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Keywords = high-strength bolt

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17 pages, 8715 KiB  
Article
Experimental Investigation of Failure Behaviors of CFRP–Al Lap Joints with Various Configurations Under High- and Low-Temperature Conditions
by Mingzhen Wang, Qiaosheng Huang, Qingfeng Duan, Wentao Yang, Yue Cui and Hongqiang Lyu
Materials 2025, 18(15), 3467; https://doi.org/10.3390/ma18153467 - 24 Jul 2025
Viewed by 300
Abstract
The failure behaviors of CFR–aluminum lap joints with diverse configurations through quasi-static tensile tests were conducted at −40 °C, 25 °C, and 80 °C. Four specimen types were examined: CFRP–aluminum alloy two-bolt single-lap joints (TBSL), two-bolt double-lap joints (TBDL), two-bolt bonded–bolted hybrid single-lap [...] Read more.
The failure behaviors of CFR–aluminum lap joints with diverse configurations through quasi-static tensile tests were conducted at −40 °C, 25 °C, and 80 °C. Four specimen types were examined: CFRP–aluminum alloy two-bolt single-lap joints (TBSL), two-bolt double-lap joints (TBDL), two-bolt bonded–bolted hybrid single-lap joints (BBSL), and two-bolt bonded–bolted hybrid double-lap joints (BBDL). The analysis reveals that double-lap joints possess a markedly higher strength than single-lap joints. The ultimate loads of the TBSL (single-lap joints) at temperatures of −40 °C and 25 °C are 29.5% and 26.20% lower, respectively, than those of the TBDL (double-lap joints). Similarly, the ultimate loads of the BBSL (hybrid single-lap joints) at −40 °C, 25 °C, and 80 °C are 19.8%, 31.66%, and 40.05% lower, respectively, compared to the corresponding data of the TBDL. In bolted–bonded hybrid connections, the adhesive layer enhances the joint’s overall stiffness but exhibits significant temperature dependence. At room and low temperatures, the ultimate loads of the BBDL are 46.97 kN at −40 °C and 50.30 kN at 25 °C, which are significantly higher than those of the TBDL (42.24 kN and 44.63 kN, respectively). However, at high temperatures, the load–displacement curves of the BBDL and TBDL are nearly identical. This suggests that the adhesive layers are unable to provide a sufficient shear-bearing capacity due to their low modulus at elevated temperatures. This research provides valuable insights for designing composite–metal connections in aircraft structures, highlighting the impacts of different joint configurations and temperature conditions on failure modes and load-bearing capacities. Full article
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15 pages, 5980 KiB  
Article
Seismic Performance of Cladding-Panel-Equipped Frames with Novel Friction-Energy-Dissipating Joints
by Xi-Long Chen, Xian Gao, Li Xu, Jian-Wen Zhao and Lian-Qiong Zheng
Buildings 2025, 15(15), 2618; https://doi.org/10.3390/buildings15152618 - 24 Jul 2025
Viewed by 180
Abstract
Based on the need to enhance the seismic performance of point-supported steel frame precast cladding panel systems, this study proposes a novel friction-energy-dissipating connection joint. Through establishing refined finite element models, low-cycle reversed loading analyses and elastoplastic time-history analyses were conducted on three [...] Read more.
Based on the need to enhance the seismic performance of point-supported steel frame precast cladding panel systems, this study proposes a novel friction-energy-dissipating connection joint. Through establishing refined finite element models, low-cycle reversed loading analyses and elastoplastic time-history analyses were conducted on three frame systems. These included a benchmark bare frame and two cladding-panel-equipped frame structures configured with energy-dissipating joints using different specifications of high-strength bolts (M14 and M20, respectively). The low-cycle reversed loading results demonstrate that the friction energy dissipation of the novel joints significantly improved the seismic performance of the frame structures. Compared to the bare frame, the frames equipped with cladding panels using M14 bolts demonstrated 10.9% higher peak lateral load capacity, 17.6% greater lateral stiffness, and 45.6% increased cumulative energy dissipation, while those with M20 bolts showed more substantial improvements of 22.8% in peak load capacity, 32.0% in lateral stiffness, and 64.2% in cumulative energy dissipation. The elastoplastic time-history analysis results indicate that under seismic excitation, the maximum inter-story drift ratios of the panel-equipped frames with M14 and M20 bolts were reduced by 42.7% and 53%, respectively, compared to the bare frame. Simultaneously, the equivalent plastic strain in the primary structural members significantly decreased. Finally, based on the mechanical equilibrium conditions, a calculation formula was derived to quantify the contribution of joint friction to the horizontal load-carrying capacity of the frame. Full article
(This article belongs to the Section Building Structures)
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29 pages, 7048 KiB  
Article
Research on Synergistic Control Technology for Composite Roofs in Mining Roadways
by Lei Wang, Gang Liu, Dali Lin, Yue Song and Yongtao Zhu
Processes 2025, 13(8), 2342; https://doi.org/10.3390/pr13082342 - 23 Jul 2025
Viewed by 195
Abstract
Addressing the stability control challenges of roadways with composite roofs in the No. 34 coal seam of Donghai Mine under high-strength mining conditions, this study employed integrated methodologies including laboratory experiments, numerical modeling, and field trials. It investigated the mechanical response characteristics of [...] Read more.
Addressing the stability control challenges of roadways with composite roofs in the No. 34 coal seam of Donghai Mine under high-strength mining conditions, this study employed integrated methodologies including laboratory experiments, numerical modeling, and field trials. It investigated the mechanical response characteristics of the composite roof and developed a synergistic control system, validated through industrial application. Key findings indicate significant differences in mechanical behavior and failure mechanisms between individual rock specimens and composite rock masses. A theoretical “elastic-plastic-fractured” zoning model for the composite roof was established based on the theory of surrounding rock deterioration, elucidating the mechanical mechanism where the cohesive strength of hard rock governs the load-bearing capacity of the outer shell, while the cohesive strength of soft rock controls plastic flow. The influence of in situ stress and support resistance on the evolution of the surrounding rock zone radii was quantitatively determined. The FLAC3D strain-softening model accurately simulated the post-peak behavior of the surrounding rock. Analysis demonstrated specific inherent patterns in the magnitude, ratio, and orientation of principal stresses within the composite roof under mining influence. A high differential stress zone (σ1/σ3 = 6–7) formed within 20 m of the working face, accompanied by a deflection of the maximum principal stress direction by 53, triggering the expansion of a butterfly-shaped plastic zone. Based on these insights, we proposed and implemented a synergistic control system integrating high-pressure grouting, pre-stressed cables, and energy-absorbing bolts. Field tests demonstrated significant improvements: roof-to-floor convergence reduced by 48.4%, rib-to-rib convergence decreased by 39.3%, microseismic events declined by 61%, and the self-stabilization period of the surrounding rock shortened by 11%. Consequently, this research establishes a holistic “theoretical modeling-evolution diagnosis-synergistic control” solution chain, providing a validated theoretical foundation and engineering paradigm for composite roof support design. Full article
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17 pages, 2698 KiB  
Article
Behavior of Demountable and Replaceable Fabricated RC Beam with Bolted Connection Under Mid-Span Compression
by Dongping Wu, Yan Liang, Huachen Liu and Sheng Peng
Buildings 2025, 15(15), 2589; https://doi.org/10.3390/buildings15152589 - 22 Jul 2025
Viewed by 203
Abstract
In order to verify the rationality and feasibility of a demountable and replaceable fabricated RC beam with bolted connection under mid-span compression, one cast-in-place RC beam and four fabricated RC beams were designed and fabricated. Through the mid-span static loading test and analysis [...] Read more.
In order to verify the rationality and feasibility of a demountable and replaceable fabricated RC beam with bolted connection under mid-span compression, one cast-in-place RC beam and four fabricated RC beams were designed and fabricated. Through the mid-span static loading test and analysis of five full-scale RC beams, the effects of high-strength bolt specifications and stiffeners were compared, and the behavior of the fabricated RC beams with bolted connections was analyzed. The test process was observed and the test results were analyzed. The failure mode, cracking load, yield load, ultimate load, stiffness change, deflection measured value, ductility, and other indicators of the specimens were compared and analyzed. It was shown that the failure mode of the fabricated RC beam was reinforcement failure, which met the three stress stages of the normal section bending of the reinforcement beam. The failure position occurred at 10~15 cm of the concrete outside the bolt connection, and the beam support and the core area of the bolt connection were not damaged. The fabricated RC beam has good mechanical performance and high bearing capacity. In addition, comparing the test value with the simulation value, it is found that they are in good agreement, indicating that ABAQUS software of 2024 can be well used for the simulation analysis of the behavior of fabricated RC beam structure. Full article
(This article belongs to the Section Building Structures)
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22 pages, 10008 KiB  
Article
Design and Testing of a Device to Investigate Dynamic Performance of Aero-Engine Rotor–Stator Rubbing Dynamics
by Qinqin Mu, Qun Yan, Peng Sun, Yonghui Chen, Jiaqi Chang and Shiyu Huo
Eng 2025, 6(7), 162; https://doi.org/10.3390/eng6070162 - 17 Jul 2025
Viewed by 207
Abstract
To analyze the wear performance induced by rotor–stator rubbing in an aero-engine sealing structure under authentic operating conditions, a transonic rotor system with double bearing is constructed. This system incorporates the disk, shaft, blades, joint bolts, and auxiliary support structure. The system was [...] Read more.
To analyze the wear performance induced by rotor–stator rubbing in an aero-engine sealing structure under authentic operating conditions, a transonic rotor system with double bearing is constructed. This system incorporates the disk, shaft, blades, joint bolts, and auxiliary support structure. The system was evaluated in terms of its critical speed, vibration characteristics, component strength under operational conditions, and response characteristics in abnormal extreme scenarios. A ball screw-type feeding system is employed to achieve precise rotor–stator rubbing during rotation by controlling the coating feed. Additionally, a quartz lamp heating system is used to apply thermal loads to coating specimens, and the appropriate heat insulation and cooling measures are implemented. Furthermore, a high-frequency rubbing force test platform is developed to capture the key characteristics caused by rubbing. The test rig can conduct response tests of the system with rotor–stator rubbing and abrasion tests with tip speeds reaching 425 m/s, feed rates ranging from 2 to 2000 μm/s, and heating temperatures up to 1200 °C. Test debugging has confirmed these specifications and successfully executed rubbing tests, which demonstrate stability throughout the process and provide reliable rubbing force test results. This designed test rig and analysis methodology offers valuable insights for developing high-speed rotating machinery. Full article
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22 pages, 2892 KiB  
Article
Investigation of Bolt Grade Influence on the Structural Integrity of L-Type Flange Joints Using Finite Element Analysis
by Muhammad Waleed and Daeyong Lee
J. Mar. Sci. Eng. 2025, 13(7), 1346; https://doi.org/10.3390/jmse13071346 - 15 Jul 2025
Viewed by 266
Abstract
Critical components in support structures for wind turbines, flange joints, are fundamental to ensure the structural integrity of mechanical assemblies under varying operational conditions. This paper investigates the structural performance of L-type flange joints, focusing on the influence of bolt grades and bolt [...] Read more.
Critical components in support structures for wind turbines, flange joints, are fundamental to ensure the structural integrity of mechanical assemblies under varying operational conditions. This paper investigates the structural performance of L-type flange joints, focusing on the influence of bolt grades and bolt pretension through a finite element analysis (FEA) study of its key performance indicators, including stress distribution, deformation, and force–displacement behaviors. This paper studies two high-strength bolt grades, Grade 10.9 and Grade 12.9, and two main steps—first, bolt pretension and, second, external loading (tower shell tensile load)—to investigate the influence on joint reliability and safety margins. The novelty of this study lies in its specific focus on static axial loading conditions, unlike the existing literature that emphasizes fatigue or dynamic loads. Results show that the specimen carrying a higher bolt grade (12.9) has 18% more ultimate load carrying capacity than the specimen with a lower bolt grade (10.9). Increased pretension increases the stability of the joint and reduces the micro-movements between A and B (on model specimen), but could result in material fatigue if over-pretensioned. Comparative analysis of the different bolt grades has provided practical guidance on material selection and bolt pretension in L-type flange joints for wind turbine support structures. The findings of this work offer insights into the proper design of robust flange connections for high-demand applications by highlighting a balance among material properties, bolt pretension, and operational conditions, while also proposing optimized pretension and material recommendations validated against classical analytical models. Full article
(This article belongs to the Section Ocean Engineering)
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20 pages, 5957 KiB  
Article
Plasticity and Fracture Behavior of High-Strength Bolts Considering Steel Shear Behavior
by Yajun Zhang, Longteng Liang, Jian Zhu and Ruilin Zhang
Buildings 2025, 15(14), 2430; https://doi.org/10.3390/buildings15142430 - 10 Jul 2025
Viewed by 284
Abstract
The accurate description of plasticity and fracture behavior is essential in numerically investigating the mechanical responses of high-strength bolts under tension, shear and coupling loads. However, based on the von Mises criterion, inputting the constitutive relation and damage model from the tensile coupon [...] Read more.
The accurate description of plasticity and fracture behavior is essential in numerically investigating the mechanical responses of high-strength bolts under tension, shear and coupling loads. However, based on the von Mises criterion, inputting the constitutive relation and damage model from the tensile coupon test into the finite element method cannot properly predict the shear behavior of high-strength bolts. Cylindrical tensile coupons and shear specimens of common and weathering high-strength bolts are tested to obtain the complete tensile and shear responses. The combined S-V model and the modified shear constitutive model are collaboratively used to calibrate and describe the tensile and shear constitutive relations of high-strength bolts, and then the Bao–Wierzbicki model is used to predict the tensile and shear fracture behaviors. Furthermore, the collaborating method is used to discuss the applicable range of tensile and shear constitutive models for high-strength bolts under a tensile–shear coupling load, based on numerical analysis against available experimental data in the literature. The loading angle of 30° along the bolt rod is defined as the cut-off to differentiate high-strength bolts under a tensile- or shear-dominated state, and the corresponding mechanical responses of high-strength bolts can be predicted well based on the tensile and shear constitutive models, respectively. Full article
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30 pages, 9068 KiB  
Article
Dynamic Behavior of Lighting GFRP Pole Under Impact Loading
by Mahmoud T. Nawar, Ahmed Elbelbisi, Mostafa E. Kaka, Osama Elhosseiny and Ibrahim T. Arafa
Buildings 2025, 15(13), 2341; https://doi.org/10.3390/buildings15132341 - 3 Jul 2025
Viewed by 248
Abstract
Vehicle collisions with street lighting poles generate extremely high impact forces, often resulting in serious injuries or fatalities. Therefore, enhancing the structural resilience of pole bases is a critical engineering objective. This study investigates a comprehensive dynamic analysis conducted with respect to base [...] Read more.
Vehicle collisions with street lighting poles generate extremely high impact forces, often resulting in serious injuries or fatalities. Therefore, enhancing the structural resilience of pole bases is a critical engineering objective. This study investigates a comprehensive dynamic analysis conducted with respect to base material behavior and energy absorption of GFRP lighting pole structures under impact loads. A finite element (FE) model of a 5 m-tall tapered GFRP pole with a steel base sleeve, base plate, and anchor bolts was developed. A 500 kg drop-weight impact at 400 mm above the base simulated vehicle collision conditions. The model was validated against experimental data, accurately reproducing the observed failure mode and peak force within 6%. Parametric analyses explored variations in pole diameter, wall thickness, base plate size and thickness, sleeve height, and anchor configuration. Results revealed that geometric parameters—particularly wall thickness and base plate dimensions—had the most significant influence on energy absorption. Doubling the wall thickness reduced normalized energy absorption by approximately 76%, while increases in base plate size and thickness reduced it by 35% and 26%, respectively. Material strength and anchor bolt configuration showed minimal impact. These findings underscore the importance of optimizing pole geometry to enhance crashworthiness. Controlled structural deformation improves energy dissipation, making geometry-focused design strategies more effective than simply increasing material strength. This work provides a foundation for designing safer roadside poles and highlights areas for further exploration in base configurations and connection systems. Full article
(This article belongs to the Special Issue Extreme Performance of Composite and Protective Structures)
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21 pages, 7734 KiB  
Article
Parametric Finite Element Simulations of Different Configurations of Partial-Strength Exposed Column Base Plate Connections
by Reza Khani, Mario D’Aniello, Roberto Tartaglia and Yousef Hosseinzadeh
Buildings 2025, 15(13), 2255; https://doi.org/10.3390/buildings15132255 - 27 Jun 2025
Viewed by 300
Abstract
The present study investigates the influence of the configurations of anchor bolts and stiffeners on the monotonic response under moment conditions in the major axis and compression force of partial-strength exposed column base plate connections in order to ameliorate their response, limiting the [...] Read more.
The present study investigates the influence of the configurations of anchor bolts and stiffeners on the monotonic response under moment conditions in the major axis and compression force of partial-strength exposed column base plate connections in order to ameliorate their response, limiting the number of welded details. Parametric finite element simulations were performed based on models calibrated against experimental results available from the recent literature. The results show the efficiency of the investigated configurations, namely, (i) the presence of rib stiffener results in high stiffness and strength with a reduction in ductility; (ii) the linear pattern of anchor bolts (e.g., rectangular distribution) is characterized by the limited contribution of the outer anchor bolts to the overall resistance of the connection; (iii) the trapezoidal pattern of the anchor bolts exhibit a better mechanical performance as well as their efficiency; and (iv) the increase in compression force influences the mechanical response of the base connection with an increase in both resistance and rigidity until the column is stable against the moment–axial force interaction. Full article
(This article belongs to the Section Building Structures)
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31 pages, 3456 KiB  
Review
Advancements in Timber–Steel Hybridisation: A Review on Techniques, Applications, and Structural Performances
by Abdulaziz Abdulmalik, Benoit P. Gilbert, Hong Guan, Tuan Ngo and Alex Remennikov
Buildings 2025, 15(13), 2252; https://doi.org/10.3390/buildings15132252 - 26 Jun 2025
Viewed by 459
Abstract
Timber–steel hybridisation offers a balanced approach by capitalising on the high strength-to-weight ratio and sustainability of the timber while also benefiting from the high stiffness and ductility of the steel, contributing to the improved performance of hybrid structural elements. This paper reviews key [...] Read more.
Timber–steel hybridisation offers a balanced approach by capitalising on the high strength-to-weight ratio and sustainability of the timber while also benefiting from the high stiffness and ductility of the steel, contributing to the improved performance of hybrid structural elements. This paper reviews key aspects of timber–steel hybridisation, with a particular emphasis on the connection methods between timber and steel, including adhesive bonding and mechanical fastening, as well as the different types of reinforcement configurations. In particular, this review covers two main types of adhesives used in timber–steel hybrid systems, namely, epoxy and polyurethane, and two primary types of mechanical fasteners, namely, bolts and screws. The mechanical performances of all hybridisation methods are reviewed. The importance of surface treatments, such as shot blasting for steel and mechanical abrasion for timber, is also discussed as a key factor in optimising adhesive bonds. Furthermore, various reinforcement configurations, including top, bottom, side, and embedded arrangements, are evaluated for their impact on the structural efficiency and fire performance. To support this evaluation, calculations have been carried out to illustrate how different reinforcement configurations influence the stress distribution in timber–steel hybrid beams. By providing detailed insights into these critical aspects, this paper serves as a valuable decision-making tool, offering guidance for researchers and industry professionals for selecting the appropriate bonding techniques and configurations to meet specific structural objectives and advance sustainable construction practices. Full article
(This article belongs to the Section Building Structures)
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18 pages, 3157 KiB  
Article
Experimental Study on Shear Performance of Longitudinal Joints in Prefabricated Invert Arch for Mountain Mining Method Tunnels
by Shiqian Zhang, Minglei Ma, Chang Li, Peihuan Ye and Zongping Chen
Materials 2025, 18(13), 3025; https://doi.org/10.3390/ma18133025 - 26 Jun 2025
Viewed by 287
Abstract
In order to improve the efficiency of highway tunnel construction and ensure the construction quality, the design concept of a prefabricated inverted arch and partial cast-in-place lining of highway tunnels by a mining method is put forward. During the assembly of prefabricated tunnel [...] Read more.
In order to improve the efficiency of highway tunnel construction and ensure the construction quality, the design concept of a prefabricated inverted arch and partial cast-in-place lining of highway tunnels by a mining method is put forward. During the assembly of prefabricated tunnel invert arches, the longitudinal joints between adjacent invert sections were subjected to shear forces due to the combined effects of the invert’s self-weight and construction equipment loads. This study investigated the shear performance of these longitudinal joints under construction loads, with a particular focus on the influence of bolt-tightening torque. Three longitudinal joint specimens were designed and fabricated, varying the bolt-tightening torque as a key parameter, and subjected to shear tests. The failure modes, load–slip behavior, and shear capacity of the joints were analyzed in relation to the tightening torque of high-strength bolts. The results indicate that when the bolt-tightening torque was set to 50% and 70% of the standard torque, the upper bolts of the joint sheared off, while the threads of the lower bolts were damaged. When the torque reached the standard value, all bolts were sheared off. The ultimate shear capacity of the longitudinal joints increased with higher bolt-tightening torque, with the optimal torque range identified as 70% to 85% of the specified standard. Ultimately, a method of calculation for evaluating the shear-bearing capacity of inverted arch longitudinal joints was proposed, with computational outcomes demonstrating a conservative bias that aligns with structural safety requirements. Full article
(This article belongs to the Section Construction and Building Materials)
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27 pages, 8178 KiB  
Article
Experiment and Finite Element Research on Mechanical Performance of Thin-Walled Steel–Wood Composite Columns Under Eccentric Compression
by Yangfa Zhu, Jianhua Shao, Anxiang Feng, Xianglan Li, Zhanguang Wang, Hongxuan Xu, Jiajun Gao and Boshi Ma
Buildings 2025, 15(12), 2114; https://doi.org/10.3390/buildings15122114 - 18 Jun 2025
Viewed by 369
Abstract
In order to conduct an in-depth and exhaustive investigation into the mechanical properties of steel tubes filled with wood, a thin-walled steel–wood composite column was elaborately designed. The damage progression, failure mode, and mechanical performance of this column under eccentric compression were systematically [...] Read more.
In order to conduct an in-depth and exhaustive investigation into the mechanical properties of steel tubes filled with wood, a thin-walled steel–wood composite column was elaborately designed. The damage progression, failure mode, and mechanical performance of this column under eccentric compression were systematically investigated through both experimental research and finite element simulations. The impacts of different numbers of bolts on the mechanical properties of the composite column were minutely analyzed, and the test results of composite columns were compared with the pure steel pipe column under the same experimental conditions. It was clearly observed that the pure thin-walled steel pipe specimen was highly susceptible to elastic instability under eccentric compression, and the high-strength and high-ductility potential of structural steel was not fully developed. However, after filling with wood and applying bolt restraints, the greater the number of bolts in the specimen of thin-walled steel–wood composite column under the identical eccentricity condition, the higher the ultimate load-bearing capacity. Specifically, the ultimate load-bearing capacity of the columns filled with wood increased by 77.78–114% in comparison with that of the pure steel pipe column. Through a meticulous comparison between the test and finite element analysis results, the error was ascertained to be in the range of 4.9–11.1%. In addition, filling the thin-walled steel tube with wood and restraining it with bolts can effectively enhance the lateral deformation resistance of the specimens, and the reduction rate of lateral deflection exceeded 50%. Moreover, the greater the number of filling bolts, the smaller the strain of components subjected to the eccentric compression occurred, and the better the mechanical properties. Full article
(This article belongs to the Section Building Structures)
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29 pages, 17587 KiB  
Article
Research on the Seismic Performance of Precast RCS Composite Joints Considering the Floor Slab Effect
by Yingchu Zhao, Jie Jia and Ziteng Li
Appl. Sci. 2025, 15(12), 6669; https://doi.org/10.3390/app15126669 - 13 Jun 2025
Viewed by 322
Abstract
Under the impetus of achieving global sustainable development goals, the civil construction industry is accelerating its transition towards high-quality, green, and low-carbon practices. Prefabricated, modular building technology has become a key tool due to its advantages in energy conservation, emission reduction, and shortened [...] Read more.
Under the impetus of achieving global sustainable development goals, the civil construction industry is accelerating its transition towards high-quality, green, and low-carbon practices. Prefabricated, modular building technology has become a key tool due to its advantages in energy conservation, emission reduction, and shortened construction periods. However, existing research on the seismic performance of prefabricated, modular, reinforced concrete column–beam (RCS) composite structures often focuses on the construction form of beam–column joints, paying less attention to the impact of floor slabs on the seismic performance of joints during earthquakes. This may make joints a weak link in structural systems’ seismic performance. To address this issue, this paper designs a prefabricated, modular RCS composite joint considering the effect of floor slabs and uses the finite element software ABAQUS 2023 to perform a quasi-static analysis of the joint. The reliability of the method is verified through comparisons with the experimental data. This study examines various aspects, including the joint design and the material’s constitutive relationship settings, focusing on the influence of parameters, such as the axial compression ratio and floor slab concrete strength, on the joint seismic performance. It concludes that the seismic performance of the prefabricated, modular RCS composite joints considering the effect of floor slabs is significantly improved. Considering the composite effect of the slabs, the yield loads in the positive and negative directions for node FJD-0 increased by 78.9% and 70.0%, respectively, compared to that of the slab-free node RCSJ3. The ultimate bearing capacities improved by 13.2% and 9.98%, respectively, and the energy dissipation capacity increased by 23%. Additionally, the variation in the axial load ratio has multiple effects on the seismic performance of the joints. Increasing the slab thickness significantly enhances the seismic performance of the joints under positive loading. The bolt pre-tensioning force has a crucial impact on improving the bearing capacity and overall stiffness of the joints. The reinforcement ratio of the slabs has a notable effect on the seismic performance of the joints under negative loading, while the concrete strength of the slabs has a relatively minor impact on the seismic performance of the joints. Therefore, the reasonable design of these parameters can optimize the seismic performance of joints, providing a theoretical basis and recommendations for engineering application and optimization. Full article
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27 pages, 9265 KiB  
Article
Seismic Behavior and Resilience of an Endplate Rigid Connection for Circular Concrete-Filled Steel Tube Columns
by Yu Gao, Peilin Zhu, Junping Liu and Feng Lou
Buildings 2025, 15(12), 2035; https://doi.org/10.3390/buildings15122035 - 13 Jun 2025
Viewed by 463
Abstract
A novel endplate bolted rigid joint is proposed in this study for connecting circular concrete-filled steel tube (CCFT) columns to wide-flange (WF) steel beams. The seismic performance and potential failure mechanisms of the proposed joint were investigated through quasi-static cyclic tests and finite [...] Read more.
A novel endplate bolted rigid joint is proposed in this study for connecting circular concrete-filled steel tube (CCFT) columns to wide-flange (WF) steel beams. The seismic performance and potential failure mechanisms of the proposed joint were investigated through quasi-static cyclic tests and finite element (FE) simulations. This study aims to address several engineering challenges commonly observed in existing joint configurations, including an irrational force-resisting mechanism, complicated detailing and installation, on-site construction difficulties, constraints on beam size, and limited repairability. By optimizing the force transfer path, the new joint effectively reduces the number of critical tension welds, thereby enhancing the ductility and reliability. The experimental results indicate that the joint exhibits adequate flexural strength, stiffness, and ductility, with stable moment–rotation hysteresis loops under cyclic loading. Moreover, full restoration of the joint can be achieved by replacing only the steel beam and endplate, facilitating post-earthquake repair. FE analysis reveals that, under the ultimate bending moment at the beam end, multiple through cracks develop in the high-strength grout—which serves as a key load-transferring component—and significant debonding occurs between the grout and the surrounding steel members. However, due to confinement from adjacent components, these internal cracks do not compromise the overall strength and stiffness of the joint. This research provides an efficient and practical connection solution, along with valuable experimental insights, for the application of CCFT columns in moment-resisting frames located in high seismic zones. Full article
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20 pages, 8463 KiB  
Article
Changes in Material Properties and Damage Mechanism of Plate Ballastless Track Under Fire and High Temperature
by Hao Jin, Yike Yang, Xinxin Zhao, Yongjian Pan, Jinhui Chu, Shuming Li, Shenglin Xu and Yulin Feng
Buildings 2025, 15(12), 1987; https://doi.org/10.3390/buildings15121987 - 9 Jun 2025
Viewed by 279
Abstract
The service status of rail, fasteners and track slabs is the key determinant of whether the ballastless track is ready for traffic after a fire. The track slab rail support bolt anchoring performance and the shoulder service performance damaged by fire were tested. [...] Read more.
The service status of rail, fasteners and track slabs is the key determinant of whether the ballastless track is ready for traffic after a fire. The track slab rail support bolt anchoring performance and the shoulder service performance damaged by fire were tested. Experiments of ballastless track slab concrete burned at different high temperatures were carried out to compare macro- and microstructural properties of the concrete under high-temperature burning to study the microstructure of hydration products after high-temperature burning and reveal the damage mechanism of the track slab concrete after a fire. The results show that the fire damage to the rail and fastener is mainly deformations, fractures and strength reduction. The degree of the fire damage of the mortar layer and base slab is much lower than that of the track slab. The main fire damage to the concrete is track and base slab cracks, spalling and gaps. The degree of the fire damage to the mortar layer and base slab is much lower than that of the track slab. The fire damage of the track slab concrete is mainly bursts, and the concrete cracks, spalling and deterioration occur layer by layer from the outside to inside. The shoulder injury is the most serious, the shear resistance is greatly reduced, the rail support is protected by the rail and fastener, the impact of the fire damage is small and the bolt anchoring performance was not decreased. The position of the track slab’s inside damage corresponds to the surface damage position. The steel bar inside the track slab is in good condition, and there is no obvious damage. The bulk expansion of the ballastless track concrete was caused by the expansion of aggregates under fire. When the expansion of aggregates is constrained by the shrinkage of hydration products, greater internal stress is generated, which is the main reason for the cracking or bursting of the ballastless track slab concrete under high temperatures. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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