The waste silty clay slurry produced during shield construction has the characteristics of high water content, low strength and small particle size and it has difficulties in rapid consolidation. How to effectively dehydrate and cure is the key to reduce environmental pollution in the process of transportation or storage. Based on the self-developed waste slurry vacuum dehydration device, this study carried out indoor dehydration model tests under four different forms of dead weight, dead weight and vacuum, dead weight stabilization and vacuum, dead weight stabilization and graded vacuum. It analyzed the distribution laws of sediment-water interface settlement, pore water pressure, dehydration volume and residual slurry moisture content after dehydration of waste silty clay slurry under different loading modes. Finally, the dewatering effect of the waste silty clay slurry was compared under different loading modes. The test results show that among the four dewatering methods, the loading method of first dewatering the waste silty clay slurry by self weight, and then applying vacuum to the bottom part of the waste silty clay slurry has the best dewatering effect on the waste silty clay slurry, which can effectively reduce the water content of the waste silty clay slurry. After dewatering the waste silty clay slurry with initial water content of 97.50%, the water content distribution range is 28.21%~34.25%, and the minimum pore water pressure can reach -72.92 kPa. Meanwhile, based on the idea of segmented linearization, a one-dimensional dehydration theoretical analysis model for waste slurry was established. This model numerically simulates the sedimentation of the sediment-water interface during the dehydration process of waste silty clay slurry, and compares the results of numerical simulation with the test results. Then the optimal loading method was explored by simulation analysis of dehydration efficiency under different loading modes. This study can provide a theoretical and practical basis for the rapid dehydration treatment of shield waste silty clay slurry.

This study carried out triaxial undrained consolidation tests on undisturbed and remolded granite residual soil with different water contents and comparatively analyzed the effect of saturation on shear deformation characteristics of undisturbed and remodeled soils.Firstly, it obtained the relationship between matric suction and shear strength index by measuring the soil-water characteristic curve and established the unsaturated shear strength expression of the granite residual soil. The results show that the degree of strain-hardening of the undisturbed and remodeled soils increases with the increase of water content and confining pressure. The stress-strain curves of the undisturbed soils are softening and the remodeled soils are hardening under low water content and confining pressure. The change pattern of stress path with water content is basically the same in undisturbed soil and remodeled soil. With the decrease of water content, pore water pressure gradually decreases during shearing process, and the effective stress path gradually approaches the total stress path. The soil-water characteristic curve of granite residual soil can be divided into three stages: saturation, transition and residual. During the dehumidification process, the residual suction of undisturbed soil is larger than that of remolded soil, and the transition area is larger than that of remolded soil. In the state of high saturation, the water contents of undisturbed and remodeled soils change little with the increase of matric suction and begin to decrease significantly with matric suction reaching the air-entry value, and the water contents change slowly in the residual stage. The influence of matric suction on the internal friction angle of soil is very small; the cohesion increases with the increase of matric suction; the adsorption internal friction angle decreases gradually; and the contribution of matric suction to the soil shear strength decreases gradually. The influence of matric suction on the effective cohesion of undisturbed soil and remodeled soil is much greater than the effective internal friction angle. The unsaturated hyperbolic model established by the regression relationship between matric suction and suction strength has a good applicability for predicting the unsaturated shear strength of residual granite soil.

Pitting induced by the marine environment has a significant impact on the safety of steel structures and its form exhibits a strong multi-scale and multi-parameter randomness. In order to effectively detect and identify damage in actual engineering, this paper systematically investigates local random pitting of steel members via experimental study, numerical simulation, and theoretical analysis based on convolutional neural networks. Firstly, under the premise of following the distribution model of pitting corrosion pit depth and the time-varying model of pitting corrosion pit diameter, the boundary and cross restrictions were imposed on the position distribution of corrosion pits using multi-parameter local random pitting numerical model. Python was utilized to generate randomness in the size, location, and number of pits, allowing Abaqus to generate a large number of finite element models of steel plates with varying rust locations and rust rates, and the mode shape samples of each finite element model were obtained. Then, the finite element model was used as a test prototype, and a large number of samples of the first six-order vibration patterns obtained from numerical tests were used to train a convolutional neural network model for identifying damage location. The accuracy of the model was verified using the finite element data set. Finally, the vibration results of the ruler test were used to further verify the accuracy of the convolutional neural network model. The study shows that the model fully considers the randomness of pitting corrosion in aspects such as shape parameters and position coordinates. The parameters are reasonable, close to the actual pitting corrosion situation in reality, and the recognition accuracy is relatively high. In numerical tests, the model achieved 95.9% accuracy in identifying pitting damage to the real area and its adjacent areas, and 81.2% accuracy in full-scale tests, meeting the requirements for the practical intelligent application of identifying steel component damage.

The current standards have not yet specified the formula for calculating the bearing capacity of Π-shaped welded square tube joints. Based on experimental validation of finite element analysis accuracy, this paper utilizes Abaqus software to numerically simulate 85 sets of joints under axial load, obtaining the ultimate bearing capacity of Π-shaped joints. Subsequently, parameter analysis and regression analysis were conducted to identify factors influencing the ultimate bearing capacity of Π-shaped joints and the modified calculation formula. The results show that the width ratio of branch pipe to main pipe β has a great influence on the ultimate bearing capacity and initial stiffness of the joint. Increasing the width of branch pipe can significantly improve the ultimate bearing capacity of the joint. The load imposed on the branch pipe is jointly borne by the bending and shear effects on the upper surface of the main pipe and the side wall of the main pipe. The failure mode of the joint also depends on β. The larger the width thickness ratio of the main pipe 2 γ, it means that the connection area between the upper flange of the main pipe and the branch pipe becomes more slender, which reduces the bending stiffness of the upper flange of the main pipe, and therefore reduces the bearing capacity and initial stiffness of the joint. The branch pipe to main pipe height width ratio η and the branch pipe spacing have a certain impact on the ultimate bearing capacity of the joint. Increasing the height of the branch pipe section and the branch pipe clearance, that is, increasing the intersection area of the branch pipe and the main pipe along the longitudinal direction of the main pipe, makes the branch pipe transfer load in the wider area of the main pipe flange. The plastic area of the node is larger and the material is more fully utilized, thus improving the carrying capacity of the node. The thickness ratio of branch pipe to main pipe τ has little effect on the ultimate bearing capacity and initial stiffness of the joint. The increase of the wall thickness of the branch pipe improves the bearing capacity of the branch pipe, but the ultimate failure of the joint is the yield failure of the upper flange of the main pipe rather than the failure of the branch pipe. Therefore, the change of the thickness of the branch pipe has no obvious effect on the bearing capacity of the joint. Based on the analysis results of the finite element model, a parameter equation for calculating the ultimate bearing capacity of welded square tube Π-shaped joints was proposed through curve fitting, and the accuracy of this equation was evaluated, providing a reference for further research and engineering applications of such joints.

The constraint effect of rectangular steel pipe on core concrete has special characteristics, and the accurate prediction of the plastic development capacity of bending members can effectively ensure the load-bearing safety. In order to improve the calculation accuracy of the sectional strength of rectangular CFST members under pure bending, this study established a multi-factor model of plastic development coefficient and an improved bending strength model based on the confinement coefficient and further considering the influence of height-width ratio and steel ratio. First of all, based on the unified theory of CFST members, the change law of plastic development coefficient of rectangular concrete-filled steel tube was studied and compared with the current standard calculation formula. Then, combined with the specification and engineering needs, 2 160 numerical simulation components of rectangular CFST members under pure bending were constructed and the refined analysis of the fiber model method was conducted using the improved constitutive relationship and component failure criterion. The influence of width-thickness ratio, height-width ratio, steel ratio and strength ratio on plasticity development coefficient was investigated to determine that the height-width ratio and steel ratio are the main factors influencing the plasticity development coefficient, and the function expressions related to the height-width ratio and steel ratio were fitted through regression analysis. Thus the multi-factor model of plasticity development coefficient and strength calculation of rectangular CFST members under pure bending were established. Finally, the bending strength improvement model was verified against the main design specifications at home and abroad by using the 128 sets of experimental data collected. The results show that the established multi-factor model of plasticity development coefficient overcomes the defects of the current specification that the calculation model is not accurate enough, and it can more accurately reflect the plasticity development capacity of rectangular CFST members under pure bending. The established improvement model of the bending strength of rectangular CFST members under pure bending solved for the ratio of the ultimate load carrying capacity to the experimental value has a mean value of 0.971 and a root-mean-square error of 0.118, indicating a good match and a higher calculation accuracy.

To verify the rationality, reliability and fault tolerance of the “two-level and two-stage” seismic performance-based design method of Guangdong standard DBJ/T 15-92—2021 “Technical specification for concrete structures of high-rise buildings”, this study designed two batches of 1∶4 scale plane RC frame structure specimens with the same seismic structure grade of first-level, second-level and third-level. During loading, iron counterweights were arranged on each floor to simulate the distributed load, and the influence of floor and floor load on the failure mechanism of frame structure was considered. The test adopted displacement-controlled single-point loading. The loading point is located at the elevation of the three-story floor beam. Before the longitudinal reinforcement of the column reaches the yield strain, it is single-cycle loading, and after the yield, it is three-cycle loading. Through the pseudo-static test, the seismic failure mode and failure mechanism of the structure were investigated, and the evolution law of seismic performance indexes such as hysteresis curves, ductility, stiffness and energy dissipation was analyzed. The test results show that the plastic hinge development paths of the specimen damage are basically the same, which conforms to the failure mechanism of the plastic hinge ductility mechanism at the beam end. The specimen has no obvious shear failure characteristics, and the bearing capacity utilization coefficient ξ can meet the seismic design requirements of “strong shear and weak bending”. The hysteresis curves of the six frame structure specimens are full, and the seismic ductility coefficient ranges from 4.36 to 6.10. The maximum value range of equivalent viscous damping coefficient is 0.125~0.165, which shows good seismic energy dissipation performance. The floor slab improves the stiffness and bearing capacity of the frame beam, which has a significant impact on the seismic failure mechanism of the specimen. The specimen maintains the seismic failure characteristics of “strong column and weak beam”, and the component importance coefficient η can ensure the seismic design requirements of “strong column and weak beam”. The failure characteristics of the specimens are random, but the overall regularity of the failure mechanism is strong, and the gradient characteristics of the specimens with different seismic structural grades are obvious.

Equivalent source method near-field acoustic holography can be applied in sound insulation measurement of the building components. When near-field acoustic holography is used to measure the sound insulation volume of components, the reconstruction parameters significantly affect the acoustic field reconstruction results. Based on the theoretical analysis of near-field holographic acoustic insulation measurement by equivalent source method, the compound sound pressure signal of the surface of the component was measured by the microphone array, and the sound insulation volume and surface normal sound intensity distribution of the component were obtained through the acoustic field reconstruction. To further investigate the influence of reconstruction parameters on the accuracy of equivalent source method near-field acoustic holography, experiments on sound insulation measurement of building components were carried out in the sound insulation room by the control variable method in comparison with the traditional sound pressure method. The results show that when the position of the equivalent source surface changes from -2 cm to -5 cm, the average error value of the reconstruction of the surface normal sound intensity increases from 3.9 dB to 5.6 dB, and the average error value of the reconstruction of the sound insulation volume increases from 5.2 dB to 6.9 dB, and the measurement error increases with the distance of the equivalent source surface, so it is suitable for the equivalent surface to be close to the sound source surface. When the holographic measurement surface distance is 4, 8, and 16 cm, the average error values of the reconstruction of the surface normal sound intensity are 0.6, 1.9, and 5.5 dB, and the average error values of the reconstruction of the sound insulation volume are 0.9, 1.4, and 4.6 dB, respectively. The measurement errors increase with the holographic measurement surface distance, so it is recommended to keep the holographic measurement surface distance within 8 cm. When the number of equivalent source points is consistent with the number of measuring points on the holographic surface, the difference with the traditional sound pressure method is only 0.84 dB. When the number of equivalent source points is inconsistent with the number of measuring points on the holographic surface, the average error values of the reconstruction of the sound insulation volume and surface normal sound intensity distribution increase to 4.6~6.8 dB. By optimizing the reconstruction parameters, the accuracy of component sound insulation measurement can be effectively improved. It has important reference significance for laboratory measurement of sound insulation performance and methods of building components and has high reference value in the practical application of sound insulation measurement technology.

At present, the expansion of Chinese cities in a sprawl way in the current rapid construction process has caused the lack of humanized quality in the new urban central space environment. The huge development scale and rapid construction process of the new urban central areas lead to the prominent “isolation” phenomenon, mainly reflected in the isolation of the block and the isolation of life. In the face of those problems, guiding the future urban spatial environment to develop in the direction of compactness has become one of the important concerns of urban design. It aims to promote the transition of cities from the expansive development of serving rapid economic growth to the quality construction of social, economic, cultural and other comprehensive benefits by creating a dense urban space environment that can carry a greater density of social, economic and cultural activities and realize the continuous cycle and symbiosis of multiple activity flows. Therefore, the paper put forward the idea of creating humanized urban space through urban design based on compact blocks. Then, taking the construction of compact blocks of urban central district as the starting point, and through the analysis of some design projects, it discussed some strategies of the urban design on the construction of human-oriented, walkable and vigorous compact block environment in the central district. The strategies are as follows: making the structure compact so that the new central area of the city can maintain a block-pattern in a walkable and suitable scale; making the texture compact so that small-scale blocks can construct block space carriers with more humanized quality; and making the functions compact so as to provide people with a variety of choices to use block space and convenient space experience, etc. By doing so, it aims to shape a compact central district block environment that is people-oriented, walkable and full of vitality, in order to realize the ultimate goal of urban design to improve the quality of space environment and provide people with a colorful and humanized urban lifestyle.

Under the background of insufficient school places and shortage of construction land in large and medium-sized cities in China, the three-dimensional design of primary and secondary school campus sports fields can form a vertical superposition of space, thereby releasing a large amount of construction land. However, the three-dimensional design of sports fields will also lead so some new design problems. Among them, the most complicated is the natural lighting of the lower space of the sports field, which facing both the problem of whether the illumination is sufficient and the problem of whether the light distribution is uniform. Domestic and foreign literature research shows that the current research on the lighting of three-dimensional sports venues at home and abroad is almost blank, which makes the current construction somewhat blind. Based on the above considerations, the study simulated the natural lighting environment of the lower area of different forms of campus three-dimensional sports venues with the parametric light environment simulation technology of the lighting simulation platform built based on Rhino, Grasshopper and Ladybugtools. And it extracted the factors affecting the lighting of the lower space of the three-dimensional sports field, including the size of the stadium, the number of overhead layers, the depth of the space, the functional layout, the location of the lighting port, and the sunshade and reflection measures. By simulating and analyzing the influencing factors, the influencing mechanisms of different factors were obtained, and the design strategies for three-dimensional sports fields to create a good natural light environment were further refined. The research feedback was formed based on the practice of optimizing the natural light environment of the student activity center of the Guangzhou Experimental Middle School project, thereby verifying the effectiveness of the research.

With the increase of traffic volume and overloading of vehicles, the mechanical properties of early arch bridges under live load can no longer satisfy the needs of modern traffic due to low design load grade, lack of effective maintenance and long term operation. To improve the mechanical performance of this kind of arch bridges, this paper proposed a cable-catenary arch combined structure. The cables were symmetrically arranged on both sides of the arch rib to form a new force system, which could change the force transmission path of the catenary arch structure and reduce the internal force of the arch structure. Under the mechanical diagram of cable-arch combined structure, the force equation of the cable-arch combined structure was established based on the elastic center method, and the analytical solution of the internal force of the arch rib was deduced by the approximate curve integration method under the vertical moving load. The reliability of the analytical solution was verified by ANSYS finite element analysis software, and the influences of design parameters such as cable constraint position, arch-axis coefficient, rise-span ratio, and axial stiffness ratio on the internal force of the arch structure under lane loading were analyzed. The mechanical properties and internal variation rules of the cable-arch combined structure were revealed. The results show that the relative error between the analytical solution of the internal force and the finite element result is within 1%. The setting of the cable changes the positive and negative interval distribution of the bending moment influence line value of the arch structure, and effectively reduces the peak value of the bending moment influence line of the arch structure, which can greatly reduce the overall bending moment of the arch structure and make the bending moment distribution more uniform. From the arch foot to the arch crown, the reduction of the bending moment and the growth of the axial force of the arch structure gradually decrease. As the axial stiffness ratio increases from 0.02 to 0.10, the negative bending moment of the arch foot decreases nonlinearly, with the maximum decrease of 63.7%; the increase of the cable force is inversely proportional to its value, and when the cables are set at 0.3L (L is the span of the arch) from the arch crown, the cable force can be increased to 1.9 times that at the axial stiffness ratio of 0.02. The influence of the rise-span ratio on the internal force of the arch structure cannot be ignored. The greater the rise-span ratio is, the greater the change in internal force of the arch structure is. The effect of arch-axis coefficient on the internal force of the arch structure can be neglected.

This paper established a numerical model of geotechnical flexible retaining wall supporting slope with FLAC^3D software, and the model was verified by the results of shaking table tests. With the calibrated numerical model, it systematically studied the influence of four factors on the dynamic response of slope, including strip stiffness, cell size, retaining wall thickness and filling elastic modulus. Additionally, it discussed the failure mechanism of the retaining wall and calculated the influence weights of each parameter. The results indicate that the stability of a retaining wall under earthquake action is closely related to these four factors. The distribution law of confining pressure and permanent horizontal displacement along elevation follows a two-stage pattern of “increase-attenuation”. Furthermore, settlement at the top of the slope presents a “V” shape distribution with smaller ends and larger middle portions. The horizontal peak acceleration exhibits a three-stage pattern of “increase-attenuation-increase” along elevation. With the increase of stiffness, the confining pressure of the cell increases, but the permanent horizontal displacement, slope roof settlement and horizontal peak acceleration decrease. With the increase of cell size, cell confining pressure, permanent horizontal displacement, slope top settlement and horizontal peak acceleration increase. With the increase of retaining wall thickness and filling elastic modulus, cell confining pressure, permanent horizontal displacement, slope top settlement and horizontal peak acceleration all decrease. Among the four influencing factors, the influence weight of cell size is the largest, and the influence weight on cell confining pressure is 0.996, while the influence weight of retaining wall thickness is the least. The retaining wall structure of geocele has good seismic performance under earthquake action, and the retaining wall structure has a certain attenuation effect on seismic energy, which can meet the requirements of seismic fortification. The research results provide guidance for the seismic design and engineering application of flexible retaining wall of geocell under earthquake action.

During slurry shield tunneling in the sandy pebble stratum, the slurry discharge pipeline will transport a large number of the large irregular pebbles, generating unstable turbulence, which causes difficulties to the determination of the pipeline pressure loss. This study designed a circulating flow test device, and the slurry used in the experiment is CMC transparent viscous slurry. And the study established a numerical model using the computational fluid dynamics-discrete element method (CFD-DEM) coupling approach. Taking pebbles with a particle size of 5~80 mm as the research object, the study investigated the effects of pebble particle size distribution, slurry velocity, pebble volume fraction, and pipeline inclination angle on the pressure loss along the pipeline, respectively. The results indicate that the pressure loss along the pipeline increases exponentially with the increase of slurry velocity under the same particle size distribution, pebble volume fraction, and pipeline inclination angle. And for horizontal pipelines, the effect of pebble particle size distribution on the pressure loss along the pipeline is not significant. In addition, for the low slurry velocity (v < 2 m/s), the pressure loss along the pipeline increases linearly with the increase of pebble volume fraction. And for the high slurry velocity (v ≥ 2.0 m/s), the pressure loss along the pipeline increases exponentially with the increase of pebble volume fraction. For inclined and vertical pipelines, the pressure loss along the pipeline firstly increases slowly with the increase of the pipeline inclination angle, and then increases sharply under the same particle size distribution, pebble volume fraction and slurry velocity, and the pipeline inclination angle at the turning point is 60°. In addition, under the action of mud buoyancy and turbulence, it is difficult for large-size pebbles to overcome their own gravity and reach a state of complete suspension. Therefore, large-size pebbles mainly move along the lower wall of the pipeline, and the pressure at the elbow of the pipeline is obviously stratified.

To provide theoretical basis for the restoration of Guangfu wooden structures, five hoop head tenon joint specimens were designed and manufactured using Merbau wood. Considering the influence of the size of mortise and tenon construction, quasi-static tests were carried out on undamaged and unreinforced joint specimens. Then, to preserve the original appearance of the building as much as possible, the damaged joint specimens mentioned above were reinforced by the Queti-type dampers that have minimal influence on the original appearance of the structure. Finally, quasi-static tests were conducted again on the reinforced joints to investigate the difference in their seismic performance and the strengthening effect of the dampers. The results show that the joint specimens reinforced with dampers exhibit significant indentations at the mortise and tenon connections when being loaded to failure. There is noticeable splitting on the outer side of the tenon of the beam and the detachment of the tenon, as well as obvious separation between the rubber and steel plate at the base of the damper. The addition of dampers to joints can compensate the decrease in force-bearing performance caused by initial damage, provide better post-damage stiffness for the damaged mortise and tenon joints, and enhance the ultimate load-bearing capacity and energy absorption capacity. After adding the damper, there occur enhancements in terms of post-damage stiffness, load-bearing capacity and energy absorption of specimens, as compared with the unreinforced joints, with the increment being more than 18%, 19% and 20%, respectively. Moreover, on the basis of the existing simplified mechanical model and in combination with OpenSees, a macro-modelling method was proposed for hoop head tenon timber structures, which helps to obtain hysteresis curves of the joints being in good agreement with the experimental results, meaning that the modelling method can effectively simulate the hysteresis energy dissipation characteristics of the hoop head tenon joints strengthened with dampers.

The pressure value of tunnel surrounding rock is an essential parameter for shallow buried tunnel design and calculation. In order to further improve the credibility of the surrounding rock pressure calculation results, the paper proposed a circular slip surface failure model based on the traditional shallow buried tunnel collapse model. Based on the nonlinear Mohr-Coulomb failure criterion, the limit analysis upper bound method was applied to derive the formulae for calculating the pressure in shallow buried tunnel surrounding rocks under the action of seismic forces. The credibility of the calculation results was verified and the influencing factors were discussed. The high credibility and accuracy of the theoretical formula was proved through comparing the results with field engineering and existing results. It also finds that the pressure of the surrounding rock is more significantly influenced by the nonlinear coefficient and the initial cohesion; the larger the nonlinear coefficient and the smaller the initial cohesion, the greater the surrounding rock pressure. As the parameter to be defined K (ratio of horizontal surrounding rock pressure to vertical surrounding rock pressure ) decreases, the horizontal rock pressure decreases and the vertical rock pressure increases. The influence of seismic forces on the pressure of the surrounding rock cannot be ignored. The surrounding rock pressure is most affected by the vertical seismic force alone, followed by the horizontal and vertical seismic force working together, and least affected by the horizontal seismic force alone. As the horizontal and vertical seismic force coefficients increase, the surrounding rock pressure also increases. The results of the study are of high reference value for the study of most tunnels, especially shallow buried tunnels that are susceptible to seismic effects.

The alignment measurement of railway bridge plays an important role in bridge health detection and the safe operation of railway. In order to improve the efficiency of alignment measurement of steel truss arch bridge in operation railway, this study constructed a complete “pure” bridge point cloud model. It took a three-span steel truss arch bridge as an example and used the terrestrial laser scanning (TLS) technology to scan the bridge members as a whole. From the three aspects of bridge alignment measurement accuracy, scanning integrity and point cloud number, the optimal number of bridge scanning stations was determined as 10. The 3DNDT point cloud registration algorithm was used to register each station one by one. The accuracy of bridge point cloud registration is 2 mm. The bridge point cloud was projected onto the xoy plane and the noise points were removed by the radius filter. The point cloud equidistant slicing and point cloud plane slicing algorithm were proposed to extract the bridge alignment, and the alignment point cloud data was exported to Auto CAD to pick up the coordinates. The point cloud slicing method was used to extract the TLS measurement value, and the total station method measurement result was compared with the original bridge alignment. In the analysis of the bridge deck alignment, the two methods measured the maximum deformation at the mid-span A₅ point as 12.69 mm and 10.29 mm. The maximum mutual difference R of the two methods is 2.4 mm, and the correlation coefficient is better than 99.93%. In the analysis of arch axis alignment, the maximum deformation of point cloud slicing method and total station method is 6.2 mm and 3.9 mm at B₄ point in the upper chord span of main truss, and 5.9 mm and 3.5 mm at B₁₀ point in the lower chord span of main truss. The maximum mutual difference R of the two methods is 3.2 mm, and the correlation coefficient is better than 99.87%, which verifies the effectiveness of point cloud slicing algorithm and the high precision of TLS measurement. There is no obvious lateral displacement in the transverse alignment of the arch axis. The verticality of the 19 suspenders obtained by the point cloud equidistant slicing remains good, and no torsion and offset occurs. The research results provide a reference for the alignment analysis and point cloud processing methods of the operating railway steel truss arch bridge, and have important practical value.

Improving the vitality of self-organized recreational path network is an important goal of urban renewal planning. Due to the discontinuity and the existence of dead end roads in the recreational path network in old towns, the comfort of residents’ recreational activities is restricted. The self-organization of recreational path network means that the top-down planning and design mode is difficult to match the needs of citizens. How to deduce the spatial vitality of recreation planning in a bottom-up mode and then identify potential land plots is an important issue to improve the quality of urban recreational path network. By taking the old town in Guangzhou as an example, this paper constructs the indicators of break degree and spatial vibrancy based on the complex network theory. Then, by using GPS trajectory data to identify the breaks in the existing recreational path network, the identification of discontinuous breaks based on citizen recreation behavior and the activation effect of urban renewal projects are quantitatively discussed, and the potential impacts brought by the implementation of renewal projects are simulated. The discontinuity analysis shows that the break degree of the recreational path network in the old town in Guangzhou is generally low, and the connection degree is good, but there are still some obvious breaks due to the street location and historical problems. Moreover, the results of spatial vibrancy deduction show that urban renewal projects have a positive impact on the self-organized recreational path network, and that the implementation plan and schedule of urban recreation quality improvement projects can be determined according to the deduction analysis results. This study makes a beneficial exploration of urban self-organizing characteristics from the perspectives of planning and transportation, and makes up for the deficiency of top-down planning in considering urban self-organized recreational path network.

The water-cooled centralized air-conditioning system is a multi-variable coupled nonlinear system with a high degree of sparsity in operational data, leading to poor generalization ability of data-driven machine learning models. A comprehensive physical model reflecting the hydraulic and heat transfer mechanisms has become a key focus of current research. However, there are some technical challenges that urgently need to be addressed, such as the complexity of variable coupling in the system, nested iterations leading to significant computational costs, and that changes in hydraulic structure due to equipment start-stop cycles necessitate frequent model reconstructions. By using continualization of discrete variables and pattern search methods to correlate resistance coefficients with branch openings, and equipment start-stop events with pump operating frequencies, it is possible to integrate discrete variables into continuous ones, reduce nested iterations, and achieve dynamic flow distribution and global hydraulic-thermal coupling calculations. This study established a multi-variable coupled physical model of a water-cooled centralized air-conditioning cold source system with external constraints such as cooling load, chilled water flow rate, chilled water supply temperature, chilled water supply-return pressure difference, and ambient temperature and humidity, enabling asynchronous adjustments of multiple independent variables including the number of chiller units, the number of chilled water pump units and frequencies, the number of cooling water pump units and frequencies, and the number of cooling tower units and frequencies. The reliability of the model was validated through a comprehensive experimental platform to explore the operational characteristics and group control strategies of chiller units, cooling towers, chilled water pumps, and cooling water pumps under different operating conditions. The research findings indicate that the simulation results of the cold source system physical model have an average relative error of less than 10%, with a few cases within 15%. The computational time for a single iteration is approximately 0.32 s. The adjustment of multiple variables can comprehensively balance the energy efficiency of each subsystem. Global optimization of the system can maximize energy-saving opportunities, addressing the shortcomings of traditional subjective empirical control in maintaining stable energy-saving effects and providing a theoretical basis for intelligent diagnostics.

As a kind of aerospace membrane material, polyimide film’s (Kapton film) creep effect is very important to its structure. In order to study its creep mechanical properties, firstly the study selected Kapton film with a thickness of 25 μm, and carried out the uniaxial creep tensile test under the four stress levels of 35%, 50%, 65% and 80% of the ultimate tensile strength. Secondly, according to the creep mechanics curves obtained, the creep characteristics of the film under different initial stresses were analyzed, and the intrinsic mechanism was discussed by combining the creep elongation. Five creep constitutive models of classical Kelvin, classical Maxwell, four-element Burgers, three-parameter generalized Kelvin and five-parameter generalized Kelvin were used to fit the experimental data, and the fitting effects of each model were compared and analyzed. The results show that Kapton film has obvious viscoelastic properties, which should be considered in the design. The initial stress has a significant effect on the creep properties of Kapton film. The greater the initial stress, the higher the strain at the initial creep stage, the higher the strain retention value at the steady creep stage, and the more obvious the viscoelasticity is. The tensile fracture stress levels in different directions lead to the differences of creep properties, and the total strain of TD (Transverse Direction) is greater than that of MD (Machine Direction) under each stress state. With the increase of the initial stress, the creep elongation of the film first increases and then decreases. This is because the influence of the initial stress on the stress state and dislocation motion inside the film is complex, and there is an equilibrium point. The five-parameter generalized Kelvin model adopted in this paper can well predict the creep properties of Kapton film, and the coefficient of determination of the fitting results is more than 0.99, followed by the Burgers model. The fitting coefficients of classical Kelvin, three-parameter generalized Kelvin and classical Maxwell model are between 0.71 and 0.86, and the fitting results meet the needs of practical engineering.

In order to investigate the effect of flange on the shear capacity of reinforced concrete (RC) beams without stirrups, this study took into the contribution of compression zone, dowel action, and aggregate interlock in tension zone, and proposed a shear capacity calculation formula for RC beams without stirrups based on the crack sliding model. To verify the accuracy of the formula, the study used the formula and major design codes to calculate the collected experimental data of 444 rectangular beams and 172 T-shaped beams, and the results were compared with the results of major design codes. Five commonly used machine learning algorithms were used for regression analysis on the collected dataset, to verify the fit of each algorithm with a small dataset to analysis on the collected data, and the fitness of each algorithm was validated with a small dataset.The results show that: the shear capacity calculation method proposed by the codes of each country is in good agreement with the test results; compared to the calculation of the codes, the addressed calculation method herein is more accurate and can effectively account for the contribution of the T-beam flange to the shear capacity; the five machine learning models selected in this paper exhibit a desirable accuracy on the test set, and the results show the same trend as calculations; it also demonstrates the applicability of the machine learning models in the calculation of the shear capacity for reinforced concrete beams.

Concrete-filled steel tube (CFST), as a kind of structure with broad development prospect, has good bearing capacity and plastic deformation ability. As a common form, rectangular concrete-filled steel tube column is widely used in engineering practice. Based on the two problems of inconsistent constraints on long and short sides and insufficient constraints on core concrete existing in practical application of rectangular concrete-filled steel tube, this study explored a new type of rectangular concrete-filled steel tube member, namely rectangular concrete-filled steel tube column reinforced by built-in profiled stirrup. Therefore, this study carried out the axial compression tests on 11 rectangular concrete-filled steel tube columns reinforced by built-in profiled stirrup, 2 rectangular concrete-filled steel tube columns with built-in racetrack stirrup, and 2 ordinary rectangular concrete-filled steel tube columns. It analyzed the influences of the coupling distance, steel tube thickness, concrete strength grade, stirrup spacing, stirrup diameter, built-in steel quantity on the axial compression bearing capacity and ductility of rectangular concrete-filled steel tube columns reinforced by built-in profiled stirrup. The findings reveal that reducing the thickness of the rectangular steel tube and embedding the resulting steel into the core concrete as profiled stirrup can effectively improve the axial compressive bearing capacity and ductility of the specimen, while maintaining the total amount of steel used. Additionally, the axial compression behavior of rectangular concrete-filled steel tube columns reinforced by built-in profiled stirrup can be divided into four stages: elastic stage, elastoplastic stage, plastic strengthening stage, and descending stage. Compared to ordinary rectangular concrete-filled steel tube columns, those reinforced by built-in profiled stirrup exhibit a more complete plastic strengthening stage. Based on the experimental results and parametric analysis, this study derived a calculation formula for the axial bearing capacity of rectangular concrete-filled steel tube columns reinforced by built-in profiled stirrup using an existing confined concrete constitutive model. This study can provide scientific basis and data reference for practical engineering applications.

As one of the typical fatigue details of the steel box girders, the U-rib butt weld in the embedded sections of the steel bridge decks is prone to fatigue cracking under the repeated action of the wheel load, and it directly affects the safe operation and durability of the bridge structures. In order to explore the fatigue cracking characteristics of U-rib butt weld on the roof of the orthotropic steel bridge decks, this paper first established a local model of the steel bridge deck using finite element simulation, and studied the fatigue stress characteristics of the U-rib butt welds in the embedded sections. Then it designed four full-scale single U-rib specimens and carried out a fatigue performance analysis of the actual structure combing with fatigue test. On this basis, the modified main S-N curve suitable for fatigue life prediction of U-rib butt welds was proposed by the structural stress method, and the fatigue crack propagation behavior of weld detail was explored based on the extended finite element method (XFEM). The results show that the longitudinal influence range of U-rib butt weld stress under the wheel load is two cross-spacer spacing, and the lateral influence range is 1.5 U-rib spacing. The arc transition area is subjected to the greatest fatigue stress amplitude and high stress concentration, which becomes a potential fatigue vulnerable point. The fatigue cracks observed in the experiment all start at the arc transition and continue to extend to the bottom edge of the longitudinal rib and the web. Based on the evaluation of the nominal stress method, the average fatigue strength of the welds is 68 MPa, which is close to the 71 MPa specified in the European Code. Compared with the main S-N curve proposed based on the equivalent structural stress method, the modified main S-N curve proposed in this research is safer and more conservative for fatigue life prediction. The extended finite element method can effectively simulate the expansion behavior of U-rib butt welds. Both fatigue tests and XFEM results indicate that the fatigue crack propagation direction depends on the location of the initial defect. When the initial defect appears on the bottom plate, fatigue cracks tend to extend along the bottom plate; but when the initial defect is located on the web plate, fatigue cracks tend to extend along the web.