawater (SS-SW) can address the shortage of natural sand by utilizing locally available resources. Meanwhile, the newly developed compression cast technology (CCT) significantly improves the micro and macro properties of concrete, enhancing its durability in harsh environments. Therefore, the combination of SS-SW concrete and CCT to form a new compression-cast SS-SW concrete can simultaneously solve the problems of materials shortage and durability issues for coastal RC structures. However, till now, research on this type of concrete is still an open issue. This paper aims to carry out multilevel investigations on the macro and micro performance of compressed SS-SW concrete. First, 69 concrete columns were tested to understand the stress-strain behavior and associated mechanical indices. The compressive strength of compressed concrete was found to be up to 1.86 times greater than that of uncompressed concrete. Meanwhile, the porosities in both mortar and the interfacial transition zone (ITZ) of concrete under a casting pressure of 15 MPa were approximately 50 % of those in uncompressed counterpart. Existing models are inadequate for predicting the behavior of compressed SS-SW concrete, leading to the development of new and accurate models to predict its compressive strength, elastic modulus, peak strain and stress-strain curve. These findings pave the way for the design and application of this kind of concrete.

Seismic Performance and Failure Mechanisms of Reinforced Concrete Structures Subject to the Earthquakes in Türkiye

Seismic Performance and Failure Mechanisms of Reinforced Concrete Structures Subject to the Earthquakes in Türkiye

Assessment of the seismic failure of reinforced concrete structures considering the directional effects of ground motions

Seismic intensity measures at different levels significantly impact the seismic damage of building clusters. Reinforced concrete (RC) structures are a type of building widely used in different regions worldwide. A large amount of field seismic damage observation data indicates that within the same seismic intensity zone, the directional effects of varying ground motions lead to significant differences in damage to RC structures on different floors. However, relatively little research has been conducted on estimating the seismic fragility and vulnerability of RC structures considering the directional effects of seismic action. To further study the directional effect of seismic motion on the damage of different floors, this study conducted dynamic time history and spectral analyses on 1472,379 acceleration records in multiple directions obtained from monitoring at nine actual seismic stations during the 2008 Wenchuan earthquake in China. This paper innovatively reports on the actual damage features of RC structures during the Mw6.2 magnitude Jishishan earthquake in Gansu Province, China, on December 18, 2023 (the most severe destructive earthquake in China in 2023) and analyses the influence of earthquake directionality on the damage to different floors of RC structures. A three-dimensional numerical model of a four-story RC frame structure was established using numerical simulation and the finite element method. Different intensity measures were taken to input seismic excitations of different intensities into the RC structure in the 0°, 30°, 60°, and 90° directions, and damage simulation analysis was conducted. The nonlinear dynamic time history curves of structures under multiple directions of seismic excitation in different intensity zones have been developed. Using the interstory stiffness and interstory displacement angle as engineering demand parameters, damage assessment curves and stress clouds for RC structures with 1–4 floors considering different seismic directional effects were generated. The analysis results and major findings indicate that the seismic sequence in the 0° direction has a relatively heavy impact on the first floor of the RC structure in zone IX, which is consistent with the actual field observation results.

The Impact of Buckling Restrained Braces in Strengthening Deficient Reinforced Concrete Structures

The Impact of Buckling Restrained Braces in Strengthening Deficient Reinforced Concrete Structures

Effect of longitudinal reinforcement ratio on residual flexural capacity of high-strength reinforced concrete beams exposed to impact loading

In this study, it was aimed to investigate the dynamic impact and post-impact performances of high-strength reinforced concrete (RC) beams, which have different ductility and load-bearing capacities. The dynamic behavior and impact damages of RC beams were compared after exposure to a constant magnitude of impact energy. The applied impact energy was obtained by dropping a mass of 360 kg from a certain height of 3 m. The cross-section dimensions and length of the specimens were selected to carry out the experiments in full-scale. The tested specimens were designed with five different longitudinal reinforcement ratios for demonstrating distinct structural behavior mechanisms that vary from pure flexure to pure shear, representing different ductilities, load-bearing capacities and potential failure characteristics. The post-impact behavior of the impacted RC beams was also assessed by performing quasi-static bending tests on the impact-damaged specimens and the obtained results were compared with the identical undamaged reference RC beams. The results demonstrated that the longitudinal reinforcement ratio (which was intentionally designed for different specimens to exhibit different structural responses from pure shear to pure flexural and different shear-flexure mechanisms) significantly influences the dynamic response and damage intensity of the beams, which, in turn, affect their post-impact static performance. Key structural characteristics, including residual displacement, ductility, energy dissipation, load-carrying capacity, and stiffness, were analyzed. It was found that the mechanical properties of the beams deteriorated markedly after impact exposure. A crucial finding of this research is the notable shift in failure modes from flexural to shear after impact, depending on the damage severity. In RC beams, shear damage remains insignificant under both impact loading and subsequent static loading when the ratio of shear strength to flexural strength (Vr/Mr) exceeds 1.5. Conversely, when this ratio is less than 1.5, the behavior transitions to being shear-critical or shear-dominant. This study presents, for the first time, comprehensive experimental results on the impact-induced damage progression, failure mechanisms, and residual behavior of high-strength RC beams. These insights are vital for understanding the performance of RC structures under impact loads and contribute significantly to the field of structural engineering, particularly in designing impact-resilient structures.

Unlocking Resilience: Examining the Influence of Fluid Viscous Dampers on Seismic Performance of Reinforced-concrete Structures in Earthquake-prone Regions

Unlocking Resilience: Examining the Influence of Fluid Viscous Dampers on Seismic Performance of Reinforced-concrete Structures in Earthquake-prone Regions

Concealed Beam in Reinforced Concrete Structures: A Performance-Based Analysis

The use of hidden beams in reinforced concrete construction is seen as an effective method of reducing excessive deflection in large spans. However, despite its presumed advantages and growing usage, no mention of it in standard civil engineering literature, codes and standards. In this paper, performance-based analysis is carried out on three different cases of slab arrangement involving hidden beams using SAP2000. The process is performed under dead and live load combination and based on the design guidelines in BS8110. The result of the performance-based analysis shows a 4%, 2% and 11% decrease in deflection, stress distribution and area of bending steel reinforcement required for the case with hidden beam in comparison with the case without the hidden beam. This indicates that the presence of a hidden beam in a slab is significant. Thus, it is recommended for reducing excessive deflection in large spans, hidden beams can be introduced.

Experimental Study on the Impact Resistance Performance of Civil Air Defense RC Walls Protected by Honeycomb Sandwich Panels

Reinforced concrete (RC) walls are extensively used in civil air defense engineering and are susceptible to low-speed impacts with high energy and massive weight during service. Therefore, it is crucial to consider the impact resistance of these walls and explore effective protection methods. The honeycomb structure, known for its energy-absorbing properties, has been widely utilized in aerospace, automotive, and maritime industries. However, there is a need for more research on applying honeycomb structures in energy-absorbing protection devices in civil engineering. This study proposes the use of honeycomb sandwich panels to protect civil air defense RC walls, creating a Honeycomb Sandwich Panel Composite RC wall (HSP-RC wall). Through pendulum impact experiments, we investigated the dynamic response of RC walls, both standard and HSP-RC walls with varying honeycomb parameters, under high-energy impacts. The goal was to evaluate the impact resistance of these RC walls, analyze the deformation differences among different HSP-RC walls, and examine the influence of honeycomb parameters on the impact protection effectiveness. The research results indicate that honeycomb sandwich panels can provide impact protection for RC walls by absorbing energy, and their protection effect is related to the parameters of the honeycomb core layer. This research result can be applied to RC structures that bear impact loads, achieving effective protection for RC structures.

Seismic Performance of Corroded ECC-GFRP Spiral-Confined Reinforced-Concrete Column

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.

Comparative Study of Reinforced Concrete Using Human Hair and Aluminum Fibres

This study investigates the efficacy of human hair and aluminum fibres as reinforcements in concrete, analyzing their impact on compressive, flexural, and tensile strengths. Different fibre percentages (0%, 0.5%, 1%, and 1.5% by weight of cement) are systematically incorporated into concrete mixtures. Compressive strength tests on cubes, flexural strength assessments on beams, and tensile strength evaluations on cylinders reveal insights into the material's load-bearing, bending, and stretching capacities. Human hair-reinforced concrete showed significant improvements in compressive strength. Results indicate a gradual strength increase in Human Hair Fibre Reinforced Concrete (HHFRC) up to an optimal percentage. At the same time, Aluminum Fibre Reinforced Concrete (AFRC) shows significant enhancement in higher fibre content. AFRC's superior mechanical properties stem from aluminum fibres high tensile strength and stiffness, enhancing bond formation and resulting in denser, stronger concrete. These findings inform the selection of fibre reinforcement for concrete structures tailored to specific project needs.

FEM simulations applied to the failure analysis of RC structure under the influence of municipal sewage pressure

The paper discusses a failure mechanism of reinforced concrete (RC) structure with steel cover that failed under the influence of municipal sewage pressure. To explain the reasons of failure, in-situ measurements, laboratory experiments and comprehensive Finite Element Method (FEM) computations were performed. Non-destructive in-situ scanning tests were carried out to determine quantity and cover thickness of embedded reinforcement bars, simultaneously, laboratory tests regarding concrete and shotcrete thickness, density and compressive strength were performed on samples prepared from core drills taken from the RC structure. FEM computations were carried out with the constitutive continuum model for concrete and steel with material parameters designated on the basis of stress–strain curves in uniaxial compression and uniaxial tension, respectively. An isotropic coupled elasto-plastic-damage formulation based on the strain equivalence hypothesis was used. In order to describe strain localization in concrete, model was enhanced in a softening regime by a characteristic length of micro-structure by means of a non-local theory. FEM analyses were carried out for different values of sewage pressure. The main attention was paid to the evolution of steel cover deformation and strain localization of the RC ceiling slab. FEM results revealed strong dependence between a bond-slip between anchors and steel cover deformation as well as between sewage pressure value and strain localization pattern of RC structure. Mechanism of the structure failure under complex loading conditions was realistically captured and its reasons were discussed in detail.

Framework for lifecycle resilience assessment of earthquake-damaged coastal RC structures considering non-uniform corrosion

Reinforced concrete (RC) structures in seismic coastal areas often suffer from the coupled effects of corrosion and earthquakes due to prolonged exposure to harsh environmental conditions. Previous research on the seismic performance of buildings primarily focused on uniform corrosion(UC), disregarding the impact of varying concentrations of chloride-ions on corrosion rate. This discrepancy will overestimate the seismic performance of building structures. The framework proposed in this study aims to evaluate the resilience of RC structures to non-uniform story corrosion(NUSC). The framework encompasses an innovative functional recovery function and considers the influence of chloride-ions concentration on the corrosion rate, time-varying initial functional function, and degradation model for corroded reinforced concrete. NUSC model is established within the proposed framework via OpenSees software. The proposed framework integrates the seismic hazard, fragility, resilience, and recovery models. A nonlinear time history analysis method is employed to simulate the structural response to the seismic action. The findings demonstrate that NUSC leads to a reduction in seismic resilience by 7.3% and 10% compared to UC when considering service times of 35 and 55 years, respectively. This indicates an escalation in seismic risk as well as a decline in structural seismic capacity.

Development of high-dispersion CLDH/carbon dot composites to boost chloride binding of cement

Chloride-induced corrosion of steel reinforcement significantly contributes to the durability deterioration for reinforced concrete (RC) structures. Calcined layered double hydroxide (CLDH) possesses a distinctive structure memory effect to adsorb anions and a nucleation effect to facilitate cement hydration, thereby demonstrating a promising potential for chloride binding enhancement of cementitious materials. However, CLDH suffers from severe agglomeration in cement composites, limiting its performance efficacy. To tackle this problem, novel high-dispersity CLDH/carbon dots (CDs) composites (CC) only at small dosages are applied to greatly improve the chloride binding behavior of cement pastes for the first time. In detail, the specific surface area of CC synthesized by simply stirring CDs and CLDH improves by 166.4 % than that of pure CLDH. Remarkably, cement pastes containing CC display a preferable chloride binding capacity; And the chloride binding substantially increases by 52.41 % when the incorporation of CC (by weight of cement) is 0.8 wt%. More importantly, according to the phase composite and microstructure analyses, the chloride binding enhancement mechanism of CC-containing cement pastes is reasonably ascribed to two effects of CC: providing nucleation sites to accelerate cement hydration and exerting the inherent chloride adsorption capacity. This boosts the formation of C–S–H gels and improves the structure memory effect and anions exchange-induced chloride adsorption, thus significantly strengthening the chloride binding of cement. This work provides a novel approach to improve the dispersity of CLDH, effectively strengthening the chloride binding of cement, thereby conductive to prolonging the service life of RC structures.

Strategies for Teaching the Reinforced Concrete Structures Course in Engineering Majors

The cultivation of engineering capabilities aims to equip engineering professionals with high-level expertise to meet the demands of society and industry development, thereby enhancing their competitiveness and career potential. This article focuses on engineering capability development, exploring teaching strategies for the Reinforced Concrete Structure course. It aims to provide insights for educators in engineering programs at universities and vocational colleges in China. By doing so, teaching plans that meet the needs of engineering capability development, laying a solid educational foundation for the healthy growth of engineering professionals in the new era, and enhancing their application of knowledge and skills can be developed.

Reducing target reliability index of concrete bridge beams through compression yielding

Damage to reinforced concrete (RC) bridges due to accidental overloading is inevitable, especially for those that deteriorate over time due to various environmental and operational factors. When significant damage occurs, it needs to be replaced. However, replacing bridges is expensive and time-consuming. This problem can be well resolved by the concept of compression yield (CY) structures. When an overload occurs, the CY block in the beam is triggered like a fuse, forcing the beam to deform in a ductile manner, thus preventing further overloads. Additionally, the damaged CY blocks can be replaced without replacing the entire beam. Due to this safer failure mode and lower cost of failure, the safety reserve of the CY beam can be significantly lower than that of the traditional RC structure, which means that the target reliability of the CY bridge needs to be re-established. The objective of this study is to develop the target reliability of CY bridge. The target reliability of structures is determined through cost optimization. The life-cycle costs for bridges are determined based on the practical construction and post-construction management process. The calculated results indicate that although the initial cost of CY beams could be higher, the losses associated with failures are significantly lower compared to RC beams. Consequently, the target reliability and life cycle costs of CY bridge can be lower than those of the RC bridge.

Cross-Sectional Capacities of Reinforced Concrete Structures Using Abaqus and Staadpro Software

Cross-Sectional Capacities of Reinforced Concrete Structures Using Abaqus and Staadpro Software