Abstract:To study the vibration and noise characteristics of elevated railway bridge structures and the influencing factors, a certain elevated railway bridge on the Shanghai-Kunming high speed railway was taken as the research object, a hybrid FE-SEA model for numerical simulation analysis was established and on-site experimental verification was conducted. Accordingly, the influence of plate thickness on structural noise and the contribution of each bridge plate subsystem to the overall noise were analyzed. The results showed that the FE -SEA method is suitable for the study of structural noise of elevated railway bridge. The peak frequency of vibration for the box girder structure is 125 Hz. and the frequency of structural noise ranges from 50 Hz to 160 Hz. The top plate and wing plate of the box girder contribute considerably to the far-field sound pressure level. The results indicated that increasing the thickness of each plate can reduce the structural noise, and this reduction is greater when the thickness of the top plate is increased.

Abstract:The finite element approach is used to create an embedded track finite element model in order to investigate the applicability of embedded track in heavy-haul railway. From the perspective of rail stress, rail displacement, and track slab displacement, the influence of truck axle load on the stress and deformation of embedded track structure are studied, and the existing embedded track structure is adjusted. According to the findings, the truck axle load has a substantial impact on the stress at the head of the rail, the stress at the bottom of the rail, and the lateral and vertical displacement of the rail. Among them, rail head stress and rail lateral displacement all exceed the regulatory requirements, but have no effect on track slab displacement. Following the replacement of 60 kg/m rail with 75 kg/m rail, the stress in the rail head was significantly reduced, but the transverse displacement of the rail still exceeded the limit value. On this basis, as the elastic modulus of filling materials increases, the stress and displacement of rails are greatly decreased, and they are all within the code limitations. It is advised that the elastic modulus of filler materials be 400 MPa.

Abstract:Whether the diaphragm wall should be considered in the seismic design of the column-free large-span subway station has not been uniformly determined. Based on the finite element numerical analysis software ABAQUS, the soil-structure static and dynamic coupling finite element models are established to analyze the influence of diaphragm wall on the seismic response of column-free large-span subway station under horizontal and vertical earthquake load. The results show that the diaphragm wall can improve the lateral stiffness of the column-free large-span subway station system, and the horizontal relative deformation of the side wall is reduced when the diaphragm wall is considered. However, the existence of diaphragm wall will magnify the vertical inertia effect of the overlying soil of the subway station, and also make the internal force of the subway station redistribute. When the diaphragm wall is considered, the end of the bottom slab is a weak seismic link, which should be properly strengthened in the seismic design.

Abstract:With the development of urbanization, the environment of foundation pit is becoming more and more complex, and the deformation control of foundation pit engineering has become more and more stringent. At present, the design of foundation pit retaining structure is still controlled by strength, and the design strength in the actual project cannot be reached due to the large deformation of conservative design. Based on the matrix theory and the principle of minimum potential energy, the deformation coordination condition of retaining pile and horizontal support is considered, the total potential energy equation of retaining pile deformation is obtained, and the deformation of retaining pile is solved. A design method of foundation pit retaining pile based on deformation control is proposed. Finally, the proposed design is verified by the field measured data of three typical projects, and the results show that the absolute error of prediction increases with the increase of the maximum deformation of the retaining pile, and the average relative error is less than 10% of the maximum deformation.

Abstract:To improve the strength of silty clay-cement mixed soil, a cement-soil mixed wall is formed by making it work together with steel bars or sections. In this paper, taking the powdered clay soil in Nanchang area as an example, based on the existing research on the performance of cement soil improver, indoor unconfined compressive strength test and permeability test were conducted on the mixed soil formed by 16 groups of silty clay improvement schemes through selecting suitable curing agents and using orthogonal test to study the effects of different ratios of cement, water glass, gypsum and quicklime on the strength performance of the improved silty clay. The results were analyzed by the range analysis and variance analysis. The results showed that the compressive strength of the mixed soil was influenced by the amount of cement, water glass, gypsum and quicklime in descending order, and the optimal ratio of cement, water glass, gypsum, quicklime and naphthalene water reducing agent was determined to be 24%, 6%, 2%, 0 and 1.5%, and was recommended to be used when the water-cement ratio was 1.5 and the moisture content of the silty clay was 12%. After screening the curing agent and optimizing the proportion, the strength of the silty clay could reach 8.6 MPa at the standard age of 28 d. Finally, the microstructure of the high -strength silty clay -cement mixed soil was analyzed by scanning electron microscope test, and the mechanism of the generation of high-strength cement mixed soil was elaborated.

Abstract:The periodic characteristics of the track structure have filtering characteristics for the propagation of vibration waves within the structure, and dispersion analysis is important for understanding the vibration transmission characteristics of the track structure. Based on the virtual spring model and the energy functional variation principle, we propose a new method to calculate the complex dispersion of the periodic structure of the rail based on the virtual spring model and the energy functional variation principle, which can consider the damping factor and the material frequency variation effect. The accuracy of the method is verified by comparing with the existing literature, and the method is used to analyze the influence law of fastener stiffness frequency variation effect, fastener damping and ballast damping on the vibration wave complex dispersion characteristics of track structure. The results show that the stiffness frequency variation effect and the fastener and ballast damping have a large influence on the attenuation domain and the attenuation speed of the vibration, which must be considered in the vibration transmission analysis of the track structure.

Abstract:The foundation pit excavation has a significant impact on the deformation of retaining structure. PLAXIS 3D is utilized for numerical simulation in this paper based on the hardening model considering the small strain characteristics of the soil, combining the foundation pit project of a subway station in Hangzhou. The influences of different excavation conditions on the deformation, axial force and surface settlement during construction are analyzed in details. Results show that there is a significant deformation difference between the left and right sides of the retaining structure of the same foundation pit. The soil layer cannot be simply regarded as horizontally distributed soil layer during the process of analysis. The pile load of the soil on the side with large deformation should be reduced, as well as the load should be distributed on the side with small deformation of the retaining structure as far as possible. Meanwhile, the horizontal displacement, surface settlement, and deformation increase gradually with the foundation pit excavation and station construction. In addition, the deformation of the diaphragm wall is significantly affected by the excavation sequence of the foundation pit. The excavation from the middle to both sides has the smallest influence on the deformation of the retaining structure, only 18.35 mm, which is about 25% less than the original condition, and has the most favorable influence on the project.

Abstract:In the development of modern logistics, the timeliness and cost of multimodal transport are factors that cannot be ignored. Aiming at the transportation goal of highway-railway-waterway multimodal transport, this paper mainly studies the path optimization problem of green multimodal transport when the dual uncertainties of transportation time and transit time follow random distribution. The multi-objective optimization model of green multimodal transport path under the dual uncertainties of transportation time and transit time is established with transportation time, carbon emissions and transportation cost as objective functions and carbon emissions as constraints. Accordingly, fuzzy adaptive genetic algorithm and fast non-dominated sorting genetic algorithm (NSGA- Ⅱ) are used to design the multimodal transport path optimization strategy. Finally, the path data from Nanchang to Berlin is used to verify the effectiveness of the proposed method and the results are compared and analyzed. This paper finds that the multi-objective optimization results based on NSGA-Ⅱ algorithm are better, which can guide the multimodal operators to adjust the transportation plans and reduce the emission of carbon dioxide, providing reference for logistics enterprises to carry out multimodal transportation.

Abstract:The purpose of this article is to explore the linkage and coordination between Quanzhou′s manufacturing industry and logistics supply chain, help build a service-oriented manufacturing industry, promote the integration of advanced manufacturing and related key industries, and promote the construction of an efficient modern logistics supply chain system. Based on the gray correlation degree model and VAR model, the correlation degree and linkage development degree of manufacturing and logistics supply chain development indicators in Quanzhou from 2002 to 2021 were analyzed. The relationship between Quanzhou′s manufacturing industry and the development of the logistics supply chain, and between the logistics supply chain and economic development indicators is relatively strong. The coordinated development of multimodal transport among various logistics transportation methods needs to be strengthened. The construction of comprehensive freight hub needs to be improved.

Abstract:In order to further study the fatigue performance of RD joint, the RD joint was subjected to central loading by simulating wheel loads, and the fatigue life of RD joint under corresponding hot spot stress range was obtained by conducting fatigue tests. The 3D solid finite element model of RD joint in steel bridge decks was established by using ABAQUS. Based on the effective numerical model, the fatigue life of RD joint was compared and analyzed by using the hot spot stress method and the critical distance theory respectively. The results show that under the same finite element mesh, the hot spot stress results obtained by two -point extrapolation and three-point extrapolation are relatively close, while the characteristic stress obtained by point method using the critical distance theory is smaller than that obtained by line method. The evaluation results obtained by FAT90 S-N curve recommended by IIW are too conservative, while the prediction results of FAT125 S-N curve are relatively close to the measured value. Compared with the hot spot stress method, the critical distance theory can get more accurate prediction results, in which the prediction errors obtained by the point method and the line method are 17% and 32% respectively. In general, both the hot spot stress method and the critical distance theory can get relatively conservative fatigue life prediction results. Therefore, the two methods are feasible and safe for fatigue behavior evaluation of typical welded joints in steel bridge decks. However, the point method has higher prediction accuracy and is also more convenient in practical application.

Abstract:The practice of lightweight parts is an important research direction in the field of mechanical manufacturing. In this study, the suspension column of the Formula Student Combustion China (FSCC) BTR-X was taken as an example. Based on the analysis of its actual force, the Altair inspire form software was employed to perform weight reduction design and topology optimization with the goal of maximizing stiffness. The stress, strain values and safety factors of two different design schemes were obtained under the condition of entering the bend with brakes, and then their advantages and disadvantages were compared. In the best optimization scheme obtained, the maximum effective stress of the BTR-X suspension column was 557.4 MPa, and the weight was reduced by 18.4% , thus improving the stability of the vehicle. Accordingly, the lightweight goal was achieved, which has certain reference value for further improving the performance of FSCC racing cars. Finally, the 3D printing molding process of the optimized suspension column structure has been successfully realized by selective laser sintering (SLS), providing a new route for the lightweight design and processing of FSCC racing cars.

Abstract:Based on the problem of earth pressure concentration in earth pressure cells, a water bladder earth pressure gauge was invented. The thickness of pressure sensing water bladder can be controlled within 5~10 mm. The pressure sensing water bladder is connected with the electronic pressure gauge through the transparent PU air pressure hose. The height position of the electronic pressure gauge needs to be fixed when the water bladder earth pressure gauge is used. A comparison test was conducted between the water bladder earth pressure gauge and the vibrating string earth pressure cell buried in soils with different compression modulus. The analysis of the results shows that, although the problem of high measured earth pressure is unavoidable, the stress concentration problem is significantly improved when the earth pressure in the stratum is tested with the water bladder earth pressure gauge compared with the earth pressure cell as the pressure sensing water bladder being thinner than the earth pressure cell. From the test results, it can be seen that the amplitude of soil pressure caused by the thickness of the test element is non-linear, which is related to the adjustment of soil particle deformation around the test element. The water bladder earth pressure gauge is used in the model test of shield tunnel response. The test results show that the water bladder earth pressure gauge is obviously different from the earth pressure cell. From the analysis of the changing trend of the test results, the test results of the water bladder earth pressure gauge are reliable and it is necessary to use a water bladder earth pressure gauge directly attached to the outer wall of the model shield tunnel to test its surrounding soil pressure. The test principle of the water bladder earth pressure gauge is simple with low cost, and the precision is high. Because of its flexible construction, the pressure sensing water bladder can be used to test the earth pressure of non-plane structure surface according to the test demand.

Abstract:Slings of arch bridges may experience axial deflection after long-term service. In order to study the influence of this phenomenon on the force of the slings, this paper designs a static tensile test scheme of axial deflection for the basic unit of the slings. Firstly, the corroded steel wire specimens were prepared by accelerated copper salt corrosion method, and the static tensile tests were carried out on the specimens at four different coaxial deflection angles （0, 10, 20 mrad and 30 mrad）. Ansys is used to simulate the test and the pitting. The results show that the weight loss rate and the average corrosion depth of steel wire increase linearly with the corrosion time, but the corrosion rate decreases quadratically with the corrosion time. The ultimate tensile properties of steel wire decrease with the increase of deflection angle. The coupling of deflection angle and corrosion accelerate the weakening of the tensile strength of steel wire. The numerical simulation is in good agreement with the experiment, which effectively verifies the law obtained by the experiment. The phenomenon of concentrated stress occurs when there are pits in steel wire, and the maximum stress increases with the increase of deflection angle.

Abstract:PSO is widely used to solve complex optimization problems in practical problems in the fields of engineering, science and management. Designing new strategies to deal with the performance and efficiency bottlenecks of the algorithm is a research hotspot in this field. In order to solve the problem that the original velocity limit strategy of PSO is relatively simple, which may easily lead to slow convergence speed and low performance of the algorithm, this paper proposes a new velocity limit strategy combining iteration and problem dimension. By analyzing the relationship of the algorithm evolutionary state evaluation to iterations and the dimension of problem for particle swarm optimization, a formula was designed to calculate the ESE influenced by the iterations and problem dimension, and calculated the velocity limit on the basis of the ESE, so a particle swarm optimization with velocity limit combining iteration and problem dimension was obtained. Finally, the algorithm was affected by iteration and problem dimensions, adaptive and scalable for solving problems in different dimensions. The results show that the strategy improves the convergence speed and accuracy. Experimental results prove the effectiveness of the algorithm.