Abstract The demand for sustainable construction materials promotes the use of industrial waste in cement‐based systems. This study examines mortars incorporating fly ash (FA) (0%, 7.5%, and 15%), waste glass, and chromite aggregates for mechanical and durability performance. Specimens underwent compressive strength, freeze–thaw, high‐temperature, sulfate attack, and ultrasonic pulse velocity tests, while microstructure was characterized by x‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy–energy‐dispersive spectroscopy. Mortars with 7.5% FA exhibited relatively high compressive strength and improved freeze–thaw resistance. The combined use of chromite and FA improved strength retention at 800°C, reaching 23 MPa with 7.5% FA and 50% chromite. The greatest sulfate resistance occurred in mortars containing 15% FA and 15% waste glass, maintaining compressive strengths of 61 and 70.9 MPa after MgSO 4 and Na 2 SO 4 exposure, respectively.
Abstract High‐rise structures are highly sensitive to wind‐induced vibrations owing to their inherent flexibility. This study proposes a life‐cycle probabilistic risk assessment framework based on Bayesian updating to systematically quantify the impact of wind‐induced fatigue on the long‐term performance degradation of high‐rise structures. A high‐rise reinforced concrete (RC) TV tower exceeding 400 m in height is selected as a case study. Based on long‐term wind speed monitoring data obtained at the site of the case structure, the annual probability of occurrence across different wind speed ranges is quantified. By combining the material S–N curve with the linear cumulative damage criterion, the average annual fatigue damage in each critical material of the structure is evaluated. The unknown parameters of the structural demand model are estimated a posteriori using the Bayesian updating method, and time‐dependent fragility curves along with their confidence intervals are constructed. Furthermore, the regional wind hazard model is integrated to quantify structural failure risk and associated uncertainty. The results indicate that wind‐induced fatigue substantially reduces the wind resistance and structural lifespan, with the failure probability increasing nonlinearly over the service period. Significant differences are observed in the sensitivity of various damage states, and the failure probability of the steel mast under a complete damage state can increase by up to 58.4%. This study demonstrates the importance of accounting for cumulative fatigue effects in the wind‐resistant design of high‐rise structures.
Abstract This study provides a pioneering and in‐depth review of fiber‐reinforced polymer (FRP) flexural retrofitting methods for reinforced concrete (RC) structural walls, addressing critical gaps in seismic retrofitting research. While FRP composites offer exceptional strength‐to‐weight ratios and installation efficiency, their application to flexural enhancement of structural walls remains underexplored, particularly regarding debonding, compressive capacity limitations, and anchorage design. The study systematically evaluates innovative strategies such as vertically oriented FRP strips to optimize moment resistance and confined boundary elements to improve ductility while rigorously analyzing their effectiveness through experimental and analytical frameworks. A comparative assessment of international design guidelines highlights inconsistencies in addressing FRP's compressive contributions and anchorage requirements, underscoring the need for standardized practices. Furthermore, this review compares the findings of various studies, including ductility levels, load‐bearing capacities, influencing parameters, and the overall performance of different FRP‐strengthening systems for RC walls. By synthesizing empirical data and proposing novel theoretical insights, this review establishes actionable principles for optimizing FRP retrofitting in structural walls under cyclic loading. Its focus on cutting‐edge methodologies, unresolved challenges, and future directions positions it as an essential resource for advancing next‐generation retrofitting technologies in earthquake engineering.
Abstract This paper presents a regression‐based methodology to estimate the Torsional Stiffness Reduction Factor (TSRF) of reinforced concrete beams under combined torsion and shear. A numerical database of 6816 samples was generated using the Combined Action Softened Truss Model (CA‐STM) implemented in Python, considering design guidelines prescribed by ABNT NBR 6118:2023. Based on exploratory statistical analysis, two simplified regression models were developed to predict the TSRF: a simple linear model dependent on shear loading and a nonlinear model accounting for torsion–shear interaction. The proposed models were applied within an iterative structural analysis framework in a practical case study using the commercial design software TQS. Results show that torsional stiffness is highly sensitive to shear interaction, as expected, and may be either underestimated or overestimated by code prescriptions. The proposed methodology provides a practical tool to support a more refined estimation of torsional stiffness reduction in reinforced concrete members, accounting for shear force, which is often neglected.
Abstract Very‐early‐strength latex‐modified concrete (VES‐LMC) is widely used for emergency pavement repairs requiring rapid opening to traffic; however, improving mechanical performance while maintaining early‐age strength remains a challenge. This study evaluates the effectiveness of VES‐LMC reinforced with polyvinyl alcohol (PVA) macrofibers, which provide structural reinforcement, crack‐bridging capability, and strong interfacial bonding with the cement matrix, potentially reducing the need for treated steel fibers or hybrid macrofiber‐microfiber systems in emergency repairs to pavements and highways. PVA macrofibers were incorporated at dosages of 4.6 (0.35%) and 9.2 kg/m 3 (0.71%), and specimens were tested at 4 h, 7 days, and 28 days. The results showed that both dosages maintained sufficient workability and air content for field placement. The PVA macrofiber mixtures achieved 4‐h compressive strengths ranging from 25.29 to 26.62 MPa, consistently exceeding the 21 MPa requirement for early opening to traffic. Compared with the control VES‐LMC, early‐age flexural, splitting tensile, and direct tensile strengths increased by up to 30.26%, 19.16%, and 26.48%, respectively, with increasing fiber dosage. Overall, the incorporation of PVA macrofibers enhances tensile performance and crack resistance without compromising early‐age strength, demonstrating its suitability for rapid repair applications requiring early opening and long‐term serviceability.
Abstract To address the low cementitious activity of recycled micro‐powder (RMP) in concrete, this study proposes a synergistic activation method combining physical grinding with NaOH alkali excitation. The effects of water‐binder ratio, RMP dosage, and NaOH concentration on the mechanical properties of recycled micro‐powder concrete (RMPC) were systematically investigated, alongside the development of a Weibull‐based axial compression damage constitutive model. Results indicate a strong negative correlation between water‐binder ratio and mechanical performance; increasing the ratio from 0.4 to 0.6 reduced 28‐day compressive, tensile, flexural, and axial strengths by 53%, 19%, 34%, and 40%, respectively. Optimal performance was achieved at 10%–20% RMP dosage, where synergistic filling and pozzolanic effects improved flexural strength by 9% and compressive strength by 2%. Dosages ≥30% caused strength declines exceeding 20%. Furthermore, 2% NaOH excitation enhanced compressive strengths by 10%, while concentrations ≥3% inhibited hydration and deteriorated performance. The developed four‐point bending load‐deflection model ( R 2 ≥ 0.99) and axial compression damage constitutive model ( R 2 ≥ 0.97) demonstrated excellent agreement with experimental data, accurately capturing the full stress–strain response. These findings provide critical theoretical guidance for the high‐value utilization of construction solid waste and the structural design of eco‐friendly concrete.
Abstract Dry joints are widely used in precast segmental bridge construction because they simplify assembly and accelerate erection. Incorporating fasteners crossing flat dry joints represents an innovative configuration for this type of connection. When fasteners are present, shear transfer results from the interaction between friction and dowel action, particularly when significant relative displacements develop. In dowel‐controlled behavior, failure may occur through flexural yielding of the fastener and/or local crushing of the surrounding concrete. Advanced materials have been proposed to enhance the performance of these joints. Fiber‐reinforced concretes, including high and ultra‐high‐performance concrete, improve the tensile behavior and crack control of the concrete matrix. This study presents 24 push‐off tests on flat joints with and without fasteners, analyzing the influence of concrete type, fiber reinforcement, confining stress, and fastener configuration. Results show that dowel action becomes dominant as sliding increases, fiber reinforcement improves ductility and shear resistance, and the number of fasteners significantly influences the shear capacity. Furthermore, the results provide experimental evidence to support the refinement of current design provisions for shear transfer in unbonded posttensioned connections.
Abstract In actual engineering practice, the uplift behavior of stud connectors in composite beams is significantly influenced by beam bending deformation. Therefore, this study examines the failure process and the ultimate bearing capacity of stud connectors embedded in beams were discussed through tests on beam specimens and finite element models (FEMs). A total of six composite beam specimens were designed and conducted uplift tests. Test results showed that all specimens failed due to concrete cone failure. Based on the correlation curves of the relative displacement ( s ) between the stud connector and beam versus load ( N ), the damage process was categorized into three stages: the elastic stage, the damage development stage, and the accelerated damage stage. Notably, in the damage development stage, it was observed that the stud root could not effectively transfer the external load. This was due to beam bending cracks which invalidated the bond between the stud root and its surrounding concrete. Consequently, an effective stud embedded height ( h ′ ef ) was introduced to quantify this adverse effect of beam bending. Furthermore, a validated FEM was used for parametric analyses. Results indicated that h ′ ef was the critical factor in determining the final concrete failure cone, and the ratio of the original stud embedded height ( h ef ) to the beam height ( h ) had a significant effect on h ′ ef . Based on the analysis results and the concrete capacity design (CCD) model, a modified bearing capacity calculation method incorporating the beam bending effect was proposed, which could predict the tensile behavior of the stud connector in composite structures more accurately.
Abstract The corrosion‐induced deterioration of steel‐reinforced bridge decks is a service life concern, especially in cold regions, where the use of deicing chemicals is common. To address this issue, glass fiber‐reinforced polymer (GFRP) reinforcement has received growing attention, owing to the GFRP's resistance to conventional corrosion. However, the structural response of bridge decks reinforced with GFRP bars is still in need of exploration to build upon the available body of knowledge and facilitate the implementation of this reinforcement alternative. The current study contributes to this ultimate goal through a unique investigation, in which short‐ and long‐term performance characteristics of two side‐by‐side bridges, one reinforced with conventional steel and the other reinforced with GFRP, were assessed and compared. For this purpose, the bridge decks were instrumented with an array of sensors at the time of construction and monitored over more than 4 years. The recorded datasets were paired with regular visual inspections to capture crack development and growth. In addition, three sets of live load tests were conducted on both bridges to understand various structural response details, including neutral axis positions and girder distribution factors. A detailed life‐cycle cost analysis was also conducted to examine economic viability aspects. The results showed that the GFRP‐reinforced bridge deck provided a satisfactory structural response without any notable degradation over time, delivering performance characteristics comparable to those recorded for the steel‐reinforced bridge deck. The firsthand information obtained from the field provided original insights into the proper use of GFRP bars as an emerging alternative for bridge deck reinforcement, especially where the risk of chloride‐induced corrosion is high.
Abstract Aiming to systematically explore the penetration resistance of corundum rubble ultra‐high performance concrete (CR‐UHPC) with varying oblique and attack angles of projectile, firstly, the laboratory‐based penetration tests (175 m/s) of a 105 mm caliber projectile on CR‐UHPC and normal strength concrete (NSC) targets were conducted using a self‐developed large‐caliber compressed air gun system. The impact resistance of the two types of targets was quantitatively compared, and the feasibility of an indoor penetration test of a large‐caliber projectile was verified. Then, a 3D meso‐scale finite element model of the CR‐UHPC target, considering the random spatial distribution and particle size of corundum rubble, was established to characterize its heterogeneity. The reliability of the corresponding numerical simulation analysis method, including the “take‐place” modeling method, material constitutive models and parameters, mesh sizes, failure criteria values, as well as contact algorithm were fully verified by comparing the predicted depth of penetration (DOP) and projectile profile with the existing 25.3 mm‐caliber penetration test on UHPC target with corundum coarse aggregate and the present conducted test. Finally, the validated numerical simulation analysis method was employed to quantitatively evaluate the penetration resistance of CR‐UHPC and traditional NSC targets under penetration of prototype warhead, that is, Small Diameter Bomb (SDB), with various oblique (0°, 10°, and 20°) and attack (0°, ±1°, and ±2°) angles, and the variations of DOP and deflection angle of projectile were analyzed. The results indicate that: (i) under the sonic‐airspeed (340 m/s) impact of SDB, the DOP in the CR‐UHPC target is only 30% of that in the NSC target; (ii) increasing the oblique angle significantly affected the DOP and projectile deflection angle. When the oblique angle increased from 0° to 20°, the DOP of CR‐UHPC and NSC targets decreased by 11.8% and 14.9%, respectively, while the oblique angle increment increased by 14.97° and 18.40°; (iii) the attack angle mainly affected the projectile deflection angle with a slight effect on DOP. When the attack angle varied from −2° to 2°, the oblique angle increment for CR‐UHPC and NSC targets decreased by 95.9% and 49.1%, respectively, and the DOP variation was within 5% in all scenarios.
Abstract This study investigated the influence of water freeze–thaw (WFT) and salt freeze–thaw (SFT) cycles on the mechanical performance and microstructure of concrete incorporating raw coal gangue aggregates (RCGA). Concrete specimens were prepared by replacing coarse natural aggregates (CNA) with RCGA at replacement ratios of 0%, 30%, 70%, and 100%. Freeze–thaw durability of specimens was evaluated in terms of surface deterioration, cubic compressive strength, mass loss, and relative dynamic elastic modulus (RDEM). In addition, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) techniques were utilized to characterize the changes in microstructure and pore characteristics of specimens after different freeze–thaw cycles. The results revealed that increasing RCGA content significantly reduced compressive strength and freeze–thaw resistance. After 75 freeze–thaw cycles, concrete with 100% RCGA showed compressive strength losses of 29.79% after WFT and 54.21% after SFT, both greater than those of conventional concrete. Compared with WFT, SFT induced more pronounced deterioration, possibly due to the formation of chloride‐induced products in the interfacial transition zone (ITZ) and the growth of harmful pores. Furthermore, a freeze–thaw damage model for RCGA concrete was proposed based on the evolution of RDEM. These findings provide a reference for durability assessment of RCGA concrete in cold regions.
Abstract An experimental program was conducted to evaluate the effectiveness of replacing conventional reinforcement by steel fiber reinforcement in the hogging region of continuous shallow beams (with redundant supports). Seven groups of steel fiber reinforced concrete (SFRC) continuous shallow beams were tested under flexural loading, simulating a strip of a slab supported by three aligned piles or columns. The tests also aimed to assess the influence of different ratios of conventional reinforcement in both sagging and hogging regions, under serviceability and ultimate limit state conditions (SLS and ULS, respectively). The results of this experimental program are used to assess the predictive performance of an analytical model for the design of SFRC beams of redundant support conditions. This model is based on the flexibility method and considers the moment‐curvature relationship to derive the flexural stiffness during the loading process of a SFRC beam. The moment‐curvature is determined by using the recommendations of the Model Code 2020 (MC2020) and the Eurocode 1992‐1‐1 (EC2). The predictive performance of the developed approach is assessed on the serviceability and ultimate limit design verifications considering the results from the experimental program. When using average values for the material properties, the analytical model using both the MC2020 an EC2 provided overpredictions in terms of load carrying capacity for SLS and ULS design verifications (up to 57% and 38%, respectively, in terms of normalized error). When using characteristic values, the overprediction was limited to 31% with the MC2020, while over‐ and under‐predictions were obtained with EC2, limited to 25%. By applying the Estimation of the Coefficient of Variation method, safe predictions were obtained using MC2020 and EC2 formulations. It was verified that normalized error of the average crack width was less than 18% when using MC2020 and EC2 formulations. Finally, numerical studies were conducted on statically indeterminate shallow beams to assess the influence of both beam scale and the replacement of conventional tensile reinforcement by fibers at the intermediate support on the ULS and SLS design verifications.
Abstract Fiber‐reinforced polymer‐reinforced ultra‐high performance concrete (UHPC) structures exhibit outstanding durability and mechanical properties. In this study, an experimental investigation was conducted on the axial compression behavior of carbon fiber‐reinforced polymer (CFRP) bar‐reinforced UHPC columns, focusing on the influence of the slenderness ratio on their structural response. The results indicated that the UHPC strain distribution along the column height remained uniform throughout loading, and all specimens reached failure under axial compression without exhibiting spalling. The ultimate compressive strain of UHPC was approximately 2500 με. Strains in the longitudinal CFRP bars were close to those in the surrounding UHPC, demonstrating effective composite action. However, the maximum strain in the CFRP bars did not reach their ultimate strain. The confinement provided by glass fiber‐reinforced polymer (GFRP) stirrups was minimal, with a maximum recorded strain of about 600 με. Subsequently, a finite element parametric analysis was performed to evaluate the effects of aspect ratio and reinforcement ratio. The numerical results revealed that increasing the aspect ratio reduced the load capacity and increased the vertical deformation of the columns, whereas the reinforcement ratio had a marginal effect on axial performance. Finally, based on section equilibrium, deformation compatibility, and the experimental and numerical results, an ultimate load capacity formula for CFRP bar‐reinforced UHPC columns was developed, incorporating the contribution of CFRP bars and a reduction factor for the aspect ratio. In comparison with existing formulas from previous studies, the proposed formula demonstrates superior precision and robustness.
Reinforced concrete (RC) dapped-end connections feature a sharp re-entrant corner subjected to high stress concentrations, leading to wide cracks under service loads and potential durability issues such as reinforcement corrosion. Effective crack control is therefore essential in the design of new dapped-end connections. Steel fiber reinforced concrete (SFRC) has shown potential to improve crack control while also enhancing ultimate strength. This study proposes a kinematics-based model to describe the response of SFRC dapped ends along the re-entrant corner crack. Appropriate constitutive relationships are used to link the deformations along the corner crack and the compression zone to the resisting forces: reinforcement and SFRC in compression and tension. The model is validated against eight large-scale tests with varying fiber amounts including detailed deformation measurements from which the resisting mechanisms and crack-opening behavior are derived. The experimental results show that a fiber amount of 70 kg/m3 reduces the crack width by about 40%, enabling compliance with code requirements. The validation demonstrates that the proposed model represents a reliable tool for designing SFRC dapped-end connections at both service and ultimate limit states.
This study investigates the residual bearing capacity (RBC) of steel slag-based artificial aggregate concrete-filled steel tube (SA-CFST) following impact loading through experimental and numerical analyses. The experiment examines the failure modes of SA-CFST during impact and the axial load-displacement curves after impacts. Finite element models are subsequently developed to analyze the influence of key parameters on RBC of SA-CFST columns. A comparative analysis evaluates the differences in RBC among SA-CFST, concrete-filled steel tube (CFST), and reinforced concrete (RC) columns. The results indicate that deformation in the residual capacity tests is primarily localized at the impact point. RBC decreases with increasing impact energy or reduced boundary constraints. The axial compression ratio (n) below 35% of compression capacity has a beneficial effect on the RBC of SA-CFST, whereas exceeding this threshold produces adverse effects. Excessive axial load leads to reduction in RBC. Under the same conditions, the RBC of SA-CFST is slightly lower than CFST, with a difference of less than 10%. In comparison, SA-CFST demonstrates 30%-60% higher residual capacity compared to RC columns, and this advantage becomes more pronounced with increasing impact energy. SA-CFST members are proven to have excellent RBC after impact, making them suitable for use in structures prone to collisions.
Bamboo is increasingly used in construction due to its low density, rapid growth, and high tensile strength, but its water absorption and expansion when in contact with fresh concrete remain key challenges. This study examined the effects of different treatments (boiling water, sodium hydroxide, boric acid) and hydrophobic agents (Aquapuls, Nanosil, Diotrol, PL04X, Polimer Sement, Mega Stone, Sikador-32) on bamboo's physical/mechanical properties, including tensile strength, strain, modulus of elasticity, and concrete bond strength (via pull-out tests). Results showed that boric acid treatment reduced mass (3.6%), increased volume (6.8%), lowered density (0.08 g/cm(3)), improved tensile strength (similar to 36%), and, following 28 days of water immersion, decreased expansion (similar to 2%). In contrast, sodium hydroxide/boiling water had opposite effects. Among hydrophobic agents, Mega Stone and Sikador-32 reduced water absorption by 75.8% and 75.4%, respectively, and increased bond strength by 713% and 568%, demonstrating that combining boric acid with selected hydrophobic treatments can effectively enable bamboo's use as concrete reinforcement.
Fatigue stresses are receiving increasing attention in structural engineering, particularly in the design of increasingly slender structures. However, the mechanical response of concrete-particularly its fatigue behavior under very high numbers of load cycles-is still scarcely understood. Conventional fatigue testing is extremely time-consuming, whereas increasing the loading frequency may lead to specimen overheating. Additionally, dynamic or inertia effects are to be considered concerning high frequency testing. This paper proposes a conceptual approach to determine cyclic stress levels causing fatigue failure in the very high cycle fatigue (VHCF). A test frequency of approximately 85 Hz, applied using a high-frequency pulsator with oscillating adapters, was found to be suitable for concrete cylindrical specimens with a diameter-to-height-ratio of 30 mm/90 mm. Potential dynamic effects of the test equipment were taken into account during result evaluation, thereby validating the proposed test method. Furthermore, the temperature increase of the specimens during testing was recorded, and its influence on the reduction of concrete compressive strength was considered. The study confirms that fatigue testing at approximately 85 Hz, when appropriately corrected for temperature effects as well as dynamic influences, provides reliable fatigue data comparable to those obtained from conventional low-frequency tests.
