Considering the poor ductility of steel frame joints with concrete floors and the susceptibility to weld damage at the beam lower flanges, this paper proposes a new type of composite joint. The joint employs a mono-symmetrical steel beam section that weakens only the lower flanges by increasing their width while reducing the width of the upper flanges. This design mitigates the upward shift of the neutral axis of the composite beam section induced by the concrete floor, thereby reducing the risk of brittle fracture in the welds of the lower flanges. Using the finite element software ABAQUS, the effects of several parameters on the hysteretic behavior of the composite joint were investigated, including the distance from the weakening start point of the lower flange to the beam-column interface, the weakening length, and the weakening depth. By comparing hysteresis curves, skeleton curves, stiffness and strength degradation curves, and energy dissipation capacity, recommended value ranges for the weakening start distance, weakening length, and weakening depth are provided.

To address the issue of additional internal forces induced in structures by conventional friction pendulum bearings during their service life, the engineering community has widely adopted thermal gap-type friction pendulum bearings. However, theoretical calculations still rely on the bilinear constitutive model of conventional bearings for simulation, which does not accurately reflect the actual mechanical behavior of the thermal gap type. This study analyzes the true constitutive relationship of thermal gap-type friction pendulum bearings and proposes a method to simulate their complex seismic response using composite bearing elements, thereby obtaining a more realistic structural seismic response. Based on a typical three-span continuous girder bridge, a comparative analysis is performed on the seismic isolation performance of systems equipped with thermal gap-type versus conventional friction pendulum bearings. Results indicate that the thermal gap-type bearings tend to induce larger displacements and lower shear forces in the bearing itself, along with significantly increased residual displacements and a slight reduction in pier bottom bending moments. Attention should therefore be paid to the selection of appropriate bearing constitutive models in the seismic theoretical analysis of structures.

This paper presents a numerical analysis of the load-bearing performance of structures in real substations subjected to localized fires. The investigated substations exhibit typical features such as large spans, wide column spacing, and floor height variations. The study examines the influence of column location （corner, center, and edge columns） and load magnitude on structural behavior under fire conditions. Results reveal notable differences in stress and deformation responses among columns at different positions. Central columns are found to be the most susceptible to thermal deformation, whereas corner and edge columns experience comparatively slower collapse progression and reduced deformation. Under identical fire and loading scenarios, central columns collapse approximately 19% faster than edge columns and 26% faster than corner columns. In addition, load magnitude significantly affects the structural load-bearing capacity, with increased uniform loads leading to an earlier critical collapse time.

When faced with stringent construction constraints, the span arrangement of steel-concrete hybrid girder cable-stayed bridges is required to reduce the edge-to-middle span ratios, which might fall below conventional values. In this case, the rapid determination of the rational span arrangement for the hybrid girder cable-stayed bridge requires further research. The span arrangement method for lower edge-to-mid ratio hybrid girder cable-stayed bridges is derived. Based on the rational dead load state of cable-stayed bridge, the calculation methods for determining the optimal range of the interface position between the steel girder and the concrete girder are given. Two scenarios of the interface position, edge-span and middle-span, are considered. Formulas are obtained to facilitate rapid design calculations. The calculation method for the minimum edge-to-middle span ratio is provided. The accuracy of the method proposed has been verified through the parameters of several completed cable-stayed bridges. This methodology has been validated by a span arrangement of Min’an Grand Bridge, which achieves the rational dead load state with an edge-to-middle span ratio below the typical values.

As the design basis for engineering structures in nuclear power plants, the rational determination of characteristic values and partial factors for equipment is relevant to the safety and reliability of engineering structures in nuclear power plants. In this paper, based on the plan drawings of some specific function rooms in a nuclear power plant, the basic information of the specific function rooms is extracted, and then the equivalent uniform floor loads are calculated. Through single-factor analysis of variance （ANOVA）, the rational classification of the specific function rooms is proposed. Based on the calculated results of the equivalent uniform floor loads in the specific function rooms, the arbitrary-pint-in-time distribution model of the sustained live load is built. And then, based on the assumption of stationary binomial stochastic process, the probability model and statistical parameters of the maximum load during the design reference period are obtained. According to the calculation method prescribed in the Chinese codes, the recommendation value for the characteristic value of floor load in nuclear power plants is suggested.

In the context of widespread cracks occurring in some underground buildings, construction activities beneath the structure may cause adverse effects. Therefore, it is essential to investigate methods for calculating and simulating the impact of cracks and their degree of influence on existing structures. Based on an underground slab-column structure of a trading market, this study simulates and calculates the crack conditions by establishing three-dimensional models with and without cracks, as well as models incorporating cracks with different parameters. Through comparative analysis, the influence of various crack conditions on the internal forces of the structure and the stiffness reduction coefficients in different directions is evaluated. The results are as follows： （1） A vertical crack influences a local area of about 1.5 meters, with very limited impact beyond this range. The deeper the crack, the greater its effect on local internal forces; the longer the crack, the wider the scope of influence along the crack direction. （2） The influence characteristics of inclined cracks fall between those of vertical and horizontal cracks, and are closer to those of vertical cracks. （3） Taking a vertical crack with a length of 2.35 m and a depth of 250 mm as an example, the internal forces of the structure are analyzed using different stiffness reduction coefficients. The results indicate that the effect on structural forces varies with the direction of the stiffness reduction. A greater reduction in stiffness leads to a more significant impact. （4） When the horizontal stiffness reduction coefficient is 0.9 and the vertical coefficient is 0.8, the calculated internal forces at key points of the cracked structure differ by less than 6.0% compared with the interface method. The internal force distribution obtained with the reduction method is similar to that from the interface method under various loads. Thus, the equivalent stiffness method is feasible for simulation calculations.

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.

A novel flange joint is proposed for single-tube lightning rod structures, improving upon conventional rigid and flexible flange designs. The innovation lies in the incorporation of a central tube, which replaces traditional stiffeners to enhance the out-of-plane stiffness of the connection. In comparison with commonly used rigid flanges, the proposed joint demonstrates reduced stress concentration and superior fatigue performance. Four types of flange joints were designed, and their fatigue lives were evaluated using ABAQUS and FE-SAFE. Results show that the new flange joint effectively alleviates the stress concentration observed in conventional rigid flanges and achieves a significantly extended fatigue life.

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.

Based on the validation of the finite element model developed in ABAQUS, the effects of the axial compression ratio, the thickness of the connection insert, and the thickness of the beam cover plate on the failure mode and seismic performance of the single-sided bolted connection joint in box-type modular steel structures are investigated. The results indicate that variations in the preload of a single-side bolt have a limited influence on the seismic behavior of the joint. In contrast, the thickness of the connection insert has a more pronounced effect. When the insert thickness increases from 6 mm to 8 mm, the ultimate load increases significantly by approximately 7%. As the thickness of the beam end cover plate increases, the bearing capacity, initial stiffness, and later-stage stiffness of the joint also increase, while the ductility decreases. The thickness of the beam end cover plate exhibits the most notable impact on the energy dissipation capacity. The total energy dissipation reaches its maximum when the cover plate thickness is 10 mm, and decreases by 13% and 19% at thicknesses of 8 mm and 12 mm, respectively. Additionally, the equivalent viscous damping coefficient declines during the later loading phase.

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.

Beam-to-column joints of H-shaped steel columns exhibit excellent seismic performance and are widely used in engineering applications. To meet the requirements of prefabricated construction, this study proposes a novel connection scheme for H-shaped steel columns, in which cover plates are employed to achieve semi-rigid connections between columns and beams in both the strong- and weak-axis directions. To investigate the seismic performance of this new type of semi-rigid joint in the weak-axis direction, low-cycle reversed loading tests were conducted on four joints with different end-plate thicknesses and axial compression ratios. The failure modes, ultimate bearing capacities, hysteretic curves, and backbone curves were obtained, and the influence of these factors on seismic performance was compared. In addition, numerical models of the tested joints were developed using ABAQUS software, and their accuracy was validated by comparing the simulation results with the experimental data. The results indicate that the axial compression ratio has little effect on the ultimate bearing capacity, whereas the end-plate thickness significantly affects both the rotational stiffness and ultimate capacity of the joints. Specifically, the joint with a 10 mm thick end plate exhibits an ultimate capacity approximately 30% higher and an initial rotational stiffness about 38% greater than that with an 8 mm thick end plate.

In support of prefabricated building applications, this study introduces a novel semi-rigid connection for H-shaped steel columns using cover plates. This design facilitates semi-rigid joints with beams in both the strong- and weak-axis directions. To evaluate its seismic performance along the strong axis, four specimens with varying end-plate thicknesses and axial compression ratios were tested under low-cycle reversed loading. The failure modes, hysteretic curves, and rotational stiffness were analyzed. Furthermore, numerical models were developed in ABAQUS and validated against the experimental results.

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.

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.

To simplify the method for calculating the allowable displacement of double-column piers with a rigid cap beam, this study combines experimental and theoretical investigations. Tests were conducted on six rectangular concrete pier columns, five of which were subjected to variable axial loads and cyclic loading, while one was under constant axial load and cyclic loading. The test results indicate that out-of-plane instability failure occurs in columns under variable axial loads when the axial compression ratio reaches its maximum, suggesting that the failure state is governed by the maximum axial force. This observation simplifies the criteria for determining the limiting curvature of plastic hinges, as specified in Clause 7.4.8 of the “Specifications for Seismic Design of Highway Bridges” （JTG/T 2231-01—2020） and Clause C5.2.2 of the “Caltrans Seismic Design Criteria” （2019）. A theoretical analysis of the mechanical behavior during lateral deformation of the double-column pier with a rigid cap beam was performed, simplifying the displacement calculation to that of a single column subjected to variable axial forces. Based on these analyses, a simplified method for calculating the allowable lateral displacement of double-column piers with a rigid cap beam in the transverse direction is proposed. The accuracy and safety margin of the simplified method were evaluated using nonlinear push-over analysis, and the results are deemed acceptable. The proposed method is straightforward and enables rapid estimation of allowable displacements, offering a useful reference for engineering design.

The Occlusive Fully Bolted Beam-to-Column （OFBBC） joint, a novel type of fully bolted steel connection, enhances the load-bearing capacity without increasing the number of bolts, offering advantages such as high structural strength, material efficiency, and ease of construction. This study investigates the seismic performance of OFBBC joints. Low-cycle reversed loading tests were carried out on three joints with 0, 4, and 6 grooves, and their failure modes, hysteretic curves, and backbone curves were obtained. The results show that joints with grooves exhibit higher load-carrying capacity and energy dissipation ability, indicating better seismic performance compared to joints without grooves. Furthermore, numerical models of the three specimens were developed using ABAQUS and validated against experimental results. The proposed OFBBC joint improves both load-bearing and energy dissipation capacities, overcoming the drawbacks of traditional fully bolted joints.

This study investigates the out-of-plane bearing performance of a novel connector for prefabricated steel frame-embedded wall systems. Compared with traditional external wall systems, embedded walls eliminate exposed beams and columns, enhancing the functionality and comfort of prefabricated steel buildings. However, traditional embedded configurations often suffer from stiffness incompatibility between the wall and steel frame, leading to mutual compression under horizontal loads and resulting in cracks or even failure at the connection, compromising structural serviceability. For this reason, this paper proposes an innovative S-shaped connector, designed to coordinate the lateral deformation of the frame while resisting vertical out-of-plane loads on the wall, such as wind loads. Four types of S-shaped connectors with different thicknesses and straight segment lengths were designed and tested together with steel frames and embedded walls. The test results show that larger thickness and shorter straight segments significantly increase initial shear stiffness and compressive bearing capacity under equal displacement, but reduce the displacement at which bolt-loosening failure occurs. The influence of thickness on out-of-plane shear stiffness and capacity is more significant than that of the straight segment length. A finite element model was developed and validated against test results, accurately capturing the deformation and load-bearing behavior of the connectors under out-of-plane loads.

To solve the problems of exposed beams and columns in external walls and the vulnerability of embedded walls under lateral loads, this study proposes an S-shaped steel connector for prefabricated steel frame-embedded wall systems. The connector relieves the constraint between wall and frame, enabling coordinated deformation under lateral loading. Four types of connectors were tested to evaluate their in-plane mechanical performance, including tensile and compressive deformation, stiffness evolution, bearing capacity, and failure modes. Based on these tests, cyclic loading experiments were conducted on steel frames with embedded walls using S-shaped connectors, as well as on bare frames, to compare the hysteretic behavior of different connector specifications. Results show that the S-shaped connector effectively reduces the lateral load transferred to the embedded wall, allowing it to remain largely uninvolved in lateral resistance. This ensures deformation compatibility between the wall and frame, prevents wall damage under horizontal loading, and maintains the building’s functional integrity. The proposed connection provides a novel solution for the reliable integration of embedded walls in prefabricated steel structures.

In structural health monitoring, sensor data often suffer from missing values due to sensor faults, inadequate maintenance, or adverse environmental conditions. When dealing with large-scale or high-dimensional time-series data, traditional data processing methods, such as linear interpolation or nearest-neighbor interpolation, struggle to accurately reconstruct the true dynamic characteristics. To address this challenge, this study proposes a Multi-source Time Series Generative Adversarial Network （MTSGAN） for data reconstruction. The proposed method is then applied to a three-span continuous beam model to accurately predict structural acceleration responses. Results demonstrate that even when the sensor fault rate reaches 60%, MTSGAN achieves high-accuracy data reconstruction, with a maximum error of only 10.3%.

Under the long-term combined effects of load and environmental exposure, steel structures are susceptible to corrosion, leading to a reduction in load-bearing capacity and compromising structural safety. For the domestically produced Q355 H-beam, bending tests were conducted on corroded specimens. Combined with changes in the geometric characteristics of the corroded cross-sections obtained via structured light scanning, the degradation law of the bending performance of the corroded H-beam was revealed. The characteristic load values of the steel beams exhibited a linear relationship with either the average or maximum degree of cross-sectional corrosion. The corrosion extent of the flanges and web changed synchronously with the overall cross-sectional corrosion degree. Accordingly, a simplified method for calculating the geometric characteristics of corroded steel beams was proposed. Predictions of the yield load and ultimate load based on the actual cross-sectional shape, the uniform corrosion cross-section, and the flange contribution method were compared. The average prediction error for the yield load using the three methods remained within 5%. The simplified approach considering only the flange area for calculating the flexural capacity showed good agreement with the experimental results.

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.

The presence of boulders and hard interbedded layers at the site poses significant challenges for pile foundation construction. This study proposes a new technique termed the “down-the-hole hammer pilot hole and pressure-grouted concrete pile method”. Compared to conventional concrete pile foundations, the proposed method demonstrates significant advantages in terms of cost, construction time, environmental protection, and safety. Vertical bearing capacity tests were conducted on single piles constructed using this technique. The results indicate that the characteristic vertical bearing capacity of the piles satisfies the design requirements. Furthermore, the findings confirm that the proposed method is well-suited for site conditions involving boulders, hard interbedded layers, and shallow bedrock.

To address the need for lightweight tuned seismic retrofitting of existing reinforced concrete （RC） frame structures, this study proposes a performance-based seismic retrofitting design method utilizing a series-parallel-Ⅱ inerter system. A dynamic model of an RC frame structure equipped with the series-parallel-Ⅱ inerter system is established. By defining dimensionless parameters including the inertance ratio, damping ratio, and stiffness ratio, the structural displacement transfer function is derived. Based on the principle that the transfer function reaches local peaks at fixed points, optimal design formulas for the inerter system parameters are deduced. A performance-based retrofitting design framework for existing RC frame structures is subsequently proposed. Taking a five-story school building in Shanghai as an engineering example, the retrofitted structure exhibits only a 1% shift in its fundamental natural period, indicating that the tuned design of the inerter system preserves the original dynamic characteristics. Elastoplastic time-history analysis shows that the maximum inter-story drift ratios of the structure in the X- and Y-directions under rare earthquakes were reduced from 1/111 and 1/130 to 1/303 and 1/280, respectively, corresponding to reductions exceeding 57%. These results satisfy the performance objective of minor damage under rare earthquakes, validating the effectiveness of the proposed method in enhancing seismic performance while maintaining the inherent dynamic properties of existing structures.

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.

This paper introduces the design methodology for the 28-meter large cantilevered structure of the Investment Promotion Center and analyzes the mechanical properties and load-transfer mechanism of the large-span spatial cantilevered truss. Using construction mechanics analysis, the entire construction process was tracked and examined, with particular emphasis on internal forces （including strain） and deformations of components during the steel structure installation and concrete slab pouring stages. A comparison with conventional design methods revealed their limitations. To address stress issues in the concrete slab of the large cantilevered structure, a new approach is proposed, which involves selecting an appropriate pouring time in combination with the preloading method to control slab stress. The study offers a valuable reference for the design of similar structures.