Search Results (1,141)

This study primarily investigates the mechanical performance of prestressed anchor foundations. Based on the assumptions of continuity, homogeneity, and isotropy of the anchor foundation and anchoring materials, a simplified elastic analysis model was developed. Using the superposition principle, the working stresses under vertical loads and bending moments were calculated, allowing for the determination of the maximum working stresses within the anchors and the foundation. Additionally, the distribution of bond strength of the prestressed tendons was analyzed, and the concept of effective anchorage length was introduced. The reliability of the model was validated through prototype testing, with the measured free segment strain values showing a high degree of consistency with theoretical calculations, with errors within 6.5%. Empirical data on ultimate bearing capacity and bond characteristics were also obtained. By integrating numerical calculations with experimental results, the performance of the anchoring system under extreme and specialized loading conditions was analyzed. The experimental results indicated that the failure modes of all anchor foundations were characterized by bond failure at the interface between the anchor and the surrounding rock mass. Based on the experimental data, a reasonable anchorage length satisfying design strength requirements was proposed. The findings provide a theoretical foundation and practical guidance for the design and application of prestressed anchor foundations in structures such as wind turbine towers. Full article

This study investigates the structural performance of TL-5 concrete bridge barriers reinforced with glass fiber-reinforced polymer (GFRP) bars at the critical deck–wall interface. Five full-scale barrier models were subjected to static load testing until failure. The wall reinforcement included four barriers with high- and standard-modulus GFRP bars using headed-end, bent, and hooked anchorage, and one with conventional steel reinforcement. The objective was to assess the load-bearing capacity, failure modes, and deformation behavior of GFRP-reinforced barriers with respect to the Canadian Highway Bridge Design Code (CHBDC) requirements. Results revealed that all GFRP-reinforced models achieved ultimate flexural capacities surpassing CHBDC design limits, with diagonal tension cracking at the corner joint emerging as the predominant failure mode. A set of new equations was developed to predict diagonal tension failure and determine minimum reinforcement ratios to mitigate such failure. Comparisons with experimental findings validated the proposed analytical approach. Among the configurations tested, barriers with headed-end high-modulus GFRP bars offered the most cost-effective and structurally sound solution. These findings support the incorporation of GFRP bars in bridge barrier design and establish a framework for future code development regarding GFRP-reinforced barrier systems. Full article

The current study investigates the influence of timber-to-concrete connection types on the behaviour of timber–concrete composite (TCC) structures employing metal web timber joists. Two groups of laboratory specimens were prepared, each comprising four samples with push-joisted beams joined by oriented strand board (OSB) and cast with a concrete layer. One group utilised compliant timber-to-concrete connections via perforated steel tape angles, while the other employed rigid connections through epoxy adhesive and granite chips. The specimens, consisting of two 1390 mm long beams of grade PS10 timber, were tested under three-point bending. Experimental results and finite element analyses demonstrated that specimens with compliant connections exhibited 14–16% greater maximum vertical displacements but only a marginal 1.79% reduction in load-carrying capacity compared to those with rigid connections. Findings indicate that connection compliance markedly affects stiffness and deflection but has a minor impact on ultimate strength. These insights can guide optimisation of TCC members with metal web joists, balancing structural performance and design requirements in sustainable timber construction. Full article

The incorporation of Basalt Fiber-Reinforced Polymer (BFRP) materials marks a significant advancement in the adoption of sustainable and high-performance technologies in structural engineering. This study investigates the flexural behavior of four-meter, two-span continuous reinforced concrete (RC) beams of low and medium compressive strengths (20 MPa and 32 MPa) strengthened or rehabilitated using near-surface mounted (NSM) BFRP ropes. Six RC beam specimens were tested, of which two were strengthened before loading and two were rehabilitated after being preloaded to 70% of their ultimate capacity. The experimental program was complemented by Finite Element Modeling (FEM) and analytical evaluations per ACI 440.2R-08 guidelines. The results demonstrated that NSM-BFRP rope application led to a flexural strength increase ranging from 18% to 44% ductility by approximately 9–11% in strengthened beams and 13–20% in rehabilitated beams, relative to the control specimens. Load-deflection responses showed close alignment between experimental and FEM results, with prediction errors ranging from 0.125% to 7.3%. This study uniquely contributes to the literature by evaluating both strengthening and post-damage rehabilitation of continuous RC beams using NSM-BFRP ropes, a novel and eco-efficient retrofitting technique with proven performance in enhancing structural capacity and serviceability. Full article

Research on the development of prefabricated foundations has been quite extensive to date, while studies on prefabricated concrete raft foundations and their connection methods remain relatively scarce. This study proposes a novel type of prefabricated raft foundation and its corresponding grouted plug-in connection. The connection comprises two prefabricated units and achieves connection via steel inserts and grouting in pre-slots, possessing numerous advantages such as convenient construction, fast installation, and high construction quality. To verify the performance of the connection node and the bearing capacity of the foundation, based on the engineering practice of prefabricated raft foundations, this study fabricated a full-scale specimen composed of three prefabricated units of the raft foundation, conducted a stacking load test on it, and carried out finite element analysis afterwards. The main conclusion is that severe flexural failure occurred near the grouted plug-in connection of the prefabricated units when the specimen failed, implying that the node region has sufficient bearing capacity. The ultimate bending moments of the specimen obtained from the experiment and finite element analysis are 736.5 kN·m and 859.5·kN m, respectively, with a difference of 14%, indicating a good agreement between them. Ignoring the effect of the upper steel reinforcements, the calculated section bending capacity of the prefabricated unit is 892.8·kN m; the ultimate bending moment of the test specimen reached 0.83 of the section bending capacity of the prefabricated unit, indicating that the proposed raft foundation and its connection method have good bending bearing capacity. Full article

In order to protect the boundary columns once tension region form on shear walls subjected to seismic loads, a new shear wall system constructed by partial-connected crossing-stiffened corrugated steel plate shear walls (PCCSWs) is proposed and investigated. Numerical modeling of the PCCSWs was conducted and validated by a similar test on single-span two-story corrugated steel plate shear wall test specimen. Some key parameters, such as material properties, height-to-thickness ratio, wave length, and width of the crossing stiffeners, were then investigated through parametric analyses, and the results of PCCSWs were compared to the results of other types of steel shear walls. And a theoretical mechanical model was developed for predicting the ultimate capacity of the PCCSWs taking basis of the parametric results. Several findings can be concluded: (1) The finite element method (FEM) simulates buckling modes and the buckling positions of corrugated steel plates and boundary columns precisely, with the errors of initial stiffness and ultimate shear resistance being less than 10%, which proves the feasibility of the FEM. (2) The optimal values on such key parameters were the height-to-thickness ratio of 510~680 at the center, wave lengths of 360~480 mm, and varying widths of crossing stiffeners which are 64.41~136.89. (3) The relative errors between the theoretical and the numerical results were within 14.17%, and most of the variations were less than 10%, indicating the effectiveness of the developed mechanical model. Full article

This paper investigates the bearing behavior of squeezed branch piles and straight-shaft piles under uplift and combined horizontal–uplift loading in silty clay strata. Utilizing a combined approach of laboratory model tests and numerical simulation, the influence of key parameters, such as the depth of the first branch and branch spacing, on the bearing capacity was systematically analyzed. The results demonstrate that under combined loading, the bearing capacity of squeezed branch piles is significantly superior to that of straight-shaft piles, with double-branch piles outperforming single-branch piles. The bearing capacity increases with the depth of the first branch and the branch spacing, reaching its optimum when the first branch is buried at a depth of 6 d (where d is the straight-shaft pile diameter). This study also reveals a unique mechanical response under combined loading: the load–displacement curves exhibit a “smoothed” characteristic, rendering the traditional inflection point method unsuitable for determining the ultimate bearing capacity. Furthermore, a significant coupled weakening effect exists between horizontal and uplift forces. However, increasing the depth of the first branch (to 6 d) and the branch spacing can effectively mitigate this effect, enhancing the pile’s stability under complex loading conditions. This research provides a crucial basis for the optimized design and application of squeezed branch piles in complex loading environments. Full article

With the increasing demand for lightweight, high-strength, and ductile structural systems in modern infrastructure, the hybrid composite column has emerged as a promising solution to overcome the limitations of single-material members. This paper proposes an innovative variant of double-skin tubular columns (DSTCs), termed as square double-skin hybrid concrete bar columns (SDHCBCs), composed of one square-shaped outer steel tube, small-diameter concrete-infilled glass FRP tubes (SDCFs), interstitial mortar, and an inner circular steel tube. A series of axial compression tests were conducted on eight SDHCBCs and one reference DSTC to investigate the effects of key parameters, including the thicknesses of the outer steel tube and GFRP tube, the substitution ratio of SDCFs, and their distribution patterns. As a result, significantly enhanced performance is observed in the proposed SDHCBCs, including the following: ultimate axial bearing capacity improved by 79.6%, while the ductility is increased by 328.3%, respectively, compared to the conventional DSTC. A validated finite element model was established to simulate the mechanical behavior of SDHCBCs under axial compression. The model accurately captured the stress distribution and progressive failure modes of each component, offering insights into the complex interaction mechanisms within the hybrid columns. The findings suggest that incorporating SDCFs into hybrid columns is a promising strategy to achieve superior load-carrying performance, with strong potential for application in high-rise and infrastructure engineering. Full article

Suction embedded plate anchors are widely used in deepwater mooring systems, which can withstand significant vertical loading. During the installation, the mooring chain is tensioned and causes the anchor to rotate, which is known as keying. With a large deformation finite element approach of the coupled Eulerian–Lagrangian method, the chain effects are incorporated into the keying of suction embedded plate anchors. The effectiveness of the proposed method is verified by numerical results and centrifuge tests. The numerical study reveals that the installation angle of the chain has a significant effect on the loss of embedment, especially combined with the effects of load eccentricity and soil strength. The losses of embedment are 0.024~0.273 and 0.217~1.755 anchor width for the installation angles of 15° and 90°, respectively. The ultimate bearing capacity factor decreases with the increasing of load eccentricity and soil strength, because a cavity is formed at the anchor back. Empirical formulae are finally developed for engineers to rapidly estimate the embedment loss and ultimate pullout capacity of suction embedded plate anchors. Full article

Hydrostatic bearings are extensively utilized in precision and ultra-precision machinery. Owing to the small oil film clearance of such bearings, they are prone to tilting under eccentric loads, which may ultimately lead to bearing failure. To investigate the eccentric load characteristics of hydrostatic bearings, a typical rectangular hydrostatic oil pad unit was selected as the research object. First, an analytical model for the eccentric load-carrying capacity of the rectangular oil pad was established. This model was then validated through computational fluid dynamics (CFD) simulations. On this basis, the static and dynamic characteristics of the rectangular hydrostatic oil pad were systematically studied. The results indicate that oil supply pressure, orifice diameter, and oil pad dimensions exert significant influences on the angular stiffness and angular damping of hydrostatic bearings. Specifically, increasing the oil supply pressure to above 3 MPa can facilitate the enhancement of anti-eccentric load capacity. Under the premise of ensuring static load-carrying capacity, a moderate increase in orifice diameter is conducive to improving anti-eccentric load capacity. When the oil pad area is fixed, adjusting the width-to-height ratio of the oil pad can modify the angular damping coefficient in the corresponding direction. However, the adjustment tends to reduce the angular damping coefficient in other directions, necessitating a comprehensive evaluation in practical applications. Full article

Accurate prediction of the ultimate bearing capacity (UBC) of single piles is essential for safe and economical foundation design, as it directly impacts construction safety and resource efficiency. This study aims to develop a hybrid prediction framework integrating Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) to optimize a Backpropagation Neural Network (BPNN). GA performs global exploration to generate diverse initial solutions, while PSO accelerates convergence through adaptive parameter updates, balancing exploration and exploitation. The primary objective of this study is to enhance the accuracy and reliability of UBC prediction, which is crucial for informed decision-making in geotechnical engineering. A dataset consisting of 282 high-strain dynamic load tests was employed to assess the performance of the proposed GA-PSO-BPNN model in comparison with CNN, XGBoost, and traditional dynamic formulas (Hiley, Danish, and Winkler). The GA-PSO-BPNN achieved an R² of 0.951 and an RMSE of 660.13, outperforming other AI models and traditional approaches. Furthermore, SHAP (SHapley Additive exPlanations) analysis was conducted to evaluate the relative importance of input variables, where SHAP values were used to explain the contribution of each feature to the model’s predictions. The findings indicate that the GA-PSO-BPNN model provides a robust, cost-efficient, and interpretable approach for UBC prediction, which aligns with current sustainability goals by optimizing resource usage in foundation design. This model shows significant potential for practical use across various geotechnical settings, contributing to safer, more sustainable infrastructure projects. Full article

To investigate characteristic stress and energy evolution law of carbonaceous shale under dry–wet cycles and fissure angle, several samples with prefabricated fissure angles were prepared and subjected to the coupled influence of dry–wet cycles and loading. The results show that the closure stress, initiation stress, damage stress, and peak stress gradually increase with the increase in confining pressure, effectively suppressing the initiation and propagation of the crack. At the same time, the total energy, elastic energy, and dissipated energy at the crack characteristic stress are enhanced by a linear function relationship, significantly improving the bearing capacity and energy storage capacity of carbonaceous shale. The dry–wet cycle is regarded as the driving force of damage, reducing the crack characteristic stress and the total energy, elastic energy, and dissipated energy of crack characteristic stress. This results in a weakened capacity of the rock samples to store elastic strain energy, ultimately contributing to the damage degradation of carbonaceous shale. The anisotropic damage of rock is controlled by fissure angle. The crack characteristic stress and the total energy, elastic energy, and dissipated energy of crack characteristic stress with a 45° fissure angle is the smallest. Finally, the energy storage level at the damage stress (Kcd) can be used as an early warning indicator for rock failure. Full article

Mixed structures with lightweight steel added stories are particularly vulnerable to damage and failure at the joints during seismic events. To evaluate the secondary seismic behavior of the joints in lightweight steel added stories after seismic damage repair, a low-cycle load test was conducted in this study. Following the initial damage, carbon fiber-reinforced polymer (CFRP) was applied for reinforcement, along with epoxy resin for the repair of concrete cracks. The experimental analysis focused on the structural deformation, failure characteristics, and energy dissipation capacity in both the original and repaired joint states. On the basis of the experimental findings, finite element analysis was carried out to examine the influence of varying CFRP layer configurations on the seismic performance of the repaired joints. The results revealed a significant change in the damage pattern of the repaired specimen, shifting from secondary surface damage to significant concrete deterioration localized at the bottom of the column. The failure mechanism was characterized by the CFRP-induced tensile forces acting on the concrete at the column base, following considerable deformation at the beam’s end. When compared to the original joint, the repaired joints exhibited markedly improved performance, with a 33% increase in horizontal ultimate strength and an 85% increase in energy dissipation capacity at failure. Additionally, the rotation angle between the beams and columns was effectively controlled. Joints repaired with two layers of CFRP demonstrated superior performance in contrast to those with a single layer. However, once the repaired joints met the required strength, further increasing the number of CFRP layers had a minimal influence on the mechanical properties of the joints. The proposed CFRP-based seismic retrofit method, which accounts for the strength degradation of concrete in damaged joints due to earthquake-induced damage, has proven to be both feasible and straightforward, offering an easily implementable solution to improve the seismic behavior of structures. Full article

In saline soil and alpine regions of northwest China, fiber-reinforced recycled aggregate concrete (FR-RAC) beams are subjected to coupled degradation from a chloride–sulfate composite salt attack and freeze–thaw cycling. Existing studies predominantly focus on natural aggregate concrete in freshwater environments or single-salt solutions, with limited documentation on the shear performance of FR-RAC beams after freeze–thaw exposure in chloride–sulfate composite salt solutions. To investigate the durability degradation patterns of FR-RAC beams in Xinjiang’s saline soil regions, two exposure environments (pure water and 5% NaCl + 2.0% Na₂SO₄ composite salt solution) were established. Shear performance tests were conducted on nine groups of FR-RAC beams after 0–175 freeze–thaw cycles, with measurements focusing on failure modes, cracking loads, and ultimate shear capacities. The results revealed that under composite salt freeze–thaw conditions: after 100 cycles, the cracking load and shear capacity of tested beams decreased by 39.8% and 22.2%, respectively, compared to unfrozen specimens representing reductions 29.6% and 82.0% greater than those in freshwater environments; at 175 cycles, cumulative damage intensified, with total reductions reaching 56.8% (cracking load) and 36.1% (shear capacity). A shear capacity degradation prediction model for FR-RAC beams under composite salt freeze–thaw coupling was developed, accounting for concrete strength attenuation and interfacial bond degradation. Model validation demonstrated excellent agreement between predicted and experimental values, confirming its robust applicability. Full article

Joint connections are critical to the overall performance of prefabricated structures. This paper proposes a novel reverse-rotation locking sleeve connection method, designed to ensure the safety of joint engineering while optimizing construction processes, improving operational efficiency, and endowing the joints with excellent seismic energy dissipation performance. To evaluate the performance of this connection method, quasi-static tests under displacement-controlled lateral loading were designed and conducted on three reinforced concrete column specimens (Specimen A: conventional reinforcement–cast-in-place monolithic; Specimen B: conventional reinforcement–reverse-rotation locking sleeve connected; Specimen C: enhanced reinforcement–reverse-rotation locking sleeve connected). The failure modes, hysteretic characteristics, skeleton curves, ductility, energy dissipation capacity, load-bearing capacity, and stiffness degradation patterns of the specimens were systematically examined. The results indicate that Specimen B exhibited the most severe damage extent, while Specimen A demonstrated the best integrity; in contrast, Specimen B showed significant and rapid degradation in energy dissipation capacity during the intermediate-to-late stages of testing; the hysteretic curves of Specimens B and C were full in shape, without obvious yield plateaus; the skeleton curves of all specimens exhibited S-shaped characteristics, and the peak loads of Specimens A and C corresponded to a lateral displacement of 21 mm, while that of Specimen B corresponded to a lateral displacement of 28 mm; compared to the cast-in-place monolithic Specimen A, the reverse-rotation locking sleeve–connected Specimens B and C showed increases in ultimate load under positive cyclic loading by 18.7% and 5.5%, respectively, and under negative cyclic loading by 40.8% and 2.0%, respectively; the ductility coefficients of all three specimens met the code requirement, being greater than 3.0 (Specimen A: 5.13; Specimen B: 3.56; Specimen C: 5.66), with Specimen C exhibiting a 10.3% improvement over Specimen A, indicating that the reverse-rotation locking sleeve–connected specimens possess favorable ductile performance; analysis revealed that the equivalent viscous damping coefficient of Specimen C was approximately 0.06 higher than that of Specimen A, meaning Specimen C had superior energy dissipation capacity compared to Specimen A, confirming that the reverse-rotation locking sleeve connection can effectively absorb seismic energy and enhance the seismic and energy dissipation characteristics of the specimens. The load-bearing capacity degradation coefficients of all specimens fluctuated between 0.83 and 1.01, showing an initial stable phase followed by a gradual declining trend; the stiffness degradation coefficients exhibited rapid initial decline, followed by a deceleration in the attenuation rate, and eventual stabilization. This indicates that the reverse-rotation locking sleeve-connected specimens can maintain relatively stable strength levels and favorable seismic performance during the plastic deformation stage. Full article