Search Results (2,097)

In recent years, traditional cast-in-place concrete construction for pre-drilling engineering in unconventional natural gas fields has generated large amounts of waste concrete, consumed significant resources, and prolonged project schedules. To address these issues, this study proposes a prefabricated pavement slab system as a green and low-carbon alternative. Based on vehicle load surveys at shale-gas well sites in southwestern China, three loading conditions (design, overload, and ultimate axle loads) were defined. Theoretical calculations were then performed for reinforcement design, crack-width control, and local bearing capacity verification. A full-scale precast slab (3000 × 1495 × 150 mm) was fabricated and tested under static monotonic loading to measure deflection, crack development, steel strain, and concrete strain until failure. Separately, a three-dimensional finite element model of a four-panel pavement system (including a mortar-leveling layer and soil subgrade) was developed in ANSYS to simulate static and, preliminarily, moving loads. The experimental slab reached an ultimate load of about 365 kN (based on a single specimen, and thus not statistically representative), with ductile bending failure and crack/deflection patterns typical of reinforced concrete. The numerical model reproduced the cracking load and peak capacity with deviations below 17% from the test data, though post-cracking deflections were underestimated. Overall, the results demonstrate that the proposed prefabricated system is structurally feasible for heavy-duty drilling sites. It enables factory production, rapid on-site assembly, and reuse after dismantling, thereby reducing construction waste, shortening timelines, and supporting energy conservation and emission-reduction goals in the context of China’s green building policies. Full article

During multi-layer winding of hoisting steel wire ropes for ultra-deep vertical shafts on double broken-line drums, abnormal winding behaviors such as rope interlocking, rope jumping and disordered rope arrangement may occur, accelerating abrasion and wire breakage, reducing load-bearing capacity and service life, and compromising operational safety. A dynamic rope-jumping discrimination approach considering transverse-vibration-induced fleet-angle variation was developed and evaluated through field tests. Meanwhile, based on the spatial trajectory model of multi-layer wound hoisting steel wire ropes and a quantitative criterion for rope interlocking, the effects of key drum structural parameters on rope interlocking were investigated. Results show that the broken-line zone is the main high-risk region for rope jumping, with the rightmost position of the third layer after the second-to-third-layer transition being the most critical location. Transverse rope vibration increases the fleet angle, and rope jumping occurs when the critical threshold is exceeded. At the three representative winding positions, the relative errors between the calculated and measured fleet angles are below 7.0%, and the predicted high-risk rope-jumping location is consistent with the field observation, providing field-based support for the model under the examined operating condition. Rope-interlocking risk is significantly higher in the broken-line zone and increases with larger fleet angles, smaller rope groove clearance coefficients and larger drum-to-rope diameter ratios. Full article

Autoclaved aerated concrete (AAC) lintels are conventionally reinforced with steel grids, which are susceptible to long-term corrosion due to moisture penetration and carbonation through the open porous matrix. This study investigates the structural performance and feasibility of AAC lintels reinforced with alternative composite grids—carbon mesh, glass rebar grids, and glass mesh—as corrosion-resistant substitutes for steel. Specimens were evaluated through four-point bending tests to evaluate flexural behavior, capacity, toughness, and production costs. The steel grid achieved the highest peak load (17.20 kN) but showed brittle failure. Carbon mesh showed a pseudo-ductile plateau over a wider deflection range (10.30 mm) and the highest flexural toughness (81,308 N·mm), yielding an 18% toughness increase over the steel control. The glass rebar grid provided the largest displacement tolerance (15.5 mm) through crack-bridging, while lightweight glass mesh showed limited load capacity (3.64 kN). Economic analysis showed that the ready-to-use nature of textile meshes simplifies handling, reduces labor, lowers pre-processing costs to about €0.004 per unit, and eliminates anti-corrosion coatings. Within the tested configurations (n = 3), these findings indicate that carbon mesh and glass rebar grids represent viable alternative reinforcement systems for AAC lintels, offering adequate load-bearing capacity, enhanced deformation tolerance, and simplified, corrosion-free pre-processing. Full article

To address the limitations of conventional temporary steel platforms, a novel lightweight temporary steel platform (LTSP) system was developed based on an inland river high-pile wharf project. The proposed system utilizes permanent rock-socketed steel tubular piles of the wharf structure as the primary load-bearing foundation and consists of welded corbels, twin I-beam main girders, secondary I-section distribution beams, and steel deck plates. A construction method integrating permanent and temporary structural components was proposed. Field measurements were conducted to investigate the vibration response characteristics of the LTSP. The results indicate that the platform exhibits relatively high natural frequencies, with all identified fundamental frequencies exceeding 14 Hz, suggesting a low risk of resonance under human-induced excitations. The lateral stiffness of the platform was found to be greater than its vertical stiffness. Pedestrian-induced vibrations were mainly concentrated near excitation locations, whereas vehicle-induced vibrations were more uniformly distributed across the platform. The permanent steel tubular piles provided effective local restraint and enhanced structural stiffness, thereby reducing vibration transmission to adjacent areas. Construction machinery generated the most significant vibration responses, particularly during simultaneous multi-equipment operations. Therefore, to ensure the safety and operational performance of the temporary steel platform, it is recommended to avoid the simultaneous operation of heavy equipment, such as rotary drilling rigs, fully loaded tanker trucks, and truck cranes. Furthermore, as the current findings are based on a single field application case, future studies should incorporate long-term monitoring and numerical modeling to further evaluate the platform’s applicability to other practical engineering projects. Full article

Grouted connection segments are key load-transfer components in offshore wind jacket structures, and their axial compressive performance is essential for the safety and reliability of the foundation system. This paper develops a finite element model of a grouted connection segment incorporating steel-fiber-reinforced high-strength grout to investigate its mechanical behavior and parametric effects under axial compression. A 1:7-scale model test is conducted to verify the numerical model through comparisons of the load–displacement response and strain responses at key locations. The steel tubes are simulated using a trilinear hardening elastoplastic model, while the steel-fiber-reinforced high-strength grout is represented using the concrete damaged plasticity model with corresponding tensile and compressive constitutive relationships and damage parameters to characterize its nonlinear response. Based on the validated model, a full-scale numerical model is established to analyze the effects of steel tube thickness, shear key spacing, shear key height, and shear key width using the control variable method. The results indicate that steel tube thickness has the most significant influence on the ultimate bearing capacity and can improve the load-bearing capacity and ductility of the structure. Shear key spacing mainly affects axial stiffness and deformation compatibility, while shear key height and width have limited effects on the ultimate bearing capacity but contribute to local deformation control and stiffness enhancement. The findings provide a validated numerical basis for evaluating the axial compressive behavior of steel-fiber-reinforced grouted connections and offer a useful reference for the design and parameter optimization of grouted connection segments in deep-water offshore wind jacket structures. Full article

Equal-leg angle-steel members are widely used as main load-bearing and bracing members in transmission towers. Under elevated-temperature environments such as mountain fires and forest fires, the elastic modulus and strength of steel degrade significantly, which may reduce the overall stability capacity of compression members and even lead to instability failure. To investigate the stability performance of equal-leg angle-steel members made of Q420 steel at uniform elevated temperatures, a shell-element finite-element model was established in Abaqus by considering temperature-dependent material properties of steel. Parametric analyses were carried out under constant compressional loading and uniform heating for the cases of pinned–pinned, fixed–fixed and eccentric–pinned conditions. The effects of slenderness ratio, stability load ratio, section dimension, and initial imperfection amplitude on the critical temperature were systematically analyzed. The results show that the critical temperature decreases significantly with increasing stability load ratio. The eccentric–pinned condition leads to a higher critical temperature than the other two conditions. The initial geometric imperfection will reduce the fire resistance of members. Based on the critical temperature method, design curves of the critical temperature for three boundary conditions were developed using the finite-element results, which are demonstrated to be more accurate than the existing Chinese and European codes. Full article

Rectangular concrete-filled steel tube (RCFST) columns are widely adopted as primary load-bearing components in engineering structures, and making reliable estimation of their axial compressive capacity crucial to structural design and safety assessment. However, existing theoretical and design equations generally rely on a series of simplifying assumptions and empirical modification coefficients, which limit their prediction accuracy and applicability. In this context, a data-driven strategy is proposed in which capacity prediction and model interpretation are integrated within a unified procedure. The proposed approach establishes the nonlinear mapping between high-dimensional input features, including geometric and material properties, and axial compressive capacity, while employing the SHapley Additive exPlanations (SHAP) method to quantify the contributions of critical input parameters to the model predictions. An experimental database comprising 745 axial compression tests on RCFST columns is established through an extensive literature survey. Prior to training, correlations within the candidate inputs are examined using Pearson coefficients. An SMA-LSSVM–ANN hybrid prediction model is then developed, in which SMA iteratively searches for the optimal combination of the LSSVM-ANN hyperparameters using mean squared error as the fitness function. Comparisons with several benchmark machine learning (ML) models and existing design-code formulations validate the predictive performance of the proposed model, which achieves an R² of 0.9571 and an RMSE of 302.84 kN on the testing dataset. Furthermore, SHAP analysis is employed to interpret the proposed model from global and feature-dependency perspectives. Global SHAP analysis identifies concrete compressive strength and cross-sectional dimensions as the dominant features, while feature-dependence analysis reveals generally positive effects of cross-sectional dimensions and material strengths and a negative effect of column length on the predicted capacity. Full article

This study quantitatively characterized the corrosion morphology evolution of Q355B steel under magnetic fields (MFs) using non-contact 3D scanning. MFs exert a threshold-dependent effect on the corrosion morphology and spatial distribution of Q355B steel; while the macroscopic mass loss rate remains largely stable across different MF intensities, the maximum local pit depth peaks at 60 mT, increasing by 42.9%. Spatial autocorrelation shifts from longitudinal long-range to enhanced transverse continuity. Depth distributions follow log-normal distributions. Under uplift, corroded helical anchor bearing capacity varies nonlinearly with MF intensity, reaching a maximum at 30 mT due to the optimal synergy between enhanced surface roughness-induced interface friction and localized cross-sectional reduction. These findings support corrosion assessment and mechanical prediction for Q355B components in MF-coupled environments. Full article

The effect of Ti content on the microstructure and mechanical properties of 1Cr10Co6MoVNbN steel was systematically investigated by comparing a low-Ti steel (LTS, 0.0066 wt.%) with a high-Ti steel (HTS, 0.02 wt.%). Increasing the Ti content was found to markedly alter the precipitate distribution and, consequently, the creep and high-temperature tensile behavior. In HTS, the higher Ti level promoted the preferential formation of (Ti,Nb)N inclusions during solidification; EDS analyses indicated that the matrix of HTS was substantially depleted of Nb, N, Mo, and V relative to LTS, consistent with this preferential nitride formation. In the tempered state, HTS exhibited larger NbC particles that were frequently attached to (Ti,Nb)N inclusions, whereas LTS contained finer, more uniformly dispersed NbC and abundant needle-like Cr₂N precipitates within martensitic laths. These microstructural differences correlated with a substantially higher 100 h creep strain in HTS compared with LTS at 550 °C and 325 MPa, and with a 550 °C tensile strength in HTS that fell below the aerospace standard requirement. Post-creep examination further revealed void formation around (Ti,Nb)N inclusions in HTS, suggesting that these inclusions act as stress concentrators that reduce the effective load-bearing area during creep. The results indicate that strict control of Ti content is essential in Nb–N-strengthened martensitic steels to avoid excessive (Ti,Nb)N formation and the associated degradation of high-temperature mechanical performance. Full article

The longitudinal seismic response of a high-pier long-span stiff-skeleton arch bridge is spatially asymmetric because unequal pier heights, the fixed–movable bearing arrangement, and arch–pier interaction create nonuniform force transfer paths, even when the installed fluid viscous dampers (FVDs) obey a symmetric velocity-dependent law. This study evaluates that response redistribution and the mitigation achieved by longitudinal FVDs under near-fault motions. A three-dimensional SAP2000 model was established using elastic beam elements for the girder, arch ribs, cap beams, and piers, Plastic (Wen) links for spherical steel damping bearings, foundation springs for pile–soil interaction, and Maxwell-type FVD links. Thirty combinations of damping coefficient and velocity exponent were first screened under an El Centro record scaled to 0.64 g. The selected case (α = 0.3 and C = 2000 kN·${\left(s/m\right)}^{\alpha }$) was then evaluated by paired analyses of models with and without FVDs under 15 records grouped descriptively as short-, medium-, and long-period pulse-like motions and non-pulse motions. Across the paired record set, the mean record-wise reductions were 21.34% for bridge-wide maximum bearing displacement, 27.56% for P2 pier-top displacement, 9.73% for bridge-wide maximum pier-base shear force, and 12.62% for bridge-wide maximum pier-base bending moment. Mean arch rib reductions ranged from 10.00% for axial force to 25.00% for bending moment. Seven of the eight monitored response metrics decreased under all 15 records; arch rib axial force decreased under 14 records and was unchanged under 1. Local force increases nevertheless occurred at several arch-supported piers in the spatial El Centro comparison, demonstrating that global mitigation does not imply spatially symmetric or uniformly beneficial component response. Within the selected record set, the medium-period group produced the largest average demands for several response measures, but this is a sample-specific observation rather than a resonance inference. Removing the extracted velocity pulse component reduced most responses, although the nonlinear original-versus-residual comparison cannot be interpreted as an additive pulse contribution. The paired record set check supports the robustness of the selected FVD case for the investigated sample, but does not establish record-independent optimality. Full article

D406A steel serves as a critical structural material for load-bearing components in aerospace solid rocket motors. To achieve an excellent strength-plasticity balance of D406A steel in this work, the quenched specimens austenitized at 890 °C were subjected to tempering treatments at 320 °C, 350 °C, 380 °C and 410 °C, respectively. SEM and EBSD characterization were adopted to systematically investigate the effects of tempering temperature on the microstructure, grain boundary characteristics, local strain, Schmid factor and mechanical properties. The results reveal that the lath martensite gradually undergoes recovery and disintegration with increasing tempering temperature, while the fraction of low-angle grain boundaries rises first and then falls, reaching the maximum value of 48.2% for the specimen tempered at 350 °C. At this tempering temperature, the KAM distribution is uniform, the Schmid factors shift toward the medium-to-high range, the proportion of grains with soft orientation increases, and the deformation coordination capacity is optimal. The specimen tempered at 350 °C exhibits an ultimate tensile strength of 1633.9 MPa, a yield strength of 1262.5 MPa and a Vickers hardness of 485.4 HV, achieving the optimal synergy between strength and plasticity. Full article

Steel wire ropes (SWRs) are exceptional load-bearing elements. However, conventional designs often treat them as passive structures, lacking strategies to actively program their ultimate load-bearing capacity and failure behaviors. To address this gap, this study systematically investigates the tunable load capacity and fracture characteristics of SWRs by developing a simplified power-law hardening elastoplastic constitutive model and a finite element framework integrated with a ductile-damage criterion. Following material parameter calibration via single-wire tests and independent experimental validation of the baseline model using 1 × 7 strand tensile tests, comprehensive numerical parametric studies were conducted to evaluate the simulation-based influence of core diameter (d_core), overall rope diameter (D), layer count (F), and strand configuration (S) on mechanical responses. The numerical results reveal that these geometric parameters act as effective tuning knobs that govern internal stress transfer pathways and ultimate load-bearing capacity. Specifically, simulations predict that increasing the $d_{\mathrm{core}}$ to 1.00 mm elevates the peak tensile force by 9.6% while maintaining a 90.07% tensile force efficiency (TFE, defined as the ratio of mean to peak tensile force). Furthermore, implementing a hybrid multi-strand architecture (SWR-S3) achieves an optimized TFE of 99.76%. These structural modifications facilitate internal strain synchronization, which effectively buffers localized stress peaks and dictates the progressive fracture sequence. Ultimately, this study demonstrates the potential of complementing traditional material enhancement strategies with active geometric parametrization. Rather than offering immediate industrial design rules, it provides a conceptual theoretical framework for exploring custom-tailored tensile strength profiles and predictable failure behaviors. However, because these advanced structural configurations are evaluated using idealized quasi-static finite element models, further experimental validation addressing real-world manufacturing constraints, residual stresses, and dynamic loading is required before practical engineering deployment. Full article

To address the challenge of deformation control in operating tunnel structures, this study investigates a novel reinforcement method for operating shield tunnels using a basalt-fiber-reinforced polymer-wrapped concrete-filled steel tube (BFRP-CFST) composite profile. Two primary study variables were considered. At the segment level, the reinforcement condition comprised two levels: unreinforced and BFRP-CFST-reinforced, with three replicate specimens at each level (US-1 to US-3 and RS-1 to RS-3, respectively). At the full-ring level, the number of installed composite profile frames comprised five levels (n = 0, 1, 2, 3, and 4), where n = 0 represented the unreinforced reference condition. A combined experimental and numerical framework was established, including full-scale four-point bending tests on individual tunnel segments and finite element simulations of full-ring linings. Experimental results demonstrate that the ultimate bearing capacity of reinforced segments increased from 534.4 kN to 921.3 kN, corresponding to a 72.4% improvement. The load level before visible cracking increased by 84.2%. At maximum crack widths of 0.2 mm and 2.0 mm, the mid-span displacement of the reinforced segments was reduced by 30.0% and 21.4%, respectively. The test observations indicate that the prefabricated composite profiles effectively delayed crack development and improved the post-cracking stiffness of the segment. Full-ring numerical simulations further showed that installing one to four composite profile frames increased the external load corresponding to a convergence displacement of approximately 10.5 cm by 12.4%, 21.1%, 28.5%, and 37.4%, respectively. Scientifically, the results reveal a staged load-transfer process in which adhesive bonding provides distributed load transfer during the initial response, while mechanical anchors maintain residual load transfer after local interface debonding; they also establish a quantitative relationship between the number of profile frames and full-ring convergence resistance. From an applied engineering perspective, the proposed profile increased the ultimate load and crack-initiation load of the segments by 72.4% and 84.2%, respectively, while its lightweight and prefabricated configuration provides a potentially rapid rehabilitation option for operating shield tunnels. Full article

Precast reinforced concrete (RC) large-panel buildings (LPBs) are a common residential construction typology in urban areas of Eastern European countries, including Albania. Due to the ageing of these buildings, which date back to the 1970s, and the country’s high seismic hazard, it is very important to assess their seismic safety. This study presents a code-based seismic assessment of a five-storey case-study building in Tirana, Albania’s capital, for which limited information was available and was solely based on the original construction specifications (due to the absence of in situ material testing). A 3D finite-element numerical model was developed using LIRA-SAPR 2024 R2 (version 24.2.0.0) software, and seismic analyses were performed using both multi-modal (response spectra) analysis and the equivalent static analysis procedures according to the current Albanian seismic design code (KTP-N.2-89) and the Eurocode 8 framework (including EN 1998-1 and EN 1998-3). Two different seismic hazard levels were considered to assess the effect of a significantly higher seismic hazard level (compared to the original design) on the seismic safety of older existing LPBs. A demand-to-capacity (DCR) assessment revealed significant structural deficiencies, at both the individual wall-panel level and the wall-assembly level. The representative interior load-bearing wall panel has inadequate flexural and shear capacity, with a DCR of 5.13 for flexure due to a very low vertical reinforcement ratio. The assessment also indicates that the vertical panel joint (D4) is the most critical component of the investigated wall assembly, since its shear capacity is governed by the tensile failure of the steel plate that connects the adjacent wall panels, corresponding to a DCR value of 13.89, indicating very high seismic vulnerability. The seismic assessment of the investigated case-study building may be useful for informing future efforts related to seismic assessment and retrofitting of similar LPBs in Albania and Eastern European countries. Full article

Bearing-grade PEEK composites are intended to improve sliding performance, but filler addition does not necessarily reduce friction. This study compared the dry sliding tribological behaviour of neat PEEK and hybrid PEEK containing PTFE, graphite, and carbon fibre against 42CrMo4+QT steel. Ring-on-block tests were performed at nominal PV values of 0.3–3.2 MPa·m/s, contact pressures of 0.87–5.82 MPa, and sliding velocities of 0.26–0.55 m/s. Each material–condition combination was tested using three independent specimens. Coefficient of friction was calculated from simultaneously measured tangential and normal forces, and subsurface temperature was recorded continuously. Initial and post-test surfaces were examined using optical and extended depth-of-field microscopy. Group mean COF values ranged from 0.052 to 0.123. Hybrid PEEK exhibited a higher numerical mean COF than neat PEEK in all six operating conditions, with relative differences of approximately 1.53–8.36%. Two-factor ANOVA estimated an overall hybrid-minus-neat difference of +0.003388 COF units (95% CI 0.001279–0.005496; p = 0.0029), whereas none of the six condition-specific neat–hybrid comparisons was significant after Holm correction. Initial temperature, maximum temperature, and baseline-normalised temperature rise were reported for every specimen and treated descriptively. Both materials reached stable sliding states without seizure or uncontrolled thermal escalation. Post-test EDF observations showed a denser pattern of fine grooves on neat PEEK, whereas hybrid PEEK exhibited comparatively smoother intervening regions interrupted by fewer but locally deeper features. Mass changes remained close to the capability of the applied balance and did not permit quantitative wear-rate comparison. The results show that the investigated hybrid formulation did not provide a dry-friction reduction advantage over neat PEEK under the tested conditions. Full article