Abstract:In recent years， modular architecture has developed rapidly in China， and the technical stamdard system has been graduallg established. A simplified equivalent frame calculation model of the modular unit with an ultra-high performance concrete （UHPC） core column was established based on the stiffness equivalence principle. Finite element calculations and experimental results， including the lateral cyclic loading tests and the pseudo dynamic tests， were compared and analyzed to verify the effectiveness of the model. Based on the proposed simplified model， the seismic performance of a six-story UHPC building structure was analyzed by Midas Gen. The calculation results show that the elastic deformation ability of the structure is excellent under frequent earthquakes， which meets the requirements of the fortification level of “no damage under frequent earthquakes”. Under the action of rare earthquakes， the damage is concentrated in the connecting of module units， and the structure remains upright after the earthquakes， which meets the requirements of the fortification level of “no collapse under rare earthquakes”.

Abstract:To study the seismic performance of double steel plates and recycled concrete composite shear walls， three groups of quasi-static loading tests with varying shear-to-span ratios were designed and completed. A numerical model was established based on these experiments to investigate the impact of recycled aggregate replacement rate and concrete strength on seismic performance. The test results indicated that the buckling phenomenon predominantly took place at the bottom of the specimens for the structural steel plates， and the shear-to-span ratio emerged as a critical factor influencing the structural failure. As the shear-to-span ratio increased， the failure mode of the specimens transitioned from shear failure to flexural failure， accompanied by noticeable bolt traces on the surface of the steel plates. As the shear-to-span ratio was increased from 1 to 1.5 and 2， the ultimate load was decreased by 25.9% and 45.0%， respectively， while the displacement ductility coefficient was increased by 9.2% and 29.7%， and the equivalent viscous damping coefficient was increased by 26.0% and 89.3%. Each specimen exhibited a failure displacement angle ranging from 1/63 to 1/45， satisfying the seismic design code requirements and demonstrating excellent deformation performance. Numerical simulations demonstrated that enhancing the strength grade of recycled concrete can significantly enhance the initial lateral stiffness and ultimate bearing capacity of the specimens. Both reducing the axial compression ratio and augmenting the strength of the external steel plates can enhance the shear capacity and lateral stiffness of the specimens. By considering the synergistic effects of concrete and steel plates and aligning with the existing design codes， a composite shear wall calculation formula was proposed， incorporating an 8%~15% redundancy factor to ensure conservative and reasonable calculation outcomes.

Abstract:A new energy dissipation device known as the low-yield-point steel corrugated pipe damper （CPD） is proposed for base-isolated structures， which possesses outstanding characteristics such as the same mechanical properties in all horizontal directions and large deformation capacity. Firstly， low-cycle reciprocating loading tests were conducted to investigate the failure mode， hysteresis characteristics， load-bearing capacity， deformation characteristics， and energy dissipation capacity of the damper. The influence of structural parameters such as corrugation height and average diameter on the mechanical performance of the damper was also tested. Subsequently， a finite element model of the low-yield point steel corrugated pipe damper was established using ABAQUS to methodically investigate the influence mechanism sof construction parameters on mechanical performance. Based on simulation analysis results， prediction formulas for mechanical performance indicators of the damper were provided. The results revealed that the failure mainly concentrated on the corrugated pipe that was consistent with the loading direction and close to the connecting plates， while the deformation on the corrugated pipe that was perpendicular to the loading direction was small. All damper specimen exhibited comparatively full hysteretic loops， demonstrating superior energy dissipation capacity and exceptional resistance to large horizontal deformations. All dampers had undergone obvious yielding and strengthening processes， the horizontal stiffness of the dampers was large before yield and decreased significantly after yield， only 20%~32% of that before yield. Increasing the height or decreasing the diameter of the corrugated pipe can reduce the bearing capacity， horizontal stiffness， and energy dissipation capacity， but enhance the deformation capacity of the damper. Increasing the strength and thickness of the corrugated pipe can significantly improve the bearing capacity， and energy dissipation capacity of the damper. The proposed computational formula can accurately predict the fundamental mechanical performance of the damper.

Abstract:To make up for the deficiency of the existing shear bearing capacity model of reinforced concrete beams with openings， a unified shear bearing capacity model was established based on the codes， considering the parameters such as the failure mode， opening shape， opening size， opening position （horizontal and vertical）， reinforcement form and concrete strength. Based on 159 test data， the unified shear bearing capacity model was estabished according to the existing codes， and the test data were used to evaluate the existing model and the unified model. The results showed that it was reasonable to establish the shear strength model according to the failure modes. The unified shear bearing capacity model had a high degree of accuracy. The average value AV， the integral absolute error IAE， and the mean relative error MRE of the shear bearing capacity model under the opening side shear compression failure mode were 1.035， 0.177， and 0.231， respectively. The AV， IAE， and MRE of the shear bearing capacity model under the shear failure mode of the chord were 1.007， 0.166， and 0.212， respectively. With the increase in concrete strength， the reliability index β gradually increased. With the increase of the opening height， the reliability index β decreased gradually. When the opening height was 0.5de （sectional effective height）， the reliability index β can still meet the requirements of the code. It is suggested that the opening height should not exceed 0.4de. In a word， the unified shear bearing capacity model established in this paper has high applicability， accuracy， and reliability.

Abstract:In order to investigate the mechanical behavior of RBP-UHPC （retard-bonded prestressed ultra-high performance concrete） cantilever beam， two full-scale RBP-UHPC variable section cantilever beams were tested based on the background of the cantilever stairs in Shanghai Opera House. The test results show that during the loading process， the key variable sections cracked in turn， and the cracks were most dense near the key sections. The farther away from the key variable sections， the shorter and sparser the cracks were. The failure position of the cantilever beam was 2.6 m away from the root of the beam. The closer the section was to the failure section， the sooner the strain of UHPC and rebar reached the elastic compressive strain of UHPC and the yield strain of the rebar. The safety margin of the failure section of the two beams was 1.97 and 1.81 respectively， which had good structural performance and can meet the strength requirements of practical engineering. A calculation model for the ultimate bending moment of RBP-UHPC π-shaped variable section cantilever beam with structural plate was proposed. Compared with the existing codes， the calculated results of the model in this paper were in the best agreement with the experimental results and were safer.

Abstract:In order to clarify the effect of different interfacial shear connection arrangements on the flexural performance of ultra-high performance concrete （UHPC） composite beams， an experimental study on the flexural performance of three steel-UHPC composite beams with different interfacial stud arrangements was completed. A nonlinear analysis method for the flexural performance of steel-UHPC composite beams based on a cross-sectional fiber model is proposed and the corresponding calculation program is compiled. The applicability of the method and program is verified by the test results. The influence of the cluster degree and shear connection degree on the flexural performance of steel-UHPC composite beams is analyzed through the developed models. The results show that： 1） For steel-UHPC composite beams with cluster degree γ≤0.5 and γ=1， the critical shear connection degrees are 0.9 and 0.74， respectively； 2） The flexural stiffness of steel-UHPC composite beam increases with the increase of the shear connection degree， but decreases with the increase of the bunching degree； 3） The shear connection degree has a significant effect on the flexural capacity and ductility coefficient of steel-UHPC composite beams. The ductility coefficient of composite beams with cluster degree γ=1 increases obviously， but when cluster degree γ≤0.5， the ductility coefficient is basically no longer affected by cluster degree. 4） For fully shear connected composite beams， the shear distribution at the interface tends to be uneven with the increase of shear connection degree at the ultimate limit state， but the cluster degree has little influence on the shear distribution at the interface at the ultimate limit state. The cluster degree γ of the steel-UHPC composite beam should not be greater than 0.5， and the shear connection degree η should not be less than 1.0.

Abstract:Modular steel structures have been developed in the background of industrialization and green development of construction. Widespread attention has been paid to the demountable modular steel structure due to its ability to reduce transportation costs greatly. Joints are key components in demountable structures and have a significant impact on the overall performance of structures. However， demountable joints are often complex in construction and the transmission paths of force are unclear. This paper analyzed the stress performance of the irregular beam-column joint in demountable modular steel structures by completing in-plane bending tests of two joints. It was found that high-strength bolts and plates fastened by them were the controlling factors of joint stiffness. Subsequently， a reliable numerical model was established to further study the rotational performance of the joint in different planes and directions of rotation， and it was determined as a semi-rigid joint according to EC3. Based on numerical analysis and theoretical derivation， approximate calculation models for the initial rotational stiffness and ultimate bending moment of the joint were proposed， respectively. Finally， a power function model was used to describe the semi-rigid performance of the joint， and the approximate model’s moment-rotation curve fitted well with the numerical results.

Abstract:Accurate identification of influencing factors of fretting fatigue is crucial for its assessment and control. To address the fracture problem of AA2024-T351 alloy under fretting fatigue， this study utilizes a crystal plasticity finite element model that incorporates microstructural sensitivity to investigate the impact of grain gradient representation on fretting fatigue in the AA2024-T351 alloy. Additionally， a submodel approach is employed to calculate the contact region of the fretting fatigue specimens， and the cumulative plastic slip is analyzed to determine the crack initiation location and predict crack initiation life. The study reveals that the grain gradient results in an uneven distribution of stress fields within metallic materials due to variations in grain sizes and grain boundary conditions. Compared to the fretting fatigue contact surface， the grain gradient exhibits a significant change in crack initiation locations in the subsurface. Moreover， the grain gradient evidently affects the crack initiation life of fretting fatigue. The research findings indicate that the distribution of grain gradient alters the plastic deformation characteristics between grains. As the grain gradient increases， the subsurface crack initiation life gradually surpasses that of the contact surface. The variation in grain gradient significantly influences the subsurface crack nucleation locations， thereby determining the tendencies of crack propagation. Building upon these research conclusions， modifying the grain gradient distribution through material processing methods effectively mitigates the crack initiation and propagation of fretting fatigue.

Abstract:To develop a damage assessment model applicable to a glued-laminated timber post and beam structural system and gain insights into its behavior under seismic conditions， a series of tests were conducted on four full-scale specimens subjected to horizontal loading. Various aspects， including the presence or absence of braces， different horizontal loading procedures， and two types of K-braces were taken into account. The obtained test results indicate that the failure mode of the pure framework is primarily concentrated at the joints and accompanied by large horizontad deformation. In contrast， specimens equipped with K-braces predominantly experienced failure modes marked by the instability of the brace components. Integrating the K-brace into the glued-laminated timber post and beam structural system effectively enhances the structure’s stiffness and maximum load-carrying capacity while reducing lateral deformations. Additionally， based on the experimental data and the failure characteristics of the specimens， a dual-parameter evaluation model considering deformation and energy dissipation was proposed. This model was capable of reflecting the damage caused by large deformations in the early stages of specimen failure and had the potential to provide a reliable theoretical basis for the reinforcement and design of the glued-laminated timber post and beam structural system and their supported components.

Abstract:In order to study the application effect of eddy current damper in the field of seismic reduction of super-wide single-rib tied arch bridge， the longitudinal and transverse eddy current dampers are set at the active bearing position of the girder of a new composite structure system of a flexible single rib tied arch bridge with backstays on an ultra-wide bridge deck， respectively. The nonlinear time history analysis method is used to calculate the motion response of the structure under earthquake. In order to facilitate the calculation and application of the eddy current damper， the damping force model was simplified， and the validity of the simplified model was verified by experiments. Finally， the relative displacement between the pier and girder， and the internal force of the arch feet are taken as the evaluation indexes to study the influence of viriable eddy current damper parameters on the seismic response of the structure. The results show that the out-of-plane stiffness of the structure system is low， and it is prone to lateral overturning under earthquake. The structure has high requirements on the bearing capacity of the arch foot. The double broken line model can be approximately equivalent to the nonlinear damping force model of eddy current dampers， which is used to describe the mechanical properties of the eddy current damper . The installation of eddy current dampers can effectively reduce the dynamic response of the bridge structure under earthquake. When the maximum damping force of the damper is determined， the seismic motion response of the structure shows a significant downward trend with the increase of the equivalent damping coefficient. The speed of decline is fast first and then slow， and finally tends to a level after the damping coefficient reaches a certain threshold. The maximum damping force parameter determines the upper limit of the damping force of the eddy current damper. When the equivalent damping coefficient is constant， the motion response of each node of the structure continues to decrease with the increase of the maximum damping force within a certain range.

Abstract:Bearing plates installed at the bottom of the box girder in the compression zone at the pier-beam joint of the box-shaped composite rigid frame bridge can increase the compression area and avoid stress concentration and local buckling of the box girder bottom plate. The force transmission mechanism and applicability of bearing plate typed pier-beam joint are not clear. The design method of the joint construction is lacking. According to the verified solid finite element calculation model， the trial design of the box-shaped composite rigid frame bridge with bearing plates is conducted. The force transmission mechanism and load bearing ratio of the bearing plate typed pier-beam joint are analyzed. A calculation method of the internal force of the pier-beam joint is established， and a parameter analysis of the arrangement of bearing plates is carried out. Results indicate that， on the basis of determining the dimensions and material characteristics of the trial design， axial pressure and axial tension are mainly transmitted through the web plate of the girder， accounting for about 60% and 50%， respectively. The force transmission mechanism of bending moment action is similar to that of axial force. The shear force is mainly transmitted through the longitudinal stiffeners on the back side， accounting for about -80%； The shear force is mainly transmitted through the bearing plate on the same side， accounting for about 80%. The deviation between the theoretical calculation results and the finite element calculation results is less than 8.8%. The theoretical calculation can be applied to the internal force calculation of the bearing plate typed pier-beam joint. It is suggested that the relative transverse spacing should be 1/6 and the relative plate thickness should be 1 in the design of bearing plate. When the pier height exceeds 15 m， the beam-pier linear stiffness ratio is greater than 0.047， and the steel girder stress of the bearing plate typed pier-beam joint is less than that of the conventional pier-beam joint. When the pier height exceeds 30m， the steel girder stress at the pier-beam joint of the box-shaped composite rigid frame bridge can be significantly reduced by using the bearing plates.

Abstract:In order to study the influence of the simulated pulsating wind field with the traditional exponential decay coefficient Cy on the buffeting response of long-span suspension bridges， frequency and time domain methods were first applied for buffeting response analysis taking three long-span suspension bridges ranging from 1 000 m to 2 000 m as the background. The results indicate that the buffet response from the time domain method， considering factors like wind load nonlinearity， is safer. Based on the time domain method， reponsesat the different spanwise position of the suspension bridge under different Cy values was analyzed. The buffet response was compared with the buffet response when Cy=16 recommended by Davenport. The results show that the buffet response of the suspension bridge does not simply change linearly with the change of Cy. The buffet displacement RMS value of the three suspension bridges at the mid-span position always remains the largest under different values of Cy； When Cy is 14， the maximum values of the vertical， lateral and torsional angular displacement response RMS values of the suspension bridge are larger than those when Cy=16， which are 1.5%， 14.6% and 26.3%， respectively. The results of the buffeting response analysis of large-span suspension bridges using Davenport’s recommended values are dangerous. When performing the most unfavorable buffeting response analysis， it is recommended to select multiple groups of Cy values for calculation.

Abstract:Traditional consolidation theory mostly based on small-strain assumption is not suitable for soft clay consolidation with large strain. Herein， a one-dimensional nonlinear large-strain consolidation model of soft soils considering non-Darcy flow and arbitrary loads was established based on the double logarithmic permeability compression model to predict the consolidation settlement of large-strain soft soil. The numerical solution to the consolidation equation was derived using the finite difference method. The reliability of this numerical solution was verified through comparison with analytical solutions and laboratory experiments. Based on the solutions， this study analyzes the impact of compression index （Ic）， permeation model parameter （α）， non-Darcy parameters （m， i1）， loading duration， and arbitrary load on soil consolidation settlement. The results indicate that under any arbitrary load， the greater Ic and α result in a smaller average degree of consolidation and the slower dissipation of excess pore water pressure， although the final settlement of soft soil consolidation settlement is only related to the size of the Ic； the greater non-Darcy parameters m and i1 results in the longer time needed to reach the final settlement value during the consolidation settlement process of the soft soil layer， which means that at the same moment in the consolidation process， the settlement of the soil layer is small. As the duration of the construction load and exponential load increases， the settlement rate of the soil layer slows down， while increasing the load cycle of the cyclic load speeds up the rate of soil layer settlement. In addition， compared to other loads， the behavior of soft soil consolidation under cyclic loading shows an obvious periodicity. These findings further enrich the theory of one-dimensional large strain consolidation for soft soil foundations， providing theoretical support for the construction of such grounds.

Abstract:The long-term service performance of road structures is closely related to the subgrade humidification state. To study the moisture-controlling effect of fine-grained soil subgrade under rainfall infiltration， the typical silty clay subgrade fills in the middle and lower reaches of the Yellow River basin in China were selected in this paper. The hydrodynamic properties of silty clay and wicking geotextile were obtained based on the test of the pressure plate instrument， and the physical model of wicking geotextile-reinforced silty clay was constructed to investigate the migration of the water in the silty clay fill under different rainfall intensities. The development of soil moisture content and matric suction was obtained with or without the wicking geotextile. Results indicate that the wicking geotextile has a higher lateral permeability coefficient （2.2 cm/s）， lower water-holding capacity， and air entry value （2.8 kPa）， which can realize the lateral drainage of water under low matric suction. The migration of water inside the soil under rainfall infiltration is subjected to the combined effect of gravity potential and matric potential， and the existence of the wicking geotextile can increase the matric suction of the soil layer by 5.1~34 kPa. The soil above the geotextile is driven by gravity potential and matric potential together， and the moisture migrates from up to down. However， for the soil below the geotextile， the matric potential needs to overcome the effect of gravity potential， and drive the moisture to migrate from down to up. The moisture content of the wicking geotextile-reinforced soil is reduced from 13.8% （light rain）~17.2% （heavy rain） in the control group to 12.6% （light rain） ~ 14.0% （heavy rain）， which can be effectively controlled within ωopt+2%， which is of great practical value for guaranteeing the long-term service life of the roadbed pavement.

Abstract:In order to investigate the mechanical properties of face-based mixed milling planes and their ontological model that is not unspecified yet. Based on the triaxial test， a nonlinear shear expansion constitutive model was constructed based on the Duncan-Chang model and the Pastor-Zienkiewicz shear expansion equation， and the stiffness matrix of this constitutive model was derived by applying the theory of infra-elasticity. Moreover， the model was developed twice with the help of the UMAT subroutine of the ABAQUS finite element software platform， which verified the model accuracy and reliability of the model. In addition， the overall sensitivity analysis and the response surface analysis of the key parameters of the model were also carried out. The results show that at about 10% axial strain， the strength of the two materials gradually reaches the residual strength under different circumferential pressures， and the volumetric strain and axial strain show a tendency to decrease and then increase， and exhibit obvious shear expansion characteristics within a certain range. The triaxial tests were simulated using a second developed UMAT subroutine， and the results showed a high degree of agreement when compared to the test results. The study index deviatoric stresses （σ1-σ3） are particularly affected by the parameters φ0，

Abstract:For the special characteristics of the behaviours of following， changing lanes and stopping in the mixed traffic flow of automated driving bus and manually driven cars， a vehicle lane-changing model considering the influence of automated driving bus is proposed based on the theory of cellular automata to study the characteristics of the mixed traffic flow containing automated driving bus. Based on the driving characteristics of automated vehicles and combined with the driving characteristics of buses at bus stops， the road sections were divided and the following and lane changing rules for autonomous buses， normal buses， and cars were constructed， respectively. Based on numerical simulation experiments， the traffic flow characteristics under different traffic densities and bus ratios were analysed. The results show that under the same road traffic conditions， the bay bus stop interferes less with the road traffic， and the lane changing and stopping behaviours of the automated driving bus have less impact on the road traffic than those of the normal bus.

Abstract:Due to its significant superiority in withstanding high internal water pressure， prestressed double-layer lining structures have been gradually widely used in water conveyance shield tunnels in recent years. To unveil the mechanical properties of the prestressed double-layer lining structure， this study innovatively employs a similar model test method combined with acoustic emission detection technology， taking the water conveyance shield tunnel of the Zhujiang Delta Water Resources Allocation Engineering as a prototype. The internal forces， contact pressures， displacements， and damage and failure of the prestressed double-layer lining structure throughout the construction and operation process are analysed. The experimental results indicate that： during the assembly stage， the segmental lining structure can independently bear the external hydrostatic and earth pressures. During the prestressing tensioning stage， both the segmental and prestressed linings are compressed around the entire circumference. As the internal water pressure is progressively applied， the axial force of the structure gradually decreases. However， under 1.5 MPa of internal water pressure， the structure still maintains most of its area under pressure. During the prestressing tensioning stage， the segmental lining and prestressed lining separate， suggesting their interaction can be essentially disregarded. During the operation stage， the areas of separation close， thus the two structures bear the load in coordination. With the progressive tensioning of the prestress， the displacement of the double-layer lining structure increases linearly， reaching its maximum value of 1.37 mm upon completion of tensioning. At this point， the section’s ellipticity is 0.012‰. The application of 1.5 MPa of internal water pressure reduces the displacement to 1.30 mm and increases the section's ellipticity to 0.20‰. During the entire loading process， the progressive damage of the double-layer lining structure undergoes an initial elastic stage and a micro-damage stage. Inside the structure， defects compact and gradually lead to damage， but no macro-cracks appear， indicating that the structure remains in a safe state.

Abstract:To investigate the performance of the belled tilted bracing， field static load tests were conducted on single piles to explore the bearing characteristics of the belled tilted strut with a bearing stratum of medium-dense silty sands. The results revealed a gradually varying Q-s curve development pattern， indicating that the strut exhibited typical end-bearing pile behavior. Three-dimensional numerical simulations exceeding the in-situ test load range were performed for single parametric analysis to identify key design factors influencing the bearing capacity of one belled tilted strut. The analysis demonstrates that the bearing stratum at the pile tip should be rationally selected according to the site geological conditions， and the reasonable bracing length can be comprehensively determined considering the slenderness ratio of concrete-filled tube. Additionally， increasing the bearing base volume significantly enhances bearing performance without compromising construction efficiency or adjacent pile safety. These findings provide guidance for the design and calculation of practical applications of belled tilted struts.

Abstract:This paper conducts a systematic study on the difficulty of accurately generating ortho-grayscale images of tunnels of any shape using point clouds obtained from mobile laser scanning. The study first obtains tunnel point cloud data using the self-developed TLSD （Tunnel Laser Scanning Detection） mobile tunnel detection system， and integrates distance threshold methods， image enhancement algorithms， clustering algorithms， and thinning algorithms to effectively handle redundant and abnormal information in the initial point cloud. On this basis， a method for generating tunnel ortho images combining longitudinal and circumferential calibration is proposed. The longitudinal calibration method uses the spacing between sleepers as a quantitative benchmark and combines intelligent labeling software to achieve effective longitudinal calibration of tunnel point cloud data. In the circumferential calibration algorithm， this paper first performs circumferential polygon fitting of the tunnel point cloud based on the Douglas-Peucker algorithm， followed by a projection center transformation. Finally， based on the equidistant division method proposed in this paper， the tunnel cross-section point cloud is simplified and calibrated to produce a grayscale image that matches the actual physical space， achieving efficient construction of ortho images of tunnels with any morphology. Test results show that the method developed in this paper can effectively improve the efficiency of measuring key geometric information and disease statistics in tunnels. The measurement accuracy of tunnel defects such as cracks and leaks reaches the centimeter level， providing accurate quantitative analysis data for tunnel service performance evaluation and management.

Abstract:Dental practice procedures are accompanied by the production of large amounts of spattered particles， and prolonged exposure of healthcare workers to high concentrations of particles may lead to occupational health problems. To effectively remove spatter particles and reduce the exposure risk of medical staff， this study proposed a novel vortex exhaust hood with long-distance and high-action benefits. Numerical simulation was used to analyze the vortex exhaust hood's flow and particle removal characteristics， comparing it to the traditional top-suction exhaust hood. The optimal working conditions of the vortex exhaust hood were explored by analyzing the effects of the velocity ratio of air supply and exhaust， horizontal and vertical air supply angles on the axis velocity， pressure distribution， and particle removal efficiency of the vortex exhaust hood. Under the condition of ideal airflow parameters， the control effect of two kinds of exhaust hoods on particles with different splashing speeds was analyzed， and the application advantages of the vortex exhaust hood were explored. The results showed that the vortex hood achieved the best working conditions when the air supply and exhaust velocity ratio was 1 and the angle of horizontal and vertical air supply was 0°， respectively. The removal efficiency of particulate matter can reach 65.9%， which was better than that of 47% of the top-suction hood. This study confirms the application potential of the vortex exhaust hood in dental practice， provides a new method for local source control in dental procedures and has a reference value for the construction of prevention and control measures for the treatment micro-environment.