Abstract:Large transverse dynamic responses will occur in the tower columns due to the lateral restriction between the tower and the main girder of the cable stayed bridge subjected to strong ground motions. In the current seismic design of cable-stayed bridges, a larger reinforcement ratio in tower columns is consequently needed to achieve the target seismic performance, leading to the increase in the number of the piles and its reinforcement ratio as well, whose engineering efficiency is therefore questionable. An incremental dynamic analysis(IDA) was conducted to study the lateral elastic-plastic perform and damage mechanism of the H-shaped concrete tower. The finite element analysis and quasi-static test were conducted to verify the IDA result and investigate the limited ductility of the tower in resisting the earthquake and to find out the reasonable performance objective and index.

Abstract:In this paper, the seismic performance of the geosynthetic reinforced soil-Integrated bridge system(GRS-IBS) structure is analyzed by conducting a set of shaking table test with a full bridge model. The results show that the GRS-IBS structure has a good seismic performance. Under the motion of Kobe seismic wave with a peak acceleration of 0.8g, the overall stability of the structure is good, and only minor deformations occur, such as surface excavation and differential settlement between the bridge beams. Under the premise of keeping the same ratio of Tf to Sv, reducing the reinforcement spacing helps to improve the seismic performance of the GRS abutment.

Abstract:A numerical computational fluid dynamics (CFD) model to simulate tornado-like vortices was proposed. The tornado-generation mechanism was similar to that of the physical generator developed at Tongji University. The feasibility of this numerical model was verified by comparing the simulation results associated with tornado-like vortices with the experimental and field observation data. Furthermore, the three wind velocity components at tangential, radial and axial directions, wind pressures, vortex radii and turbulence characteristics of tornado-like vortices at three swirl ratios were investigated. The result shows that, with the increase of swirl ratio, the maximum tangential velocity and the radius of vortex core increase when the pressure and the standard deviation of tangential velocity around the tornado-like vortex center decrease. In addition, the single tornado-like vortex gradually breaks down and develops into a double-core structure.

Abstract:In order to explore the damage mechanism and protection technology of concrete hollow block filled wall subjected to the synergistic effects of blast and fragments, a model of block filled wall, fragment, and explosive was established by using ANSYS/LS-DYNA, and a numerical simulation of the damage caused by fragments and blast wave was conducted. The difference of the displacement response of the block filled wall under the action of shock wave, fragment, and a combination of the two was analyzed, and the influence of different block strengths, wall rib ratios of hollow block, mortar strengths, and mesh densits on the displacement response of block filled wall was investigated. The reinforcement effect between polyurea elastomers, polyurea elastomers and steel mesh reinforcement was compared. The numerical results show that the modeling method is reliable. The displacement of the masonry filling wall is greater than that of the two under the composite action of prefabricated fragments and shock waves. The increase of the strength of the block and the thickness of the thickened hollow block is beneficial to the anti explosion of the wall, and the strength of the mortar has little effect on the failure of the wall. The effect of steel wire mesh and polyurea elastomer joint reinforcement is better. Densified wire mesh has a better reinforcement effect.

Abstract:In order to simulate the water movement in the unsaturated remolded loess under ponding and rainfall conditions, an improved infiltration model based on the modified Green-Ampt model and the model proposed by Wang Wenyan et al., which can reasonably consider the effect of suction at wetting front and the water content profile, was proposed. The reliable method for determining the parameters needed in the model based on the modified GreenAmpt model and the numerical method for solving Richard’s equations was also recommended. The research results show that the improved model can more accurately predict the movement of wetting front and the water content change at measured points in the onedimensional ponding infiltration test, compared with the modified Green-Ampt model and the model proposed by Wang Wenyan et al. When the unsaturated hydraulic conductivity function was determined directly by the improved wetting front advancing method in the ponding infiltration test, the results are closer to the measured values compared with those parameters indirectly determined by the saturated permeability test and water retention curve. For rainfall infiltration, the water profile after runoff obtained by the improved model is similar to that obtained by the numerical method, especially for the soil with a higher dry density.

Abstract:This paper studied the commonality and personality of bridges at network level, summaried, and generalized the intrinsic rules according to their similar deterioration patterns. A network-level assessment and prediction method was proposed, for the first time, based on multi-source data. For large quantities of inspection reports, monitoring reports and bridge design drawings, the data integration and regulation process was conducted in order to extract key parameters and data sets applying to neural network of structures and components. A series of deterioration models were generated incorporating maintenance effects, based on which the condition assessment and deterioration prediction was realized for bridge populations. Based on the highway network in Shijiazhuang, an example was presented to verify the systematization and effectiveness of the proposed method for the purpose of bridge network management and decision-making.

Abstract:To depict the cross-line overtaking behavior of non-motorized vehicles at mixed flow road section, this paper analyzed the characteristics of cross-line overtaking behavior and defined the key parameters first, and then proposes the overtaking elapsed time estimation model for non-motorized vehicles based on survival analysis. It utilizes 160 field trajectories of cross-line overtaking non-motorized vehicles to calibrate the proposed model. In order to verify the effectiveness of the model in mixed flow, it further applies the model and integrates it with the car-following model, the lane-changing motivation model, and the gap acceptance model to the self-developed microscopic traffic simulation package TESS NG by adopting the classic micro-simulation model VISSIM as the evaluating benchmark. The result shows that the simulation accuracy of TESS NG is 90.12% in terms of estimating the overtaking elapsed time of non-motorized vehicles, which is far better than the 67.4% achieved by VISSIM and the relative error of median survival time is 2.56% which is 43.58% less than that of VISSIM.

Abstract:A prediction model was established for the high-speed train equivalent pass-by duration at a speed of 300 to 380 km?h-1, and the corresponding calculating program was written. Based on the test and analysis of high-speed train noise, the directivity index, multi-source model and travel time correction were utilized to adjust and improve the numerical study of dipole source acoustic radiation. The validity of the prediction model was checked against the 300 to 380 km?h-1 experimental results, which was in good agreement. The equivalent pass-by duration coefficient of high-speed trains increases gradually with the increase of speed and presents an opposite tendency at the near field and far field distance. The previous conclusion that the equivalent pass-by duration at the near field is equal to l/v is no longer true at high speed.

Abstract:Based on the prediction method for the coexistence of the rail rolling contact fatigue (RCF) crack initiation and wear growth, the influence of track geometric irregularity on wheel-rail contact position distribution, rail wear, and fatigue damage were taken into consideration. The distribution probabilities of wheel-rail contact positions on the rail were introduced to disperse the wear and fatigue damage accumulation in the rail. The conclusion shows that the distribution range and probabilities of the wheel-rail contact positions will change with the wear growth and profile evolution influenced by the track geometry irregularity. Then the scope of the wear on the rail surface and the fatigue damage inside the railhead will widen and the damage rate will be reduced. For the 75 kg/m rail as the high rail in the curve of 800 m radius in heavy-haul railway, the growth rate of the average wear is 3.813 1 μm? 10-4 cycles before RCF crack initiates and the crack initiation life is 318 292 cycles. The growth rate of the average wear and the crack initiation life predicted by the above method are about 15.92% lower and about 14.66% higher than those predicted by the method without considering the track geometry irregularity respectively. Moreover, the crack initiation position is a little farther away from the rail center.

Abstract:A novel low-temperature early-strength accelerator was designed with three components, such as calcium bromide, lithium bromide, and triisopropanolamine. Besides, the early strength property and its influence on the comprehensive performance of concrete were studied at 5 ℃. In addition, the early strength mechanism of the early strength accelerator was discussed. The results show that the low-temperature early-strength accelerators make the 1, 3, 7, and 28 day compressive strengths of C50 concrete cured at 5 ℃ increase by 57%, 32%, 23%, and 12% compared with the contrast sample, respectively, and the strength development is close to that of the contrast sample cured at 20 ℃. Moreover, the low-temperature early-strength accelerator will increase the dry shrinkage of concrete slightly, and the electric flux of concrete before 56 d will increase by 0.7% to 10.1%. At 5 ℃, new types of hydration products such as bromine-containing C-S-H gel and calcium aluminum oxide bromide hydrate (Ca₄Al₂O₆Br₂·10H₂O) are generated through hydration reaction. There are also much needle-rod-like ettringite and flake Ca(OH)₂ crystals formed in the pores or embedded in the surface of the gel products. Therefore, the structure of the samples will become denser, due to the refinement of pore size and the reduction of total pore porosity.

Abstract:A method for establishing the lane changing steering model was presented, which was based on the steering target aiming point of the driver and was oriented to the steering maneuver layer. Based on the characteristics of the emergency lane changing, a lateral trajectory model was established. Combined with the theory of far and near aimed point, a driver steering model of lane changing was established and the distribution characteristics of gain factors were studied. The research results show that the steering model performs well when explaining realistic emergency steering behavior.

Abstract:In order to solve the small target detection convolutional neural network algorithm, the PVANet convolutional neural network structure was improved to conduct the experiments of traffic sign detection on the TT100K traffic sign data set. The shallow feature extraction, deep feature extraction, and HyperNet multilayer feature fusion modules were improved. The experimental results show that the improved PVANet convolutional neural network has an excellent detection ability for small target objects, and the corresponding traffic sign detection algorithm can achieve a higher mAP (mean average precision).

Abstract:The EHT (equivalent homogenous temperature) was calculated by using the coupling model of CFD and human thermoregulation model. The effects of air conditioning velocity, temperature, and solar radiation on overall EHT， mean skin temperature, and dry heat loss were compared, and the contribution ratio of the these factors were calculated. The results show that the influence of air conditioning is greater than that of solar radiation, in which the influence of the supply air temperature is most significant. Finally the fitting equation of the three factors and EHT were obtained, and a new idea to improve air conditioning controlling based on the fitting equation was proposed.

Abstract:In this paper, the 3/4 open-jet closed circuit model wind tunnel with a ratio of 1∶15 was taken as the research object. By placing the Ahmed body model with different proportions, the combination of experiment and numerical simulation was conducted to study the influence of blockage ratio on nozzle wind speed measurement by using the nozzle method and the plenum method. The results indicated that, for different blockage ratios, the measurement error of the plenum method was slightly larger than that of the nozzle method, but the sensitivity of the plenum method to the correction coefficient was significantly lower than that of the nozzle method i.e., more working conditions could be corrected with fewer correction coefficient for plenum method, which meant that the plenum method was easier to be corrected.

Abstract:Finding out the factors influencing the utilization rate of regenerative braking energy of Urban Rail Transit(URT) vehicles is of great significance for improving the scientificity of energy-saving measures in URT operation. Based on a built simulation model, the scenario analysis method was used to quantitatively analyze the influencing factors of departure interval, time difference, passenger load, traffic density and road condition on regenerative braking energy utilization rate and traction energy consumption of traction substation. The main factors were given. The multi-condition simulation of the low regenerative braking utilization indicate that the opening times of train braking resistance and the occurrence times of low voltage at the station are strongly correlated with the utilization of regenerative braking energy and power quality of the station. Taking the departure interval of multi--period operation of Shanghai metro line as an example, the simulation strategy of URT departure interval was discussed to guide capacity allocation of the stationary energy storage system. The results of this paper can provide reference for the formulation of energy-saving measures for URT.

Abstract:An efficient willow tree algorithm is proposed to price CVA (credit valuation adjustment) with WWR(wrong way risk), which can also calibrate the default probability by credit swap spreads. Besides, some numerical experiments are presented to illustrate the accuracy and efficiency of the proposed method.

Abstract:As one of the most important tools to manage the risk of volatility, a lot of attention has been paid to volatility index options. In order to price these options, a willow tree of underlying index was built in the constant elasticity of variance model. Then, the value of volatility index at each node in the willow tree of underlying index was determined. Next, the willow tree of volatility index was used to price volatility index options by backward induction. Finally, an efficient way to price volatility index options was proposed. Numerical results show that the pricing results given by the willow tree are consistent with the results obtained from nested Monte Carlo simulation when the number of nodes on each time period in the willow tree is bigger than 200.

Abstract:The stated preference (SP) method is a way to study people’s preferences through experiment design, often implemented with discrete choice models to estimate the parameters. This paper focuses on deriving the effective sample size for SP experiments which guarantees accurate parameter estimations by proposing an easy-to-operate and comprehensive framework. By applying the framework on an empirical study, a linear model is estimated which reveals that the number of factors and levels, scale of parameters, sample size, and the experimental design strategy have significant impacts on the accuracy of parameters. The effective sample size estimation models of three design strategies are obtained, based on which some practical principles for SP experiment design are proposed.

Abstract:The safety risks of prefabricated concrete structure in the construction phase are identified through field research and conference discussion, and are quantitatively evaluated by using Bayesian network. The results show that the probability of prefabricated components instability during hoisting is the highest, followed by prefabricated components toppling, and the violent sloshing of prefabricated components during hoisting. To deal with these safety problems, concrete risk control measures are proposed from a microcosmic perspective of site management, design and construction coordination in project and a macrocosmic perspective of development environment in industry. A multi-angle and multi-stage construction risk prevention and control mechanism is constructed, which will provide reference for construction safety management of prefabricated concrete structure.

Abstract:To improve the order picking efficiency in the fishbone aisle warehouse, a chaotic SAPSO (Simulated annealing particle swarm optimization algorithm) was proposed based on the picking path distance calculation model and the picking path optimization model with the minimum distance of the picking path as the optimization objective. The chaos theory was introduced to improve the global convergence property. The SA (simulated anneaing algorithm) was adopted to make the algorithm able to jump out of the local optimization and achieve global optimization. Finally, the outperformance of chaotic SAPSO algorithm to solve order picking optimization on fishbone aisle warehouse was verified by the simulation results and the comparison with other algorithms, and it provides a new solution to order picking problem in fishbone aisle warehouses.