Search Results (413)

Openings in two-way reinforced concrete (RC) slabs are frequently incorporated for architectural and functional purposes, such as providing pathways for mechanical, electrical, and plumbing services. While necessary, these openings can significantly compromise the structural performance of slabs, particularly by reducing their capacity to resist punching shear, an effect that is especially critical when the openings are located near column–slab connections. This paper provides a detailed review of the existing research, examining how various opening parameters such as their size, shape, and position affect key structural performance metrics including their stiffness, ductility, and failure modes. The findings highlight that opening geometry is a major determinant of a slab’s overall behavior. Notably, the proximity of openings to column faces is identified as a critical factor that can substantially influence the extent of strength degradation and failure mechanisms. Furthermore, this review identifies a significant research gap concerning the behavior of slabs with openings under non-standard loading conditions, such as seismic activity, blasts, and impact loads. It also emphasizes the need for further investigation into the long-term performance of such slabs under adverse environmental influences, including elevated temperatures, corrosion, and material degradation. By consolidating the current knowledge and identifying unresolved challenges, this review aims to guide engineers and researchers in developing more robust design strategies and performance-based solutions for RC slabs with openings, ultimately contributing to safer and more resilient structural systems. Full article

This study introduced basalt fibres as a reinforcing material and employed notched beam three-point bending tests combined with digital image correlation (DIC) technology to comprehensively evaluate key fracture parameters—namely, initial fracture toughness, unstable fracture toughness, fracture energy, and ductility index—of expanded polystyrene (EPS)-based geopolymer concrete with different mix proportions. The results demonstrate that the optimal fracture performance was achieved when the basalt fibre volume content was 0.4% and the EPS content was 20%, resulting in respective increases of 12.07%, 28.73%, 98.92%, and 111.27% in the above parameters. To investigate the toughening mechanisms, scanning electron microscopy was used to observe the fibre–matrix interfacial bonding and crack morphology, while X-ray micro-computed tomography enabled detailed three-dimensional visualisation of internal porosity and crack development, confirming the crack-bridging and energy-dissipating roles of basalt fibres. Furthermore, the crack propagation process was simulated using the extended finite element method, and the evolution of fracture-related parameters was quantitatively analysed using a linear superposition progressive assumption. A simplified predictive model was proposed to estimate fracture toughness and fracture energy based on the initial cracking load, peak load, and compressive strength. The findings provide theoretical support and practical guidance for the engineering application of basalt fibre-reinforced EPS-based geopolymer lightweight concrete. Full article

Prefabricated construction elements are widely used in both large- and small-scale projects, serving structural and infrastructural purposes. One notable application is in power transmission poles, which ensure the safe and efficient delivery of electricity. Despite their importance, limited research exists on the structural and modal behavior of reinforced concrete power poles. This study presents a comprehensive modal analysis of such poles, focusing on how factors like modulus of elasticity, height, and lower/upper inner and outer diameters influence dynamic performance. A total of 3240 finite element models were created, with reinforced concrete poles partially embedded in the ground. Modal analyses were performed to evaluate natural frequencies, mode shapes, and modal mass participation ratios. Results showed that increasing the modulus of elasticity raised frequency values, while greater pole height decreased them. Enlarging the lower inner and upper outer radii also led to higher frequencies. Regression analysis yielded high accuracy, with R² values exceeding 90% and an average error rate of about 6%. The study provides empirical formulas that allow for quick frequency estimations without the need for detailed finite element modeling, as long as the material and geometric properties remain consistent. The approach can be extended to other prefabricated structural elements. Full article

This article presents a review on the applications of basalt fibers and their composites in infrastructures. The characteristics and advantages of high-performance basalt fibers and their composites are firstly introduced. Then, the article discusses strengthening using basalt fiber sheets and BFRP bars or grids, followed by concrete structures reinforced with BFRP bars, asphalt pavements, and cementitious composites reinforced with chopped basalt fibers in terms of mechanical behaviors and application examples. The load-bearing capacity of the strengthened structures can be increased by up to 60%, compared with those without strengthening. The lifespan of the concrete structures reinforced with BFRP can be extended by up to 50 years at least in harsh environments, which is much longer than that of ordinary reinforced concrete structures. In addition, the fatigue cracking resistance of asphalt can be increased by up to 600% with basalt fiber. The newly developed technologies including anchor bolts using BFRPs, self-sensing BFRPs, and BFRP–concrete composite structures are introduced in detail. Furthermore, suggestions are proposed for the forward-looking technologies, such as long-span bridges with BFRP cables, BFRP truss structures, BFRP with thermoplastic resin matrix, and BFRP composite piles. Full article

The use of both structural steel and reinforced concrete is common in civil and military infrastructure projects. Anchorage plays a crucial role in these systems, serving as the key element that connects structural components and secures attachments within complex composite structures. This research focuses on evaluating the performance of steel–concrete column connections under the combined effects of lateral loading and fire exposure. Additionally, the study investigates the use of carbon fiber-reinforced polymers (CFRP) for strengthening and repairing these connections. The research methodology combines experimental testing and finite-element modeling to achieve its objectives. First, experimental investigation was carried out to test two groups of steel-reinforced concrete column specimens, each group made of three specimens. The first group specimens were designed based on special moment frame (SMF) detailing, and the other group specimens were designed based on intermediate moment frame (IMF) detailing. These two types of design were selected based on seismic demands, with SMFs offering high ductility and resilience for severe earthquakes and IMFs providing a cost-effective solution for moderate seismic zones, both benefiting from ongoing innovations in connection detailing and design approaches. Then, finite-element analysis was conducted to model the test specimens. High-fidelity finite-element modeling was conducted using ANSYS program, which included three-dimensional coupled thermal-stress analyses for the six tested specimens and incorporated nonlinear temperature-dependent materials characteristics of each component and the interfaces. Both the experimental and numerical results of this study show that fire has a more noticeable effect on displacement compared to the peak capacities of both types of specimens. Fire exposure results in a larger reduction in the initial residual lateral stiffness of the SMF specimens when compared to IMF specimens. While the effect of CFRP wraps on initial residual lateral stiffness was consistent for all specimens, it caused more improvement for the IMF specimen in terms of post-fire ductility when compared to SMF specimens. This exploratory study confirms the need for further research on the effect of fire on the concrete–steel anchorage zones. Full article

To address the challenges of slow construction and high self-weight in steel–concrete composite floors for rural light steel frame structures in China, a new prefabricated floor system was developed. This system features prefabricated slabs made from recycled concrete, connected via reinforced shear pocket joints. In seismic environments, assembly floor joints often become vulnerable points, making their shear resistance particularly crucial. This study investigated the shear performance of this new type of floor joint, examining the effects of various parameters such as joint configuration, stud diameter, recycled concrete strength, and grout strength. A refined finite element model was established for an in-depth parameter analysis. The research revealed stud–shear failure as the mode of floor joint failure under different design parameters. The detailed design of the new joint structure ensures safety in the floor joint area. Increasing stud diameter, recycled concrete strength, and grout strength all contributed to enhancing the joint’s shear capacity and stiffness, with stud diameter having the most significant impact. Higher recycled concrete strength improved shear capacity, although its influence decreased beyond a certain threshold. Optimal reserved hole diameter proved beneficial for enhancing joint shear performance, with a diameter of 40 mm showing superior performance. Full article

Understanding the structural behaviour of flat plate systems during fire exposure is critical for ensuring the safety of occupants and emergency personnel. Flat slabs, a widely used structural system, undergo significant thermal deformations in fire, which increase demands on supporting columns and reduce the stiffness and strength of concrete and steel. While experimental fire tests have provided valuable data to understand the behaviour of isolated components of flat slabs, numerical analysis is the only route to comprehending the structural behaviour of full-scale flat plate structures during fire exposure. ABAQUS is commonly used for modelling reinforced concrete (RC) structures under fire, with two prevailing techniques: (1) solid element modelling for concrete and truss reinforcement and (2) shell element modelling with embedded steel layers and line-column elements. However, uncertainties remain regarding the influence of modelling parameters such as dilation angle and concrete tensile stress, and the impact of surface fire exposure has not been comprehensively studied. This study presents a novel contribution by conducting a detailed numerical investigation of a full-scale flat plate structure exposed to fire using both modelling approaches. The shell-element model was validated against experimental data and used to evaluate the effect of dilation angle and tensile strength assumptions. A unique aspect of this work is the assessment of fire exposure on different slab surfaces, including bottom, top, and both, which provides insights into slab deflections and column displacements under different surface fire exposure scenarios. The structure was then modelled using solid elements to systematically compare modelling techniques. The results highlight key differences between approaches and guide for selecting the most suitable modelling strategies for fire-exposed flat plate systems. Full article

This article includes tests of the deflection and load-bearing capacity of reinforced concrete beams exposed to chloride ions. This work forms part of the verification of a newly developed model for estimating the intensity of the corrosion current of the reinforcement, which assumes the possibility of estimating the corrosion parameter based on a detailed analysis of the element deformation. The model assumes the use of the inverse problem, which is based on the analysis of deflection as a result of the partial impact of the corrosion process on the main reinforcement in the reinforced concrete element. This article presents, in detail, the course of the conducted tests, including the results of the deflection measurements with simultaneous measurements of the intensity of the corrosion current of the reinforcement during the test. As part of this research, a gravimetric analysis of the loss of reinforcement mass caused by the ongoing corrosion process was also performed. The main objective of this research was to experimentally verify the adopted model of the new diagnostic method, which fully confirmed the model assumptions. The obtained research results confirmed the validity of the assumptions adopted in the theoretical model, which was further confirmed by analytical calculations. Full article

Reinforced concrete structures often require retrofitting due to damage caused by natural disasters such as earthquakes, floods, or hurricanes; deterioration from aging; or exposure to harsh environmental conditions. Retrofitting strategies may involve adding new structural elements like shear walls, dampers, or base isolators, as well as strengthening the existing components using methods such as reinforced concrete, steel, or fiber-reinforced polymer jacketing. Selecting the most appropriate retrofit method can be complex and is influenced by various factors, including initial cost, long-term maintenance, environmental impact, and overall sustainability. This study proposes utilizing an artificial neural network (ANN) to predict sustainable and cost-effective seismic retrofit solutions. By training the ANN with a comprehensive dataset that includes jacket thickness, material specifications, reinforcement details, and key sustainability indicators (economic and environmental factors), the model was able to recommend optimized retrofit designs. These designs include ideal values for jacket thickness, concrete strength, and the configuration of reinforcement bars, aiming to minimize both costs and environmental footprint. A major focus of this research was identifying the optimal number of neurons in the hidden layers of the ANN. While the number of input and output neurons is defined by the dataset, determining the right configuration for hidden layers is critical for performance. The study found that networks with one or two hidden layers provided more reliable and efficient results compared to more complex architectures, achieving a total regression value of 0.911. These findings demonstrate that a well-tuned ANN can serve as a powerful tool for designing sustainable seismic retrofit strategies, helping engineers make smarter decisions more quickly and efficiently. Full article

Past studies have offered insights into how graphite-derived graphene oxide (GDGO) can improve the mechanical properties and alter microstructural characteristics of concrete. These advantages can significantly impact the construction industry regarding cost, sustainability, and efficiency. However, the high cost of GDGO can make commercial implementation unattainable. This paper comprehensively investigates coal-derived GO as a cost-saving alternative to commercial GDGO while achieving comparable concrete performance. Different GO proportions were incorporated into concrete mixes through laboratory experiments to determine the effect on mechanical properties and microstructures. In this research, concrete mixes were formulated by replacing a portion of cement with coal-derived GO and adding this GO as an additive to concrete at varying percentages (0.05%, 0.10%, 0.25%, 0.50%, 1%, and 1.5% by weight of cement). The study revealed flexural, split tensile, and compressive strength improvements of 3.3%, 2.3%, and 21.2%, respectively, at a minimal 0.05 wt.% GO replacement. Optimal inclusions of GO as an additive ranging from 0.05 to 0.25 wt.% were identified to exhibit a maximum increase in mechanical properties. More precisely, adding 0.10 weight percent of GO as an additive to concrete showed increases in flexural, split tensile, and compressive strengths of 14.05%, 9.7%, and 34.2%, respectively. Furthermore, detailed analyses, including modulus of elasticity, Poisson’s ratio, heat of hydration, and microstructural analysis provided comprehensive insights into the enhanced mechanical performance of GO-incorporated concrete. Additionally, the study revealed a lower Ca/Si ratio in GO concrete, further validating the reinforcing properties of the GO. Full article

The connection zones between precast concrete composite slabs and composite walls commonly experience severe reinforcement conflicts due to protruding rebars, significantly reducing construction efficiency. To address this, a novel slotted concrete composite slab–composite shear wall (SCS-CW) connection without protruding rebars is proposed in this study. In this novel connection, rectangular slots are introduced at the ends of the precast slabs, and lap-spliced reinforcement is placed within the slots to enable force transfer across the joint region. To investigate the static performance of SCS-CW connections, four groups of connection specimens were designed and fabricated. Using the structural detailing of the connection zone as the variable parameter, the mechanical performance of each specimen group was analyzed. The results show that the specimens demonstrated bending failure behavior. The key failure modes were yielding of the longitudinal reinforcement in the post-cast layer, yielding of the lap-spliced reinforcement, and concrete crushing at the precast slab ends within the plastic hinge zone. Compared to composite slab–composite wall connections with protruding rebars, the SCS-CW connections demonstrated superior ductility and a higher load-carrying capacity, satisfying the design requirements. Additionally, it was revealed that the anchorage length of lap-spliced reinforcement significantly affected the ultimate load-carrying capacity and ductility of SCS-CW connections, thus highlighting anchorage length as a critical design parameter for these connections. This study also presents methods for calculating the flexural bearing capacity and flexural stiffness of SCS-CW connections. Finally, finite element modeling was conducted on the connections to further investigate the influences of the lap-spliced reinforcement quantity, diameter, and anchorage length on the mechanical performance of the connections, and corresponding design recommendations are provided. Full article

In 2022, a working party (fib TG 8.9.3) was formed to try and better develop critical chloride (C_crit) distributions for use in modelling new structures and assessing existing structures. The authors of this paper are leading TG 8.9.3. and are in the process of writing a Bulletin (the Bulletin) that will detail how C_crit values have been developed since the 1970s. The Bulletin notes that chloride-induced corrosion initiation modelling based on C_crit is not intended as a sole durability assessment tool for structures exposed to chloride. It is recognized that voids and moisture at the bar can control corrosion activation virtually independent of chloride content, but in most cases sufficient voids and moisture are present so that the arrival of adequate chloride triggers corrosion activation of the reinforcement. So, durability verification by modelling restriction of chloride penetration, so that the concentration at the bar is less than that commonly found to cause corrosion, seems appropriate. This empirical approach was first fully detailed in fib Bulletin 34 A key part in the empirical model is the ‘adequate chloride to trigger corrosion activation’ C_crit. Although C_crit has a wide distribution and has different distributions in different environments and concrete compositions, its use in modelling provides greater design flexibility and improved confidence compared to the Deemed-to-Satisfy (DtS) rules included in most codes. Because of the limitations in DtS provisions, modelling provides more effective designs by incorporating specific criteria for a broad range of exposures, materials, and construction methods. This paper proposes that a lower bound for C_crit distributions for a range of materials and exposures can be developed from published papers. This paper includes C_crit distributions for steel fibres, carbon steel (above and below water), high tensile steel, galvanized steel, and stainless steels. These are expected to be recommended in the Bulletin. Full article

This study investigates the failure modes and damage extent of reinforced concrete (RC) columns under the combined action of eccentric blast loading and axial compressive loading through experimental tests and numerical simulations. Field blast tests were performed using half-scaled-down models for close-in airburst tests. The effects of charge mass, explosive position, and axial load on the failure modes and damage levels of RC columns under close-range blast loading were investigated. Eight experimental datasets of blast overpressure were obtained, and curve fitting was performed on these data to establish an empirical formula, thereby enhancing the predictive accuracy of blast effect assessment in practical engineering scenarios. The test results indicated that when the explosive position is closer to the column base, the structural failure mode becomes closer to shear failure. To further interpret the experimental data, a detailed finite element model of RC columns was developed. Numerical simulations of RC columns were conducted using the RHT model. The rationality of the model was validated through comparison with experimental data and the SDOF method, with dynamic response analyses performed on cross-sectional dimensions, the longitudinal reinforcement ratio, the scaled distance, the explosion location, and axial compression. An empirical formula was ultimately established to predict the maximum support rotation of RC columns. Studies have shown that when the explosive position is closer to the column base, the structural failure mode approaches shear failure, and axial compression significantly increases the propensity for shear failure. Full article

Bridges are assets in every society, and their deterioration can have severe economic, social, and environmental consequences. Therefore, implementing effective asset management strategies is crucial to ensure bridge infrastructure’s long-term performance and safety. Roadmaps can serve as valuable tools for bridge asset managers, helping bridge engineers make informed decisions that enhance bridge safety while maintaining controlled life cycle costs. Although some bridge asset management roadmaps exist, such as the one published by the United States Federal Highway Administration (FHWA), there is a lack of structured research roadmaps that are both region-specific and adaptable as guiding frameworks for similar studies. For instance, the FHWA roadmap cannot be universally applied across diverse regional contexts. This study addresses this critical gap by developing a research roadmap tailored to Idaho, USA. The roadmap was developed using a three-phase methodological approach: (1) a comprehensive analysis of past and ongoing Department of Transportation (DOT)-funded research projects over the last five years, (2) a nationwide survey of DOT funding and research practices, and (3) a detailed assessment of Idaho Transportation Department (ITD) deficiently rated bridge inventory, including individual element condition states. In the first phase, three filtering stages were implemented to identify the top 25 state projects. A literature review was conducted for each project to provide ITD’s Technical Advisory Committee (TAC) members with insights into research undertaken by various state DOTs. Moreover, in the second phase, approximately six questionnaires were designed and distributed to other state DOTs. These questionnaires primarily covered topics related to bridge research priorities and funding allocation. In the final phase, a condition state analysis was conducted using data-driven methods. Key findings from this three-phase methodological approach highlight that ultra-high-performance concrete (UHPC), bridge deck preservation, and maintenance strategies are high-priority research areas across many DOTs. Furthermore, according to the DOT responses, funding is most commonly allocated to projects related to superstructure and deck elements. Finally, ITD found that the most deficient elements in Idaho bridges are reinforced concrete abutments, reinforced concrete pile caps and footings, reinforced concrete pier walls, and movable bearing systems. These findings were integrated with insights from ITD’s TAC to generate a prioritized list of 23 high-impact research topics aligned with Idaho’s specific needs and priorities. From this list, the top six topics were selected for further investigation. By adopting this strategic approach, ITD aims to enhance the efficiency and effectiveness of its bridge-related research efforts, ultimately contributing to safer and more resilient transportation infrastructure. This paper could be a helpful resource for other DOTs seeking a systematic approach to addressing their bridge research needs. Full article

The structural behavior of precast concrete segmental bridges is very important to investigate, and the necessity is increased under the effect of being exposed to severe environmental conditions, such as freezing and thawing cycles. In this study, nonlinear finite element analysis (NLFEA) was adopted to address the behavior of reinforced shear keys where they were very small and distributed within the overall depth of the connection region. The effect of the amount of lateral confinement was investigated using six values (1, 2, 3, 4, 5, and 6 MPa), along with the effect of different freezing-thawing cycles (0 (undamaged), 100, 200, 300, and 400). Simulation was accomplished using the direct static shear method, where vertical loading was applied. The simulated models were first validated using experimental data from the literature, where the overall structural behavior was captured well. Thirty NLFEA models were simulated, and results were reported in terms of the load-deflection characteristics and the detailed cracking propagation process. It was found that increasing the lateral confinement will increase the shear strength capacity of the confined joint, in addition to increasing the ultimate deflection and initial stiffness values. Furthermore, a new formula was introduced for calculating the shear capacity compared with experimental data, NLFEA results, literature models, and AASHTO predictions, where good matching was observed, with a minor margin error. Full article