Abstract:To improve the serviceability of footbridge， a semi-active tuned mass damper（STMD） with variable mass and damping is proposed， which can not only adjust its own mass and frequency in real time to adapt to the dynamic characteristics of the footbridge through the water pump and electromagnetic valve， but also adjust its own damping coefficient in real time to improve the effect of energy dissipation through changing the air gap of eddy current damping. First， the variable mass and damping algorithm and model test of STMD are introduced. Then， a case study is conducted based on the probabilistic random model of crowd excitation. Afterwards， the 100 times acceleration response of the structure without control， with an optimized passive TMD， variable mass STMD， variable damping STMD and variable mass and damping STMD under random synergistic crowd is studied. Through the maximum， mean and standard deviation of the three comfort evaluation indexes of the 100 groups of acceleration， root mean square（RMS） value， and maximum 1-s RMS value， the control performance and robustness of different TMDs are analyzed. The results show that structural dynamic responses vary greatly due to the randomness of crowd and body parameters. In general， STMD with variable mass and damping has the best control performance， whose standard deviation is also the smallest， indicating the best robustness.

Abstract:Reliable live load value is the prerequisite for reliability design of civil engineering buildings， and the collection of live load samples is the key data foundation for load modeling. Aiming at the problems of difficulty in entering households， weighing， low efficiency， and small samples that exist in the traditional research methods of sample collection and weighing in households， and based on the research thinking of big data， a new research method of residential persistent live load based on panoramic VR（virtual reality） house viewing system is proposed. Through the VR system of open network platform， multi-source heterogeneous data such as pictures and videos， combined with Internet resources， comprehensive network crawler， and other means， live load investigation is realized by non-weighing method， and practical research is conducted by taking residential buildings as examples. The characteristic value of residential live load was obtained by statistical analysis and load combination of 4 676 rooms in 9 cities （with a total area of nearly 75 000 square meters）. The results show that the standard deviation of sustained live loads significantly increases at any given time， the time of live load variations is different among different cities， which， overall， presents a decreasing trend. The combination of VR system and internet big data can achieve efficient and convenient residential live load surveys， forming a new research method for live loads.

Abstract:Superelastic shape memory alloys have superior self-recovery properties， which can ensure the perfect self-centering performance of structures in engineering seismic applications. However， their energy dissipation capacity is very limited because of the flag-shaped hysteresis curve， which is difficult to meet the seismic demand of structures in earthquakes. Therefore， this paper explores to maximize the energy dissipation capacity of shape memory alloy system while preserving the self-recovery performance， via combining superelastic shape memory alloy with friction dampers. First， it conducts an in-depth study of the balance design concept of self-recovery and energy dissipation of shape memory alloy and proposes the system balance parameter and corresponding design formula. Then， it demonstrates the practicality of the balanced design concept and the accuracy of the theoretical design formula by the superelasticity performance test of shape memory alloy， the simple friction damper test， and the combined tensile test. The balance design concept proposed and its successful verification can well promote and guide the engineering seismic application of shape memory alloy.

Abstract:Large direct shear tests were conducted on the in-situ graded coral sand in the South China Sea and the interface between the coral sand and polypropylene biaxial geogrid under different normal stresses. The test results show that the shear stress-shear displacement curves of coral sand and reinforcement-soil interface show obvious strain softening characteristics. The peak shear strength lines of both show a bilinear form， and the residual shear strength lines of both show a good linear relationship. The average interface friction ratio between coral sand and geogrid at all levels of normal stress is about 1.37， which is much higher than that between siliceous sand and geogrid， indicating that the reinforcement effect can be mobilized in the reinforced coral sand. During the shearing process of coral sand and reinforcement-soil interface， the samples generally experienced a “relative shear shrinkage-relative shear dilatancy-relative shear shrinkage”， and reinforced coral sand can significantly reduce the shear shrinkage deformation. The relative breakage rates of the samples in the direct shear test and the reinforcement-soil interface direct shear test are close and increase with the increase of the normal stress. The Duncan-Chang model and shear softening model are used to respectively describe the pre peak and post peak of shear stress-displacement curves of the South China Sea and polypropylene biaxial geogrid interface. The interface constitutive model established can well reflect its shear characteristics.

Abstract:In order to ensure the stability and the serviceability of high filling foundations， the field monitoring of the high filling project of Baihetan Hydropower Station is introduced， and the settlements of the original foundation and the filling are analyzed in this paper. The influencing factors such as the height of filling， compaction degree， time， and variation of groundwater on the settlement are discussed. The results indicate that the settlement of the high filling project with gravel filler is caused by the original foundation and the compression of the filling. The settlements of the original foundation and the filling account for 39.7% and 60.3% of the total settlement， respectively. The proper increase of foundation compaction degree is an effective measure to control the foundation settlement. Different fitting models are used to predict the settlement of high fill foundations， and it is found that the exponential model can successfully predict the settlement of the high filling project. The impoundment in the reservoir causes the groundwater level in the filling area to rise， and the instantaneous wetting deformation of the soil accounts for 60.9% of the total wetting deformation. The increase and dissipation of pore water pressure are mainly affected by groundwater level and filling load. A linear relationship between the magnitude of excess pore water pressure and the filling load is observed and the coefficient is 0.021， indicating that the soil is stable. The excess pore water pressure gradually dissipated after completion.

Abstract:To quantitatively consider the environmental and social impacts of engineering structures at the planning and design stage， a comprehensive life-cycle sustainability cost framework and corresponding computational models are proposed. In terms of environmental impacts， the costs of preventing and controlling air， water， and soil pollutants are used as quantitative indicators， the environmental costs arising from engineering activities， traffic detours and congestion are modelled， and the environmental cost rates of common construction materials and fuels are summarized. In terms of social impacts， social cost calculation models are proposed， covering construction and traffic safety， passenger and freight transportation， regional economy， residential environment， and public services. The parameter values and calculation methods for life-cycle sustainability costs are illustrated with the comparison and selection of maintenance schemes for coastal bridges. For bridge maintenance schemes that occupy lanes， the sum of environmental and social costs far exceeds the direct economic costs， while maintenance schemes that do not occupy lanes have fewer environmental and social costs. Furthermore， among these maintenance schemes， the sustainability of the epoxy coating scheme is superior to that of the electrochemical chloride extraction scheme.

Abstract:To investigate the electroosmosis coefficient of saturated soil and its influencing factors， a simple and convenient test device for electroosmosis coefficient was developed， which can ensure that the water content and void ratio of the sample are relatively stable during the electroosmotic test， and the influence of hydraulic seepage caused by the difference of the two ends of the sample is eliminated. An electroosmotic test of saturated remolded clay samples with five different void ratios was conducted by using this device. The results show that the water discharge is proportional to time under the condition of low voltage and small void ratio. On this basis， the influence of potential gradient and void ratio on the electroosmosis coefficient was discussed. The results show that the electroosmosis coefficient increases with the increase of potential gradient or void ratio and is approximately linear with the increase of potential gradient and void ratio， and the void ratio has a great influence on the electroosmosis coefficient.

Abstract:In non-aqueous phase liquid（NAPL） permeation test of saturated clay，NAPL-clay interactions can lead to sample shrinkage and sidewall leakage，which affects the reliability of the test results. Kerosene permeation tests using consolidation permeameter were conducted on Shanghai mucky clay to investigate the influence of vertical consolidation pressure p_v and the soil structure on sidewall leakage and test results. The test results show that for intact samples with a flocculation structure， sidewall leakage occurred at p_v = 50 kPa and 200 kPa， resulting in an overestimation of permeability coefficient， while reliable test results can be obtained at p_v = 400 kPa. However，for remolded samples with a dispersed structure，sidewall leakage still existed even at p_v = 400 kPa. Based on the pore distribution of the intact soil sample and the test results at p_v = 400 kPa，the characteristics of NAPL permeation in Shanghai mucky clay are discussed in detail. These results are valuable for understanding the migration characteristics of NAPL pollutants in coastal soft clay.

Abstract:In order to design an elevation surface of the airfield area that meets the standards and has the lowest cost， this paper divides the skeleton and the twisted surface in the airfield area. The upper-level planning determines the specific position of the skeleton from a global perspective. Based on the results of the upper-level planning， the lower-level planning aims at the degree of fitting between the local surface and the natural ground， connecting the skeleton and optimizing the design of the twisted surface. These form an optimization model of the airfield area elevation design based on bi-level programming. Finally the genetic algorithm is used to solve the problem. The elevation design example of Sanming Airport calculated by using this model shows that the drainage， slope， and slope section design of the optimized model meet the existing requirements， and compared with the actual project， it is more in line with the natural terrain. The filling volume is reduced by 7.50%， the total earthwork is decreased by 8.06%， and engineering cost is reduced by 10.73%.

Abstract:This paper aims to predict the rutting depth more accurately and simplify the prediction process. First， the effective temperature for rutting of semi-rigid base asphalt pavement in 10 sites was calculated based on the full-thickness asphalt pavement temperature field prediction model and rutting prediction model. Then， the effect of asphalt layer thickness and site factors on the effective temperature were analyzed. Afterwards， a prediction model was established， incorporating the depth， annual average temperature （AAT）， and annual rainfall （AR）. Finally， the model was verified and compared with other existing models. The results show that the asphalt layer thickness only has a significant effect at a depth of 0.5 cm， and the site significantly affects each sublayer. A model with a better extensibility and robustness is proposed based on the distribution characteristics of effective temperature along the depth. Combined with the regional correction factor， an effective temperature prediction model considering regional differences is established. Compared with the existing models， the effective temperature model established in this paper is suitable for different design conditions， materials， and traffic volumes.

Abstract:This paper investigates the analysis method of the optimal service flow rate of the expressway on sunny and rainy days. First， the distribution characteristics of flow， speed， and occupancy rate on rainy and sunny days are analyzed using coil loop data. Then， the K-S test is used to confirm the significant difference in traffic flow on sunny and rainy days. The capacity and the bottleneck breakdown analyses are performed on rainy and sunny days， respectively. It is shown that the V/C calculated according to the current standard does not apply to the analysis of the level of service （LOS） of rainy-day traffic flow， and there is a limitation in emphasizing the maximum throughput and inaccurate information after the bottleneck breakdown. Therefore， this paper proposes an academic idea of maximizing the service traffic volume while taking into account a certain operating speed and provides the concept of optimal service flow rate and its determination method. It， then， establishes a three-dimensional K-means clustering model with integrated flow-speed-occupy to obtain the traffic state clustering results before and after breakdown on rainy and sunny days. The results explain the relationship between service flow rate and LOS before and after breakdown， and point out that the pre-queue transition flow can be used as the optimal service flow rate.

Abstract:To address the issue of model mismatch and performance degradation caused by uncertainties in the motion state of a preceding vehicle within adaptive cruise control （ACC） systems， a strategy for ACC by improving the prediction of the state of the preceding vehicle was proposed. Initially， the future acceleration trajectory of the preceding vehicle is predicted using a time convolutional network （TCN）， which makes use of historical speed and acceleration information. Subsequently， the acceleration predicted is employed as a disturbance to formulate the predictive control model for the ACC system. Finally， simulation experiments are conducted on the Matlab-Carsim joint simulation platform. The experimental results demonstrate that favorable predictive results for vehicle acceleration are achieved by the TCN. Furthermore， compared to the traditional model predictive control （MPC）， the improved method leads to the reduction in velocity tracking errors and the enhancement in responsive speed of the following vehicle towards changes in the speed of the preceding vehicle.

Abstract:The regional rail network is characterized by numerous lines and sections， complex composition of transportation capacity resources and great differences in passenger and freight demand. The quality of train diagrams is directly related to the overall transportation potency of the regional rail network. Based on potency in terms of capacity， efficiency and quality， a five-level evaluation index system is built. For version difference analysis， a version comparison evaluation method is developed， integrating the gray relevancy and the horizontal pull-off grade methods. For quality inspection， a section comparison evaluation method is developed based on the K-MEANS++ and the improved TOPSIS. Case studies on three different versions of the railway network train diagram in Shanghai Railway Group show the 0620 version is the best in version comparison and performs well in section comparison. The evaluation results are multi-dimensional and hierarchical， and provide a decision-making basis for the preparation and adjustment of the train diagram.

Abstract:The optimization of operation scheme of through freight train from container central station considering fluctuating container throughput is proposed. The objective function intends to minimize the total time of container accumulation and train reformation. The model considers some constraints including the station classification capacity， the classification tracks number， and the container flow formation scheme uniqueness. The daily average container throughput is counted， and the formation plan of through freight train from container central station with certain container throughput is obtained. Then， the daily dynamic container throughput is directly adopted to establish the operation scheme of through freight train from container central station with fluctuating container throughput. Afterwards， a method of transforming random constraints to deterministic constraints is developed to deal with the daily dynamic container throughput， and a meta-heuristic based on filtering-updating-connecting wagon flow sequence is given to obtain the container train operation scheme. Finally， the experimental scenarios are given to test the through train operation scheme models with daily average container throughput and daily dynamic container throughput. Under the container throughput fluctuation range of ±10%， ±15%， ±20%， and ±25%， the feasibility measure of the model with daily average container throughput is respectively 77.2%， 72.4%， 68.4%， and 51.6%. However， the feasibility measure of the model with daily dynamic container throughput arrives at respectively 96 .0%， 92.8%， 88.2%， and 77.2%. Obviously， the latter has more advantages.

Abstract:To solve the gear whine problem of the high-speed electric drive transmission system， the vibration response analysis and structural optimization design method of high-speed stage gear system of electric drive transmission were discussed based on the traditional method of the gear modification and the dynamic meshing stiffness calculation of transmission system. First， the high-speed stage gear system was divided into the gear pair unit and the discrete shaft unit， and the bearing-housing unit was coupled. The modularized equations of motion for the corresponding units were built and the system dynamic model was established. Then， the mathematical model of dynamic meshing stiffness was deduced and vibration response was calculated under the exciting force which was the product of transmission error and dynamic meshing stiffness. Afterwards， based on an electric drive transmission system， a comparative analysis of vibration response simulation result and test result was conducted， and the validity of system dynamic model and the vibration response analysis through dynamic meshing stiffness were verified. Finally， with the change of different layout forms and component structure， the influence of different gear pair layouts and component structures on the dynamic meshing stiffness and transmission error were studied. The structural optimization scheme was made and test result of before and after optimization were compared. The results show that the optimized scheme vibration response of high-speed stage gear system drops significantly and the problem of gear whine is effectively improved. The research can provide new idea for the design of electric transmission gear systems.

Abstract:To realize the application of NH₃/H₂ blended fuel in internal combustion engines， an internal combustion Rankine cycle model of NH₃ / H₂ blended fuel was established in this paper based on Cantera. Additionally， the numerical simulation of combustion process of internal combustion Rankine cycle NH₃ / H₂ blended fuel engine under the conditions of different ammonia hydrogen mixing ratios， excess air ratios， and water spray volumes was conducted. Finally， the influence of different boundary conditions on combustion characteristics was analyzed from the perspectives of thermodynamic cycle efficiency and typical pollutant emissions. The results show that the increase of excess air ratio and in cylinder water spray volume improve the thermodynamic cycle efficiency by 2.66% and 7.00% respectively， hence the effect of water spray is more significant. Besides， NO is the main NO_x pollutant emitted at the end of fuel combustion. Water spray in the cylinder is beneficial to the reduction of NO_x emissions. After the application of the water spray technology， the emission of NO and NO₂ in combustion products is reduced by 37%.

Abstract:To meet the design requirements of a rotary direct-drive servo valve for a small length-to-diameter ratio compact structure of the drive motor， an annular traveling wave type ultrasonic motor was designed starting from the demand of 200 Hz dynamic response of the servo valve power level. The basic working principle of the ultrasonic motor is analyzed and the stator-rotor friction transmission model of the ultrasonic motor is established. An ultrasonic motor characteristic test bench was built and the torque-speed test was conducted， based on which， the analysis of the influence characteristics of ultrasonic motor drive frequency and drive voltage was performed. The results show that the ultrasonic motor has the maximum working efficiency at a drive frequency of 49.8 kHz， the servo valve speed and torque working demand can be satisfied when the drive voltage is greater than 110 V， and the maximum working efficiency can be approached under a drive frequency of 49.8 Hz and 110 V drive voltage condition.

Abstract:Most state-of-the-art stereo matching networks construct 4D cost volume to preserve the semantic information of the image， which increases the computational cost of the network. To solve this problem， a network named EDNet++ with a two-stage combined cost volume and a multi-scale dynamic attention is proposed. First， a correlation cost volume is constructed based on global and coarse-grained disparity search range， which is used as a guide to construct a fine-grained combined cost volume on the local disparity search range. Then， the dynamic attention mechanism based on residuals can adaptively generate spatial attention distribution according to the intermediate result information， and the effectiveness of this method is proved by the transfer experiment. The comparison experiments on various public data sets show that EDNet++ can achieve a good balance between accuracy and real-time performance compared with other methods.