最新刊期
- 摘要：Existing calculation models for the peak characteristic parameters of the uniaxial compressive stress-strain curve of corroded stirrup-confined concrete generally suffer from insufficient cross-dataset generalization ability, which severely limits their application in practical engineering. To address this issue, based on 112 axial compression test data of circular-section corroded stirrup-confined concrete columns, this study takes the peak stress and peak strain of the stress-strain curve as prediction targets. Six algorithms, namely Support Vector Regression (SVR), Artificial Neural Network (ANN), eXtreme Gradient Boosting (XGBoost), K-Nearest Neighbors (KNN), Categorical Boosting (CatBoost), and Random Forest (RF), are employed to establish prediction models, and the SHAP method is utilized for interpretability analysis. The results indicate that SVR exhibits the best performance in predicting both peak stress and peak strain, achieving coefficient of determination values of 0.940 and 0.938 on the test set, respectively. SHAP analysis reveals that, under the premise of considering the reduction in net cross-sectional area and yield strength of rebars due to corrosion, corrosion of both longitudinal and stirrup rebars still exerts a non-negligible additional influence on the axial compressive mechanical properties of corroded stirrup-confined concrete. Compared with existing empirical models, the proposed model demonstrates superior prediction accuracy for peak characteristic parameters and exhibits favorable generalization ability, providing a more accurate tool for the calibration of stress-strain constitutive models of corroded stirrup-confined concrete.关键词：corroded stirrup;einforced concrete beams;machine learning;uniaxial compressive behavior;peak characteristic parameters;constitutive model2|0|0更新时间：2026-07-28
- 摘要：To study the effects of pre-tensile stress on the post-fire mechanical properties of Q460 high strength structural steel (HSSS), a series of thermal-mechanical tests were carried out. First, the steady-state test method was adopted to obtain the ultimate strength at elevated temperatures, which was taken as the basis for determining the pre-tensile stress. Subsequently, static tensile tests were conducted on specimens subjected to heating and cooling in air under constant pre-tensile stress. The test parameters included five stress ratios and six maximum experienced temperatures. The test results indicated that the effects of pre-tensile stress on the post-fire mechanical properties of Q460 HSSS were significant, depending on both the stress ratio and the maximum experienced temperature. Compared to the stress-free benchmarks, the post-fire elastic modulus, yield strength, ultimate strength and ultimate elongation of pre-stressed specimens ranged from 91% to 115%, 83% to 116%, 88% to 102%, and 83% to 136%, respectively. When the maximum experienced temperature did not exceed 500 ℃, pre-tensile stress was found to enhance the post-fire strength and stiffness. However, after experiencing higher temperatures, it led to a reduction in both strength and stiffness. This degradation increased with greater stress ratios and higher maximum experienced temperature. Therefore, it is critical to fully consider the adverse effects of pre-tensile stress when the maximum experienced temperature reaches or exceeds 700 ℃, especially under high stress ratios. Based on the test results, formulas for the post-fire mechanical properties of Q460 HSSS considering the effects of pre-tensile stress were established.关键词：high strength structural steel;pre-tensile stress;post-fire;mechanical properties0|0|0更新时间：2026-07-25
- 摘要：To investigate the effect of shell powder on the hydration behavior and mechanical properties of a high-volume slag cement system, the effects of different shell powder addition levels (0%, 10%, 20%, and 30%) on the 28-day mechanical properties were evaluated, the hydration products and microstructural evolution were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The results indicate that an appropriate amount of shell powder improves the distribution of hydration products and increases matrix densification through particle filling and heterogeneous nucleation. When the shell powder replacement is 10%, the 28-day compressive and flexural strengths reach 43.5 MPa and 8.9 MPa, respectively, showing a significant increase compared to the reference group without shell powder; SEM observations reveal reduced porosity and improved interfacial bonding in this group. XRD and FTIR analyses show enhanced CaCO₃-related peaks and changes in hydration-related absorption bands, suggesting that shell powder mainly affects the hydration structure through physical filling and nucleation. Excessive shell powder leads to increased unreacted particles and loose interfaces, causing strength reduction. The study demonstrates that a 10% shell powder replacement is optimal.关键词：shell powder;high-volume slag cement;hydration mechanism;microstructure6|2|0更新时间：2026-07-20
- 摘要：Conventional sand reinforcement materials are associated with high carbon emissions and environmental pollution, necessitating sustainable alternatives. This study employs agar gum as a biopolymer binder to treat poorly graded river sand (SP) from Xinyang, Henan Province. The effects of agar gum content (0.5%–2.0%, expressed as the mass percentage of agar gum powder to dry sand), curing time (3 d–28 d), and curing temperature (20 ℃–60 ℃) on the unconfined compressive strength (UCS) of treated sand were investigated, with microscopic reinforcement mechanisms examined via scanning electron microscopy (SEM). The results show that UCS increases significantly with increasing agar gum content; the 28-d UCS of specimens with 2% agar gum reaches 638.5 kPa, which is 3.35 times that of specimens with 0.5% agar gum. Seven days of curing achieves over 90% of the 28-d strength, and UCS exhibits a strong negative correlation with residual moisture content. As curing temperature rises from 20 ℃ to 60 ℃, UCS increases by an average of 11.78% per 10 ℃ increment. Based on cementation states, six typical failure modes are identified: specimens with high agar gum content (≥1.5%) and sufficient curing (≥7 d) exhibit brittle shear failure, whereas those with low content (≤1%) and short curing (≤3 d) show progressive failure. Additionally, microscopic reinforcement mechanisms including particle coating, pore filling, and interparticle bridging are discussed.关键词：agar gum-treated sand;compressive strength;scanning electron microscope;microscopic mechanism9|5|0更新时间：2026-07-17
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Fire resistance of steel-concrete continuous composite beams under combined bending and torsion AI导读
摘要：Traditional fire resistance research has predominantly focused on pure bending or pure shear conditions, while the structural fire behavior under coupled bending and torsion remains insufficiently understood. In this paper, a three-dimensional nonlinear thermo-mechanical coupled model of steel-concrete composite beams, validated by experimental data, is developed using the finite element software ABAQUS. The evolution of key mechanical characteristics with temperature—such as mid‑span deflection and twist rate, sectional bending moment and torque, and stress distribution patterns—is investigated. The results show that under the combined action of elevated temperature and flexural-torsional coupling, the composite beam undergoes significant torsional deformation accompanied by flexural deflection at mid‑span, and typical failure features including local buckling of the steel beam and concrete slab cracking appear at the intermediate support section. Meanwhile, complex internal force redistribution of both bending moment and torque occurs along the beam length. As temperature increases, the effect of sectional warping stress gradually intensifies, exerting a notable influence on the stress distribution pattern and the ultimate failure mode of the structure. At elevated temperatures, due to the different stiffness degradation rates of concrete and steel beam, shear stress continuously redistributes at the interface between the two materials and within each material itself, ultimately forming a new equilibrium state. Therefore, in the fire resistance design of composite beams under combined bending and torsion, the adverse effects of warping stress and shear stress redistribution should be fully taken into account.关键词：continuous composite beams;fire resistance;combined bending-torsion;warping stresses;internal force redistribution8|5|0更新时间：2026-07-14 -
Experimental study on dynamic performance of frame structure building under rockfall impact load AI导读
摘要：In order to study the dynamic response, failure mechanism and impact resistance of frame structure building under the impact of rockfall, nine sets of rockfall impact tests on the frame structure building model under different working conditions were carried out based on the self-designed sliding track test device. The experiment considered four key factors: rockfall mass, release height, number of impacted columns, and toe distance. Following the orthogonal test design method, the failure modes, peak impact force, and peak acceleration were used as evaluation indicators to systematically analyze the multi-factor coupling effects and their sensitivity. The results indicate that the failure modes of the frame structure building exhibit multi-scale evolution characteristics from ‘material to component to global structure’, which can be classified into five levels: minor damage, slight damage, moderate damage, severe damage, and complete damage. Among the factors considered, the number of impacted columns is the most sensitive factor affecting the overall structural stability. Dynamic response analysis reveals the energy dissipation mechanism where impact energy transitions from a local impulse to global inertial forces. The peak acceleration and impact force of the impact column are 9.91-25.42 m/s2 and 178.95-565.24 N, respectively. The empirical formula derived from the simplified model does not consider the structural plastic energy dissipation. By introducing the plastic energy dissipation reduction coefficient KP, the error range between the measured impact force and the empirical formula is -9.98% to 13.50%. By introducing the plastic energy dissipation reduction coefficient to modify the empirical formula for impact force derived from the theoretical model, the error range between the measured impact force and the revised formula is -9.98% to 13.50%.关键词：frame structure building;rockfall impact;dynamic performance;peak impact force;peak acceleration11|9|0更新时间：2026-07-13 - 摘要：A power series analytical solution based on complex variable functions is proposed for the calculation of the stress field and thickness design of the grouting prestressed lining of circular hydraulic tunnel. This method establishes the contact relationship and stress boundary conditions between the surrounding rock and the lining, and solves the potential functions of both to achieve precise calculation of the stress at any position. The calculation model can comprehensively consider the influence of the in-situ stress field, the timing of lining support, internal and external water pressure, grouting pressure, and the shape and mechanical parameters of the surrounding rock and lining on the bearing system. To achieve the optimal design of the lining thickness, a mapping relationship between the lining thickness and the extreme value of the circumferential normal stress at the inner boundary is further established, which can solve the optimal lining thickness that meets the structural safety requirements under operating and maintenance conditions. The formula derivation and example studies show that: Under the condition without grouting, timely support can produce a pre-compression effect on the lining, and its effect depends on geological conditions, support timing and support system parameters. This factor cannot be ignored in the analysis of maintenance conditions; The core mechanism of grouting pre-compression is to increase the load-sharing ratio of the surrounding rock. The better the quality of the surrounding rock, the greater the potential of grouting pre-compression; When tensile stress is defined as positive and compressive stress as negative, the maximum circumferential normal stress of the lining is located in the direction of the minimum in-situ stress. Under operating conditions, it does not monotonically increase with the lining thickness. The minimum value is located in the direction of the maximum in-situ stress and monotonically increases with the lining thickness under maintenance conditions. Combining the two can determine the optimal thickness.关键词：circular hydraulic tunnel;prestressed lining;grouting pressure;internal and external water pressure;theory of complex functions16|12|0更新时间：2026-07-10
- 摘要：High Altitude Hermetically Pressurized Buildings (HAHPBs) are a new form of construction composed of multiple modular units. By pressurizing and supplementing oxygen within each compartment HAHPBs can effectively address issues such as altitude sickness. Unlike the basic load-bearing components of ordinary buildings, the fundamental structural unit of an HAHPB is a framed steel compartment. Therefore, existing fire safety design codes for ordinary buildings cannot be directly applied to HAHPBs. Based on the building functions and structural characteristics of HAHPBs, this study compares and analyzes fire safety design codes to determine the required fire resistance rating of HAHPBs. Then, a finite element model of the HAHPB was established, and a thermo-mechanical coupling method was adopted to investigate the structural temperature field evolution, stress distribution, and deformation response under standard fire conditions with different vertical loads and internal-external pressure difference conditions, thereby determining the fire resistance limits under different conditions. Additionally, the fire resistance performance of the HAHPB structure under realistic fire scenarios with non-uniform heating was investigated through a CFD-FEM coupling method based on coordinate mapping. Results show that when the internal-external pressure difference of the pressurized cabin exceeds 0.04 MPa, the fire resistance limit fails to meet the required rating, and fire protection measures become necessary. Under realistic fire scenarios, the temperature rise of the structure is limited because of the short fire duration and the pressurized cabin is able to satisfy the chosen fire resistance requirement without additional fire protection.关键词：High altitude hermetically pressurized buildings;Fire resistance;CFD-FEM coupling;Thermo-mechanical behavior13|8|0更新时间：2026-07-06
- 摘要：To address the insufficient cementation efficiency and limited reaction controllability of sand-clay mixed earthen heritage soils during one-step mixing for rammed repair, this study focuses on typical sandy rammed earth from the Jiadan earthen site of Diaoyucheng, Chongqing. A microbial-induced urea pre-hydrolysis method was proposed, and specimens were prepared using a one-step mixing procedure under laboratory-simulated rammed repair conditions. The mechanical properties, salt resistance, color compatibility, and microstructural evolution of the sandy earthen heritage soil with different calcium hydroxide contents were systematically investigated. The results show that the 28-day unconfined compressive strength of the synergistically treated specimens reached a maximum of 9.20 MPa, approximately six times that of the untreated group, which was about 1.53 MPa. After five salt-resistance cycles, the M4 group retained the highest residual strength of 1.48 MPa, indicating relatively good structural stability. The total color difference ΔE* of all treated specimens was less than 3.0, indicating limited influence on the appearance of the heritage soil. Scanning electron microscopy observations further revealed the presence of calcium carbonate precipitates and bridging structures between soil particles. These results demonstrate that, within the scope of this study, the synergistic action of microbial-induced urea pre-hydrolysis and calcium hydroxide can improve the one-step mixing performance and structural characteristics of sandy earthen heritage soil. This study provides a new technical perspective and experimental basis for the rammed repair of earthen sites.关键词：sand site soil;microbial mineralization;tamping repair;mechanical properties;microstructure17|13|0更新时间：2026-07-06
- 摘要：To investigate the heavy metal leaching characteristics of red mud co-solidified by cement and phosphogypsum and to establish a quantitative correlation between mechanical properties and leaching behavior, solidified specimens were prepared using Bayer-process red mud as the primary raw material, with ordinary Portland cement and phosphogypsum as composite solidifiers. The leaching behavior of four characteristic heavy metals (Se, V, As, and Sb) was evaluated using the horizontal oscillation method and the sulfuric-nitric acid method, respectively. The results show that: The cement-phosphogypsum composite solidifier exerted a pronounced synergistic inhibitory effect on heavy metal leaching from red mud; under the optimal mix proportion of 20% cement and 12% phosphogypsum with 90-day curing, the leaching concentrations of all target heavy metals met the Class Ⅲ limits of GB 3838-2002 and GB/T 14848-2017 under both leaching methods. Pearson correlation analysis revealed a significant negative correlation between the unconfined compressive strength of the red mud–cement–phosphogypsum solidified matrix and the heavy metal leaching concentrations, based on which an exponential function model was established, providing a convenient approach for indirectly estimating heavy metal leaching levels through strength measurements. The heavy metal immobilization mechanisms involve four aspects: alkaline chemical precipitation, adsorption and physical encapsulation by calcium silicate hydrate (C-S-H) gel, structural fixation and ionic substitution within ettringite, and retardation by microstructural densification. Under the optimal mix proportion, the leaching concentrations of phosphate (0.191 mg/L) and fluoride (0.895 mg/L) also satisfied the Class Ⅲ surface water limits.关键词：red mud;co-solidify;cement-phosphogypsum;heavy metal leaching;solidification/stabilization23|10|0更新时间：2026-07-01
- 摘要：High-strength weathering steel (HSWS) is widely utilized in engineering structures such as bridges and buildings due to its high strength and superior corrosion resistance. Coastal and mountainous regions in China are characterized by high humidity and salt spray, posing severe corrosion hazards to steel structures in service. However, research regarding the mechanical property degradation and constitutive models of HSWS under long-term corrosive conditions remains insufficient. In this study, high-strength weathering steel Q460NH and low-alloy high-strength steel Q460 of the same strength grade were selected as research objects. Accelerated neutral salt spray (NSS) corrosion tests were conducted on 36 tensile specimens for a duration of up to 180 days. Corrosion test results indicate that, under identical corrosion durations, Q460 exhibits a consistently higher corrosion mass loss rate than Q460NH steel, while displaying more severe damage morphology. The uniaxial tensile test results demonstrate that under short-term corrosion (<60 days), the fracture surfaces are predominantly flat or arc-shaped. As the corrosion period extends to 60 days and beyond, the fracture surface morphology changes to oblique or jagged. The mechanical properties of both steels exhibit a linear downward trend with the increase of the corrosion mass loss rate η, among which the elongation at break is the most sensitive to corrosion. Finally, based on a modified two-stage nonlinear Ramberg-Osgood constitutive model, a linear regression relationship between the second-stage hardening index m and η was established.关键词：high-strength weathering steel;neutral salt spray;mechanical property degradation;constitutive model19|15|0更新时间：2026-06-15
- 摘要：Structural insulation composite panels have emerged as a new type of cladding material with promising applications in the construction industry. To systematically investigate the lateral resistance of cold-formed thin-walled steel-framed walls clad with these panels, tests were first conducted on self-tapping screw connections used to join the structural insulation composite panels to the steel frame. The study primarily examined the effect of screw edge distance on the performance of the screw connections. The results indicate that: All self-tapping screw connection specimens failed due to edge tearing of the panels. When the screw edge distance was increased from 15 mm to 25 mm, the average yield load and peak load increased by approximately 49.65% and 48.31%, respectively. The increase in screw edge distance significantly improved the performance of the screw connections. Further monotonic and low-cycle loading tests were conducted on two full-scale structural insulation composite panel cladding walls. This yielded the failure modes of the composite walls, load-displacement curves, and lateral performance indicators such as shear strength and lateral stiffness. The results indicate that both wall specimens experienced buckling at the base of the compression-side columns, failure of the diagonal bracing, severe damage at the corners of the panels, and failure of the self-tapping screw connections around the panel periphery. Based on these results, recommended values of 5.74 kN/m and 1 474.24 kN/m·rad are proposed for the shear capacity and lateral stiffness, respectively, of single-sided 75 mm structural insulation composite panel-clad walls. Finally, a calculation method for the elastic lateral stiffness of cold-formed thin-walled steel walls clad with structural insulation composite panels was proposed using the superposition principle. This method was compared with experimental results to verify its validity.关键词：cold-formed thin-walled steel;structural insulation composite panels;lateral resistance;self-tapping screw connections;elastic lateral stiffness26|24|0更新时间：2026-06-11
- 摘要：To address the problems of late-stage strength regression and high drying shrinkage associated with traditional cement accelerators, this study utilized coal gangue as a raw material to prepare a chlorine-free and low-alkali mineral setting accelerator via calcination and acid leaching. The preparation process parameters, acceleration mechanism, and the influence on the properties of cement-based materials were investigated. The results indicate that the prepared mineral setting accelerator primarily consists of aluminum sulfate and amorphous SiO₂ particles. When replacing cement at a mass ratio of 10%, the initial and final setting times of the cement paste were shortened by 42.1% and 37.4%, respectively, and the 28-day compressive strength increased by 16.7% compared to the control group. Moreover, no regression in later-age strength was observed within the 30% incorporation range. When the mineral setting accelerator dosage was 10%-30%, the drying shrinkage rate of the cement mortar ranged from 0.075% to 0.080%, which is close to the 0.074% of the blank group, indicating ideal volume stability. XRD and SEM analyses reveal a synergistic effect between the silicon and aluminum components in the mineral setting accelerator: aluminum ions induce the rapid formation of ettringite, while the amorphous silica provides nucleation sites and a high pozzolanic effect, thereby achieving cement acceleration, strengthening, and drying shrinkage resistance.关键词：coal gangue;accelerator;process parameters;acceleration mechanism;drying shrinkage24|19|0更新时间：2026-06-06
- 摘要：To investigate the axial compressive behavior of square geopolymer concrete-filled steel tubular (GCFST) stub columns at elevated temperatures, the target temperature was selected as the primary experimental parameter, while the outer dimensions, wall thickness, and steel strength of the steel tube were also varied. A total of 10 short-column specimens filled with C40 slag–fly ash geopolymer concrete were designed and fabricated. Elevated-temperature heating tests and axial compression tests were subsequently conducted to determine the temperature distribution and mechanical performance of the specimens at 28 °C, 200 °C, 400 °C, 600 °C, and 800 °C. The failure modes, ultimate load-bearing capacities, and load–displacement responses under different testing conditions were systematically obtained. The experimental results indicate that for specimens with a larger confinement factor, the ultimate bearing capacity at 200℃and 400 ℃ increased by 6% and 9%, respectively, compared to that at ambient temperature. In contrast, specimens with a smaller confinement factor showed a slight decrease. This suggests that a stronger confining effect from the steel tube amplifies the thermal densification of the geopolymer concrete at 200-400 ℃. When the temperature reaches 600 ℃ and above, the bearing capacity of both types of specimens drops significantly. Subsequently, a sequentially coupled thermal-stress finite element model was established using ABAQUS. Validated against the test data, the model accurately simulates the thermo-mechanical response of such components. Parametric analysis results show that increasing the confinement factor helps to enhance it.关键词：square concrete-filled steel tubular stub column;geopolymer;axial compressive behavior;constant-temperature loading;finite element analysis;confinement factor20|11|0更新时间：2026-06-04
- 摘要：To investigate the thermal insulation performance of intumescent fire-retardant coatings and establish the simplified calculation formula among thermal resistance, shape factor and heating time, steel plates with thicknesses of 8 mm, 12 mm, 16 mm, 20 mm and 24 mm were sprayed with 2.0 mm, 3.0 mm and 4.0 mm of intumescent fire-retardant coatings. Heating tests were performed on the specimens under the ISO-834 standard heating condition. The temperature-time relationship of the specimens was recorded. After the tests, a qualitative comparative analysis of the expansion performance of the specimens under different working conditions was carried out, and the thermal resistance under different working conditions was calculated based on the temperature rise curves. The results show that the temperature rise curves of the coated specimens present three stages: rapid temperature rise, constant temperature and slow temperature rise. Two thermal resistance peaks appear during the heating process of the intumescent fire-retardant coatings, with the first peak being approximately one-third of the second, and the latter eventually decreasing to a value close to that of the first. Intumescent fire-retardant coatings can significantly reduce the heating rate, and the fire resistance time of coated specimens can be extended by 3 to 4 times compared with uncoated ones. Two calculation formulas are established based on equivalent thermal resistance and average thermal resistance. The comparison indicates that the average thermal resistance is about 23.6% higher than the equivalent thermal resistance, and the formula using equivalent thermal resistance is conservative when calculating the temperature rise of components.关键词：intumescent fire-retardant coating;thermal insulation performance;equivalent thermal resistance;standard temperature rise;calculation method33|22|0更新时间：2026-06-01
- 摘要：To evaluate the residual seismic capacity of reinforced concrete (RC) frame structures exposed to acidic atmospheric environments, this study first investigated the degradation patterns of seismic performance in RC beams and columns subjected to acid rain corrosion through accelerated corrosion tests and quasi-static tests. A numerical analysis model for time-dependent corroded RC beams and columns was established using the OpenSees platform, and its accuracy was validated against experimental results. Based on this numerical model, a time-dependent vulnerability model for corroded RC beam-column components was developed through pushover analysis. Using peak ground acceleration (PGA) as the ground motion intensity measure (IM), a numerical model of a typical RC frame structure was constructed, and incremental dynamic analysis (IDA) was performed. By integrating the component vulnerability model, the damage proportion of components in corroded RC frame structures under different service lives, seismic fortification intensities, and structural stories was obtained. Subsequently, a structural seismic capacity assessment method based on component damage proportion was employed to evaluate the residual seismic capacity of corroded RC frame structures under various damage states. The results indicate that the seismic capacity of RC frame beams and columns deteriorates to varying degrees with the increase of acid rain spraying cycles (NARSCs). Specifically, under severe corrosion (NARSCs = 480), the peak load and plastic rotation of beam components can decrease by 17.67% and 22.50%, respectively. When the service life is less than 30 years, the degradation rate of seismic capacity in corroded RC frame structures is relatively slow. As the service life extends, the degradation rate accelerates significantly; particularly after 58 years of service, the residual seismic capacity generally drops below the 80% safety threshold. However, increasing the fortification intensity and reducing the number of structural stories can effectively enhance its seismic capacity.关键词：acidic atmospheric environments;acid rain corrosion;reinforced concrete frame;seismic capacity32|41|0更新时间：2026-06-01
- 摘要：To improve the axial compressive performance of cold-formed thin-walled steel composite walls, a cold-formed thin-walled corrugated steel plate with foam concrete composite wall (CTCFW) was proposed. Four full-scale specimens were tested under axial compression to investigate the effects of connection details and corrugation orientations on the axial behavior of the composite walls. The failure modes, load-displacement curves, and characteristic parameters were obtained, and the influences of different configurations on the load-bearing capacity, stiffness, and ductility were analyzed. The experimental results indicate that the specimens with embedded corrugated steel plates mainly failed by local buckling, whereas those with perimeter-plate-connected corrugated steel plates mainly exhibited global out-of-plane instability. Compared with the specimens with embedded corrugated steel plates, the axial compressive capacities of CTCFW-3 and CTCFW-4 increased by 92.09% and 78.58%, respectively, while the initial stiffness increased by 221.43% and 121.43%, respectively. Compared with the specimens with horizontally arranged corrugated steel plates, the axial compressive capacities of CTCFW-1 andCTCFW-3 with vertically arranged corrugated steel plates increased by 21.69% and 30.90%, respectively, indicating that vertically oriented corrugated steel plates participated more effectively in resisting axial compression. Based on the combined action of the cold-formed steel frame, corrugated steel plate, and foam concrete, a formula for predicting the axial compressive capacity of CTCFW was proposed using the superposition principle. The difference between the calculated and test results was within ±10%.关键词：cold-formed thin-walled steel;composite wall;corrugated steel plate;foam concrete;axial compressive performance29|20|0更新时间：2026-05-29
- 摘要：To address the engineering demand for understanding the load-carrying capacity and failure mechanisms of purlin–bracket–inclined beam connections in fixed photovoltaic (PV) support systems, a series of systematic monotonic static loading tests was conducted to investigate the influence of key structural parameters on the mechanical behavior of the joints. The test variables included bolt hole configuration (circular hole and slotted hole), bolt type (M10 ordinary bolts and M12 high-strength bolts), and the presence or absence of a bracing tube in the inclined beam. During testing, load–displacement responses, bolt pretension evolution, and strain distributions around bolt holes were synchronously monitored to elucidate the load transfer mechanism and failure evolution characteristics of the connections. The results indicate that two primary failure modes were observed: bearing failure of the purlin bolt hole wall and bolt pull-out failure at the inclined beam connection. Both modes are closely associated with the local bearing capacity of the hole wall and the redistribution of internal forces within the joint. The hole configuration and bolt type exert significant effects on the initial stiffness, ultimate load-carrying capacity, and deformation capacity of the connections. High-strength bolts enhance the pre-slip stiffness and ultimate resistance, and improve the overall mechanical stability of the joint. Slotted-hole connections exhibit greater sensitivity to the presence of bracing tubes; the installation of bracing tubes strengthens local confinement, improves deformation compatibility, and mitigates the rate of pretension loss. Based on the combined analysis of load–displacement curves and strain measurements, the mechanical response of the joints can be categorized into three stages: elastic stage, slip development stage, and failure stage. The plastic evolution in the local bearing zone governs both the ultimate load-carrying capacity and the final failure path.关键词：photovoltaic fixed support;high-strength bolted connection;static loading test;bearing capacity;failure mode;structural parameters29|30|0更新时间：2026-05-27
- 摘要：The effects of process parameters on the carbonation performance and microstructure of steel slag-based CO2 sequestered fiber sheet (CSFS) were investigated. An orthogonal experimental design was employed to investigate the effects of forming pressure, carbonation curing time, CO2 pressure, and curing temperature on the CO2 uptake, saturated flexural strength, and water absorption of CSFS. The optimal process parameters for mechanical performance were determined as follows: forming pressure of 30 MPa, CO2 pressure of 0.3 MPa, curing temperature of 20 °C, and carbonation curing time of 24 h. Range analysis indicated that curing temperature had the most significant effect on all measured properties, followed by carbonation curing time, while CO2 pressure and forming pressure exhibited comparatively minor effects. Microscopic analysis shows that the carbonation reaction of steel slag generates calcite-dominated calcium carbonate crystals, which fill pores and deposit on the surface and interior of pulp fibers, thereby enhancing the interfacial bonding between fibers and the matrix. Pore structure tests indicate that the optimized process parameters can effectively reduce porosity and refine the pore size distribution. The production cost of CSFS is lower than that of traditional fiber cement flat sheets, while offering comprehensive benefits including solid waste resource utilization, CO2 sequestration, and low-carbon building material applications.关键词：steel slag;CO2 sequestered fiber sheet;process parameters;carbonation performance;microstructure24|18|0更新时间：2026-05-27
- 摘要：Driven by the tunnel piston effect, unorganized ventilation airflow (UVA) through platform screen doors exerts a considerable influence on subway station cooling and heating loads. Thus, accurate UVA prediction is indispensable to energy-efficient HVAC system design. This study presents an intelligent prediction framework fusing parametric Computational Fluid Dynamics (CFD) and deep learning. Based on incompressible fluid governing equations and the k-ε turbulence model, 2D transient numerical simulations were conducted via ANSYS Fluent, with the results serving as the model’s training dataset. A novel dimensionless parameter, the relative distance ratio (RDR), was introduced to depict the coupling effects of train length and piston shaft distance. Simulation scenarios covered blockage ratios, RDR values, and four piston shaft operational states, and were validated by field measurements (RMSE=0.062 m/s, MAPE=34.8%, R²=0.939). On this basis, a conditional encoder-decoder model was constructed to predict the full UVA wind speed time series from static design parameters. The model exhibited excellent generalization performance, delivering high-accuracy predictions for four untrained working conditions (R² > 0.94, MAPE < 22%) and effectively capturing transient wind-speed peaks during train operation. This proposed framework acts as a powerful UVA prediction tool, providing technical support for the energy-saving design and intelligent control of subway ventilation systems.关键词：subway station;unorganized ventilation airflow (UVA);piston effect;CFD simulation;deep learning;encoder-decoder model29|16|0更新时间：2026-05-26
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