Search Results (7,439)

The Horned Lizard Optimization Algorithm (HLOA) is a newly proposed swarm intelligence optimizer mimicking the defensive and survival behaviors of horned lizards. The original HLOA suffers evident drawbacks when tackling high-dimensional, multimodal and heavily constrained complicated optimization problems. Rapid decline in population diversity in late iterations and insufficient local optimum escape strategies further trigger premature convergence and unsatisfactory optimization precision. To systematically address the above deficiencies and boost the global optimization and engineering applicability of HLOA, this paper proposes a hybrid-strategy improved Horned Lizard Optimization Algorithm (HSHLOA). First, an improved uniform Logistic chaotic mapping replaces conventional random initialization. It enhances the ergodicity and uniformity of initial populations across search spaces and upgrades the quality of initial solutions and population diversity. Second, an adaptive optimal guidance strategy is constructed via nonlinear dynamic adjustment factors. It prioritizes global exploration in early iterations and strengthens local exploitation in later iterations to accelerate convergence and raise optimization accuracy. Third, a lens imaging learning strategy is embedded. It generates adaptive opposite solutions following dynamic convex lens optical imaging rules, strengthens the capability to escape local optima and mitigates premature convergence. To verify the optimization performance of the proposed algorithm, comparative experiments are conducted on the CEC 2017 benchmark test suite under 30-dimensional and 100-dimensional high-dimensional settings. Seven mainstream swarm intelligence algorithms are selected for benchmark comparison. Quantitative analyses cover convergence rate, optimization precision, numerical stability and local optimum escaping ability. Experimental results reveal that HSHLOA outperforms all peer competitors on unimodal, multimodal, hybrid and composite functions with remarkable superiority. The proposed HSHLOA is further applied to three typical constrained engineering optimization cases, including reinforced concrete beam design, three-bar truss design and pressure vessel design. Application results prove that HSHLOA satisfies all engineering constraints steadily and obtains superior structural schemes with higher efficiency. The reliability and superiority of HSHLOA for practical engineering problems are therefore verified. Full article

This paper investigates the seismic performance of precast concrete shear-wall subassemblies connected by post-cast ultra-high performance concrete (UHPC) zones and short lap-spliced reinforcement with a lap length of $10d$, where d denotes the diameter of the reinforcement bar. Seven quasi-static cyclic tests were conducted, including one cast-in-place control specimen, five specimens with horizontal UHPC back-cast joints at the wall base, and one exploratory specimen with both horizontal and vertical UHPC back-cast joints. The variables considered were the joint arrangement and the axial compression ratio. The specimens with horizontal joints generally exhibited compression-flexure-dominated damage, and the crushing zone shifted from the wall-footing interface to the ordinary concrete immediately above the UHPC back-cast zone. The specimen with the vertical joint (TW6) exhibited bending-shear damage, accompanied by limited in-plane lateral slip at the beam–wall joint and shear damage of several vertical bars. Specimen TW2, with an axial compression ratio of 0.30, was identified as a construction-quality-sensitive case because an insufficient local UHPC cover caused splitting damage and reduced hysteretic stability. The strain measurements indicate that, within the limits of the present instrumentation, the 10d lap in the UHPC zone provided effective stress transfer in the tested specimens; however, direct interface-slip and bond-slip tests are still required for generalized design verification. Under an axial compression ratio of 0.20, TW1 and TW6 showed comparable seismic indices to the cast-in-place specimen, but the conclusions are limited to the tested configurations. All specimens reached ultimate drift ratios greater than 1/100, and their seismic performance is discussed together with failure mode, stiffness degradation, energy dissipation, and connection reliability. Full article

The huge demand for natural sand in the global construction industry has caused resource shortages and severe environmental issues. Meanwhile, China produces massive annual iron tailings, and their stockpiling poses prominent potential safety hazards. At present, numerous investigations have been carried out on the fundamental properties of concrete prepared by replacing natural sand with iron tailings sand (ITS). However, most studies are limited to single replacement ratios and conventional strength mix proportions. Systematic research focusing on high-replacement-ratio systems, long-term durability performance, and supporting practical construction technologies for engineering applications remains insufficient. Obvious gaps still exist regarding the key mechanisms and practical operation standards for high-value and large-scale utilization. Against this background, this paper prepares concrete with three strength grades (C30, C40, C50) and six ITS replacement ratios (0%, 20%, 40%, 60%, 80%, 100%). Cube compressive tests and prism axial compressive tests are conducted, combined with SEM microscopic microstructure analysis. Axial compression tests and bearing capacity research are further carried out on reinforced concrete short columns (RCSC) with the optimal replacement ratio. The results show that concrete compressive strength increases first and then decreases with the rise in iron tailings sand concrete (ITSC), with 60% identified as the optimal replacement ratio. At this ratio, the compressive strength of C30, C40 and C50 concrete increases by 24.3%, 11.5% and 12.9%, respectively, while the bearing capacity of short columns rises correspondingly by 18%, 14.1% and 8.1%. Microscopic test results reveal that ITS exerts both physical filling and chemical active effects. Its fine particles fill internal pores inside the matrix and refine the pore structure. Meanwhile, the reactive mineral components contained in ITS can participate in the hydration reaction of the cementitious system, accelerate the hydration rate and generate more dense hydration products. Therefore, ITS facilitates the hydration process and improves the mechanical properties of concrete. A calculation method for the axial bearing capacity of RCSC incorporating ITS is proposed via theoretical analysis. This study provides a theoretical basis for preparing concrete by replacing natural sand with ITS. Using ITS as aggregate is expected to alleviate tailings stockpiling risks, reduce natural sand consumption, and realize solid waste resource recycling. It also offers valuable references for the green development of the construction industry and safety protection in mining areas. Full article

The enhancement of reinforced concrete (RC) beams using externally bonded carbon fiber-reinforced polymer (CFRP) systems and shape memory alloy (SMA) systems has been growing in recent years, but its comparison is not generalizable unless it is based on an equal basis of stiffness. In this paper, an equivalent axial stiffness approach is applied to study the effect of CFRP and SMA plates on RC beams. The following four beam configurations were considered: Unstrengthened control beam, beam strengthened with a 5 mm SMA plate, beam strengthened with a 5 mm CFRP plate, and beam strengthened with an 18.96 mm SMA plate, which was chosen to provide similar axial stiffness as the 5 mm CFRP plate. The finite element model was created using ANSYS and compared with experimental results from the literature, and was further validated with a mesh sensitivity study. The test results indicated that all strengthening systems had a better flexural response than the control beam, but with varying degrees of improvement depending heavily on the amount of stiffness provided by the strengthening material. The control beam showed the first signs of cracking and had the lowest resistance. The moderate improvement was seen in the 5 mm SMA plate, which increased the load corresponding to the first crack to 50.2 kN from 41.7 kN. The 5 mm CFRP beam and the stiffness-equivalent SMA 18.96 mm beam, on the other hand, were able to significantly improve the first-crack load to 77.6 kN and 82.97 kN, respectively. In terms of flexural strengthening performance, stiffness equivalence takes into account the first-crack load of the performance of the SMA beam, which shows that SMA can provide flexural strengthening performance comparable to, and even higher than, that of the CFRP system in terms of crack-initiation resistance. The overall performance of the strengthened beams was also found to be better than the control beam in terms of the post-cracking stiffness and moment—curvature relationships. These results indicate that a stiffness-equivalent framework is more rational than comparing the two strengthening systems directly in terms of thickness, and in this way, the ability to compare the advantages and disadvantages of the two systems. The conclusions, however, should be understood based on the assumptions of the numerical model, such as the perfect bond assumption at the interface and the use of a simplified monotonic material model used for SMA. Additional studies should be conducted that incorporate debonding, cyclic loading, temperature, and field size verification. Full article

To investigate the stress evolution, deformation behavior, and failure characteristics of composite-reinforced prestressed concrete hollow square piles (PHSC piles) under bending, a four-point bending test was conducted on a full-scale PHSC500 (340) hollow square pile specimen with a length of 7000 mm, a square section of 500 mm × 500 mm, and a hollow core diameter of 340 mm. The test was used to obtain load–deflection curves, crack propagation patterns, deformation responses, sectional strain distributions, and failure modes. In addition, an ABAQUS finite element model was established to compare the bearing capacity, stiffness degradation, and ductility of different pile types with varying prestressed and non-prestressed reinforcement ratios. The results show that vertical cracks changed their propagation direction at the edge of the tensile zone in the flexural–shear region of the PHSC piles and developed into a critical diagonal crack with a width of 1.7 mm. The specimen ultimately exhibited a shear–compression failure mode. During the failure stage, the midspan deflection increased rapidly as the load rose from 710 to 740 kN, with the deflection increasing from 24.88 to 32.00 mm. The load–midspan deflection curve obtained from the finite element analysis was generally consistent with the experimental results. Moreover, the predicted damage concentration zones corresponded well to the experimentally observed crack locations, indicating that the model can be used to analyze relative variations under different parameter conditions. The combination of prestressed and non-prestressed reinforcement improved the flexural capacity and ductility of the PHSC piles. However, ductility did not increase monotonically with the prestressed reinforcement ratio. These findings provide a reference for evaluating the flexural performance of PHSC hollow square piles and optimizing their reinforcement parameters. Full article

Reinforced concrete (RC) beams are crucial load-bearing members in multistory buildings. Due to architectural modifications, increased service loads, or construction deficiencies, these members often require flexural strengthening to restore or enhance their performance. The use of prefabricated reinforced ultra-high-performance fiber-reinforced concrete (UHPFRC) plates has recently emerged as a promising strengthening technique. When attached to the tension, compression, or both faces of RC beams, these plates provide noteworthy structural benefits. This study presents a detailed investigation—using nonlinear calibrated finite element (FE) models—into the flexural strengthening of RC beams using reinforced UHPFRC plates. A total of 18 large-scale RC beams were explored, including two control specimens and 16 strengthened beams. The control specimens comprised one beam with a tensile steel ratio close to the minimum code thresholds and another with a conventional reinforcement ratio typical of standard design. The strengthening schemes were developed to enhance the flexural capacity of the first control beam to a level comparable to the ideal reference specimen. A simplified analytical tool was developed to estimate the peak load of control and strengthened specimens for the design of upgrading schemes. The parametric study in the FE matrix examined the effects of reinforcement type within the UHPFRC plates (steel or glass fiber-reinforced-polymer (GFRP) bars), plate location (tension side, compression side, or both), bonding method (adhesive, mechanical, or combined), and end anchorage condition (with or without fiber-reinforced polymer (FRP) U-wraps). The beams’ behavior was evaluated in terms of load-deflection response, stiffness, and failure mode. The results demonstrated that combined adhesive–mechanical bonding with compression-side UHPFRC plates provided the most efficient and reliable strengthening technique. Full article

This study experimentally investigates the structural behavior of steel–concrete composite beams with circular web openings under monotonic loading to evaluate the effects of opening location and number on structural performance while maintaining feasibility for integrating mechanical, electrical, and plumbing (M.E.P.) systems. Six simply supported composite beam specimens were tested, including one reference beam without openings and five beams with 80 mm diameter circular web openings. The investigated variables were limited to the presence, number, and longitudinal location of the openings, while the beam dimensions (IPE160 section, 2.8 m clear span), material properties, reinforcement details, shear connector arrangement, and loading conditions were kept constant. The study addresses a specific research gap: Previous studies have primarily focused on the effects of opening number and size on ultimate load capacity, with limited systematic investigation of how opening location influences not only ultimate load but also stiffness and ductility. Openings were strategically placed in three critical zones: the shear zone (low stress region), the bending zone (high moment region at mid-span), and the region under load points. The experimental results demonstrated that opening location is more critical than opening number. Openings in the shear zone achieved the best performance with only 2.13% reduction in ultimate load capacity, making it the preferred location for service openings. Openings in the bending zone (mid-span) or under load points caused reductions ranging from 9.62% to 11.70%, attributed to interference with high bending stresses. Notably, the configuration with ten openings achieved a load reduction similar to the two-opening configurations when located in the shear zone, confirming the dominant role of location over opening number within the experimental program. These results support a location-driven design philosophy for composite beams with web openings. However, these findings are restricted to the present experimental configuration—specifically 80 mm circular openings, IPE160 steel section, 2.8 m clear span, and the tested loading condition—and should not be generalized to composite beams with different geometric parameters, material properties, or loading conditions without additional research. Full article

Acoustic emission (AE) signals associated with different damage processes in reinforced concrete (RC) beams often show overlapping feature distributions, making unsupervised identification difficult. In this study, three RC beams were tested under loading-induced damage, freeze–thaw damage and reinforcement corrosion conditions, and 490 valid AE samples were obtained. Seven AE parameters were selected to construct the clustering feature set. To enhance the separation of different damage-related AE signals, a kernel K-means clustering framework was adopted, and the coyote optimization algorithm was used to optimize the kernel function type and key parameters based on the Gap Statistic. Comparative analysis with K-means, FCM and GMM was also conducted. The results show that the COA-optimized kernel K-means method achieved the best overall clustering performance, increasing the mean ACC by 10.35 percentage points compared with K-means and by 2.49 percentage points compared with GMM. Its mean ARI was also higher than that of GMM by 0.0330, while the standard deviation of ACC decreased from 7.73% to 4.19%. Class-level results indicated that loading-induced AE signals were more readily identified, whereas freeze–thaw and corrosion signals were more affected by feature overlap. Feature interpretation further showed that the main misclassified samples were located in transitional feature regions. The results suggest that COA-based kernel optimization can improve the clustering separation and stability of AE signal identification for different damage types in RC beams. Full article

The anti-floating punching failure of basement slabs subjected to groundwater uplift remains insufficiently understood due to the complex stress state and lack of applicable design guidance. This study investigates the punching behavior of a damaged basement slab in Shenzhen, China, using a three-dimensional finite element model developed in LS-DYNA with the Concrete Damage Plasticity (CDP) model. The model was validated against field observations and experimental data, with a prediction error of less than 8%. The results show that anti-floating punching failure evolves from crack initiation in the anchorage zone to damage propagation and final penetration. Increasing the slab thickness from 400 mm to 600 mm significantly alleviated tensile damage concentration and improved stress redistribution. Increasing the concrete compressive strength from 20 MPa to 60 MPa enhanced punching resistance and delayed crack development, but promoted localized brittle failure. Enlarging the foundation pad from CT-6 to CT-9 effectively reduced stress concentration and improved the overall anti-punching performance, whereas the influence of column size was limited. A comparative assessment of three reinforcement measures further revealed their respective applicability under different engineering conditions. The study clarifies the anti-floating punching mechanism of basement slabs and provides a theoretical basis for the anti-floating design and reinforcement optimization of underground structures. Full article

This study investigates the blast-protective performance of RC slab strengthened on the blast face with various concrete protective layers under contact-detonation loading. The research focuses on analyzing shock wave propagation characteristics, peak pressures at measurement points, energy absorption capacities of the protective layers, the development of damage, and the governing failure mechanisms of the RC slab. The protective layers used for structural reinforcement include Steel Fiber-Reinforced Cellular Concrete (SFR-CC), Asphalt Concrete (AC), Rubberized Concrete (RBC), and Foamed Concrete (FC). Among these, the maximum support rotation angle of the structure strengthened with the SFR-CC concrete layer (T-1) is 0.20°, indicating significantly less damage and deformation compared to other protective schemes. Based on the damage coefficient calculated from the remaining sectional moment of inertia of the protected RC slabs, the destruction grades of the structures at different concrete protective schemes were classified. Among these, the SFR-CC layer exhibits the most effective attenuation of shock wave peak pressure. Additionally, the maximum support rotation angle of the structure strengthened with the SFR-CC concrete layer is 0.20°, indicating significantly less damage and deformation compared to other protective schemes. Damage grades were assigned according to a coefficient derived from the residual sectional moment of inertia of the protected RC slabs. The SFR-CC configuration (T-1) gives the lowest damage index, 0.178, approximately 64.5% below that of the NC scheme, and is classified as slight damage. In contrast to the severe damage sustained by the protected RC slabs strengthened with the NC concrete scheme, those strengthened with the AC, RBC, and FC protective layer schemes exhibit only a moderate damage grade. Empirical formulas predicting the damage index of protected structures under the combined effects of varying blast charges and concrete layer thicknesses were further developed for rapid damage assessment. Full article

Early-stage structural design requires rapid exploration of large design spaces, where the initial sizing of reinforced concrete members shapes downstream material use, cost, and the number of design iterations. Conventional predimensioning relies on experience and simplified formulae, while finite element analysis remains too slow for iterative use. This study presents a multi-task graph neural network surrogate that predicts per-element Eurocode compliance together with the required reinforcement for reinforced concrete slab-and-column buildings in one pass. A shared GraphSAGE encoder, trained on 2562 synthetic building graphs from automated finite element simulations, feeds one head for a compliance probability and another for reinforcement quantities. Because the rule-based Eurocode check is a hard pass-or-fail decision that does not vary smoothly with the design, the surrogate learns a continuous, differentiable compliance probability in its place, demonstrated for two representative criteria, one per element type, namely the $l/250$ deflection limit for slabs and the 4% reinforcement-ratio limit for columns. Across five random seeds, cost-sensitive focal-loss training that weights missed non-compliance above false alarms reached 90.9% balanced accuracy and held the share of non-compliant elements wrongly passed as compliant at 6.1% for columns and 1.6% for slabs, with a mean reinforcement error near 2% of the normalised target range. Inference averaged approximately 0.5 ms per building, between five and six orders of magnitude faster than the finite element analyses. A differentiable, multi-task graph surrogate therefore supports fast, cost-sensitive compliance screening for early-stage predimensioning, serving as a seed for gradient-based design exploration and a starting point for finite element verification. Full article

The growing importance of embodied carbon (EC) in building decarbonisation requires transparent, context-specific Life Cycle Assessment (LCA) approaches. This study develops a practical framework for quantifying cradle-to-site EC (A1–A4), combining detailed post-construction material quantification with a structured data selection methodology. Carbon factors (CFs) are primarily sourced from geographically representative Environmental Product Declarations (EPDs) and evaluated through a reliability framework that incorporates material similarity, geographical proximity, and data completeness. An Analytic Hierarchy Process (AHP) is further applied to select representative values for key materials such as ready-mix concrete. The application of this framework highlights the critical influence of data representativeness on EC results and demonstrates a transparent and reproducible approach for reducing uncertainty in early-stage assessments. The case study yields a total EC of 228 kg CO₂e/m², with structural materials identified as the main carbon hotspots: ready-mix concrete accounts for approximately 40% of total impacts, reinforcing steel for around 11%, while masonry systems, infill, and levelling layers contribute a significant additional share. Together, these materials represent slightly more than 75% of total embodied emissions. Beyond the numerical results, the study shows that a limited number of material categories dominate the carbon footprint, enabling targeted decarbonisation strategies. The proposed framework is designed to be transferable to similar building contexts and supports more robust, data-driven decision-making in the Portuguese construction sector and beyond. It is particularly relevant in regions where locally representative environmental data are not necessarily sufficient, as it provides a structured approach for developing embodied carbon assessments under such condition. Full article

Carbonation treatment can effectively address defects in recycled aggregates (RA) while achieving CO₂ sequestration, thereby improving properties of recycled aggregate concrete (RAC). However, the compressive strength of carbonated recycled aggregate concrete (CRAC) is governed by complex interactions among multiple parameters, and existing machine learning (ML) studies often rely on heterogeneous literature data with limited parameter coverage, resulting in constrained predictive accuracy. To address this issue, this study established a robust ML framework for precise strength prediction. By integrating published literature with original experimental results, a dataset of 226 groups was constructed, incorporating 12 key parameters across RA properties, carbonation processes, mix proportions, and concrete age to systematically compare three ML models (GPR, SVM, EDT). To enhance model transparency, global sensitivity analysis used the SHapley Additive exPlanations (SHAP) method, while X-ray diffraction (XRD), scanning electron microscopy (SEM), and microhardness tests were employed to reveal reinforcement mechanisms at the phase, microstructural, and micromechanical levels, supporting the connection between intelligent prediction and mechanistic explanation. Results show that the GPR model exhibited the highest predictive performance and generalization capability (R² = 0.98 for training, R² = 0.94 for testing; RMSE = 1.08 MPa), outperforming comparative models in handling high-dimensional nonlinear relationships. SHAP analysis identified concrete age, water–cement (W/C) ratio, and the initial crush index of the RA as the primary factors, while carbonation process parameters, particularly relative humidity, carbonation pressure, and carbonation time, exerted significant regulatory effects on strength. XRD results qualitatively confirmed the formation of CaCO₃ after carbonation, while SEM and microhardness analyses indicated that carbonation products contributed to pore filling and interfacial transition zone (ITZ) strengthening, providing a physical basis for both macroscopic performance improvement and model reliability. This study provides a scientific, data-driven solution for the mix design optimization and performance prediction of CRAC, delivering substantial environmental and economic benefits. Full article

Beam–column joints are critical elements in reinforced concrete (RC) frame structures. They are subjected to complicated load mechanisms in the event of earthquakes, which often leads to non-ductile damage in the form of shear cracking failure and concrete spalling. With recent advances in computer vision techniques, an image-based methodology is implemented for effectively assessing the seismic damage of RC beam–column joints. Specifically, this study integrates digital image correlation (DIC)-derived strain fields with microplane damage theory to identify concrete surface damage, and subsequently, fractal dimension analysis is employed to quantitatively evaluate the damage metric. The proposed image-based analysis procedures are implemented to investigate the damage evolution of six full-scale RC beam–column joints subjected to quasi-static loading tests. The damage results derived using fractal dimension analysis are compared with those computed using conventional mechanics-based damage models. It is observed that the fractal-based damage index of the RC joints agrees reasonably well with the stiffness-based damage index. The damage curves reveal that the DIC-assisted fractal dimension analysis provides an effective means for automated identification of the surface damage pattern as well as damage progression of RC beam–column joints under seismic loading or other complex loading scenarios. Full article

Soil–Structure Interaction (SSI) is known to influence the seismic response of structures; however, its implications for the classification of dual wall–frame systems within the framework of Eurocode 8 remain insufficiently understood. This study investigates how SSI affects not only the global response but also the code-based classification of a reinforced concrete dual wall–frame system. A 9-storey prototype building is analyzed using fixed-base and flexible-base models, considering linear-elastic, nonlinear static (pushover), and nonlinear dynamic (time-history) analyses. As expected, the results show that SSI induces a significant redistribution of seismic forces, reducing the contribution of shear walls and increasing the role of frames. As a consequence, the system classification shifts from wall-equivalent dual to frame-equivalent dual, or even toward frame-dominated behavior under Eurocode 8. A comparison with ASCE/SEI 7-16 reveals that such classification changes are less pronounced due to broader system definition limits. The findings highlight that SSI influences not only structural demand but also key design parameters, including behavior factors and force distribution assumptions. This underscores the need for consistent consideration of SSI effects in both analysis and system classification within seismic design codes. Full article