Abstract:The overall stability is the essential requirement of the structural design of super-tall buildings. A single driven constraint optimization design method based on the sensitivity of the stiffness-weight ratio was proposed to control the P-Δ effect (additional effect of gravity caused by horizontal deformation of structure) of super-tall buildings. Stiffness-weight ratio, the ratio of stiffness to gravity load, is an important parameter that affects the P-Δ effect. Based on the principle of virtual work and the method of equal increment analysis, the formulas of sensitivity coefficients were deduced, and the sensitivity coefficients of a two-story plane frame were calculated as an example. The feasibility of the proposed method was verified theoretically. Finally, the proposed method was applied to a super-tall building with a building height of 468 meters. And after adjusting the dimensions of components, a total cost of 9.391 million yuan was saved. The feasibility of the proposed method was illustrated by this engineering case. The results show that the proposed method can reasonably distribute the materials to different component groups for a super-tall building structure with the stiffness-weight ratio as a driven constraint, which can realize the economical and practical structural design.

Abstract:To investigate the rationality and the effective connection mode of the superimposed surface of the superimposed type retaining wall, three types of new precast cantilever concrete retaining wall (the keyway superimposed type retaining wall, the truss bar superimposed type retaining wall and the spiral bar superimposed type retaining wall) were proposed. Static loading tests were carried out for three kinds of new precast retaining walls and two groups of control retaining walls. The results show that the deterioration degree of bearing capacity of the three new retaining walls is limited (within 15%) compared with the cast-in-place retaining wall. The superimposed type retaining wall is an effective mode of precast retaining wall, which has good applicability and feasibility. Among three kinds of the precast retaining wall, the truss bar superimposed type retaining wall has a reliable superimposed surface, strong crack resistance, good integrity, and better bearing capacity. Therefore, the truss bar is an effective way to improve the connection performance of the superimposed surface.

Abstract:By using the Boussinesq solution, the formulas for calculating the vertical additional stress of the foundation center under the action of conical and truncated cone shaped load were given. The attenuation of vertical additional stress with depth was found much greater than that under other types of loads. By using the elastic finite element method, the vertical additional stress coefficient diagram of any position of foundation under the action of conical load was given, and the calculation problems of vertical additional stress and ground settlement at any position under the conical and truncated cone shaped load were solved. A case study was carried out to testify the necessity of using the proposed method to give the axisymmetric additional stress solution. Furthermore, a calculation example was given to analyze the mutual influence rule between the vertical additional stress of the foundation and the surface settlement under the action of two conical mountains.

Abstract:Two geotechnical centrifuge model tests with a similar ratio of 1:100 were performed to investigate the reinforcement effect of inclined piles for the existing pile-net composite foundation on soft soil overlying sloping base. The test results show that due to the reinforcement of inclined piles, the post construction displacement (vertical and horizontal) on the top of the embankment is reduced effectively and the development of the settlement difference on both sides of the embankment top can also be controlled. Meanwhile, reinforced by the inclined piles, the horizontal and vertical displacement of the pile top of the slope pile and friction pile in the existing composite foundation can be restrained effectively, and the damage of the geogrid and the generation and development of the asymmetrical “basin” settlement of the composite foundation can be prevented. In addition, the horizontal thrust in the existing composite foundation can be reduced and the stiffness and stability of the foundation can be improved significantly by inclined pile reinforcement. The research shows that the inclined pile is an effective measure to reinforce the existing pile-net composite foundation on soft soil overlying sloping base.

Abstract:A dynamic guidance solution based on “digital twin-driven model” for fire evacuation was proposed to solve the prevalent problems of building emergency evacuation. And this model can also solve the problems that the current expression of building safety evacuation was mainly two-dimensional, and the evacuation path planning couldn’t be carried out in real time and dynamically according to the development trend of fire, and the location of people couldn’t be considered. The proposed method used BIM (building information modeling) and IoT (internet of things) to build a digital twin-driven model for evacuation, integrated the information of space, indoor environment and personnel location in the proposed model, and used Dijkstra algorithm for evacuation path planning. Taking a building in the bobsleigh and sled stadium of the 2020 Beijing Winter Olympic Games as an example, the proposed model could well realize the functions of real-time collection of environmental information, 3D visualization of indoor layout, fire alarm, indoor personnel positioning, evacuation path planning, etc.

Abstract:Taking the test pipeline of urban water supply and drainage network base as an object, the field experiment was carried out on a buried depth 0.6 m water pipe with a diameter of 100 mm, to explore the feasibility of 3D ground-penetrating radar (GPR) in detecting pipeline leakage. Perpendicular to the pipeline, 31 parallel test lines were set around the leak-point and the C-scan GPR data were collected in the experiment. By comparing the 2D radar profile and 3D migration imaging of radar data before and after the leakage, it is found that 3D GPR can detect and identify the geometric shape of the underground target more effectively, and determine the scope and size of the surrounding soil infiltration area caused by the leakage of underground water pipes, so as to determine the leakage location

Abstract:In order to obtain the true mechanical response of UHPC（ultra-high performance concrete） pavement of steel bridge deck, a field loading test was carried out on Tongji Road steel bridge in Shanghai. The strain response characteristics of pavement under static load, dynamic load and in operation period were analyzed. Results show that the maximum tensile strain area of the pavement layer is on the top of the pavement layer which is above the U-shaped rib side, and 0.25 m from the diaphragm plate longitudinally. The direction of the maximum tensile strain, with a value of 25.1×10^-6, is transverse. The dynamic response characteristics of UHPC pavement under dynamic load are different from those of steel bridge asphalt pavement. The tensile strain value of UHPC pavement only decreases with the increase of loading speed. And the dynamic response curve of strain has three kinds of waveforms, and shows three kinds of changing characteristics with the increase of velocity. During operation period, the extreme value of the tensile strain of UHPC pavement is obviously larger than that of static load, but the dynamic response characteristics are consistent with those of dynamic load.

Abstract:In order to study the mechanical properties of bolted joint for U-ribs in the composite bridge deck, a full-scale composite deck specimen with wide U-ribs was designed. The mechanical properties of this bolted joint were tested by fatigue loading test, and the stress of joint was analyzed by finite element model. The test results show that the crack is initiated from the vicinity of the bolt hole of based plate and propagated to the hand-hole. And the finite element analysis indicates the stress concentration located at 1/3 hole diameter from the hole edge near the head row bolt hole of the based plate is obvious, and the concentration coefficient is about 2.5; the configuration of hand-holes and the dimensions of splice plates or bolt holes have little influence on the stress concentration of the bolt hole of the based plate. Compared with the 8 mm thick U-ribbed composite plate or the conventional steel bridge deck, the stress of the bolt hole of the joint mother plate of the proposed composite plate is much larger, but its fatigue strength also meets the requirements of the code.

Abstract:For the emergency collision avoidance condition, a new method of path planning and a path tracking feedback preview driver model were proposed and designed. Firstly, a collision avoidance path planning method based on Sigmoid curve and physical limitation was proposed, and a driver model combined with optimal curvature preview and closed-loop feedback steering correction was established to achieve the fast and precise tracking of the planned path. Then, the effectiveness of the collision avoidance path planning and the path tracking feedback preview driver model was verified by CarSim+Simulink offline co-simulation platform. Finally, based on the self-modified test vehicle, a real vehicle test was carried out to verify the feasibility and real-time of the proposed path planning method and driver model. Both the simulation and real vehicle test results show that, the planned path and driver model for collision avoidance can control the vehicle to avoid obstacles quickly and safely.

Abstract:Conventional evaluation indices for road ride comfort cannot adapt to scenarios where vibration information is distributed randomly in the space or time domains. To overcome these deficiencies, local impact and vibration perception window concepts are proposed to characterize vibration information; a characteristic vibration dose value is determined to demonstrate that humans are sensitive only to major vibrations and the proximity between successive vibrations. The proposed index is optimized using an orthogonal test and shows better correspondence with actual human sensations when compared to the results of frequency weighted root mean square, maximum transient vibration value, and vibration dose value.

Abstract:A method combining sampling expansion with geographically weighted Poisson regression (GWPR) was proposed to estimate the road network traffic volume with limited observation values. Firstly, a sampling expansion method based on the spatial similarity was employed to correct the imbalance missing data. Then, the GWPR was employed to estimate the hourly traffic volume of the lane considering the influence of the geometric characteristics of the road and the built environment. Results show that: compared with traditional linear models and GWPR with the original sample set, the proposed combination model has the best estimation performance. In addition, the local spatial heterogeneity of the relationship between independent variables and traffic volume is also well captured.

Abstract:A novel low-cost monocular vision based robot end pose measurement method was proposed, and the kinematic parameters identification of a 6-DOF manipulator was designed and implemented. By using the hierarchical measurement method and the absolute coding method with calibration plate, the problems such as the small measurement range and the large influence of the camera distortion on the measurement accuracy in the current visual measurement process were solved. The robot calibration process was simplified by using the kinematic parameter identification model based on position error and monocular vision measurement system. Finally, the practicability and effectiveness of the proposed scheme were verified by experiments.

Abstract:In order to reduce vehicle energy consumption and control battery state of charge(SOC) at the same time, a multi-objective energy management strategy based on particle swarm optimization (PSO) was proposed for a power-split HEV. The proposed strategy adopted a two-layer structure. The inner layer used the equivalent consumption minimization strategy (ECMS) that considered mode switching to optimize the operation mode and operating point, so as to achieve the goal of energy saving. The outer layer used PSO to optimize the equivalent factor iteratively to achieve the control of battery power. Then, a vehicle simulation model based on the real vehicle control strategy was used to verify the optimization effect. Simulation results show that, the energy management strategy combined with PSO and ECMS can achieve the dual goals of reducing vehicle energy consumption and controlling battery SOC.

Abstract:In order to improve the efficiency of retrofit design, the parametric flow channel model of a torque converter was established and three-dimensional flow field simulation calculation was also carried out. The reliability of the parametric model was verified by comparing simulation results with the experimental data. On this basis, the influence of torus design parameters, such as relative section area, flatness ratio, the radial ratio of torus and the radius of inlet and outlet, on the performance of the torque converter was studied respectively, and the influence degree of each design parameter on the performance of the torque converter was compared and analyzed. The results show that relative section area has the greatest influence on the stall capacity factor of pump, but has the least influence on stall torque ratio and maximum efficiency; flatness ratio, pump outlet radius and the radius of stator inlet and outlet all have great influence on stall torque ratio, while pump outlet radius has the greatest influence on maximum efficiency. The results provide a theoretical reference for the optimal design of a torque converter.

Abstract:The леоновский’s stratum true thickness formula is widely accepted and used by lots of geologists, but some problems still exist. Based on the actual situation, the calculation formula of stratum thickness was deduced, the range of the stratum thickness value and the influence of angle error were analyzed, and the problems of zero data, negative data and negative thickness of the stratum thickness were discussed. Finally, the case study was carried out to verify it. The results are obtained as follows: ①the леоновский’s formula only contains two kinds of field measurement and omits one kind of field measurement, so the calculation formula of stratum thickness is corrected; ②the range of F-data of stratum thickness is 0~1,and the F-data has different variation characteristics in three field survey situations respectively, but the maximum values are all obtained when the stratum dip direction is nearly vertical to the ground slope where the measure line passes, and the minimum values are all obtained when the stratum dip direction is nearly parallel to the ground slope where the measure line passes; ③the error influence of true dip angle, slope angle as well as the acute angle between the guiding line direction and the stratum strike has different variation characteristics in three field conditions, but both the true dip angle and the slope angle error have the greatest influence on the thickness calculation when the stratum trend is nearly parallel to the ground slope direction where the measure line passes, meanwhile, the acute angle between the guiding line direction and the stratum strike has the greatest influence on the stratum thickness when the acute angle is smallest; ④When the measure line is the translation line, the stratum thickness is zero; the concept of the negative stratum thickness only has its sense in the modified form of леоновский’s formula, which just indicates that the measure line crosses from the upper stratum surface to the lower stratum surface; the negative data of the calculation using the леоновский’s formula is caused by that the леоновский’s formula lacks one kind of field measurement, and the negative data isn’t equal to the negative thickness; the calculated values of the corrected formula are all positive values, which are in line with the objective reality, meanwhile it can be used to calculate the total stratum thickness combining with the structural analysis. The above knowledge has a guiding role in the selection of field measured profile and guiding line direction as well as the calculation of indoor stratum thickness and total thickness, and has an important value in the scientific research and production based on stratigraphic knowledge.

Abstract:In order to reduce the negative impact of the U.S. increase in tariffs on some goods imported from China, and to help the enterprise make decisions on orders of products manufactured by Chinese suppliers before the increase in tariffs, a U.S. enterprise in a transnational supply chain affected by the Sino-U.S. trade war was taken as the research object. The decision included whether to transfer Chinese orders to other countries after tax increase and the retail price of products sold in the United States. Based on each order distribution scheme, the profit model was established and solved to get the optimal scheme. The analysis results show that both Chinese and American enterprises in the transnational supply chain have been negatively affected by the tariff increase. In addition, the sensitivity analysis of several parameters affecting the decision results was carried out, and some suggestions were given based on the analysis results.

Abstract:The foreign exchange reserve asset considering the needs of transaction, precautions, financial risk management and speculation in turn was proposed. Based on the multi-objective programming model, the optimal scale and structure of China’s foreign exchange reserves in three different situations were studied. The proposed model could give priority to high priority demand and measure the scale and proportion of asset allocation at the same time. The research finds out: in terms of scale, China’s foreign exchange reserves do have the problem of “scale over matching”. The total amount of over matching is about 1.3-2.0 trillion US dollars, which is mainly caused by the “passive” growth caused by transactional demand from 2006 to 2011, and the scale of foreign exchange reserves has changed reasonably since 2011; in terms of structure, China’s foreign exchange reserves should be dominated by bonds and US dollar assets, and the proportion of bonds and US dollar assets should be kept at about 60% ~ 70%. However, the high correlation between China’s actual foreign exchange reserves and US dollar price changes indicates that China’s foreign exchange management authorities may overestimate the impact of US dollar price changes on foreign exchange reserve decision-making for a long time.

Abstract:A multi-objective planning model for product line design of real estate projects under government constraints and project constraints was established, which included both floor-area ratio constraints, building density constraints and government price constraints, as well as time constraints, cost constraints and funding constraints. The proposed model was used to determine the product mix ratio, pricing and promoting strategy of real estate projects. Due to the complexity of the proposed model, the genetic algorithm was used to obtain the approximate optimal solution. Finally, a real estate project was used to test the practicability of the proposed model.