To investigate the influence of milled-cut steel fiber （MSF） on the flexural behavior and toughness of plain concrete, four-point bending tests were conducted on C50 concrete matrixes with different volume fractions of steel fiber （0%,0.6%,1%,1.4%）. The flexural behavior,cracking mode,and failure mechanisms of milled-cut steel fiber reinforced concrete （MSFRC） was analyzed. The evaluation methods for flexural toughness of fiber-reinforced concrete in domestic and international standards were studied to assess their applicability. The results indicate that the maximum equivalent flexural strength of the MSFRC is 1.8 times than that of plain concrete. Upon surpassing the critical fiber volume fraction of 1%, the material displays multiple cracking characteristics,with strain hardening behavior observed at an enhanced fraction of 1.4%. The method specified in JG/T 472—2015 steel fiber reinforced concrete is applicable for characterizing the flexural toughness of milled-cut steel fiber reinforced concrete. The increase in fiber volume fraction enhances the flexural deformation capacity of concrete and improves the post-cracking flexural toughness within the small deflection range.

In order to investigate the fire resistance of post-earthquake steel beams insulated with lightweight and high ductile fire-resistive engineered cementitious composites （FR-ECC）, reversed cyclic loading tests and fire tests were conducted on the steel beams. The finite element method was used to analyze the temperature field distribution and displacement change response of the steel beams subjected to fire tests under constant load conditions. The validity of the finite element models was verified by comparing with the test results, and extended parametric analyses of steel beams protected with FR-ECC materials were carried out. The research results show that the established ABAQUS finite element analysis model can effectively simulate the heat transfer process and displacement response of steel beams protected with fireproof coatings subjected to fire tests under constant load conditions. Through extended parameter analysis, it can be concluded that the higher the load ratio, the lower the fire-resistance limit temperature and the shorter the fire-resistance limit time; As the thermal conductivity of FR-ECC decreases, the heating process of the steel beam slows down, and the ultimate fire-resistance time becomes longer. Changes in thermal conductivity have the greatest impact on the steel beam in the undamaged state of the fireproofing.

To support China's dual carbon goals, this study explores the use of recycled glass aggregates as a sustainable alternative in concrete. Traditional mix design methods are often inadequate for capturing the nonlinear effects introduced by glass aggregates and involve high trial costs. Based on 331 experimental mix designs, five machine learning models （ANN, SVR, DT, RF, XGBoost） were developed to predict the 28-day compressive strength of concrete, aiming to enhance prediction efficiency and design efficiency. Results show that XGBoost and RF achieved the highest accuracy on training and testing sets （R²=99.3% and 88.5%）, while ANN and RF demonstrated the best generalization on three newly developed concrete materials （R²=92.2% and 93.4%）. SHAP analysis was further adopted to interpret feature contributions, confirming the models' interpretability and robustness. This study highlights the practical potential of machine learning in supporting the efficient design of eco-friendly concrete materials.

A crack detection method for cylindrical members based on binocular stereo vision and spatial projection restoration is proposed. By this method, the image point of the crack edge on the image plane of the left camera is selected as the projection point, and the side surface of the cylindrical member is selected as the projection cylinder surface. Based on the obtained world coordinate of the projection point and the equation of the projection cylinder surface, the world coordinate of the actual crack edge point can be obtained by calculating the intersection of the line connecting the coordinate origin and the projection point and the projection cylindrical surface. In this way, the spatial shape of the crack can be restored, and further, based on this, the characteristic value of the crack can be detected. The method proposed can realize oblique photography of cracks, truly restore the original spatial shape and size of cracks, and improve the recognition accuracy of cracks. At the same time, this method only needs to perform binocular camera calibration once and perform stereo matching on a limited number of feature marker points based on their geometric features to obtain all the required calculation parameters. It has high computational efficiency, good matching effect, and the detection accuracy is not sensitive to illumination changes. This method solves the defect that the traditional 3D reconstruction technology based on binocular stereo vision is difficult to directly extract the crack boundary on the 3D point cloud of the structure surface, and is suitable for crack identification and parameter extraction of cracked surface of cylindrical members.

This paper is based on the engineering background of super-tall towers in earthquake prone areas, comprehensively arranges the position, various deformation amplification devices, viscous damping parameters and other key contents to carry out the selection and analysis of viscous damping systems under wind and earthquake double excitation. Taking a 396 m super-tall tower as an example, the design of viscous damping systems under wind and earthquake double excitation is studied. Research has shown that viscous damping vibration reduction systems have a certain control effect on different modal responses, which can effectively improve the comfort, stiffness, and strength performance of structures under wind and earthquake conditions. Reasonable placement of dampers, deformation amplification devices, and parameter selection can achieve more efficient vibration reduction efficiency.

Textile Reinforced Ultra High Ductile Cementitious Composites （TR-UHDCC） are advanced materials characterized by high strength, high ductility, crack resistance, and durability. Compared to traditional masonry reinforcement materials, TR-UHDCC exhibits superior performance. Based on existing experimental research results, this paper introduces the Hashin damage criterion to account for the damage behavior of the fiber grid, establishing a three-dimensional finite element model for TR-UHDCC. This model accurately simulates the stress-strain curve of TR-UHDCC and its corresponding characteristic points （cracking stress and strain, peak stress and strain, ultimate stress and strain）. Using this model, the effects of fiber grid distribution rates and the tensile strength of UHDCC on the characteristic points of TR-UHDCC were studied. Finally, a theoretical calculation model for the tensile load-bearing capacity of TR-UHDCC was developed based on the sectional force equilibrium relationship. The calculated values from this model align well with experimental and parametric analysis results, with an average error of only 3.63%.

Ultra-High-Performance Concrete （UHPC）, a cementitious composite material with high strength, ductility and durability, is now widely used for wet joints of overlapping rebar connections in prefabricated structure. Effective bonding and anchoring of the steel bars in early-age UHPC is an important guarantee for rapid assembly construction. In this paper, pull-out tests were conducted on rebars in UHPC specimens at 3-day age, considering the effects of development length on the bond-anchorage behavior. The results show that： （1） two failure patterns appeared in the tests, namely, the rebar pullout failure without yielding and the rebar pullout failure with yielding; （2） for the anchorage design of rebar in 3-day age post-cast UHPC joints, a cover thickness greater than 2.5 times the diameter of the rebar is recommended; （3） for the HRB400 rebar in UHPC at 3-day age, the critical yield development length is 6 times the diameter of the rebar, which effectively reduces the development length compared with that of normal strength concrete; （4） the calculation formula for the development length in the Code for Design of Concrete Structures （GB 50010—2010） is reliable and relatively safe, but it is recommended to relax code limit conditions of tensile strength for UHPC.

Cement-based materials containing fiber are widely used in engineering structures. In order to study the bonding properties between steel fibers and cement matrix, this research investigated fiber pullout performance of steel fiber in cement mortar and high-strength grout. The bonding properties were evaluated by the indexes of maximum pullout load,energy dissipation and average bond strength. The test results show that the shape of the pullout load displacement curve in the high-strength grout is similar to that of the ordinary cement mortar. The mechanical anchoring effect exists between the deformed fibers and the matrix, and the maximum pullout load and energy dissipation are significantly increased compared with that of the straight fibers. Compared with the straight fiber, the average bond strength and energy disspation of the hooked fiber of ordinary cement mortar matrix are increased by 180.8% and 126.8%, respectively. In high-strength grout, the increase is 363.3% and 474.7% respectively. When the steel fiber has an inclination angle, the process of the pullout is usually accompanied by the spalling of the ordinary cement mortar matrix and the plastic deformation of the steel fiber. The increase of embedding depth will increase the pullout load and energy dissipation, but it may cause the fiber breakage for the waved fiber.

Chinese mortise and tenon joints present significant historical and cultural value. Recently, BIM-based structural parametric design has been increasingly promoted and applied. Through the digital model, the entire life cycle of traditional structure will be recorded for their conservation. This paper summarizes the shape characteristics of typical mortise and tenon joints. Based on dimension feature, family templates of mortise and tenon joints were developed on the Revit platform, which improves modeling efficiency and accuracy.

With the recent development of the Hengsha Xinzhou Park, the demand for wharf construction has risen steadily, while the complex engineering-geological conditions pose challenges to pile design and construction. This paper characterizes the site's geology by analyzing the stratigraphic profile and mechanical parameters of the seabed soils. Based on the geotechnical investigation data, the engineering-geological conditions for pile foundations were evaluated. The results indicate that soft and liquefiable soil layers may adversely affect the stability of piles, necessitating appropriate engineering countermeasures. Using a simplified scour-resistance test apparatus, scour tests were carried out on the seabed soils. The findings reveal that sandy silt and clayey silt have relatively poor resistance to scour; therefore, scour countermeasures are required. The studies will provide essential technical support for the development of the Hengsha Xinzhou Park and the regional economy.

The current structural fire resistance research has relatively few studies for localized fire scenarios, and the test results are relatively scarce. Based on this, this paper attempts to build a realistic fire test platform, and adopts two fire source forms, jet fire and pool fire, to heat the H-shaped columns and record its thermal results. In terms of numerical simulation, unlike the iterative coupling method that applies the concept of adiabatic surface temperature, this paper realizes the two-way direct coupling of fluid-solid heat transfer by unifying the fire analysis with the thermal analysis using the CFD method. The distribution rules of the spatial velocity field and temperature field were explored in the fire analysis model, and the thermal characteristics of steel columns in different fire source environments were explored in the thermal model. The correctness of the direct coupling method was verified by comparing experimental data with simulation results. In addition, the theoretical and empirical formulas are applied to explore the distribution law of convective heat transfer coefficient of the steel column surface.

In the current research on seismic reduction design of school buildings using viscous fluid dampers, attention is often paid to the main structures such as teaching buildings and dormitory buildings, while neglecting the corridor space that plays an important role in the overall spatial organization of the campus. In order to study the application of viscous fluid damper in school corridor space, this paper takes the corridor space between teaching buildings in a primary school in Shanghai as an example for seismic reduction design. Firstly, conduct frequent earthquake analysis on the structure, and the results meet the requirements of the specifications. Secondly, conduct elastic time history analysis under fortification earthquakes and compare the seismic reduction effects when including the foundation layer or not, the arrangement of dampers in the inner or outer frame, the number of dampers changed, the floor of dampers changed, and determining the seismic reduction plan. Finally, conduct elastic-plastic time history analysis under rare earthquakes to calculate structural damage, energy dissipation, and drift ratio. The research results indicate that viscous fluid dampers can provide certain energy dissipation under earthquake action and are an effective seismic reduction method for school corridor spaces.

This paper addresses the limitations of materials used in viscoelastic dampers for high-rise buildings and develops a new type of viscoelastic damper with styrene-hydrocarbon copolymer thermoplastic elastomer as the core energy-dissipating material. Cyclic loading tests were conducted on two specimens of the novel damper. The test results demonstrate that the damper utilizing this material offers advantages such as large deformation capacity, low temperature sensitivity, and strong energy dissipation capability, providing full and stable hysteretic curves under various temperatures. Based on these findings, a structural design methodology for the new damper is proposed. A practical super high-rise building is adopted as a case study to complete the damper layout, and time-history analysis is performed to verify the effectiveness of the proposed method. This study provides a reference for the engineering application of the new viscoelastic damper in seismic and wind-resistant design of high-rise buildings.

Pore size distribution （PSD） significantly affects the water-retention and seepage characteristics of unsaturated soils. By assuming that the PSD of soil follows a fractal law and that soil volume deformation affects the PSD via changes in the fractal dimension, a fractal-based equation describing the evolution of PSD during soil volume deformation is proposed. This equation combines intrinsic constraints between the pore size ratio and the fractal dimension. Consequently, models for the unsaturated soil water retention curve （SWRC） and the relative hydraulic conductivity curve （RHCC） that consider the evolution of PSD are derived. The model parameters can be calibrated using water retention curve data from soil samples with two different initial porosities, enabling prediction of the SWRC and RHCC under various deformation states. Finally, the proposed model is validated against seven sets of experimental data, demonstrating that the hydraulic model based on fractal theory effectively describes the impact of volume deformation on the water retention and seepage characteristics of unsaturated soils.

For the key issue of one-pass full-section excavation construction of an underground ventilation station with multiple bifurcations, this study takes the Suzhou International Rapid Logistics Corridor Phase II Project—Yangtze River Road South Extension Project as the engineering background. Given the structural complexity of the underground caverns in the ventilation station, the structural unit containing the main cavern is selected, and a three-dimensional numerical model is established. The model is used to analyze the spatial structural response, deformation characteristics, and surrounding rock evolution of the underground cavern group, with emphasis on the cross-section and large-span connection sections of the ventilation station. The analysis verifies the feasibility of the proposed construction method and can provide valuable references for the design and construction of similar underground projects under comparable conditions.

The bearing capacity of the existing wall after plugging reinforcement is studied. Considering the influence of stress lag effect, original stress level, opening rate and plugging material performance on the bearing capacity of the masonry wall after plugging, the corresponding calculation method is given. The results show that the use of the original masonry mortar and block materials can not meet the bearing capacity requirements of the wall ; improving the strength of masonry mortar and block materials can only meet the bearing capacity requirements of some walls ; the use of high ductile concrete to reinforce the wall is an effective means of repair, but there is also the possibility that it cannot meet the demand for bearing capacity.

Openings are often used in cast-in-situ concrete hollow floors and the current direct design method does not consider the influence of the openings. In this paper, 270 case studies on 3x3 span box filler hollow floors with openings were analyzed using software ABAQUS. The effects of four parameters on the moment distributions of the hollow floors were investigated, i.e., the opening position, opening area ratio, slab span ratio and the beam-slab relative flexural stiffness ratio. The obtained results included the moment distribution coefficients for control sections of the floor strips, as well as the moment distribution coefficients for column strips. These results were also compared with the coefficients recommended by the code. It was found that the opening in the hollow floor weakened the section stiffness at the opening position, reduced the moment distribution coefficients of the section, and consequently increased the moment distribution coefficients of other sections. In the presence of an opening, the recommended values in the code are appropriate for the moment distribution coefficients for control sections of both the interior and end span. However, the moment distribution coefficients for the column strips in the code are not applicable and it is recommended to adopt the moment distribution coefficients proposed in this paper for the column strips,which account for openings.

In the design of general non-prestressed reinforced concrete structural components, the ultimate limit state calculation of bearing capacity and the crack width check are the two main calculation tasks according to the standards. Due to the influence of crack width control verification, the reinforcement in some components often cannot reach the design value of material tensile strength used in the calculation of bearing capacity limit state. Therefore, it is necessary to consider the influence of both factors when selecting and configuring reinforcement materials. In this article, based on different strength grades of steel bars and different types of fiber-reinforced polymer bars, formulas for calculating the utilization ratio of reinforcement strength for crack width control under various loads such as dead load, live load, and hydrostatic pressure are derived according to the relevant design codes’ formulas for bearing capacity limit state and crack width control verification. Corresponding numerical solution methods are provided, which enable a macroscopic understanding of the utilization of material strength in crack control situations. Finally, a program is developed to plot the calculation results into graphs, summarizing the patterns of the results and providing guidance for structural design optimization and material selection considerations.

Steel-structured fully indoor substations are the preferred solution for urban green substations, offering advantages such as land conservation and stable operation. However, once a fully indoor substation suffers earthquake, it will lead to enormous economic losses. Additionally, traditional seismic design overlooks the structure-equipment interaction, resulting in designs that tend to be unsafe. In this study, the coupling model and the main structure model were established respectively for a 110 kV steel-structured fully indoor substation. The coupled model accounts for the structure-equipment interaction, while the main structure model treats equipment as floor loads. Subsequently, dynamic characteristic analysis （to obtain key parameters such as natural vibration frequencies and mode shapes） and time-history analysis were conducted on the two types of models. Finally, the Incremental Dynamic Analysis （IDA） method was adopted： by adjusting the peak ground acceleration （PGA） of seismic waves, the response indices of the main structure and equipment under different seismic intensities were quantified, so as to comprehensively evaluate the seismic vulnerability of both. The results show that： （1） The acceleration amplification effect of the 2nd-floor GIS （Gas Insulated Switchgear） equipment bushings is significant （with an average value of 4.2 and a maximum value of 5.1）, which is much greater than that of the 2nd-floor slab, making the bushings prone to damage due to excessive acceleration during earthquakes; （2） The structure-equipment interaction exerts a notable impact： the maximum difference in amplification factors between the coupled model and the main structure model is 20%, and the maximum difference in inter-story drift angles is 15%; （3） Under the action of some seismic waves, the torsional displacement ratio of the coupled model exceeds 1.2, so torsion reduction measures need to be implemented; （4） Under the same seismic intensity, the failure probability of electrical equipment is far higher than that of the main structure. For instance, when PGA=1.0g, the equipment damage probability reaches 60%, while the main structure barely collapses.

The frame-damping-framed-tube structure is a new structural system in which the “damping-framed-tube” is used to approximate the core tube, with the frame bearing all vertical loads. This paper investigates the feasibility of applying this new structural system in the development of upper cover of urban rail transit. Elastic analysis under frequently occurred earthquake and elastoplastic time history analysis under rarely occurred earthquake were carried out. Analysis results show that the elastic and elastoplastic inter-story drift of the well-designed upper cover frame-damping-framed-tube structure of urban rail transit can meet the requirements of design standards. Under rarely occurred earthquake, the damping walls yield adequately and dissipate energy, with an additional damping ratio of whole structure up to 1.82% and that of upper cover structure up to 3.45%, showing excellent energy dissipation and seismic mitigation effects. Compared with conventional frame-core tube structures, the elimination of the core tube reduces the dead load of the upper cover structure, improves the load distribution in the transfer level, and benefits the design of the structure below the platform. It indicated that the new structure is suitable for the development of upper cover of urban rail transit. This paper also discusses the influence of the structure below the platform on the performance of frame-damping-framed-tube structure. Compared to being embedded on the ground, the seismic response of high floors of the upper cover frame-damping-framed-tube structure is amplified due to the whipping effect. Therefore, it is necessary to appropriately increase the stiffness and bearing capacity of the damping walls on the high floors to fully utilize their energy dissipation capacity.

Based on the problems found in the post-evaluation process of the square steel pipe adding elevator structure and comparing the advantages and disadvantages of different systems, the technical feasibility of adopting H-shaped steel adding elevator structure is discussed. By analyzing the overall index of the model with different entry forms, floors, ground roughness categories and other multi-factors and multi-levels, the optimal member cross section of H-shaped steel structure under different conditions is obtained. The safety of the connection joints is verified by bearing capacity calculation and finite element analysis. Special analysis is carried out on key issues such as structural performance of adding elevator structure under rare earthquake and calculation method of stiffness of the bottom floor of half-floor entry. An implementation project is used to evaluate the economy of H-shaped adding elevator structure. The analysis results show that： the H-shaped adding elevator structure has the advantages of simple connection, easy inspection and maintenance, high degree of assembly, and convenient on-site construction; the reasonably designed H-shaped adding elevator structure can meet the design requirements of the current code, and the deformation of the components and the level of stresses are low; it is more reasonable to use the shear-bending stiffness statistical stiffness ratio of the bottom floor of the half-floor entry structure with the consideration of the stiffness of the beams in the interstorey; reasonably constructed bolted-welded or fully bolted column connections and beam-column connection joints can meet bearing requirements; H-shaped adding elevator structure has a slight economic advantage over square steel tube structure. The research results of this paper can be used as the technical reserve for the preparation of design guidelines.

Concrete-filled circular steel tubes （CFCSTs） are widely used in high-rise and long-span structures for their superior bearing capacity, ductility, and construction efficiency. However, the axial compressive capacity calculation provisions for CFCST short columns differ between Chinese and foreign codes. Therefore, it is essential to evaluate the calculation accuracy of the axial compressive bearing capacity formulas for CFCST short columns in various national codes. To this end, the two research methods （“hoop theory” and “unified theory”） were reviewed, and the differences in axial compression capacity using the two theories were compared. The calculation provisions of the axial compressive capacity for CFCST short columns in Chinese and foreign codes were introduced in detail, and the similarities and differences in the formulas were briefly analyzed. Based on a large amount of concrete material test data and 378 CFCST short column axial compression test results, conversion relationships for various concrete material indexes were established to unify the axial compression test results, and the calculation accuracy of each code formula was further analyzed. The results show that the axial compressive bearing capacity ratios using “hoop theory” and “unified theory” increase and then decrease as the confinement index increases, and the ratios are related to the core concrete compressive strength confinement improvement factor. The calculation accuracy of the “hoop theory” and “unified theory” formulas in “Technical code for concrete-filled steel tubular structures” （GB 50936—2014） is comparable, and the calculated values are closer to the average values, with the lowest safety margin. The calculation accuracy of “Recommendations for design and construction of concrete filled steel tubular structures” （AIJ—2008） is second, and the calculation accuracy of “Design of composite steel and concrete structures-Part 1.1： General rules and rules for buildings” （EN 1994-1-1： 2004） is lower than that of AIJ—2008, but higher than that of “Specification for structural steel buildings” （AISC 360‒22）.

Yichun West Railway Station is the highest-latitude high-speed railway station in China and the first prefabricated canopy station constructed in permafrost regions under severe cold climate. The structural performance of prefabricated canopies is significantly affected by soil frost heave. In this study, a finite element model of the canopy structure is developed to simulate the impact of frost heave on pile foundations. Parameters such as freeze-thaw cycle duration, deformation magnitude, and freeze-thaw position are analyzed. The research reveals the influence patterns of frost heave on the structural behavior of prefabricated canopies, offering a basis for ensuring their safe application in severely cold regions.

Apparent defects in underwater concrete structures are significantly challenged by complex environmental factors including water turbidity, variable lighting conditions, and flow velocity. These interferences lead to difficulties in defect localization and low recognition accuracy during underwater inspections. To address these limitations, this study proposes an intelligent recognition framework based on deep learning. The methodology integrates three key components： generation of a multi-scenario defect database replicating complex underwater environments; application of small-sample expansion and image enhancement algorithms for robust preprocessing; implementation of the YOLOv5 target detection algorithm for multi-category defect identification and localization. Experimental results demonstrate that the proposed approach achieves a mean average precision （mAP） of 83% and a recognition precision exceeding 83%. This framework effectively mitigates accuracy degradation caused by underwater environmental complexities and limited sample sizes, providing a reliable technical solution for automated structural health monitoring of submerged infrastructure.

With the increasing span of building structures, traditional precast concrete floor slabs are no longer suitable. Therefore, a new type of prestressed concrete prefabricated bottom plate integrated with a long-span steel pipe truss is proposed. In this study, static load tests were carried out on three large-span prestressed concrete prefabricated floor slabs with steel pipe trusses of different widths （each spanning 8,400 mm）. The cracking patterns, deformation behavior, load-deflection curves, concrete strain, as well as strains in the steel tubes and web members were obtained. Based on the experimental results, the influence of various parameters on the mechanical properties of the prefabricated bottom plate was further investigated through numerical simulation. The test results indicate that cracks initially occur above the top support of the slab and subsequently develop at the bottom mid-span of each span. The cracking load of the prefabricated bottom plate decreases as the plate width increases. Specifically, the cracking load of the specimen with a plate width of 4,200 mm decreases by 20.61% compared to that of the 2,100 mm-wide specimen. The arrangement of supports alters the mechanical performance of the prefabricated bottom plate and effectively restrains the overall deformation of the specimen. Moreover, the number of supports, the diameter of the steel pipe, and the truss span are found to have a significant influence on the bearing capacity of the prefabricated bottom plate, while the truss height has a relatively minor effect.

The fatigue properties of LY100, LY160, and LY225 low-yield-strength steels were investigated. The effects of strain rate on the fatigue life, crack initiation, and propagation cycles of these steels were examined, along with an analysis of the fracture mechanism. Cyclic loading tests were conducted in accordance with the relevant specifications for metal energy dissipators. The results indicate that the low-yield-strength steels exhibit superior fatigue performance. As the steel grade increases, the fatigue life shows a slight improvement. Variations in strain rate do not significantly affect the fatigue life of the material. The fatigue fracture of low-yield-strength steels is characterized as ductile fracture. The fracture process involves the propagation of multiple micro-cracks into macroscopic cracks, followed by instantaneous rupture. The studied steels meet the requirements for metal energy dissipators and demonstrate good fatigue performance.

A combined base-isolation system incorporating isolation bearings and additional dampers can effectively mitigate seismic forces and control the deformation response of the isolation layer to a certain extent. However, under multi-level seismic excitations, combined isolation systems employing conventional viscous dampers generate excessively high damping forces, which compromise the isolation effectiveness. To address this issue, a viscous damper with overload protection （VD-OP） and its corresponding combined isolation system are proposed in this study. The design, fabrication, and experimental testing of the VD-OP were conducted, and a mechanical model describing its nonlinear damping and overload protection characteristics was established based on experimental data calibration. The effectiveness of the VD-OP combined isolation system and its advantages in multi-level vibration control were verified. The results indicate that the proposed VD-OP system exhibits a velocity-dependent nonlinear damping mechanism and force-limiting capability, effectively preventing excessive damping forces induced by high-level seismic excitations, enhancing isolation efficiency, and controlling the acceleration response of the isolated structure. The performance-based design approach proposed in this study provides practical guidance for the implementation of VD-OP systems and offers a reference for the seismic mitigation design of structures in high-intensity seismic regions.

A computational fluid dynamics （CFD） method is employed to analyze the influence of longitudinal spacing on the flow field around a photovoltaic array and the resulting wind load on the panels. The validity of the numerical simulation is confirmed through comparison with wind tunnel test results. The findings indicate that longitudinal spacing significantly affects the wake flow field behind the first row, causing the wind load on the second row to be the most sensitive to changes in spacing. Moreover, it is observed that the second row can experience considerable torque when the longitudinal spacing is small. In contrast, the wind load on the third to the eighth rows is only marginally influenced by the longitudinal spacing and generally decreases as the spacing is reduced.

To enhance the stability and flood control capacity of aged earthen embankments, a coating material prepared from polylactic acid （PLA） binder, water, and sand was selected and laid on the slopes and crests of the embankments. Tests were conducted on simulated embankments, where photographic equipment combined with an image measurement and analysis system was employed to compare the blocking effect between untreated earthen embankments and those coated with the material during overtopping breaching. The results revealed that applying the PLA coating altered the breaching pattern and delayed the breaching process, with a 5cm-thick coating completely preventing breaching. This study provides a reference for the ecological reinforcement of aging embankments.

Four types of novel lightning rod flange joints were designed, and cyclic loading tests were conducted to investigate their hysteretic performance under horizontal repeated loads. The failure modes, stress development and distribution patterns of the flange joints were examined. The load-displacement hysteretic curves, skeleton curves, stiffness degradation, energy dissipation capacity, and ductility coefficients of the four flange joint types were compared. The results show that the rigid flange joints （S1, S2, and S3） exhibited local buckling on the compression side and steel tube tearing on the tension side at the bottom of the specimens, while the flexible flange joint （S4） failed due to fracture of the weld between the upper steel tube and the flange plate. The rigid flange joints with a ring plate or a core tube demonstrated better ductility than the conventional rigid flange joint. Reducing the stiffeners and bolts in the flange joint （as in specimens S2 and S4） led to decreases in initial stiffness and energy dissipation capacity, whereas adding a core tube effectively improved the hysteretic performance.

With the development of super-tall building structures, the economy has become the focus of the owners in the design. The core tube is an important component for lateral force resistance and vertical force transmission, which has a great impact on the structural cost. In this study the design of core tube structure in typical super-tall buildings is investigated by using intelligent optimization algorithm. First, a number of engineering cases of super high-rise buildings around 300m high are collected, the common parameters for super-tall structure are summarized, and a typical super-tall building structure model is established accordingly. The advantages and disadvantages of each optimization algorithm are briefly analyzed, and the computational efficiency is compared. Then, the design process of the core tube combined with the intelligent optimization algorithm is proposed, the mathematical model of constraint optimization is established, and the constraint conditions related to the specification and construction are introduced into the optimization process using the penalty function method. Finally, the method is used to optimize the wall thickness of the core tube with different outer frame stiffness and different coupling beam height, and the distribution law of the wall thickness after optimization under different conditions is provided.

To investigate the synergistic mechanism of the interface between recycled aggregate concrete （RAC） and normal concrete （NC） and promote its engineering application in composite structures, this study explores the shear resistance and failure mechanisms of the RAC-NC interface through direct shear tests and numerical simulations. Bonded RAC-NC interface specimens were designed and fabricated, and direct shear tests were conducted to analyze the interfacial shear capacity and failure modes. A numerical model was established using ABAQUS finite element software and validated against experimental results. The results indicate that the interfacial shear capacity significantly decreases with an increase in the replacement ratio of recycled coarse aggregates. When the replacement ratios of recycled coarse aggregates were 25%, 50%, 75%, and 100%, the interfacial shear capacity decreased by 9.9%, 15.0%, 20.8%, and 26.4%, respectively, compared to normal concrete. The finite element model effectively simulated the peak shear load during failure, with errors between simulated and experimental results within 10%. This study reveals key factors influencing the shear performance of the RAC-NC interface and provides a theoretical basis for the design and reinforcement of recycled concrete composite structures.

With rational application, energy dissipation technology can help structures meet stiffness requirements under seismic conditions, and demonstrates high applicability to high-rise buildings in high-intensity zones. The weak connection scheme using lead-rubber bearings not only satisfies the normal serviceability requirements under minor earthquakes and wind loads, but also controls the structural joint width within the allowable range during major seismic events, while avoiding the adverse effects associated with a rigid connection scheme. Taking two high-rise connected buildings as an example, this paper investigates the design of energy dissipation technology and high-rise connections. First, in response to the limited size of the core tube, viscous damping walls are installed in suitable locations to fulfill stiffness demands, and the stories where viscous damping walls perform most effectively are identified through calculation and analysis. Second, based on the features of high-rise connections, a weak connection scheme is selected after comprehensive comparison, utilizing lead-rubber bearings at the connection points. Finally, reliable anti-collision and anti-fall measures are designed, and the seismic performance objectives of the structure are established, providing a reference for similar projects.

In order to study the safety of the precast concrete composite structure, which was suitable for the single-column double-span underground metro station, low-reversed cyclic loading tests were conducted on large-scale models of the bottom joint of outer wall which was the key part of the structure. The results showed that the failure patterns of the composite specimens were similar to that of cast-in-place （CIP） specimen, all of which were compressive bending failure at the bottom of the wall and the upper edge of the haunching, and both the composite specimens with single-skin wall and double-skin wall had good structural integrity. The P-δ hysteresis loops of the composite specimens and the CIP specimen were generally full, showing a stable hysteresis response, and the bearing capacity of all the specimens can meet the design requirements. The ductility coefficients of the two composite specimens were both 3.1, which were about 3.3% higher than that of the CIP specimen. The energy dissipation capacity and stiffness degradation of the composite specimens were similar to those of the CIP specimen in general. On the basis, the influence of different designed details on the seismic performance of the bottom joint was further analyzed through the finite element analysis. The results showed that the bearing capacities of the composite specimens were close to that of the CIP specimen when the connecting steel bars of the composite walls were designed according to the principle of equivalent bearing capacity of the bottom sections.

Based on the pulsation method, the dynamic characteristics of a column-less steel spiral stair were tested, and the natural frequency and damping ratio of the steel stairs were obtained. Based on the test results, a numerical model was established to study the comfort and influencing factors of the column-less steel spiral stairs. The research results show that the comfort of the steel stair meets the requirements of the current Chinese design code. Change of the constraint conditions at the end of steel stairs and adjusting the stiffness of arc beams supporting them can significantly impact the comfort of column-less steel spiral stairs.In addition, in order to facilitate the design, based on the above analysis, an approximate calculation formula for the natural vibration frequency of the column-less steel spiral stairs was proposed, which can be used to estimate the natural vibration frequency of such steel stairs and predict the comfort level in the preliminary design stage. It provided some reference for the design and comfort analysis of similar stairs in future.

In response to the load-bearing characteristics of rigid and flexible flange joints in single steel tube lightning rods and based on an analysis of a collapse accident, this study proposes four new types of flange joints. These designs incorporate a core pipe to enhance the joint's bending stiffness. The static load performance and patterns of stress distribution of the new joints and a traditional rigid flange joint were analyzed using ABAQUS finite element software. The results showed that the new flange joints exhibited bearing capacity and flexural stiffness comparable to those of the traditional rigid joint. Moreover, the new designs demonstrated a significant improvement in mitigating stress concentration. This enhancement is beneficial for improving the fatigue performance of the lightning rod flange joints.

The layout scheme of guyed pole waist ring cable has an important influence on the efficiency and safety of UHV transmission tower erection construction. In order to study and obtain an economical, reasonable, safe and reliable layout scheme of holding pole waist ring cable, according to the real size of GGTY2 × 7t / 16-1000 type landing electric rotating double flat arm holding pole, this paper uses the finite element analysis method to establish the holding pole-waist ring-cable coupling mechanical analysis model under the condition of UHV transmission tower assembly. The mechanical characteristics of holding pole and cable under different working conditions and different typical waist ring cable layout schemes are calculated. Through the analysis of the displacement of holding pole and the tension of cable, the optimal arrangement scheme of holding pole waist ring cable is obtained. The coupling calculation method and analysis conclusion of pole-waist-strut coupling obtained in this paper can provide technical support for UHV transmission tower assembly and improve the efficiency and safety of construction assembly.

Currently, the main connection methods between square steel tubes include welding, flange connection, sleeve connection, and splicing connector connection. Based on the existing research results of various connection joints, this article proposes a new type of fully bolted column-column splicing joint that uses angle steel as the splicing connector. Firstly, monotonic loading tests were carried out on two column-column joint specimens with different splicing lengths and bolt arrangement forms under combined compression-bending-shear loading conditions, and the influence of the length of the connecting member and the arrangement form of the bolts on the ultimate bearing capacity and stiffness of the joint was analyzed. Finite element analysis software was used to simulate the monotonic loading tests, and the numerical simulation results were compared with the test results to verify the accuracy of the numerical model and obtain the mechanical performance of the two types of joints under monotonic loading. The research results show that the failure process of the specimen using the fully bolted column-column splicing joint with square steel tubes can be divided into three stages, namely, elastic stage, elastic-plastic stage, and failure stage. The longer the splicing member of the joint, the higher the ultimate bearing capacity and stiffness of the specimen. However, the stiffness of specimens using connecting joint is smaller than that of general column components without joint.

In this paper, the fire resistance of high-strength fire-resistant steel bending members is studied by finite element numerical simulation in ABAQUS. Based on the existing test results, the finite element model established by the thermo-mechanical method is verified, and the effects of load ratio, slenderness ratio and steel strength grade on the fire performance of high-strength fire-resistant steel bending members are further analyzed. The results show that the load ratio has a great influence on the fire resistance of the members, while the slenderness ratio and steel strength grade have little influence on the critical temperature of the members. The fire resistance of the bending members gradually decreases with the increase of the load ratio. Finally, the stability parameters for high-strength fire-resistant steel bending members at elevated temperature are proposed by modifying the existing specifications, which are validated by the test results and finite element simulation.

The leakage issue at assembly joints of prefabricated pipe galleries poses a serious threat to their safety and stability, making efficient and accurate leakage detection a pressing need. This paper proposes a leakage location detection method for assembly splicing nodes in prefabricated pipe galleries based on cyclic frequency characteristics. First, ultrasonic technology is employed to collect pulse reflection signals from the nodes and determine their positions. Second, the cyclic spectral density of the node pulse reflection signal is established, from which the cyclic frequency characteristics are extracted. The principal component analysis method is introduced to reduce the dimensionality of the features, thereby improving feature accuracy. Finally, the quantum swordfish algorithm is used to optimize the LSTM network, and the reduced cyclic frequency characteristics are input into the optimized network to achieve leakage location detection at the assembly joints of the prefabricated pipe gallery. Experimental results demonstrate that the proposed method achieves high accuracy in feature extraction, leakage detection, and node localization.