Abstract:Based on a series of wind tunnel tests conducted on the rigid model of an actual high-rise building, wind dynamic interference effects on the target building of the proposed super high-rise building and other surrounding buildings were investigated. The results show that upon completion of the proposed building upstream, the shielding effect of it will generally reduce the along-wind mean aerodynamic force of the existing buildings downstream. However, the vortex shedding in its wake may lead to a significant increase in the acrosswind peak wind load of the existing buildings downstream, which means that these downstream buildings under the original structural design may no longer be safe.

Abstract:Based on the experimental study of 4 bolted-side plates (BSP) beams, a numerical finite element analysis using OpenSees was conducted on the entire loading process and the shear failure of BSP beams.The nonlinear behaviors of materials and slip model on the interface between steel plate and concrete beam were taken into account. The results of the finite element analysis were found to be in good agreement with the experimental results. The main parameters affecting the behavior of BSP beams were analyzed, including the number of rows of anchor bolts, anchor bolt spacing along the beam, steel plate depth, steel plate thickness, yield strength of steel plate, anchor bolt diameter, concrete strength and so on. The results show the influence of the parameters on the shear bearing capacity, longitudinal and transverse slip, which provides basis for the strengthening design of BSP beams.

Abstract:An earthquake-damaged eight-storey recycled aggregate concrete frame model was retrofitted by using epoxy injection and steel energy dissipation devices，then shaking table test was conducted to investigate earthquake response of the retrofitted frame and damping effect of the steel dampers. Based on the test results, damage observation, dynamic characteristic, acceleration and displacement response of the test model were analyzed, furthermore, stiffening and damping effects contributed by the steel dampers to the primary frame were discussed. The test results indicate that inter-storey stiffness degradation can be reduced by hysteretic damping effect of the steel dampers, and acceleration response can be effectively controlled under strong earthquake excitations. Yielding sequence of the steel dampers along the floors starts from the middle floor towards the upper and lower floors. Deformations of the steel dampers installed at the middle floors increase greatly, dissipating a large amount of input seismic energy.

Abstract:To study the effect of shear creep on long-term deformation of large span concrete bridge, aiming at the problem of shear creep coefficient, an experimental device and test method based on torsion was proposed for shear creep test. Three groups of shear creep members were tested to obtain creep coefficient curve lasted in 375 days. And based on the modification of axial compression creep model of current specification, the rules of shear creep progress was analyzed with finite element(FE) analysis verification. The results show that the shear creep test device based on torsion can be used to load the concrete element effectively. And creep coefficient formula deduced from torsion creep can be used for test data analysis. The C30 concrete shear creep ultimate value is 2.26~2.63 times of specification compression model. The early aged shear creep progressed smaller than compression creep, but accelerated in the later age. Torsion and other significantly shear effected structures should consider shear creep action in creep analysis.

Abstract:Based on existing research results on grout sleeve splicing for reinforced bars, insufficient grouting defects in actual projects were simulated by controlling artificially the content of grout. Monotonic tension tests were carried to study the performance of mechanical properties and deformation. High-stress reversed tension and compression test and large-deformation reversed tension and compression test were carried to study the mechanical performance under minor and major earthquakes respectively. The content of grout was the only influencing factor in the test. The thickness of grout above the bar reflected the level of the grout content in horizontal connection, the upper steel’s anchorage length reflected grout content in vertical connection. The test results show that two categories of failure pattern might happen, pullout or fracture of the bar, which was decided by the bond capacity, between the bar and the grout, together with the tensil capcity of the bar. The bond capacity is mainly affected by grout content.

Abstract:Large-span steel structures will inevitably cause some relaxation under the influence of actual engineering operations or environmental influences. After the cables are loosened, the force system must be readjusted to a new equilibrium, which will cause the internal forces of the members increase or decrease, and affect the structural safety. The designed cable-truss structure with a span of 6 m as the object, the experiment on relaxation of cable was done. A study was made of the influence to spoke cable-truss structure when different cable was loosened. It is concluded that the effect of relaxation on the loop cable is most obvious, and the loop cable is defined as the relaxation sensitive component, the most unfavorable structure occurs when all the lower radial cables are relaxed. Based on the reliability theory, the influence of different cable tensions on the reliability of the spoke cable truss structure and the sensitivity of different parameters of the structure were obtained by the response surface method and Monte Carlo method, the safety assessment could be performed for the prestress loss of the spoke cable truss structure.

Abstract:A two-and-a-half-dimension finite element method (2.5D FEM) was established to investigate the surface vibration of the unsaturated ground subjected to moving loads caused by high-speed trains. The track structure was simplified as an Euler beam resting on an unsaturated porous half-space. The Galerkin method was used and the governor equations of unsaturated soil of 2.5D in frequency-wavenumber domain was derived by applying the Fourier transform with respect to time and the load moving direction. The influences of train speed and water saturation of unsaturated ground on ground vibration and excess pore water pressure are analyzed. Results show that, at the track center, the displacement amplitude largely decreases when the water saturation decreases from 100% (fully saturated) to 99% (nearly saturated); for a given speed, the ground vibration displacement of unsaturated ground attenuates faster with time than the saturated ground. At 8 m away from the track center, the displacement amplitude of the unsaturated ground is larger than that of the saturated ground when the train speed is below 250 km?h-1; as the speed increasing, the duration time of the unsaturated ground vibration displacement becomes shorter as the speed increases, while of the saturated ground it becomes longer. The displacement amplitude at 200 km?h-1 is larger than the other speed near the track (less than 5m) and attenuates rapidly at an equal rate. The rebound phenomenon of acceleration may occur at some train speed, and the location is strongly related to the train speed. The excess pore water pressure is mainly distributes within 4.5 m below the ground surface and the maximum amplitude is located at 1.5~2.0 m depth and decreases significantly as the water saturation decreases.

Abstract:With the increasing of the production and scale of raft-culture in Qinhuangdao coastal water, the characteristics of hydrodynamic and environment were changed by layout of a large number of breeding cage. A hydrodynamic and water quality model was calibrated and validated by the physical experiment of raft-culture and observation data. The validated model was used to simulate the hydrodynamic and pollutant transport process respectively with or without the raft-culture. The influence mechanism of the raft-culture on hydrodynamic and the pollutant transport was studied. It reveals that flow in the culture zone can be obstructed where the velocity decreases obviously; the velocity reduction in a higher density raft-culture zone is larger than that in a lower density zone; pollutant transport is obstructed by raft-culture, which leads the impact of obstruction concentrates inside raft-culture zone and the impact degree decreases progressively toward the sea from the raft-culture zone.

Abstract:This paper aims to explore the impacts of connected and automated vehicles (CAV) on traffic flow efficiency based on in-depth microscopic simulation studies using cooperative gaming method. First, the Gipps car-following models were integrated into an improved cellular automata model to mimic the regular vehicle’s driving behavior. Then, cooperative gaming method integrated with enhanced Q-learning was employed as the modeling platform for CAV, to strengthen the capability of the simulation system in realistically reproducing CAV lane changing and car following behavior. Finally, a 2lane freeway stretch was applied to our simulations, and with extensive simulation studies we obtained some promising results. The study results suggest that the impacts of CAV are quite positive. The inclusion of CAV considerably improves traffic flow, mean speed, and traffic capacity. Such understanding is essential for research concerning CAV as well as the CAV implication for future traffic management and control.

Abstract:Aiming at the traffic design and signal control for the tandem intersection, the traffic conflict technology was used to analyze the traffic safety of the sorting area. The results show that the traffic volume is one of the main factors. On this basis, the robust optimization model of tandem intersection was established by taking the stochastic variation of the traffic volume into consideration. Then, the improved NSGA-II algorithm was used to solve the model and the minimum deviation analysis for subjective and objective information(MDASOI) method was used to analyze the optimization results and the robust optimal scheme was obtained. Case analysis and comparison results show that the proposed model can get an optimal timing method by taking into account the interference of import traffic volume stochastic variation. Compared with the traditional Highway Capacity Manual(HCM) and Australian Road Research Board(ARRB) timing method, this model could reduce the average vehicle delay of about 28.80% and 6.29% and the maximum queue length of about 32.43% and 7.41%. Compared with the example scheme, the optimization scheme of this model can reduce traffic conflicts of the left and right by 23.8% and 11.1%, which improves the safety benefit of the whole intersection.

Abstract:In order to precisely describe the interactions and develop accurate simulation models, an analysis was made of the characteristics of bicycle group and the dynamic multistep decision process of drivers, based on which a three-layer modeling framework consisting of drivers’ perception, decision making and action were proposed, and a modified social force model was used for simulation and model evaluation. The results can give further support to build a more reliable microscopic simulation platform and provide ideas for autonomous vehicles.

Abstract:A new modeling approach based on frequent and equidistant speed measurements was proposed. Driving simulation experiments were carried out to collect free-flow speed data on mountainous freeways. Operating speed profile was derived and grade, curvature, super-elevation, and dynamic sight distance variables extracted from upstream and downstream segments were used to estimate a generous operating speed prediction model. Results showed that as the expected, the average grade and curvature of the segment, the maximum superelevation and the existence of reverse curve decreased the drivers’ speed and the curvature differential between the downstream and upstream segment also reduce the speed. The adjusted R2 of the operating speed model was 0.74 and the averaged absolute prediction error for training set and testing set were both under 3 km?h-1. This study took the advantage of high resolution speed data collected from driving simulator and provided a new methodology to model continuous speed data. The results indicated the effectiveness and capability of the proposed modeling strategy.

Abstract:This paper models the arrival and departure tracks utilization scheme adjustment problem on the basis of arrival and departure tracks time-space resources discretization from a microscopic description perspective. A binary integer programming model was built to solve the adjustment problem. The model’s objective was to minimize the sum of weighted total train delay as well as the arrival and departure tracks utilization cost of trains with a consideration of the trains safe and satisfying arrival and departure, also a genetic algorithm-simulated annealing hybrid algorithm was designed to achieve a satisactory adjustment. A case study was made of a railway passenger station to verify the effectiveness of the model and algorithm. Results show that the propased model can describe the adjustment problem accurately, and obtain the solution within a relatively short period of time with the designed algorithm, thus, realtime adjustment for arrival and departure tracks utilization scheme is achieved. In addition, the adjustment results can provide guidance on the timetable rescheduling for the train dispatchers.

Abstract:In suburban rail transit line, the operation of fast-slow trains can be well adapted to uneven spatial and temporal distribution of the passenger flow. However, due to the use of nonparallel operation diagram, the proportion of fast and slow vehicles, the distribution and quantity of the overtaking station, the interval of train departure and so on, all have different influence on the carrying capacity of the line. In order to study the influence mechanism and internal relationship of carrying capacity with different parameters of suburban line under fast-slow mode, a calculation idea was put forward, and then the calculation and expression of the carrying capacity was established by considering the quantity of overtaking and the proportion of fast and slow vehicles. Shanghai Metro Line 16 being taken as an empirical study, the proposed methods were proved effective. This study results contribute to a theoretical reference for the calculation of the carrying capacity of suburban line under fast-slow mode.

Abstract:A volume fraction prediction method of hydration products of the paste containing silica fume with low water to binder ratios was proposed, which considered the cement hydration mechanism and silica fume reaction mechanism with low water to binder ratios and modified the shrinking-core model. The comparison of calculation results of the proposed method, expeimental results and theoretical results of Power Model and Jensen Model showed that the proposed method was capable of simulating the hydration process and predicting volume fractions of different hydration products well; When no silica fume was mixed, volume fractions of unhydrated cement and chemical shrinkage calculated by the proposed method were basically the same as that of Power Model while volume fractions of hydration products of the proposed model were close to that of Jensen Model with silica fume.

Abstract:An intelligent vehicle cooperative driving strategy based on non-cooperative model predictive control (MPC) was proposed. Firstly, the cooperative driving model was presented, in which the shared control of the vehicle was realized. Next, the cost functions of the driver and the control system were obtained. Then, the Nash equilibrium solution of the non-cooperative MPC was achieved. At last, simulations were used to verify the advantages and effectiveness of the strategy. It is shown that the Nash equilibrium solution of the non-cooperative MPC can be achieved by a non-iterative method. And gradual handover of the driving privilege is realized by using the updated confidence matrixes of the driver and the control system. Simulations based on Matlab show that the noncooperative MPC cooperative driving strategy can deliver the driving privilege from the driver to the control system gradually when the intelligent vehicle encounters danger. And this strategy can guarantee that the driver is in the control loop all the time.

Abstract:An investigation was made on a diesel bus certified to CHINA V emission standards, and a test was conducted on the bus cycle on a heavy chassis dynamometer in China typical cities, the buses of which were fueled with diesel (D100), 5%, 10%, 20% waste cooking oil bend with diesel fuel (i.e. B5, B10, B20 respectively) to understand the emission characteristics of soluble organic fraction (SOF) and polycyclic aromatic hydrocarbons (PAHs). The results show that SOF component emitted by CHINA V bus is mainly concentrated on fine particles with size of 0.1~0.5 μm, fatty acids are mainly composed of even carbon fatty acids with 8~18 carbon atoms, as well as the alkane component’s carbon number is 16~36, the alkane component has a bimodal distribution as the number of carbon atoms increases. And the number of rings of PAHs is mainly 3rings or 4rings. Compared with diesel, the particulate matter quality, fatty acid, alkane and PAHs emission factors of CHINA V bus fueled with biodiesel reduces, the ratio of SOF in particulates increases, 3-ring PAHs declines, and the particulate matter toxicity of biodiesel is basically the same as that of diesel.

Abstract:The bogie areas of a high-speed train are the focus of aerodynamic drag reduction research. A 7-parameters model of high-speed train underbody structure was established by spline curve method. The influence laws between underbody structure parameters of a high-speed train and aerodynamic drag were studied by computational fluid dynamics and Latin hypercube sampling (LHS) experimental method. The results show that 27%, 37%, 39% and 22% aerodynamic drag changed in the three cars model, head, middle and tail car with varying underbody parameters, respectively. The height of side cover, height of cowcatcher, radius of bogie cavity leading edge are most sensitive parameters to drag of three car model. However, the influences between underbody structure parameters and the aerodynamic drag are different for the three cars model and each car model. In order to achieve a better drag reduction, it is necessary to consider the aerodynamic design of underbody structures of the head, middle and tail car, respectively. The underbody structure parameters mainly influence the aerodynamic drag of the underbody structure by affecting the mean velocity beneath the train body, therefore, the aerodynamic drag of a high-speed train is influenced.

Abstract:Once urban land price and liquidity fluctuate sharply, risk contagion may occur and the credit defaults event of urban construction investment company (UCIC) relying deeply on the land market may be triggered. Firstly, this paper studies the mechanism of land risk’s contagion effect on the credit of UCIC theoretically based on the balance sheet theory through three channels, namely land price fluctuation-collateral value channel, land price fluctuation-capital channel and liquidity-financing channel. Secondly, the study identifies 52 urban construction investment companies in China as research samples, and the directed acyclic graph (DAG) technology and vector auto regressive (VAR) model are employed to verify the risk contagion mechanism. The empirical results of the three channels show that: Urban land price fluctuation has significant short-term influence on UCIC’s credit defaults, and its risk contagion effects take place through land price fluctuation-capital channel signifying UCIC’s financing ability. Urban land fluctuation has significant amplificated long-term influence on UCIC’s credit defaults through the liquidity-financing channel. The contagion effect via investment, revenues and cash payment risk does not have significance.

Abstract:Aiming at the duopoly competition model of a dual channel retailer and a pure online retailer, This paper establishes demand model and profit model respectively. The results show that the pricing order affects the retailer’s profit and delaying the pricing time will gain more profit. At the same time, we also analyze the influence of the products substitution on the profit, price and sales volume. Under the condition of mature channels and products, the higher the degree of substitution is, the higher the profit, price and sales volume are. When the degree of product substitution is large, retailers are not only competitive but also complementary. At this point, retailers should strengthen cooperation to drive the growth of the overall market.