Search Results (55)

This study investigates the mechanical behaviour of timber–concrete composite (TCC) floor members with an innovative adhesive connection reinforced by granite chips, glass fibre yarn net in the epoxy adhesive layer, and polypropylene (PP) fibres in the concrete layer. Laboratory tests involved three groups of specimens subjected to three-point bending over a span of 500 mm with specimen lengths of 550 mm. Group A specimens exhibited crack initiation at approximately 8 kN and partial disintegration at an average load of 11.17 kN, with maximum vertical displacements ranging from 1.7 to 2.5 mm at 8 kN load, increasing rapidly to 4.3 to 5 mm post-cracking. The addition of reinforcing fibres decreased the brittleness of the adhesive connection and improved load-bearing capacity. Finite element modeling using the newly developed Verisim4D software (2025 v 0.6) and analytical micromechanics approaches demonstrated satisfactory accuracy in predicting the composite behavior. This research highlights the potential of reinforcing the adhesive layer and concrete with fibres to enhance the ductility and durability of TCC members under flexural loading. Full article

This study investigated the structural behavior of slab-on-grade (SOG) specimens constructed using two materials: conventional concrete reinforced with steel mesh and high-ductility fiber-reinforced cement composites (HDFRCC) containing 1.2% polyethylene (PE) fiber without steel reinforcement. The compressive strengths of conventional concrete and HDFRCC were 37 MPa and 54 MPa, respectively. The average flexural tensile strength of HDFRCC was 3.9 MPa at first cracking and 9.7 MPa at peak load. Punching shear tests were performed under three loading configurations: internal (center), edge, and corner loading. Crack patterns and load–displacement responses were analyzed for both material types. Under center loading, the experimentally measured load-bearing capacities were 174.52 kN for conventional concrete and 380.82 kN for HDFRCC, with both materials exhibiting reduced capacities under edge and corner loading. Analytical predictions demonstrated close agreement with the experimental results for conventional concrete but significantly underestimated the load capacity of HDFRCC SOG. This discrepancy is attributed to the strain-hardening and crack-bridging mechanisms inherent in HDFRCC, which contribute to enhanced strength beyond conventional analytical predictions. In terms of failure mode, the conventional concrete SOG exhibited the expected flexural failure. In contrast, the HDFRCC SOG experienced either flexural failure or a combination of flexural and punching failure, in contradiction to the analytical prediction of exclusive punching shear failure. These findings indicate that the punching shear resistance of the HDFRCC SOG is substantially higher than predicted. Full article

Steel-reinforced concrete (SRC) structures combine steel skeletons with concrete components, improving load-bearing capacity and streamlining construction. In this study, four full-size lattice SRC members were tested under pure bending to validate fundamental assumptions and were further analyzed numerically. The experimental specimens demonstrated a 15.3% increase in ultimate load-carrying capacity and an average 58.7% increase in the ductility index compared with conventional members. Notably, the improvement in ductility was substantially greater than the enhancement in load-bearing capacity. In parallel, a load-bearing capacity formula for lattice SRC members was proposed, yielding an error margin of 0.136 when compared with existing formulae for section steel members. The flexural strength predictions of formulae derived from simplified elastic–plastic theory and numerical analysis agreed with the test results. Full article

Recent studies have confirmed the effectiveness of using natural fibers and fiber-reinforced polymer (FRP) composites as methods to improve the mechanical properties of timber structures. This improvement is particularly evident in static and dynamic flexural and shear performance. Moreover, there is a paucity of literature pertaining to numerical models that predict the non-linear behaviour of low-quality timber beams reinforced with natural and man-made fibers. The present article expounds upon a shear bending study of timber beams reinforced with bars in addition to other materials. The experimental study yielded the following findings: the best properties were obtained with hybrid reinforcement, in comparison to the reference beams. The enhancement of load-bearing capacity and stiffness for beams that have been reinforced with pre-stressed basalt bars was found to be the most advantageous, with increases of approximately 17% and 8%, respectively. Natural fibers exhibited slightly lower values, with an increase in load-bearing capacity and stiffness of approximately 14% and 3%, respectively, when compared to beams that had not been reinforced. Moreover, the numerical analyses yielded analogous results to those obtained from the experimental study. The numerical models thus proved to be a valid tool with which to study the influence of the reinforcement factor. Full article

This study investigates the mechanical performance and failure mechanisms of large-span, cast-in situ hollow-core floor slabs with square-box core molds under vertical loading. A combination of in situ tests and refined numerical simulations was used to investigate the slab’s behavior. An 8 m × 8 m hollow slab from the Xinluzhou Industrial Park in Hefei, China, was subjected to five-stage cyclic loading up to 9.0 kN/m² using a distributed water tank system. Real-time strain monitoring showed that the slab remained within the elastic range, exhibiting a linear strain-load relationship and bidirectional bending stiffness, with less than 5% deviation between the X and Y directions. Finite element analysis, incorporating a concrete plastic damage model and a bilinear steel model, replicated the experimental stress distribution, with errors of less than 6.9% for reinforcement and 8.8% for concrete. The simulation predicted an ultimate load-bearing capacity of 27.2 kN/m², with initial failure indicated by diagonal cracks at the column capital edges, followed by flexural cracks at the slab mid-span. These findings clarify the bidirectional bending behavior and stress redistribution, characterized by “banded gradient” and “island-shaped” stress zones. This study provides valuable insights and design optimization strategies to improve the structural performance and safety of hollow-core floor slabs in high-rise buildings. Full article

The strengthening of reinforced concrete (RC) beams with aluminum alloy was typically implemented in a symmetrical configuration. To evaluate the flexural performance of strengthened beams, four machine learning (ML)-based models, namely Random Forest (RF), Xtreme Gradient Boosting (XGBoost), Adaptive Boosting (Adaboost), and Light Gradient Boosting Machine (LightGBM), were developed for predicting the flexural bearing capacity of aluminum-alloy-strengthened RC beams. A total of 124 experimental samples were collected from the literature to establish a database for the prediction models, with 70% and 30% of the data allocated as the training and testing sets, respectively. The K-fold cross-validation method and random search method were used to adjust the hyperparameters of the algorithm, thereby improving the performance of the models. The effectiveness of the models was evaluated through statistical indicators, including the coefficient of determination (R²), root mean square error (RMSE), and mean absolute error (MAE). Additionally, absolute error boxplots and Taylor diagrams were used for statistical comparisons of the ML models. SHAP (Shapley Additive Explanations) was employed to analyze the importance of each input parameter in the predictive capability of the ML models and further examine the influence of feature variables on the model prediction results. The results showed that the predicted values of all models had a good correlation with the experimental values, especially the LightGBM model, which can effectively predict the flexural bearing capacity behavior of aluminum-alloy-strengthened RC beams. The research achievements provided a reliable prediction framework for optimizing aluminum-alloy-strengthened concrete structures and offered references for the design of future strengthened structures. Full article

Recycled aggregate concrete incorporating glazed hollow beads (GHBRC) achieves the dual objectives of energy conservation and emission reduction by combining recycled coarse aggregate with glazed hollow bead aggregate, aligning with the construction industry’s “dual-carbon” goals for the development of low-carbon concrete. This study systematically investigates the flexural performance of GHBRC beams to establish calculation formulas for ultimate limit state bearing capacity and serviceability limit state verification. Six full-scale GHBRC beams were tested under simply supported conditions with two-point symmetric mid-span loading. Three critical variables (concrete composition, longitudinal tensile reinforcement ratio, and stirrup reinforcement configuration) were examined. Experimental results indicate that GHBRC beams exhibit failure modes consistent with conventional concrete beams, confirming the validity of the plane section assumption. At identical reinforcement ratios, GHBRC beams demonstrated a 3.1% increase in ultimate bearing capacity and an 18.78% higher mid-span deflection compared to ordinary concrete beams, highlighting their superior deformation performance. Building on methodologies for conventional concrete beams, this study recalibrated key short-term stiffness parameters using a stiffness analytical method and proposed a computational model for mid-span deflection prediction. These findings provide theoretical and practical foundations for optimizing the structural design of GHBRC beams in alignment with sustainable construction objectives. Full article

This study explores the use of recycled brick powder (P_RB), derived from waste bricks, and calcined recycled slurry powder (P_CRS), sourced from waste cement blocks, as partial replacements for cement and fly ash in concrete. These materials can be utilized to produce concrete with favorable engineering properties. Five concrete mixtures with varying P_RB/P_CRS proportions were prepared. Uniaxial monotonic compression tests were conducted to generate stress-strain curves for each mixture. Corresponding physical superposed slabs were fabricated, and finite element (FE) models were developed for each slab. Both physical testing and explicit FE simulations were performed to evaluate the flexural performance of the slabs. The results demonstrated that the flexural performance of the P_RB/P_CRS recycled micro-powder concrete slabs was comparable to that of conventional concrete slabs. Notably, the slab incorporating a 1:1 mixture of P_RB and P_CRS instead of fly ash exhibited the highest yield and ultimate bearing capacities, reaching 99.3% and 98.4% of those of the conventional concrete slab, respectively. The FE simulations accurately predicted the flexural performance, with maximum deviations of 8.9% for the yield load and 6.5% for the ultimate load. Additionally, the simulation-based energy time-history curve provides valuable insights into the progression of slab cracking. This study contributes to the advancement of research on the engineering and mechanical performance of concrete members incorporated with P_RB/P_CRS. Full article

Engineered Cementitious Composite (ECC) has emerged as a promising solution with which to address the longstanding challenge of cracking in the tensile zone of reinforced concrete beams. This study conducts an experimental and analytical exploration of the flexural performance of ECC-concrete composite beams reinforced with hot-rolled ribbed steel bars. Sixteen beams, featuring diverse reinforcement ratios and ECC layer thicknesses, underwent rigorous testing through a four-point bending setup. The experimental findings underscore a substantial improvement in crack resistance and flexural bearing capacity of ECC-concrete composite beams reinforced with steel bars. Building on these results, a theoretical model was formulated to predict the moment-deflection responses of ECC-concrete composite beams incorporating steel bars. Furthermore, practical and simplified methods were introduced to predict flexural bearing capacity and effective moment of inertia, as well as anticipate failure modes, offering a user-friendly approach for engineering applications. Validation of the proposed approaches was achieved through simulation results, demonstrating a high degree of accuracy when compared with the experimental outcomes. Moreover, the average crack width at serviceability limit states of composite beams was sensitive to specimen size and the yield strength of steel bars, and a size effect was also observed for ductility expressed as deflection. Full article

This research advocates for the use of basalt fiber-reinforced polymer (BFRP) bars and recycled tire steel fibers to reinforce concrete beams. Six concrete beams were constructed using different volume contents of recycled tire steel fibers (0, 0.5%, 1.0%, 1.5%) and BFRP reinforcement ratios (0.48%, 0.75%, 1.08%). Mechanical properties tests were conducted to investigate the flexural characteristics and failure modes of beams utilizing the non-contact full-field strain displacement measuring technology–digital image (3D-DIC) technology. The recycled tire steel fiber (RTSF) improves flexural performance, which contributes to inhibiting crack propagation, reducing flexural deformation, and improving the first cracking and ultimate loading capacities. Under the same reinforcement ratio, in comparison to ordinary BFRP beams, the cracking load of BFRP-RTSF beams increased by 17.73%, 23.76%, and 42.94%, respectively, and the ultimate bearing capacity increased by 4.03%, 5.85%, and 13.21%, respectively. In addition, a modified calculation model of bearing capacity considering RTSF tensile strength is proposed. The predicted values of BFRP-RTSF beams match well with the experimental values. Full article

This research investigates the flexural performance of slabs reinforced with high-strength steel-strand mesh (HSSM) and engineered cementitious composites (ECCs). By employing finite element analysis (FEA) and theoretical modeling, this study aims to deepen the understanding of how these materials behave under bending stresses. A finite element model was developed to simulate the nonlinear behavior of ECCs during bending, considering critical elements such as tensile and compressive damage, as well as bond–slip interactions between the steel strands and the ECCs. Furthermore, a theoretical model was created to predict the load-bearing capacity of HSSM-reinforced ECC slabs, incorporating variables like reinforcement ratios, slab dimensions, and material characteristics. The findings reveal that increasing the reinforcement ratio substantially enhances both flexural stiffness and load-bearing capacity while reducing deflection. Comparisons between the FEA results, the theoretical forecasts, and the experimental observations show close alignment, validating the proposed models. This work provides important insights for optimizing the design of HSSM-reinforced ECC slabs, highlighting their potential improvements in structural systems that demand high flexural performance. Full article

Reinforced concrete beam bridges are usually retrofitted by a steel plate or FRP. However, these two methods tend to result in disadvantages, e.g., construction complexity and debonding failure, owing to the corresponding material properties. In this study, a steel- and CFRP-based method is proposed to achieve the merits of typical retrofitting methods by combining a CFRP plate, a steel plate, and angle steel. To investigate the effect of the cooperative strengthening, six full-scale beam specimens were designed and are evaluated through a monotonic four-point bending test. The failure mode, load–deflection relationship, critical parameters, and crack development are systematically and sequentially analyzed. Finally, a predicting method is proposed to calculate the flexural capacity. The retrofitted beam is characterized by an acceptable load-bearing capacity and deformation capacity. With continuous retrofitting, the crack load and ultimate load can be improved up to 84.9% and 4.41 times, respectively. The steel plate and angle steel function in both the load bearing and the anchorage to the CFRP plate contributes more to the ultimate bearing capacity after the steel components yield. Finally, a calculating model is shown to accurately predict the ultimate bearing capacity after retrofitting, with an average error of 4.03%. Full article

The BlueDeck profiled steel sheeting system offers an innovative composite flooring solution, integrating high-strength steel sheets with reinforced concrete to form a unified structure. This study aimed to evaluate the development of full composite action, the ultimate bearing capacity, and the flexural stiffness of the system. A comprehensive experimental programme involving 18 four-point bending tests and 6 shear tests was conducted to quantify the mechanical interaction between the steel deck and concrete slab. This study specifically examined bending capacity and vertical deflection, comparing the results with predictions from AS/NZS 2327. It was found that the system consistently achieved full composite action, with composite specimens demonstrating higher flexural stiffness and load-bearing capacity as the concrete depth increased. For example, specimens with 200 mm slab depths exhibited a 60% improvement in ultimate capacity compared to those with 150 mm slabs, while those with 175 mm depths saw a 27% increase. Additionally, the BlueDeck system showed an 81% improvement in de-bonding resistance in thicker slabs. The experimental results exceeded the bending moment and deflection limits prescribed by AS/NZS 2327, confirming that the system is structurally sound for use in buildings. This study provides quantitative evidence supporting the system’s compliance with Australian standards, highlighting its potential for improving construction efficiency through reduced material use, while maintaining structural integrity under imposed loads. Full article

To study the flexural performance of fiber-reinforced polymer (FRP) grid–polymer cement mortar (PCM)-composite-strengthened RC beams, the finite element numerical simulation of FRP grid–PCM composite RC beams is carried out using ABAQUS to analyze the effects of the amount of FRP grid reinforcement, the type of FRP grid material, and the geometry of FRP grid on the flexural performance of reinforced concrete beams and to establish the flexural capacity calculation formula of FRP grid–PCM-reinforced RC beams in case of debonding failure, based on analysis of the influencing factors. The results show that increasing the reinforcement of the FRP grid and increasing the stiffness of the FRP grid can improve the flexural bearing capacity of RC beams, and the change of FRP grid geometry has little effect on the flexural bearing capacity of RC beams. The established formula for calculating the flexural bearing capacity of FRP grid-reinforced concrete beams can better predict the flexural capacity of reinforced concrete beams under peeling failure. Full article

An experimental study of cold-formed thin-walled steel unequal-leg angles (CFTWS-ULAs) under axially oriented pressure is presented in this paper. Firstly, the initial imperfections and material properties of the angle specimens were measured in detail. The angle specimens were tested under fixed-ended conditions. The results of the experiments showed that the angle specimens with small slenderness ratios were susceptible to local buckling, the angle specimens whose legs had high slenderness ratios and low width–thickness ratios were found to easily suffer from the occurrence of flexural buckling, and the angle specimens whose legs had high width–thickness ratios were found to easily suffer from the occurrence of interactive buckling between local buckling and flexural buckling. The finite element analysis of the ULAs was conducted using ABAQUS6.14 finite element software by creating a model. The buckling modes and ultimate bearing capacities of the test specimens were compared, and the finite element analysis verified that the established model built using the finite element is credible and subsequent parametric analysis was performed. The slenderness ratio had the most significant impact on the ultimate bearing capacities of the unequal-leg angles, as indicated by the analysis results. When the width–thickness ratio and the width ratio of the legs fell within a specific range, the ultimate bearing capacities of the unequal-leg angles increased as the width–thickness ratio and the width ratio of the legs increased. Finally, the comparison results showed that the design strengths predicted by the specifications were very conservative, because the local buckling and torsional buckling were calculated at the same time. Therefore, a recommendation was proposed that the calculation of the load-carrying capacity of an unequal-leg angle should ignore torsional buckling. Full article