Abstract:Considering the problem of negotiation of air traffic rights resources, this paper studies the game relation between the two sides of the negotiation based on the strategic negotiation relationship and the principle of equivalence of value. On the basis of the bargaining power, compensation of related industries, value of reserved space, and lost value by resource vacancy, a method was proposed to describe the value of the issue of air traffic rights resources, and the material income matrix aimed at different types of issues was established. Based on the theory of reciprocal preference, the reciprocal motivation and ex-parte-patronage motivation were proposed to describe the psychological utility brought by the game behaviors of the negotiators in the context of strategic negotiation relationship, and the sequential reciprocal game model based on reciprocal psychological utility was constructed. Numerical simulation was carried out and the validity of the model was verified. Results show that when the two sides of the negotiation were in a reciprocal relationship, the game behavior strategy was decided by the reciprocity sensitivity coefficient, issue scale of air traffic rights resources, and the relationship between the value of reserved space and the lost value by resource vacancy. The negotiation problem was identified to correspond to six value game scenarios, which were mainly determined by the value range of the issue.

Abstract:In order to study the dynamic response of continuous beams with arbitrary boundary conditions, a mechanical model of intermediate elastic supported beams with arbitrary constraints at both ends was established, and the method of solving its vibration frequency was given. The theoretical solution to the dynamic response of the beam under moving load was derived by means of mode superposition method. A MATLAB program was written to solve the equation, and the results obtained by the proposed method were compared with the values obtained by the finite element method through calculation example, which verified the correctness, precision, and application scope of the proposed method. The influence of the boundary conditions on the vibration response of the structure was analyzed. Results show that the higher order modes of the continuous beam with intermediate elastic support under arbitrary constraints at both ends were obviously different from those of the continuous beam with simple or fixed supports at both ends. The amplitude at the boundary of the higher order mode curve was larger because of the elastic boundary condition. Under the action of moving load, the maximum downward displacement of the beam appeared in the middle of the span, while the maximum upward displacement appeared in the ends of the beam. Positive bending moment and negative bending moment alternately appeared in each section of the beam body, and the positive bending moment in the middle of the span and the negative bending moment at the end points were the most significant. The fluctuation period of the mid-span displacement became longer when the moving velocity of the load increased. Compared with different boundary conditions, the variation amplitude of mid-span deflection of elastic support at both ends was between fixed support at both ends and simple support at both ends. The stiffness of rotational spring at both ends affected the vibration amplitude of the structure, while the stiffness of rotational spring had a more obvious effect on the maximum vibration displacement of the structure.

Abstract:To reasonably assess the local wind environment around bridge decks, the CFD method was used to simulate the wind fields around a slotted box bridge with wind barriers. Experiments on the local wind environment of the model of Xihoumen Bridge girder were carried out, and field measurements of the bridge were conducted for verification. The wind barriers of the bridge deck were optimized and compared, and the wind environment characteristics of the slotted box girder with wind barriers were analyzed. The CFD method was adopted for simulating the local wind environment of the bridge deck installed with different types of wind barriers. The variation rules of wind speed at different positions of lanes along different heights were analyzed, and the influences of types, heights, and porosities of wind barriers on the crosswind reduction factor were quantified. Results show that the CFD method could provide highly accurate results and reveal more detailed characteristics of actual flow-fields around the bridge deck. The deviation was between 3% and 9%, which met the accuracy requirement of engineering application. Wind barriers had significant effects on reducing the wind speed under the condition of crosswind, and wind speed reduction on different lanes was about 30%–50%. The effective wind reduction regions of wind barriers were closely related to the height-width ratios, heights, positions, and porosities of the barriers, among which porosity was the crucial factor that decided the crosswind reduction effects of wind barriers. In addition, compared with integrated box girder, the wind speed on the downstream surface of the slotted box girder was obviously lower than that on the upstream surface due to the dredging effects of the center slot.

Abstract:To investigate the mechanical response of soil caused by the expansion of cavity under the action of seepage in the process of soft soil grouting, based on the generalized Tresca yield criterion and the non-correlated flow criterion, the elastoplastic solution to the problem of cavity expansion of grouting in saturated soft clay was derived combined with the elastoplastic boundary conditions in consideration of the comprehensive effects of nonlinear seepage and strain softening factors. The differences of the calculation results of seepage field, stress field, and displacement field of the soil around the cavity with or without considering the action of seepage were compared and analyzed through calculation examples, and the influence of the nonlinear seepage coefficient m was further discussed. Results show that the radius of the plastic zone and the radial stress in the high-speed nonlinear seepage mode were both smaller than those under the Darcy linear seepage state, and the greater the degree of nonlinearity was, the smaller the value was. The radial displacement was less affected by the nonlinear seepage coefficient m, and it was basically the same in the two modes. Hence, the influence of non-Darcy seepage of groundwater on the cavity expansion pressure should not be underestimated. When studying such problems in the future, the influence of different seepage states should also be fully considered, so that the calculation results are closer to the actual situation.Symbol`@@

Abstract:To improve the synergy between overlapping bus lines and reduce the capacity resource waste, a bus dispatching optimization method for overlapping lines was proposed considering passenger transfers. Based on the relative positions between the passenger origin-destination and the overlapping sections, passengers were divided into three categories, and the bus travel process of different categories of passengers at the stations in the overlapping area was investigated. In consideration of the passenger transfer behaviors on the overlapping bus lines, a departure interval collaborative optimization model was established, which takes the minimum total passenger travel time and minimum bus operating cost as objects and is constrained by departure interval, first departure time, and capacity limitations. The model was solved by genetic algorithm. Taking three overlapping bus lines in Harbin as an example, results show that after the model was optimized, the bus operating cost was reduced by 15.2%, total travel time of passengers reduced by 6.7%, and waiting time of passengers for three categories reduced by 3.2%, 33.2%, and 18.6% respectively, which verified the effectiveness of the model. The research results provide a new perspective for the theoretical research of static dispatching methods for overlapping lines.

Abstract:This paper aims to study the problem of excessive cost caused by the single material distribution mode in the production process in consideration of optimal cost. To minimize the total cost of material distribution, an improved material distribution combinatorial optimization model based on batch distribution and kit distribution modes was proposed. The model was then applied to a case study of the assembly line of automobile production workshop to provide the optimal design of material distribution and verify the effectiveness of the model. Experimental results show that compared with the batch distribution and kit distribution modes, the improved combinatorial optimization model could reduce the cost by 83.6% and 70.8% respectively, and meanwhile exhibited better robustness. The kit distribution mode was more likely to be chosen for delivering the materials loaded in pallets than materials loaded in cartons. Under full constraint conditions, the kit distribution mode was more likely to be adopted. The priority of influencing factors of distribution mode choice was: total stacking area at the edge of production line, rated loading capacity of tractor , and rated loading capacity of forklift. The results of this paper can provide suggestions for workshop management.

Abstract:In order to accurately identify factors affecting the occurrence and severity of crashes on ice-snow covered freeways, an integrated model based on fault tree and Bayesian network was developed. Three directed arcs were added into the transformed Bayesian network. Leaf nodes were divided into three states according to the crash severity, and the conditional probability table of the leaf nodes was updated. Bayesian network reverse reasoning and sensitivity analysis were carried out based on the proposed integrated model. Results show that high risk factors including low visibility, adverse weather (rain,fog,snow), trucks, non-lighting at night, lack of driving experience, speeding, and insufficient headway mainly induced the occurrence of crashes on ice-snow covered freeways. Overloading, trucks, and illegal driving tended to increase the crash severity under ice-snow conditions. The integrated model of fault tree and Bayesian network is expected to provide a new perspective for the analysis of crash factors.

Abstract:To simplify the calculation method of bending capacity for preflexed composite beams in current standard, the calculation method of plastic bending capacity was deduced based on the theory of plasticity, and a simplified calculation method of bending capacity for preflexed composite beams was put forward from the aspect of security. The bending capacity of seven experimental beams was calculated by the simplified calculation method, the elastoplastic calculation method in the standard, and a deduced calculation plastic method. Nonlinear finite element analysis was carried out on the preflex beams by the general finite element analysis software Abaqus, and the calculated results were compared with measured results to verify the accuracy of the proposed calculation method. Results show that the differences between the results calculated by the proposed method and those by the elastoplastic method were less than 2% for the seven experimental beams. The calculated values were slightly smaller than the measured and simulated values and showed good agreement, which could satisfy the requirements of calculation accuracy and safety in practical projects. The proposed simplified calculation method of bending capacity was simpler than the method in existing standards and the plastic method, which could be used in the calculation of cross-section bending capacity for preflex beam bridges. Based on the research results, an example of preflex simply supported beam bridge calculated by the proposed method was given, which could provide reference for practical projects.

Abstract:To analyze the impact of mix proportions on the performance of geopolymer concrete (GC), the effects of the ratio of fly ash (FA) to granulated blast furnace slag (GGBS), the sodium silicate modulus, and the content (mass fraction) of sodium silicate on the mechanical properties of geopolymer concrete were studied. Further, the microstructure of geopolymer concrete was investigated by means of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and mercury intrusion porosimetry (MIP) tests. Results show that with the increase in curing age, the degree of polymerization was higher, the amount and types of gel observed in SEM images increased, and the macroscopic strength of geopolymer concrete was higher. The decrease in the modulus of sodium silicate resulted in the decrease in Si/Al ratio and increase in Na⁺, which promoted the formation of gel and made the geopolymer concrete exhibit higher mechanical properties. A decrement in the ratio of fly ash to slag, i.e. the increase in the amount of Ca in the system, promoted the generation of gel. When the content of sodium silicate increased from 20% to 25%, Si/Al ratio increased from 1.31 to 3.37, and the microstructure density and macroscopic strength of geopolymer concrete samples were improved. However, when the content of sodium silicate was excessive, Si/Al ratio decreased from 3.37 to 2.00, and the formation of gel was difficult, showing a lower strength of the geopolymer concrete samples. Reducing the modulus of sodium silicate and increasing the proportion of slag can both promote the polymerization, which is helpful to the improvement of the mechanical properties and the compactness of the microstructure of geopolymer concrete.

Abstract:To investigate the deformation law of submerged floating tunnel (SFT) subjected to underwater explosion-moving load, the underwater explosion process was simplified to the stages of shock wave load and bubble motion based on the Cole shock wave load semi-empirical formula and Vernon bubble motion equation. The Grade I vehicle load of highway was simplified to the moving load sequence. A dynamic model of SFT considering underwater explosive load, moving load, and fluid effect was established based on the D’Alembert’s principle. The four order Runge-Kutta method was adopted to solve the differential equations of motions, and the proposed model was verified by using the existing data and formulas. Finally, the effects of explosive load and moving load on the deformation of the tunnel were discussed. Results show that the impact factor  could greatly promote the increase in the maximum displacement of SFT. Compared with =0.1, when the impact factor increased by 2 times and 4 times, the maximum displacement of the tunnel increased by 4 times and 10 times under explosive load alone. With the increase in the explosive amount, the bubble load frequency increased exponentially, with the increase in the water depth of the explosion point, the bubble load frequency decreased in inverse proportion. In the cases of different explosive amounts and water depths, the bubble load frequencies were all less than 3 Hz, which was close to the low-order frequency of the tunnel and easily led to resonance. Under the action of underwater explosion and moving load, the maximum displacement of SFT was affected by the combined effect of the position and speed of the moving load, and the explosion was more harmful to the tunnel when the vehicle ran at the fastest speed until the mid-span.

Abstract:To investigate the shear mechanism of hybrid steel fiber reinforced concrete (HSFRC) deep beams, the effects of concrete, steel fiber, web reinforcement, and longitudinal reinforcement on the shear bearing capacity of HSFRC deep beams were taken into consideration, and steel fibers were incorporated into the tensile system of HSFRC deep beams. The calculation method for the shear bearing capacity of HSFRC deep beams was developed based on the softened strut and tie model (SSTM). Then, shear tests on four HSFRC deep beam specimens were conducted to evaluate the proposed method and further investigate the effects of steel fiber volume and web reinforcement ratio on the shear behavior of HSFRC deep beams. Results show that the designed procedure of the proposed calculation method was reasonable, which could accurately predict the shear bearing capacity of the specimens. The increase in the steel fiber volume could decrease the growth rate of the strain of HSFRC and increase the maximum strain of HSFRC. The web reinforcement ratio had little effect on the strain of HSFRC, but the increase in its volume could inhibit the development of the strain of reinforcement. The increase in the steel fiber volume could improve the bearing capacity, deformation capacity, and initial stiffness of the specimens. With the increase in the web reinforcement ratio, the shear capacity increased and the stiffness degradation was delayed, but the deformation capacity of the specimens first increased and then decreased.

Abstract:To adapt to the travel needs of urban agglomeration passengers and maximize the overall benefits of the system, a problem of collaborative range and collaborative route optimization selection of urban agglomerations was proposed based on the marginal benefit theory. A super network model of multi-mode and multi-link traffic system in urban agglomerations was constructed, and factors such as the correlation strength of passenger flow and transfer facilities were considered to generate a collaborative route candidate set. The routes of the super network were divided into on-going sections and transfer sections, and the generalized travel cost of the multi-mode travel routes was established. The route choice behaviors of passengers in urban agglomerations were constructed by using three-tier nested Logit model. On this basis, a bi-level programming model was established with the optimization objective of maximizing social welfare. Genetic algorithm and successive averaging method were used to solve the upper and lower models and the collaborative transportation range and collaborative routes were determined based on the theory of diminishing marginal benefits. Finally, the Beijing-Tianjin-Hebei Urban Agglomeration was taken as an example to illustrate the performance and application of the model. Results show that there was marginal benefit in the scale of collaborative transportation routes, and the optimized collaborative routes could basically meet the travel demand of Beijing-Tianjin-Hebei Urban Agglomeration. It provides reference and theoretical guidance for the implementation of collaborative operation of multi-mode transport in urban agglomerations in China.

Abstract:To reduce the influence of wheel-rail noise on the area along the metro railway on the ground, active noise barriers were arranged near the metro track. The low-frequency noise could be significantly reduced by the active silencing system, and the high-frequency noise could be significantly reduced by the noise barrier. To guide the design of active noise barrier, the influence of secondary source parameters on metro noise field was studied. Based on the boundary element theory, a semi-free field model consisting of train, noise barrier and track was established. The correctness of the model was verified based on the measured data of Beijing Metro Line 13. The secondary sources were then arranged in the model along the longitudinal direction of the track with equidistance. By analyzing the numerical results, the most reasonable position of secondary sources, the silencing frequency, the silencing area boundary, and the silencing quantity were determined. A mathematical model of secondary sound interfering with noise was constructed to verify the rationality of the simulation conclusions. Results show that the most reasonable position of the secondary sources and the track axis were separated by a noise wave length. The height of the most reasonable position of the secondary sources was equal to that of the noise source. The most reasonable position of the secondary sources had a longitudinal interval shorter than half the noise wave length. Secondary sound could significantly reduce the wheel-rail noise of 150-320 Hz, and there was a positive correlation between silencing area and frequency. The silencing effect of bilateral secondary source array arranged on left and right sides of the train was better than that of unilateral sources arranged on one side. Setting secondary source arrays on the basis of noise barriers could generally decrease the total sound pressure level (SPL) in the sound shadow area by 3-12 dB, and the amplification value outside the sound shadow area basically did not exceed 3 dB, and the sound field in the train had little change.

Abstract:To reduce the effect of snow deposition on railway lines caused by snow-drifting and study the structure and layout of snow fences that can have maximum protection effect, a numerical analysis model of snow-drifting based on Euler multiphase flow model was established, and the applicability of the numerical model was verified by an engineering example. The variation characteristics of snow amount inside and outside the railway cutting area and on both sides of the snow fence were investigated under the conditions of different porosities, heights, and layout distances of snow fences. Through L16 (4⁵) orthogonal test, the main factors affecting the volume of snow deposition inside and outside the railway cutting area were obtained. Results show that the snow distribution patterns of the proposed numerical model inside and outside the cutting area and on both sides of the snow fence were consistent with those in the field test section. The structure of snow fences mainly affected the snow volume deposited outside the cutting area, while the main factor affecting the amount of snow inside railway cutting area was the distance between snow fence and roadbed. The distance of snow deposition on the windward side of the snow fence was about 20 m, and that on the leeward side of the snow fence was generally 10–12 times of the height of the snow fence. In the orthogonal test, the optimal combination of snow fence structure and layout distance could decrease the snow volume on the top of roadbed caused by snow-drifting by at most 26.17%. According to the distance between snow fence and cutting area, the snow deposition amount and position could be changed by adjusting the snow fence porosity and height to increase the effect of the snow fence.

Abstract:To optimize the geometric design of dedicated freight corridors on highways and reduce the probability of truck accidents, PC-Crash software was used to conduct accident simulation tests with speed, horizontal curve radius, longitudinal slope, superelevation slope, hard shoulder width, widen value of curve, adhesion coefficient, and vehicle type (heavy trucks and articulated trains) as risk factors. The significant risk factors were screened by binary Logistic regression analysis, and the prediction model of roadside accident probability on dedicated freight corridors was constructed. Based on the probabilistic prediction results and the thought of "cumulative frequency curve method", the probability thresholds of potential blackspot and frequent blackspot of roadside accidents were given, and the identification method of roadside accident blackspot on dedicated freight corridors was proposed. In view of the sections with frequent occurrence of roadside accidents on dedicated freight corridors, the optimization geometric design of dedicated freight corridors was carried out by using classification and regression tree (CART) algorithm. Results show that the importance of significant risk factors on roadside accidents from the largest to the smallest was as followings: speed, horizontal curve radius, adhesion coefficient, vehicle type, hard shoulder width, longitudinal slope, and superelevation slope. For the dedicated freight corridor section with horizontal curve radius of R≤400 m and operating speed of 60 km/h＜v≤80 km/h, the longitudinal slope should be ＜4%; if this design requirements were not met, the superelevation slope should be ≥4%. For the section of dedicated freight corridor with operating speed of 80 km/h＜v≤100 km/h and horizontal curve radius of 400 m＜R≤800 m, the hard shoulder width should be ≥2.25 m. Additionally, increasing the hard shoulder width had a significant effect on reducing the risk of roadside accidents for heavy trucks.

Abstract:To investigate the main skeleton structure and void ratio in mineral aggregate (VMA) of porous asphalt concrete (PAC), according to the porosity of PAC, all mineral aggregates were divided into four parts: larger size aggregate (LSA), dominant aggregate size range (DASR), potentially disruption aggregate (PDA), and interstitial component aggregate (ICA). The main skeleton void structure formed by DASR was analyzed, the particle size range of each aggregate part was determined, and the calculation method of the void ratio in main skeleton was proposed. Based on the volume method, the physical model for VMA of PAC was developed by introducing the filling mechanism of ICA, interference of PDA, and substitution effect of LSA, which had a good prediction effect compared with compaction test results of PAC-13 and PAC-10. Results show that for the main skeleton void structure formed by DASR, ICA mainly played the role of filling the skeleton voids. The interference of PDA though occupied part of the skeleton voids formed by DASR, increased the main skeleton voids to a certain extent. LSA with larger particle size also increased the void ratio of the main skeleton structure after replacing part of DASR. LSA, PDA, and ICA had different directionality effects on the void ratio of main skeleton formed by DASR. In the initial aggregate grading design of PAC, there is no need to prepare test specimens, and the corresponding VMA can be predicted by determining the critical particle size of the four aggregate parts according to the grading curves. It is convenient to determine the best gradation by using this model, which greatly reduces the experimental workload for PAC mixture design. In conclusion, the proposed model is reasonable and effective, and has a good prediction effect.

Abstract:In order to explore the influence of inorganic micro-powder fillers on the fatigue performance of asphalt mortar, nine kinds of commonly used inorganic micro-powder particles in three types were used as additive mineral materials, and the morphology characteristics, filler types, and particle sizes of the micro-powder particles were investigated. The morphology characteristics of the micro-powder particles were characterized by SEM, the influence of different kinds of micro-powder fillers on the fatigue properties of asphalt mortar was studied by dynamic shear rheometer (DSR), and the fatigue life of asphalt mortar was compared and analyzed by indexes N_f50 and N_DER. Results show that under SEM, the hydrated lime particles had more surface pores and complex surface texture, and the fatigue performance of the asphalt mortar was greatly improved with the decrease in the particle size of the inorganic micro-powder filler under dynamic shear rheological test. With the same particle size, due to the special morphology characteristics and chemical compositions, the fatigue performances of hydrated lime and cement were better than that of limestone. Compared with N_f50, the fatigue life meaning of N_DER was clearer, the numerical value was easier to determine, and the obtained fatigue life loading times were smaller. The use of N_DER in asphalt pavement structure design and material selection is safer, so it is recommended to adopt N_DER for the analysis of the fatigue life of mortar.

Abstract:In order to investigate wind turbine blade icing, this paper takes the blades of 300 kW wind power equipment as research object. According to a slicing-reconstructing idea, the blades were divided into finite sections. Based on the physical process of blade icing, the boundary element method was adopted to calculate the flow field of wind turbine blade icing. The Lagrangian method was used to numerically calculate the process of water droplets colliding with the blade surface. The ice growth process was simulated through iterative calculation and ice shape reconstruction, and a three-dimensional rime ice growth model of wind turbine blades was thus obtained. The influence of different wind speeds on the rime ice growth of blades was analyzed on the basis of numerical simulation. Results show that rime ice growth was affected by both external environment and blade airfoil. Ice accumulated at the leading edge of the blade; the icing thickness increased slowly from the root to the middle of the blade, and rapidly from the middle to the tip of the blade. As the wind speed increased, the icing thickness and ice coverage area increased, and the ice-covered area moved from leeward to windward. In addition, wind speed had greater impact on the icing of blades from the middle to the tip.

Abstract:In order to describe more complex nonlinear dynamic characteristics and obtain chaotic signals that are more suitable for engineering applications, a flux-controlled memristor was used to replace the coupling parameter in the improved four-dimensional Lü chaotic system, and a new five-dimensional memristive hyperchaotic system was proposed. The rich dynamic characteristics of the new system were studied by using conventional nonlinear analysis methods such as phase diagram, bifurcation diagram, and Lyapunov exponential spectrum. On the basis of the new system, by introducing an absolute value function into the system to make it reach a new polarity balance, a new conditionally symmetric memristive hyperchaotic system was constructed. Results show that the new memristive system could exhibit extreme multistability phenomena dependent on the initial states of the memristor, sustained chaotic or hyperchaotic dynamics, and offset-boosting control behaviors. In particular, when changing the system parameters and taking appropriate initial states, a unique coexisting extreme multistability phenomenon was observed. The conditionally symmetric memristive system could generate an infinite number of pairs of coexisting attractors with opposite polarities and similar attractor sizes. The existence and achievability of the new system was verified through circuit simulation using Multisim, so that the hyperchaotic system can be better applied in practical engineering fields such as secure communications.