Search Results (980)

To overcome the dual bottlenecks of scarce actual strong earthquake records and high computational costs of nonlinear time history analysis, this study proposes a fast prediction method for structural nonlinear response that integrates systematic seismic sample expansion and machine learning technology by studying mature methods in the industry. A total of 500 ground motion records were created through the application of the amplitude scaling approach. Subsequently, the development of the steel frame structure was carried out through the application of the Abaqus software(Abaqus 2021 Edition) for the purpose of carrying out the nonlinear time history analysis to obtain the maximum interstory drift ratio (IDR) as the target response parameter. The XGBoost model was optimized to obtain improved results through the application of various evaluation criteria. Subsequently, the Shapley Additive exPlanations (SHAP) tool was applied to “open the black box” model to obtain the coupled effect of the various parameters, including displacement-related intensity measures such as RMSD and PGD on the maximum IDR during significant structure deformations. The method developed within this research has the potential to be a powerful tool for the prediction of the seismic responses. The method can be used in many areas, including probabilistic seismic demand, fragility assessment, and rapid evaluation of earthquake damage. Full article

Hinge joints are critical structural components that connect precast girders and enhance the load-bearing capacity and serviceability of multi-girder bridges. Damage to hinge joints can significantly reduce the structural integrity of a bridge and may even lead to bridge collapse. This study numerically investigated the effects of hinge-joint damage on the mechanical performance and inter-girder connections of a hollow-slab girder bridge using a surface-based cohesive behavior model. Hinge-joint damage was simulated in the finite element software ABAQUS (version 2022) using bond-performance degradation at the slab–hinge joint interfaces. The effects of damage location and severity on the stress distribution within the hinge joints were evaluated. The results reveal that damage in two hinge joints produces stresses 15% higher than those caused by damage in a single hinge joint. This indicates a weak superposition effect among multiple damaged joints. Additionally, stress fluctuations at key points Nos. 1 and 2 are significantly greater than those at key points Nos. 3 and 4. These findings provide valuable guidance for improving the durability and crack resistance of hinge joints and designing and maintaining multi-girder bridges. Full article

This paper presents a methodology to evaluate the entire process of thermal evolution and fracture failure within stay cables subjected to sheath fires. Computer software FDS 2021 and ABAQUS 2021 are applied to build a sequentially thermos–mechanics coupled method integrating thermal, structural, and fracture dynamic analyses in stay cables under sheath fire exposure conditions. Herein, three representative fire scenarios including full-circumferential, top-side, and bottom-side ignition are reconstructed. Further, 127 individual wires, accounting for interstitial cavity radiation and contact heat transfer, are utilized to perform analysis on sectional temperature in stay cables. The results indicate that the ignition mode dictates the cross-sectional temperature gradient, with localized ignitions inducing highly asymmetric thermal fields and pronounced internal bending moments. Elevated temperatures trigger a progressive load redistribution from the degraded fire-facing wires to cooler internal layers. Ultimately, abrupt global fracture occurs when the residual ultimate load-carrying capacity intersects with the actual applied tension, resulting in a fracture morphology that closely corresponds to the spatial thermal distribution. Furthermore, the structural capacity degradation exhibits three distinct time-dependent stages: a slow degradation stage, a sharp decline stage, and a recovery stage. Among the analyzed scenarios, full-circumferential ignition induces the most drastic overall capacity reduction, while bottom-side ignition poses a markedly greater rupture risk than top-side ignition. Full article

To systematically investigate the effects of C-shaped and rectangular steel frames on the seismic performance of assembled composite shear walls, this paper, based on the validation of existing pseudo-static test results, employs ABAQUS software to establish refined finite element models, and carries out parametric analyses on C-shaped steel-frame composite shear walls (CSCSWs) and rectangular steel-frame composite shear walls (RSCSWs). With shear-span ratio, axial-load ratio, boundary frame steel plate thickness, and concrete strength grade as variables, a total of 28 numerical models are designed to systematically examine the influence laws of each parameter on bearing capacity, ductility, energy dissipation capacity, and failure modes, and to reveal the performance differences in the confinement mechanisms of the two cross-sectional types. The results indicate that: as the shear-span ratio decreases from 3.0 to 1.0, the bearing capacity increases by up to 171%, but the ductility drops by up to 43%, and the failure mode shifts from flexure-dominated to shear-dominated; increasing the steel plate thickness can simultaneously enhance bearing capacity and ductility, with the peak load increasing by up to 52% and cumulative energy dissipation by over 110%, the mechanism being the synergistic enhancement of the flexural contribution of the boundary frame and the passive confinement effect on the core concrete; increasing the axial-load ratio can improve bearing capacity by about 24%, but significantly impairs ductility and energy dissipation capacity, and it is recommended that the design axial-load ratio be controlled between 0.26 and 0.43; the concrete strength grade has a limited effect on bearing capacity, and as the strength increases, brittle characteristics emerge, leading to a ductility decrease of about 12%; therefore, provided that the strength requirements are met, enhancing the concrete strength grade should not be taken as the primary technical approach for improving the seismic performance of such structures. Comparing the two cross-sectional types, the rectangular cross-section, by providing more uniform and effective lateral confinement, exhibits superior bearing capacity, ductility, and energy dissipation to the C-shaped cross-section across the entire parameter domain, and its performance advantages are more pronounced under conditions of high axial-load ratio and large shear-span ratio. Full article

Prefabricated post-pouring UHPC (ultra-high performance concrete) beam–column joints have the advantages of strong integrity, excellent seismic performance and good durability, but there are also problems of easy cracking of old and new concrete interfaces and concrete near the interface. Therefore, a new type of post-cast UHPC joint is designed in this paper. The joint is connected by post-cast UHPC at the beam and column sections far from the core area, and the keyway is set in the connection section to solve the defect that the old and new interfaces easily crack. The refined finite element model of the joint was established by using the finite element software ABAQUS (2023). Through the simulation of 10 working conditions, the typical failure modes and seismic performance of the joint were discussed in depth, and the influence of key parameters such as the lap length of steel bars, the strength of steel bars and the strength of post-pouring UHPC was analyzed. The results show that the joint cracks first appear at the junction of the beam–column core area and develop along the cut-off interface between ordinary concrete and UHPC. No macroscopic cracks were observed in the post-pouring UHPC connection section, and the structure was finally destroyed due to the crushing of ordinary concrete. Increasing the lap length of the steel bar can improve the peak bearing capacity and stiffness of the joint, but it will accelerate the stiffness degradation. Increasing the strength grade of steel bars can significantly improve the bearing capacity and stiffness of the joints, but the energy dissipation capacity is slightly reduced. In addition, the improvement effect of UHPC strength is closely related to the strength of steel bars: when an HRB500 steel bar is used, high-strength UHPC can show better bearing capacity, stiffness and energy dissipation performance, while the improvement effect is not significant when an HRB400 steel bar is used. The research results can effectively inhibit the development of interface cracks and provide a theoretical reference for the subsequent full-scale test and the seismic design of precast joints with post-cast UHPC connections. Full article

The current internationally largest-diameter and thickest-wall oil and gas transmission line pipe of X80 grade (API Spec 5L) manufactured by longitudinal submerged arc welding (LSAW) is the X80 OD 1422 mm × 32.1 mm straight-seam LSAW pipe, which approaches the limit of manufacturing equipment capability. To overcome the 29-pass limitation of the conventional JCO (J-forming, C-forming, O-forming) forming process for steel pipes, this study conducts a three-dimensional finite element numerical simulation analysis based on ABAQUS 2022/Explicit (explicit dynamic finite element solver within the commercial finite element software Abaqus) to investigate the JCO forming process of this extreme-specification pipe. An innovative involute lower die is designed, enabling a reduction in the forming process to 25 passes. The residual stress and plastic strain distributions in the formed pipes from both the 25-pass and 29-pass processes exhibit consistent patterns, characterized by higher values at the surface layers and lower values in the core region, with the inner surface showing higher stress and strain levels than the outer surface. The maximum residual stress (231.7 MPa) and maximum plastic strain (0.03787) of the 25-pass pipe are slightly lower than those of the 29-pass pipe (231.9 MPa and 0.03859, respectively). In terms of geometric accuracy, the 25-pass process yields an opening gap of 118.8 mm, marginally better than the 118.98 mm of the 29-pass process, and produces a smoother outer circumference profile after forming. These results demonstrate the superiority of the 25-pass process with the novel involute die configuration. The subsequent engineering application validates that the established finite element model possesses high predictive accuracy and practical guidance value. This study provides a breakthrough solution to the technical challenge of excessive forming passes in the JCO forming of the extreme-specification X80 OD 1422 mm × 32.1 mm pipe, achieving a reduction in forming passes while maintaining forming quality, significantly improving efficiency, and reducing manufacturing costs. Full article

Reinforced concrete (RC) structures are susceptible to crack initiation and propagation during service, making accurate numerical simulation of crack behavior essential for assessing structural durability and safety. Current numerical approaches for simulating concrete cracking include smeared/continuum approaches, extended finite element method (XFEM), phase-field methods, and meso-mechanical models. In particular, smeared/continuum approaches (e.g., smeared crack and plastic-damage models such as CDP) indirectly reflect cracking through diffusive damage fields without providing explicit geometric information on crack locations and propagation paths. The XFEM module in commercial software is further restricted to first-order elements and encounters difficulties in simulating multi-crack propagation. These limitations indicate that further development of complementary crack-simulation frameworks is warranted. To this end, this paper presents a cracking simulation framework for RC members within the theoretical framework of the Specified Stress Method, adopting an adaptive degree-of-freedom strategy to balance computational accuracy and efficiency. The method introduces inelastic strain as an additional unknown and establishes a variational principle and the corresponding virtual work equation. Concrete cracking is described by specifying the stress on the crack plane to zero, so that the crack-surface stress remains zero after cracking, thereby avoiding the issue of damage reversibility and improving computational convergence. The method requires neither a predefined crack path nor remeshing after cracking. Unlike smeared/continuum approaches that rely on diffusive damage fields, the crack propagation paths, distribution characteristics, and evolution of multiple cracks are characterized through the spatial distribution of cracked integration points within the finite element mesh. In the present implementation, crack initiation is governed by the maximum tensile stress criterion, and a linear elastic constitutive model is adopted for concrete as a deliberate simplification to establish and verify the core computational mechanism of the framework. The proposed method was examined through three numerical examples. First, comparison with theoretical solutions confirmed the algorithm’s correctness in simulating cracking in heterogeneous RC tension members. Second, comparison with experimental results demonstrated qualitatively consistent crack propagation trends and load–displacement responses for RC beams under mixed-mode cracking; the calculated ultimate load of the plain concrete beam is lower than the experimental value, which is attributable to the use of the maximum tensile stress criterion without fracture energy considerations, and certain crack morphology deviations are observed due to the neglect of reinforcement–concrete bond-slip. Third, a multi-crack simulation of an under-reinforced RC beam showed that, whereas the XFEM module in ABAQUS captures only a single dominant crack near the mid-span, the proposed algorithm predicts multiple distributed cracking zones on both sides of the mid-span, qualitatively consistent with the typical flexural cracking behavior of under-reinforced RC beams; the algorithm also supports second-order elements (e.g., C3D20R) unavailable in the ABAQUS XFEM implementation. While the method is still in an exploratory stage, these results confirm the feasibility and potential of the Specified Stress Method as a complementary framework for RC cracking simulation, providing a basis for further development. Full article

A recently published experiment introduced a novel masonry concrete block masonry retaining wall system designed to resist lateral soil pressure by arch action. The system demonstrated several advantages: minimal deflection, ease of construction, cost-effectiveness, and aesthetic appearance. Despite the success of this system, the deflection profile of the wall was unexpected and could not be reproduced through numerical analysis, preventing complete characterization of the structural system. To define the parametric behaviour of this type of structure, a three-dimensional finite element simplified micro-model of the arch wall was developed using ABAQUS software version 2020 and verified against the experiment and existing analytical methods. The influences of the arch rise-to-span ratio, wall height, and grouting pattern were explored. The results revealed that arched retaining walls responded in a combination of arch action and cantilever behaviour, with the cantilever component diminishing with increasing wall height and curvature. For a given wall width, hollow arched walls sustained higher pressures than a conventional grouted flat wall. A hollow arched wall with a rise-to-span ratio of 0.25 resisted 37% more soil pressure than a grouted planar wall of the same height and span. Arch action was thus demonstrated as an effective mechanism for masonry retaining walls. Full article

Sustainable agricultural production requires environmentally friendly weed management solutions. Steam-based thermal weed control is a promising alternative to conventional herbicide-based weed management. However, optimizing steam delivery systems remains computationally expensive due to the repeated simulation-based design evaluations required. This paper presents a design optimization framework for a novel root-targeted steam injection module intended for integration into an autonomous agricultural platform for sustainable thermal weed management. The mechanical behavior of different nozzle geometries was evaluated using finite element analysis using the ABAQUS/CAE software, generating the simulation dataset used for optimization. To reduce the computational cost associated with repeated finite element simulations, a Kriging surrogate model was constructed from this dataset and coupled with an evolutionary optimization algorithm to identify the optimal nozzle geometry. The evaluated nozzle geometries exhibited maximum stresses ranging from 5.12 to 20.41 N/mm². The stress value predicted by the Kriging model for the optimized configuration was validated through an additional finite element simulation, showing a deviation of only 6.6%. Furthermore, an artificial neural network model implemented in PyTorch 2.7.1 was trained on the simulation dataset and used as an independent validation tool to estimate the stress corresponding to the optimized nozzle geometry, with a prediction deviating by approximately 5.4% from the corresponding finite element result. The proposed approach significantly reduces computational cost while maintaining high accuracy in stress prediction, enabling the identification of a structurally reliable nozzle geometry for sustainable herbicide-free thermal weed management. Full article

Historical buildings represent a fundamental component of cultural heritage, and their preservation is of paramount importance for future generations. In the context of Turkey, Ulu Mosques represent a distinctive architectural and historical phenomenon, erected during the periods of the Seljuk, Principalities, and Ottoman empires, primarily serving as centres for Friday and Eid prayers. The location of these mosques in city centres is indicative of their role as symbols of both cultural identity and social power. Nevertheless, it is an established fact that earthquakes have caused serious damage to many historical masonry structures over time. This study investigates the seismic behaviour of the historical Ulu Mosque located in Uşak province, Türkiye. To this end, three-dimensional finite element models of the mosque were created, and both linear and nonlinear time-history analyses were conducted using ABAQUS/Standard v10 software. The analyses were performed using the ground motion record of the 1999 Kocaeli (Izmit) earthquake, which had a moment magnitude of Mw = 7.4. In the nonlinear analyses, the Concrete Damage Plasticity (CDP) model was employed to represent the nonlinear behaviour and damage mechanisms of masonry materials under earthquake loading. The objective of the present study is twofold: firstly, to enhance the comprehension of the manner in which historical masonry mosques respond to seismic effects, and secondly, to identify areas that are vulnerable to damage. Stress limits were exceeded in these areas. Tensile stress has been identified as the primary factor in damage occurrence. This situation can be attributed to the inherent resilience of masonry structures in resisting compressive stresses. Stress limits were exceeded in these areas. Tensile stress has been identified as the primary factor in damage occurrence. This situation can be attributed to the inherent resilience of masonry structures in resisting compressive stresses. Full article

To overcome the inherent drawbacks of cast-in-place reinforced concrete bracing—such as long construction periods and difficult demolition—as well as the relatively high construction cost of steel structure bracing, while fully incorporating the respective technical advantages of these two traditional support systems, this paper proposes a novel hybrid prefabricated reinforced concrete (RC)–steel structure foundation pit bracing system. In order to investigate the overall bearing capacity variation in the standard components of this structure under complex external forces in foundation pits, a numerical model was established using the finite element software ABAQUS. The study examines the trend of the axial compressive bearing capacity of a single standard beam segment as the steel thickness of its external stiffening sleeve varies, as well as the effects of eccentric loading, oblique loading, and the presence or absence of auxiliary supports on the structural bearing capacity of multi-segment beam assemblies. The numerical analysis results show that the bearing capacity of a single beam segment exhibits a strong correlation with the variation in sleeve thickness, and a fitting curve of compressive strength as a function of thickness was derived. For the multi-segment assembly, an increase of 1 mm in the load eccentricity in the Y and Z directions reduces the ultimate peak load by approximately 20.95 kN and 23.94 kN, respectively; in the XY and XZ planes, an increase of 1° in the eccentric angle of the oblique load reduces the peak ultimate bearing capacity by about 6.02 kN and 9.67 kN, respectively. Auxiliary supports have a relatively minor influence on the structural bearing capacity. This research thoroughly explores the bearing capacity of the prefabricated steel–concrete composite and steel structure foundation pit bracing under complex working loads, providing strong support for engineering design and demonstrating broad application prospects. Full article

Shock wave propagation in a layered ceramic–polymer–metal (CPM) composite armor was investigated numerically using the Abaqus^© (2024) software in a plate-impact configuration, in which a copper impactor impacts a CPM plate that serves as an intermediate layer between the impactor and a protected target representing human bone. The resulting motion of the CPM back surface closes a pre-calibrated gap, initiating a secondary impact on the protected target. Because the transmitted loadings depend on the complex interaction of compressive and release waves within the layered system, the effect of gap distance on impact response is difficult to predict. Therefore, the primary objective of this study is to develop an improved understanding of the shock-mitigation mechanisms within the CPM system that enable the target to survive the impact event. The particle-velocity history at the midplane of the protected target was used to compare responses at different gap distances. The gap effect is influenced by geometry under uniaxial strain conditions, as well as by the materials’ wave speed and shock impedance. The observed trends arise from the combined effects of geometry under uniaxial strain conditions, material wave speed, and shock impedance mismatch, which govern the evolution and interaction of the compressive and release waves at different gap distances. The CPM configuration was examined over a 1–10 mm gap, and a detailed analysis was conducted for the representative gap distances of 1–3 mm. The results indicate that the midplane velocity of the protected target depends strongly on the gap distance, with a 1 mm gap producing the highest midplane velocity, followed by gaps of 3 mm and 2 mm. The CPM response depends on differences in the timing and strength of compressive and release waves reaching its free surface before gap closure, as shown by velocity histories and x–t diagrams. Full article

To study the changes in circumferential internal forces of an existing shield tunnel when an overlapping tunnel passes through, a surrounding pressure redistribution model for overlapping tunnels was established to calculate the circumferential surrounding pressure of the existing tunnel. Combined with an engineering case, a detailed three-segment tunnel model was created using Abaqus 2023 finite element software. The circumferential forces of the tunnel were applied to the model, and the circumferential internal forces of the segments were extracted to study the variation law of segment circumferential internal forces. The research results indicate the following: (1) During the excavation of overlapping tunnels, the circumferential surrounding pressure of the existing tunnel decreases, and the circumferential surrounding pressure at any position exhibits a symmetric “8”-shaped distribution. (2) During the excavation of the new tunnel, the circumferential internal forces of the existing shield tunnel increase. In front of the excavation face, the additional internal forces of the tunnel decrease with distance, while within approximately 6 m behind the excavation face, the additional internal forces of the tunnel increase sharply. (3) As the angle between the line connecting the axes of the two tunnels and the z-axis increases, the additional internal forces of the existing tunnel decrease; as the clear distance between tunnels increases, the circumferential internal forces of the existing tunnel decrease, and the additional bending moments and additional shear forces approximately show linear variation. Full article

Shared bikes are frequently parked in disorder, resulting in low efficiency of manual collection and transfer and heavy workload for maintenance staff. Random parking across various areas forces shared bikes to occupy sidewalks and fire exits, damaging urban landscapes and disrupting traffic order. To tackle these industrial pain points, this paper develops an integrated intelligent robot system equipped with functions of multi-pose grasping, automatic transfer and fixed-point delivery of shared bikes, which can effectively address the drawbacks of low efficiency and high labor costs in traditional manual maintenance. This paper focuses on the completion of the robot’s overall mechanical structure design, stiffness–precision collaborative optimization model construction, finite-element static simulation verification, 1:7 scaled prototype development and performance testing. Firstly, the overall layout design of the multi-posture adaptive floating clamping mechanism, transfer-bearing frame, and Mecanum wheel omnidirectional mobile chassis is completed, and the structural parameters and assembly benchmarks of the core components are clarified. Secondly, a stiffness–precision coupling optimization model is established, and the static analysis under extreme load conditions is carried out through Abaqus finite-element software, which verifies the rationality of 45# carbon steel material selection and the safety of structural strength. Subsequently, a 1:7 scaled principle prototype is developed, and repetitive grabbing and transfer tests are carried out to verify the system operation feasibility, stability and grabbing accuracy. Finally, the statistical analysis of the test data and the horizontal comparison of similar schemes are completed. The test and simulation results show that the maximum stress of the system under extreme working conditions is 131.21 MPa, which is far lower than the allowable stress of 355 MPa of 45# steel, and the safety factor reaches 2.71. The maximum total deformation is 4.0552 mm, which is concentrated at the end of the front-end clamping mechanism, and is within the allowable stiffness deviation range of the transfer system. The average value of the single clamping positioning error of the scaled prototype is 0.476 mm, with a 95% confidence interval of 0.457–0.495 mm, which is converted to a positioning error of ≤3.4 mm for the full-scale prototype, which is far better than similar industry solutions. The average time of a single complete grabbing and transfer operation is 12.38 s, which is more than 45% higher than the traditional manual mode. The structural design, grabbing accuracy and operation stability of the robot designed in this paper all meet the requirements of actual working conditions of urban sidewalks, which can effectively reduce the intensity of manual labor and improve the operation and maintenance efficiency of shared bicycles. It has strong engineering application value and can provide reference for the design and manufacturing of intelligent collection and transfer systems for shared two-wheelers. Full article

In this study, the seismic vulnerability of the Ferdowsi School building in Tabriz is investigated. The research began with comprehensive fieldwork, during which exploratory surveys and in-depth technical inspections of all structural components were performed. Experimental testing of prismatic masonry specimens was carried out to evaluate their mechanical characteristics, and the resulting properties were then incorporated as input parameters into the numerical model. The seismic vulnerability assessment was then carried out using nonlinear static (pushover) analysis, applying a lateral load pattern proportional to the first vibration mode of the structure. For numerical simulation, the building was modeled in the ABAQUS finite element software using the macro-modeling technique. The results of the nonlinear static analysis indicated that the building does not possess sufficient load-bearing capacity at the target displacement. Damage was primarily concentrated in the form of cracking in the masonry walls as well as in the dome-shaped sections of the roof, requiring the implementation of a seismic retrofitting scheme to enhance the structure’s seismic performance. To rehabilitate the structure, horizontal and vertical reinforced concrete beams were introduced as confining elements for the masonry walls and subsequently applied in the strengthening project. Furthermore, due to the presence of a domed roof at the first-floor level, it was strengthened using FRP composite materials to enhance tensile capacity and ductility. At the second-floor level, where the roof structure is made of timber elements, a steel cable system was employed to improve its strength and diaphragm action. As for the third-floor timber truss roof, the connections were upgraded and reinforced to provide reliable force transmission and to maintain the overall integrity of the structural system. Following the implementation of the retrofitting measures, the structural model was re-analyzed using nonlinear static analysis. The results demonstrated that the proposed strengthening scheme successfully increased the structural capacity up to the target displacement level and satisfied the intended performance requirements. In the final section of the paper, the implementation details of the retrofitting interventions, as well as the practical experiences gained during the implementation process, are presented and discussed. Full article