To study the real dynamic response regularity of asphalt pavement structure under dynamic load, a road test was conducted for three types of typical asphalt pavement. Dynamic and static deflection basins were established.The characteristics of the dynamic deflection basin were studied.The set-in dynamic strain sensors at the bottom of the surface layer collected the dynamic strain response under falling weight deflectometer (FWD) load. Results show that the static deflection basin is deeper than the dynamic deflection basin, but the range of the latter is larger than that of the former.The characteristics of the two deflection basins differ.The change trends of dynamic response with an increase in FWD load reflect nonlinear characteristics.The dynamic strain of three typical asphalt pavements at the bottom of the surface layer does not induce fatigue failure in the pavement structure.The longitudinal strain is larger than the lateral strain.Different prediction models on dynamic strain on the basis of dynamic deflection basin parameters are established.

Given the characteristics of anti-cracking layer asphalt material and the shortage of existing research on the subject, thermoplastic styrene-butadiene rubber (SBS), crumb rubber modifier (CRM), and plasticizer (DBP) were used as modifiers to develop a composite modified asphalt suitable for the anti-cracking layer. A reasonable modifier dosage was determined through ductility, penetration, softening point, and elastic recovery tests. Pavement performance of the composite modified asphalt was evaluated through dynamic shear rheological test, viscosity and mechanical performance temperature scanning, as well as fatigue and low-temperature bending beam tests to determine the best dosage of rubber powder. Test results showed that the optimum SBS, DBP, and CRM dosages were 5%, 4%, and 4%, respectively. The new composite modified asphalt exhibited good pavement performance and could satisfy the requirements for the anti-cracking layer. The results of this study could provide an important reference for a rational choice in asphalt material for the anti-cracking layer, and consequently, extend the service life of pavement structures.

To study the change law of the dynamic characteristics of soft soil, particularly the inadequate bearing capacity of highway and railway roadbeds induced by traffic loads, the soft soil in Yingkou area was taken as the research object. A series of dynamic strength and dynamic modulus tests were performed under different dynamic stress amplitude amplitudes, consolidation ratios, confining pressures, dynamic stress amplitudes, consolidation confining pressures, consolidation ratios, vibration frequencies, soft soil dynamic strains, dynamic strengths, dynamic backbone curves, dynamic moduli, and dynamic damping ratios. The results show that (1) Yingkou soft soil has a significant structural property. A strain turning point was found in the ε_d-N and dynamic curves. The deformation of soil increases rapidly when the strain is larger than this turning point. (2) Dynamic strength increases as consolidation confining pressures increase, but the influence of consolidation ratio and vibration frequencies on soft soil dynamic strength is not limited to an increase or decrease. (3) The dynamic modulus increases as consolidation confining pressure, consolidation ratio, and vibration frequencies increase, whereas dynamic damping ratio decreases with increasing pressure and ratio but increases with increasing vibrational frequency. The above results provide a theoretical basis for studying the insufficient bearing capacity of highway and rail roadbeds caused by long-term cyclic loads.

According to the condition of the virtual work rate equation in the limit state, the formula for safety factor of multi-level slopes with benches is deduced by using the theory of the limit analysis upper bound method and strength reduction technical. However, overall and local instability occur for the limit analysis upper bound method. The location of the most dangerous sliding surface is determined by an optimization procedure that employs sequential quadratic programming. The most dangerous sliding surface is determined by separately calculating a plurality of the sliding surface to identify the slip surface with the least safety factor (it has the worst stability). The overall and local stabilities of a three-level slope are discussed and compared by analyzing the examples and parameters used. Results show that the minimum factor of safety calculated in this is slightly smaller than that of the existing results, and the most dangerous sliding surface obtained in this study is also similar to the method is established. Parametric analysis shows that the local instability of the slope occurs when the slope angle increases in homogeneous multi-level slopes. The stability of high slopes can be improved and the construction difficulty can be reduced by adding steps. Research results on high slope engineering have practical value.

Cracking is one of the major distresses impacting pavement quality, serviceability, and lifespan. Thus, accurate, precise, and complete cracking detection is important in the maintenance, performance evaluation, structure, and material design of pavements. Given that the results of pavement crack image recognition tend to contain noises and intermittent crack segments, an automatic crack detection algorithm based on the connectivity checking of pixels and crack block levels was proposed. First, a pavement image was enhanced on the basis of a self-adaptive grayscale stretch. The image was then segmented into background and foreground (potential cracks) on the basis of self-adaptive OTSU segmentation and 8-direction Sobel gradients. The potential crack image was denoised through connectivity checking. Finally, 32 pixel×32 pixel crack blocks were detected and optimally connected to form the final crack image. Examples show that the results of the proposed algorithm maintain enhanced integrity and continuity for improving connectivity at both the pixel and block levels. Performance tests were also conducted on 10 pavement images (512 pixels×512 pixels) for global OTSU segmentation, 8-direction Sobel detection, Canny detection, and the proposed algorithm. The proposed algorithm achieved both the highest precision (86.60%) and recall (90.68%), which resulted in the best F score (F₁=88.30%).

Using nonlinear numerical methods, the structural systems of cables system, stiffening beams, pylons, and bearing systems are comparatively analyzed. This study demonstrates the technical feasibility of suspension bridges with a 3 500 m main span and Carbon Fiber Reinforced Plastic (CFRP) main cables. Using fine finite element structural simulation, the parameter sensibility of a suspension bridge structural system with a 3 500 m main span and CFRP main cables is analyzed, and the influence of structural parameters on the static and dynamic performance of super-long span suspension bridges is discussed. In combination with numerical analysis of a structural system model, the optimum structural system of a suspension bridge with a 3 500 m main span and CFRP main cables is determined. The physical model is set up to allow theoretical measurements of the anchorage, sliding, and bending moment of the CFRP main cable strands as well as static load and fatigue testing. A bond-type anchorage that can be applied to real bridges is developed, which has an anchorage efficiency coefficient of 100%. The sliding resistance and bending performances are verified: the frictional coefficient between CFRP main cable strand and saddle is about 0.5, the frictional coefficient between the CFRP main cable strand and clamp is up to 0.331, the bending strength of the CFRP wire at the saddle point is over 90% of its tensile strength, and there is almost no bending problem at the clamp. A bridge prototype design is produced based on the test results.

Residual stress exists in piles before load transferring from the upper structure to the pile head. The resulting mechanism of residual stress distribution in piles after unloading and the influencing factors are analyzed and compared with those of pile foundations with negative skin friction conditions. An instrumented bored pile was measured after a vertical compressive static loading test to obtain the distribution of residual stress and deformation. The results indicate that (1) the distribution of residual stress in the pile is similar to that in a pile foundation with negative skin friction on the piles due to the soil-constrained piles fully springing back, which is equivalent to prestress exerted by the surrounding soil on the pile; (2) compared with negative skin friction, the shaft resistance induced by residual stress is smaller, and the residual stress does not affect the settlement of the pile foundation; (3) the magnitude of residual stress is closely related to the pile size, properties of the soil, and stiffness of contact surface between the pile and the soil.

Using the flat steel-box girder of China's Sutong Cable-stayed Bridge as a research object, its temperature field is long-term monitored and analyzed based on bridge's structural health monitoring system. The temperature distribution characteristics of the girder are investigated using the temperature data, and the transverse and vertical thermal differences are analyzed in detail. Using statistical methods, the corresponding probability distribution models of the temperatures and the temperature differences of the flat steel-box girder are established, and the standard values of the temperature and temperature differences within a certain return period are determined. The analysis results reveal that (1) there exist dominant vertical temperature differences between the top and bottom plates, with definite transverse temperature differences in the top plate and negligible transverse temperature differences in the bottom plate of the flat steel-box girder; (2) the temperature probability density distributions of the flat steel-box girder can be well described by the weighted sum of two normal distributions, and its temperature difference probability density distributions can be well described by the weighted sum of two Weibull distributions.

On the basis of the load-structure model and FEM and taking the secondary lining of the Qingdao-Rongcheng intercity railway tunnel as a research object, sensitivity analysis of the influencing factors on the secondary lining's internal forces is conducted via the sensitivity coefficient method. The influencing factors are the elastic resistance coefficient of surrounding rock, the secondary lining thickness, the elastic modulus of secondary lining, and the lateral pressure coefficient, whose values are taken from engineering practice. The analysis result shows that (1) to crown bending moment, the descending order of the sensitivities of the influencing factors are secondary lining thickness, elastic resistance coefficient of surrounding rock, lateral pressure coefficient, and elastic modulus of secondary lining; (2) to crown axial force, the descending order is lateral pressure coefficient, elastic resistance coefficient of surrounding rock, secondary lining thickness, and elastic modulus of secondary lining; (3) to crown vertical displacement, the descending order is elastic resistance coefficient of surrounding rock, secondary lining thickness, lateral pressure coefficient, and elastic modulus of secondary lining; and (4) for the safety factor of the crown cross section, the descending order is elastic resistance coefficient of surrounding rock, lateral pressure coefficient, secondary lining thickness, and elastic modulus of secondary lining.

Safety coefficient and surface settlement were chosen as evaluation indictors for non-self-stabilizing weak strata and basic self-stabilizing weak strata. Fluid mechanical interaction is used to analyze the pre-reinforcement scope and strength parameters in this numerical method. Moreover, the scope of lateral reinforcement is discussed based on the damage modes of tunnels in stratums with different depths. The study shows the following: (1) The thickness and stiffness of reinforced regions must meet certain conditions simultaneously to obtain a better surface settlement; (2) The thickness of reinforced region must be approximately 2-2.5 m and the stiffness of reinforced region should be increased until it is six times that of the original stratum to guarantee stable stratum stability in non-self-stabilizing stratums; (3) The thickness should be 1.5-2 m for basic stability strata, and the stiffness should be increased until it is five times th at of the original stratum. Finally, the scope of consolidation given the damage mechanism of formation is verified through numerical calculation.

By using the system analysis method and game theory of governmental placement of urban bus stops, operation of transit enterprises, and travelers' choice of trip mode, transit line, and bus stop location, the research objectives of this study are to solve the bi-level programming problem for optimized urban bus stop placement with elastic demand and to establish a bi-level programming model. The upper-level goal of the government and transit enterprises for choosing bus stops from possible selections is to minimize travelers' total travel cost, to minimize bus operating cost, and to maximize the bus trip volume. The lower-level goal of the traveler for choosing travel mode, transit lines, and final bus stop is to minimize his generalized cost within equilibrium of the traffic assignment. A genetic algorithm is adopted in the concrete optimization solution. The game analysis of different decision agents and the concrete restriction of bus stop location are considered using the bi-level programming method for ultimate selection of the bus stops. Moreover, the feasibility and correctness of the method are proved.

A short-term traffic prediction model VHSSA (prediction model based on vertical and horizontal sequence similarity algorithm) is proposed for accurate traffic prediction and dynamic route planning. The model is based on the similarity of vertical and horizontal sequences and analyzes historical traffic time series data and cyclic similarity characteristics of traffic volume in urban roads. The model can overcome the deficiency of the traditional model VSSA (prediction model based on vertical sequence similarity algorithm), which focuses only on vertical cyclic sequence similarity. Complete data are transformed into basic sequences that reflect basic characteristics and fluctuant sequences as well as variation characteristics by utilizing the wavelet transformation function. This transformation can achieve both basic and complete sequence prediction. For complete sequence prediction, the paper corrected the fluctuant sequence based on confidence interval and overlapped it with the basic sequence. Verification experiments are conducted to compare the basic and complete sequences of VHSSA and VSSA. Results show that VHSSA prediction is better than VSSA prediction, and the error probability of VHSSA is lower than that of VSSA; the prediction error can meet the actual requirement.

The evaluation of the adaptability of expressway systems is a multiple-objective comprehensive evaluation problem. First, the concept of the adaptability of an expressway is defined, the 2-level index system to influencing factors include highway network layout, traffic operation quality, social influence, and environmental impact is established, and the calculation method or the basis of some indexes are given. Moreover, the membership relationships are discussed, the evaluation indexes are classified, and their weights are calculated, and also a fuzzy comprehensive evaluation model suitable for evaluating the adaptability of an expressway system is put forward. Finally, a numerical example indicates that the proposed method is suitable for the evaluation of the adaptability of an expressway system.

The fundamental diagram is the graphical representation of the relations between traffic flow, speed, and density, and has long been the foundation of traffic flow theory and transportation engineering. Eighty years after the seminal Greenshields model, a variety of models have been proposed to mathematically represent the speed-density relation. Speed-density relation models play an important role in understanding how a shock wave propagates through traffic, as well as determining level of service. In this paper, 10 typical speed-density relation models are summarized and analyzed by parameter calibrations and fitting errors using Beijing Expressway data. The results show that fitting errors for speed-density models are not sensitive to using different sets of field data, whereas some physically meaningful parameters, such as free-flow speed and jam density, vary widely under different sets of field data. The Newell and Logistic models demonstrate good stability. This research provides practical support for optimizing speed-density relation models and model parameter calibration.