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.

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%.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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 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.

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.

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.

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.

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.

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.

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.

Ground motion spectral shape characteristics have a great importance to analysis of the seismic fragility of reinforced concrete frames. The incremental dynamic analysis （IDA） on a five-story reinforced concrete frame structure is carried out using 9 groups of ground motions which take into account the different parameters. Using the IDA, the seismic fragility curves corresponding to different damage states and collapse margin ratios （CMRs） are obtained based on the maximum inter-story drift ratio （θ_max）, the average values and dispersion of the maximum residual inter-story drift ratio （RIDR_max） corresponding to the 50% exceeding probability with different damage states and the limit of performance index of RIDR_max corresponding to different seismic performance grades are proposed. The results show that the conditional mean spectrum （CMS） of different spectral shape parameters （ε）, magnitude （M） and earthquake distance （R） significantly influence structure seismic fragility analysis; the ε, M and R have a significant influence on RIDR_max of the structure when the damage is small, but the effect will be no longer obvious when the damage is greater.

Precast concrete small box girders are extensively adopted in China owing to their lightweight, high construction efficiency, and cost-effectiveness. However, strength variations between wet joints and box girder concrete may trigger differential shrinkage and creep during construction, potentially causing early cracking. Consequently, selecting appropriate materials for repair and pre-maintenance is paramount. This study investigates the mechanical properties of three cementitious crystalline waterproofing materials （Oriental Yuhong PCC-501, Kaiton T1, and Cybers Concentrate）, one interface agent （Huanyu Xiupu-SP）, and two high-strength mortars （Huanyu Xiupu SJ40F and Sikadur 31CFN）. All experiments were conducted in strict compliance with relevant standards, encompassing tests for wet surface bonding strength, compressive strength, and flexural strength. Furthermore, twelve brushing schemes with varying application sequences were designed for bridge implementation, with the optimal construction order determined through field analysis. The results demonstrate that among the cementitious materials, Oriental Yuhong exhibits the highest wet substrate bonding strength, while Kaiton achieves superior impermeability. The interface agent attains a 14-day tensile bond strength exceeding the minimum standard requirement. Among high-strength mortar materials, Sikadur 31CFN demonstrates optimal performance in flexural, compressive, and tensile strength. The optimal brushing sequence entails the sequential application of cementitious crystalline waterproofing materials, interface agents, and high-strength mortars. However, further research is necessary to identify the most effective material combinations.

The study of the mechanical behavior of a single pile under lateral loads is an important topic in geotechnical engineering. Among various methods, the p-y curve method considers the soil nonlinearity and provides a more accurate reflection of the pile's horizontal bearing behavior compared to the traditional “m” method. Most existing p-y curve models are based on summaries of experimental data, with unclear physical meanings of model parameters and difficulties in determining their values. Therefore, a p-y curve model that reasonably considers the stress-strain characteristics of soil is established based on the pile-soil interaction mechanism. Firstly, based on the Airy stress function, the stress distribution function of the soil around the pile is obtained. Subsequently, the Duncan-Chang model and the small strain model are introduced to describe the small strain nonlinearity of the soil elements around the pile. The p-y curve expression for a laterally loaded pile is ultimately obtained by integrating the strain of the soil. The required parameters of this p-y curve, such as E₅₀ and S_u, can be obtained from consolidated undrained triaxial tests or field tests, while small strain parameters G₀ and γ_0.7 can be obtained from resonant column tests or wave velocity tests. Finally, through comparison with field tests, model tests, and the API code methods, the accuracy and practicality of this p-y curve model are verified.

In order to study the freeze-thaw performance of mortar in roofing structure, the freeze-thaw cycles tests were carried out on three roof models of different types of mortar, and the damage evolution rules of three types of mortar were analyzed. The development law of strain of different types of mortar under freeze-thaw environment was studied by using refined finite element model, and the rationality of the test results was verified. The finite element simulation and test results show that the tensile strain of cement mortar is large under the action of freeze-thaw cycles. In the 50th cycle, the strain value has reached 100 με, indicating that cement mortar has cracked, and the strain peak value continues to increase with the increase of freeze-thaw cycles. The peak strain of polymer mortar and polypropylene fiber mortar is small, and the peak strain of the two mortars does not increase with the increase of the number of freeze-thaw cycles within 100 times of freeze-thaw cycles, so the polymer mortar or polypropylene fiber mortar has a better freeze-thaw performance.

A large number of medical equipments in the hospital building are movable with casters, which are prone to large slippage and easy to disconnect from the power plug or collide with other objects under earthquakes, thus adversely affecting the medical function of the hospital. In this paper, based on the calculation formula of the slip response of rigid blocks, a large number of incremental dynamic time history analyses are carried out on wheeled medical devices with different caster states. The horizontal excitation input considers the different floor acceleration responses of typical hospital buildings （seismic isolated, non-isolated） under different site characteristic periodic ground motion sets. The analysis results show that the use of PFV （floor peak velocity） as the floor motion intensity index of wheeled medical equipment can effectively reduce the discreteness of the vulnerability data. The site characteristic period, floor location and dynamic characteristics of the building structure have little influence on the fragility of wheeled medical equipment, while the state of casters has a greater impact, and the wheeled equipment when the casters are locked is less susceptible to damage. Finally, the fragility curve of wheeled medical equipment is proposed, which can be used in the subsequent evaluation of the seismic resilience of hospital buildings.

To investigate the bearing capacity and restoring force model of steel tube-eolian sand recycled concrete columns, five specimens with varying eolian sand replacement ratios were designed, and pseudo-static tests were conducted. A comparative analysis was performed on the hysteresis curves, backbone curves, and stiffness degradation of each specimen. The experimental results indicated that the specimen with a 30% eolian sand replacement ratio exhibited relatively superior seismic performance. Based on the experimental data, as well as the established backbone curve model and stiffness unloading equation, a restoring force model for the column was developed. This model accurately reflects the hysteresis characteristics of the specimen and is suitable for elastoplastic seismic response analysis of steel tube-eolian sand recycled concrete columns.

To assess stirrup stress in reinforced concrete beams under concentrated loads, ATENA software was employed to perform nonlinear finite element analysis of shear behavior in test beams. This study compiled shear test data from 158 reinforced concrete beams with stirrups subjected to concentrated loads （shear-span ratio ≥2.5）. Using a validated finite element model, we calculated the stress in stirrups intersected by the critical diagonal crack at the ultimate limit state of bearing capacity. Results demonstrate that the 45° truss model substantially underestimates stirrup shear resistance in ultimate limit state conditions. We recommend revising GB/T 50010—2010 （Code for Design of Concrete Structures） to adopt a stirrup effectiveness coefficient of 1.25 in the shear capacity design formula for reinforced concrete beams, along with corresponding adjustments to the concrete contribution term.

To ensure that the PHC short pile foundation of the heliostats meets the accuracy requirements of pile top deformation, this paper relies on a single pile horizontal static load test of a certain project and uses ABAQUS finite element analysis software to conduct nonlinear numerical analysis of the pile-soil integration under pile top static load. By comparing the numerical simulation results with the experimental data, the accuracy of the numerical calculation model is verified, and based on this, the foundation design is carried out. Four measures to improve the anti deformation ability of the short pile structure are proposed, and the enhancement effect is compared and analyzed from three aspects： the bending moment distribution map of the pile body, the displacement distribution map of the pile body below the ground, and the load displacement curve of the pile top. The following conclusions are drawn through analysis： the foundation designed in this article meets the requirements of deformation and crack resistance; Under the soil conditions of this project, when L_u is less than 4.66 m and L_d is greater than 4.34 m, and the bending moment of the pile at the ground meets the crack resistance requirements, the horizontal displacement of the pile top can meet the requirement of less than 25mm; The measures 1, 3, and 4 proposed in this article can enhance the ability of the pile body to resist deformation, while measure 2 has limited effectiveness. In engineering, one or more of these measures can be referred to as needed to improve the stiffness of the pile body and achieve the goal of controlling deformation.

The internal force distribution of the high-level well is complex and variable in different construction stages, and the construction design can only be carried out after clarifying the internal force distribution. This article is based on the construction of a high-level well Jiaxing City. A numerical software is used to establish a model and study the distribution and variation of internal forces in each stage of the construction. The results show that the axial force on the wellbore changes from a compressed state to a tensile state. The magnitude of the axial force increases linearly with depth in the sinking stage, while in other stages, it shows a pattern of small upward and large downward; The maximum bending moment is relatively small in the sinking stage, significantly increases in the bottom sealing stage, increases in the horizontal bending moment and decreases in the vertical bending moment during the top pipe stage, and increases in both the operating and long-term operating stages; The underground section is basically the same as the operating phase. According to the calculation results of internal forces, the thickness of the wellbore can be optimized to a variable thickness, and the above ground section steel bars can be optimized to be prestressed steel bars to resist the influence of temperature difference. The internal force analysis results and optimization design ideas in this article can provide reference and inspiration for similar projects in the future.

This study proposes a lightweight and industrialized pretensioned composite small box girder structure combining Ultra-High Performance Concrete （UHPC） and ordinary concrete （NC）, leveraging the superior mechanical properties of UHPC. Compliance verification with the Swiss ultra-high performance fibre reinforced concrete structural code and the Chinese bridge design code confirms that the composite beam satisfies Class A prestressed component requirements while achieving a 30% weight reduction compared to conventional NC box girders of identical span. To validate flexural performance, a bending failure test was conducted on a scaled specimen. As observed, upon ordinary reinforcement yielding, the UHPC at the bottom edge completed tensile strain hardening with strains of 1 930-2 100 με, developing fine cracks below 0.2 mm width. Steel strand yielding marked the stiffness degradation inflection point, where UHPC compressive strain at the top edge reached 1 060 με （below its ultimate strain）, followed by steel fiber pullout and tensile zone stress redistribution. Final failure occurred due to NC top slab crushing, yielding a displacement ductility coefficient of 2.3. Scaling analysis incorporating a structural importance factor of 1.1 indicates that for the prototype beam, the partial factor for vehicle loads under fundamental combinations is 2.03 （exceeding the standard 1.4）, while the frequent value coefficient under frequent combinations is 0.87 （surpassing the standard 0.7）. The pretensioned system demonstrates enhanced prestressing efficiency in UHPC sections and effective post-cracking material collaboration, confirming its viability for practical applications.

In recent years, the concept of prefabricated assembly bridges has extended from superstructures to substructures, and it is rapidly advancing towards fully prefabricated bridge construction. As a major form of modular prefabricated components for bridge piers, centrifugally prefabricated reinforced concrete pipe piers have realized industrialized manufacturing. However, there is still a lack of necessary research on their mechanical properties under lateral low frequency cyclic loading. This study employs numerical simulation verified by test data to analyze and compare the seismic performance under lateral low frequency cyclic loading between socketed centrifugally prefabricated pipe piers and cast-in-place solid piers that has been widely applied. The results indicate that socketed prefabricated piers possess equal seismic resistance to that of cast-in-place piers, thus having a broad range of engineering applications in assembly bridge constructions. Finally, the study analyzes the primary factors which influence the seismic performance of centrifugally prefabricated pipe piers and provides recommendations for improving their seismic resistance for future engineering practices.

This paper addresses key design considerations for single-layer mesh shell structures in public service projects in Jiaxing City, Zhejiang Province, encompassing mesh and component selection, extraction and division of structural benchmark surfaces, support configuration, primary load determination, structural stress analysis, and node design. The results demonstrate that a rationally designed single-layer steel mesh shell structure can support heavier roof ceramic panel systems with reduced member dimensions. Utilizing the Grasshopper component in Rhino software enables precise control of model data. Through analysis and statistical calculation of internal forces, diverse support forms are implemented to optimize support costs. By integrating spatial geometry and building functions, structural components and columns are strategically arranged to enhance grid shell stability. The computational process incorporates wind load data from wind tunnel tests and temperature stress effects. Design values are derived by enveloping results from combined and individual modeling analyses, with stress ratios, displacements, stability, and node strength all satisfying code requirements.

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.