Abstract:According to the structural details of core regions, precast concrete frame structures are generally divided into two types, i.e. precast concrete frame structures with cast-in-place core regions and precast concrete frame structures with precast concrete core regions. Based on systematic investigations of relevant studies in China and abroad, the structural characteristics, mechanical behaviours and design methods of different types of precast concrete frame structures are summarized. On this basis, the domestic and foreign technical specifications of precast concrete frame structures are introduced, and the future research and development work is also prospected.

Abstract:In this paper,the seismic response of a three-span fault-crossing continuous girder bridge subjected to near-fault pulse-like seismic ground motions is calculated considering the fling-step effect. Typical near-fault pulse-like ground motion records are selected and nonlinear response history analyses are adopted in an asynchronous excitation scenario. The effect of cable restrainers on the seismic response of fault-crossing bridges is investigated under different fault locations. In addition, parametric analyses on lateral restraining displacement and lateral stiffness of the cable restrainer are conducted. Results show that using the cable restrainer can effectively mitigate the displacement response of fault-crossing bridges while it enlarges the pier-bottom moment; seismic responses of a fault-crossing bridge are more sensitive to changes in the lateral restraining displacements of the cable restrainer.

Abstract:Based on a series of sectional model wind tunnel tests, the effects of gap distance ratio on aerodynamic interference and vortex-induced vibration (VIV) performance of parallel twin-deck bridge were studied. The results show that the maximum amplitude of VIV and the lock-in wind speeds increase significantly compared with a single-deck bridge due to the aerodynamic interference effect; the most unfavorable range of gap distance ratio is 2~4, with the largest maximum amplitudes of VIV and a wider lock-in wind speed range; there is a phase lag in the vibration of two decks, which is affected by reduced wind speed, the amplitude of upstream deck and gap distance ratio.

Abstract:The finite element program,which has been verified by the full-scale collapse test of steel portal frame structure under fire, is used for simulation in this paper. Then two-dimensional and three-dimensional finite element models are established, and the parameter analysis is carried out. The effects of the heating condition of steel member, foot stiff, span-depth ratio, fire protection, section temperature gradient, load ratio, wind load and secondary components on the collapse mode of steel portal frame structure under fire are mainly studied. Four typical collapse modes are summarized. The results show that the finite element model(FEM) can accurately predict the collapse behavior of steel portal frame structure under fire. The heating condition of steel member, the foot stiff, the load ratio and the secondary component have the most significant influence on the collapse mode, while the wind load, the fire protection, the section temperature gradient and the span-depth ratio have little effect on the collapse mode. In addition, the collapse law of steel portal frame structure under non-uniform fire is summarized systematically.

Abstract:In this paper,a nonlinear numerical model of bearing capacity for quasi-rectangular shield tunnel structure is established. In the model, the material nonlinearity, the geometric nonlinearity are all taken into consideration. Three groups of test structrures under limit working condition are simulated numerically. The results of the numerical simulation and full-scale ring tests are compared to verify the correctness and effectiveness of the model. Then the key parameters are analyzed to investigate the mechanical behavior of the structure. The results show that the failure of the structure originates from the failure of longitudinal joints,and eventually the structrure reaches the ultimate bearing capacity due to the failure of T block. According to the numerical analysis, the structural failure mode is related to the mechanical properties of longitudinal joints, segments and interior column. The ideal failure mode of the structure is that the bearing capacity of longitudinal joints is fully utilized, while the reinforcement of segment is yielded which leads to the ductile failure mode of the structure.

Abstract:Based on the review of the concept of total strength S_u and the principle of “ method”, it is pointed out that directly substituting the strength parameters of c_cu and φ_cu by triaxial consolidated undrained shear test, and the strength parameters of c_cq and φ_cq by direct shear test into Rankine’s earth pressure is a uncorrected analysis method. It results in the misleading of the application of the total stress analysis method. According to the principle of the two kinds of test, the formulations of total strength S_u using the strength parameters of c_cu,φ_cu, and c_cq,φ_cq are derived. Then, according to the principle of “ method”, correct earth pressure equations applied to unloading condition in excavation are presented. Based on the new equations, the analysis methods given in several domestic standards or specifications are discussed. Finally, different kinds of strength parameters in earth pressure analysis are evaluated with analysis examples.

Abstract:By using the transparent soil materials and the Matlab image processing technology, a model experiment of high-pressure jet remediation agent transport in transparent soil was done to obtain the migration process of agents visually and non-intrusively. For studying the migration characteristics under the different void ratios, particle size distributions, and osmotic pressure differences, the model tests were conducted and the comparison of migration rate and distribution area was made. The results show that the migration rate decreases with the decrease of large particle size content, void ratio and osmotic pressure difference, and there is a similar quadratic function relationship between the factors and migration rate; the distribution area of agents enlarges with time elapsed, and the period of agent migration can be divided into two stages, i.e. rapid growth stage and slow growth stage.

Abstract:A lane transformation-based sight distance calculation model for highway identification was proposed, along with the characteristics and demands of actual traffic flow in the diverging area. In the model, the reaction time of recognition from inner side lane to exit and the distance required by drivers to transform lanes once are considered. The results show that different from the Design Specification for Highway Alignment, the model defined the driving behavior meaning and ranges of decision sight distance. Nevertheless, the recommended minimum decision sight distance calculated by the model is of unique selectivity.

Abstract:The influential factors which can describe the connection between cities when it comes to intercity trip distribution were analyzed based on the intercity travel purpose. The effect of the connection between headquarters of enterprises and their subsidiaries on the intercity travel demand was discussed, and a variable of headquarters-subsidiaries links was put forward. The quantification method of the variable was also included. The variable was used to construct the intercity trip distribution forecasting model, and the model was calibrated by using 2010 Inter-Regional Travel Survey data and economic census data in Japan. Finally, the variation of the headquarters-subsidiaries links with time was discussed. The results show that the forecasting model performs better after adding the variable.

Abstract:An intelligent generation model of dispatching commands is proposed in this paper. The model consists of a neural network and a dispatching command modification module. A sequence-sequence (seq2seq) model based on a long-term and short-term memory（LSTM) network is built, the training is performed using early-warning text information as input into the model. Five scheduling command modification strategies are put forword and the error-prone information is modified to obtain the final scheduling command. It is shown that the model has the ability to generate dispatching commands by using early-warning text information. The introduction of a command correction module can effectively improve the quality of dispatching command generation.

Abstract:The determination of wear thresholds by the methods of wear vertical depth and wheel cycles was presented. The effect of wear thresholds on the prediction of rail profile, wear growth rate, fatigue damage, crack initiaiton position and life was analyzed. The results show that the error by the cubic interpolation spline with different wear thresholds to smooth rail profiles can be ignored. The wear thresholds have little effect on the average wear growth rate and an obvious impact on the fatigue damage. With small wear thresholds, such as the wear depth h≤0.04 mm or the wheel cycles t≤3.0×10⁴, the predicted crack initiation position and life is close to each other. The simulation efficiency is slightly lower. Compared with the results at smaller wear thresholds, the predicted crack initiation position at larger wear thresholds has a deviation of less than 5.0%. The crack initiation life has a maximum deviation of 13.5%. And the simulation efficiency is increased by 50%~60%.

Abstract:An active control strategy of maglev train suspension system based on artificial intelligence load estimation system is proposed in this paper. Firstly, the mathematical model of single-point levitation is given, and the open-loop instability is proven by the Routh-Herwitz criterion. Secondly, considering the load characteristics and the real-time suspension changes, a multi-layer artificial neural network is constructed to control the output of the control variables for the suspension system. Thirdly, the non-dominated sorting genetic algorithm (NSGA) is used to optimize the system parameters. The results show that the proposed control method has better robustness and can still keep relatively small error under large load disturbance.

Abstract:Taking the low-speed maglev vehicle in Maglev Transportation Engineering R&D Center of Tongji University as the research object, the design and optimization of control algorithm for multi-point levitation under nonlinear time-varying disturbance is discussed in this paper. Firstly, the nonlinear mathematical model of multi-point levitation is established, and the output errors of each levitation point are compensated based on cross-coupling control algorithm. Compared with the single-point PID control algorithm, the feedback control algorithm based on cross-coupling can overcome the shortcomings of the previous control algorithm based on the hypothesis of complete decoupling and has high control accuracy and strong robustness. Finally, the effectiveness of the cross-coupling feedback control algorithm is verified by experiments.

Abstract:In this paper, a flexible levitation control method for maglev vehicle-guideway system is proposed based on full-state feedback theory and is compared with traditional stiff control method. The relationship between track stiffness and maglev system stability is investigated. Then, the responses of the system under different irregularity excitations are tested. Results show that the traditional stiff control method without considering the movement of track requires high track stiffness. The system is very sensitive to irregularity,which results in oscillation and instability. However, the flexible control method with considering the movement of track has relatively low requirement for track stiffness and can be stable under different irregularity inputs.

Abstract:A variable capacitor based electrostatic energy harvester including a high elastic electret film was designed. The effects of structure parameters on the output power of the capacitor were studied by finite element method (FEM) and the structure of the capacitor was optimized. The experimental data are in agreement with the FEM calculations. The resonance frequency and output power can be adjusted by pre-stretching electret film and varying seismic mass. For an energy harvester, consisting of a fluorinated polyethylene propylene (FEP) electret film with an active area of 3 cm² and a surface charge density of 0.6 mC·m^-2, a V-shaped counter electrode with a depth of 4.0 mm, and a seismic mass of 0.06 g, an output power of 870 μW was achieved at its resonance frequency of 20 Hz and sinusoidal acceleration excitation of 1g.

Abstract:A point cloud instance segmentation method based on superpoint graph(ISPG) is proposed in this paper. The correlation between the adjacent points of point cloud objects is extracted based on superpoint graph structure. Then, the scene scanned by a sensor is divided into uniform geometric elements to represent the point cloud classes with same attributes. Finally, a graph convolution network is used to implement instance segmentation. It is shown that the method has an accuracy of 48.9% on Stanford’s large 3D indoor spatial dataset S3DIS when the IoU threshold is 0.5.

Abstract:A combination of behavioral and electroencephalogram (EEG) experiments was adopted to analyze the effect of appearance characteristics (shape, color, material) and its familiarity (low, medium, high) on product identity. Before the experiment，subjective evaluation data from participants were obtained through questionnaires and hypotheses were proposed. The EEG experiment is based on the classic learning-recognition paradigm，with the experimental materials of 3(shape, color, material)×3(low, medium, high) hybrid design. The results show that low and high familiar color characteristics, low familiar shape characteristics, and high familiar material characteristics can enhance product identification degree.