This study investigated the effect of interfacial water on the performance of asphalt pavement. Composite asphalt beams were used to carry out the four-point bending fatigue test and the direct shear test. Road construction was simulated, and the effects of interlayer water sprinkle amount and water immersion time on the shear strength and fatigue life of the composite beams were analyzed. The water damage mechanism of the composite beams under different water sources was determined by laser scanning with the longitudinal profile of the beams. Results show that the effect of immersion time on the shear strength of the composite beams is greater than that of interlayer water sprinkle amount. Under the same test conditions, the logarithmic decay rate of fatigue life increases with increasing interlayer water sprinkle amount or prolonged water immersion. However, the increase trend changes depending on immersion time, that is, it obviously slows down with time. With the increase in interlayer water sprinkle amount, the bending stiffness modulus loss of the composite beams increases nonlinearly to an amount less than 10%. Moreover, the bending stiffness modulus loss increases gradually with prolonged water immersion. It reaches 31% and then stabilizes after 5 days. Laser scanning shows that interlayer sprinkling creates a small gap in the interstitial interface of the composite beams, whereas water immersion forms a large area of peeled aggregate inside the upper interface mix. These results indicate that water immersion causes serious damage to the composite beams.

Similar materials of rock mass and cement mortar were prepared and similar bolt was selected to study the anchoring mechanism of rock slope. Three kinds of drawing specimens with different anchoring lengths were constructed, and static drawing test analyzed the shear stress distribution on two anchoring interfaces of bolt-mortar and mortar-rock mass. The axial force decreases exponentially with the increase of the anchoring length. The shear stress of the two anchoring interfaces presents a unimodal distribution that first increases and then decreases along the anchoring length. The three stages of the anchor solid drawing processare as follows:the interface undergoes elastic deformation, plastic deformation, and debonding and slip. The shear stress distribution on the anchoring interface of rock slope is obtained for the first time by similar model tests. A new anchoring mechanism is proposed to become not only an important reference value for the related tests but also for the design and construction of the slope anchorage.

The additional load caused by vehicles is an important consideration in the design of highway retaining structures. This study investigated the additional earth pressure of retaining wall caused by vehicle load. Combined with the construction of a cantilever retaining wall in the Liandu-Jinyun section of 330 National Highway Expansion Project, a series of soil pressure boxes was embedded above the floor of the retaining wall and on the inside of the vertical plate. After the wall was constructed, a 30 t dump truck was used as the load source and asked to stop at designated places, the additional vertical and lateral earth pressure caused by vehicles (static load) was tested, and the test results were compared with the calculated results obtained using the standard uniform distribution method in the current highway design code and the Boussinesq solution of elastic mechanics. Results reveal that the additional lateral earth pressure along the wall shows a nonlinear distribution, the maximum value appears in the middle of the wall, and the peak value decreases as the distance of the truck from the retaining wall increases. The distribution pattern of additional vertical earth pressure on the floor in the cross-section direction is also non-linear. Agreat difference exists between the measured and calculated results. Using the uniform distribution method to determine the additional lateral earth pressure caused by the vehicle load may underestimate the bending moment or anti-overturning moment resulting from the additional lateral earth pressure, which may cause failure of the anti-bending and anti-overturning abilities of the retaining wall to meet the requirements. For the variable section retaining wall (the wall section size decreases with the wall height), the shear strength of the middle and upper parts of the wall may be insufficient, and shear failure may occur. The tested additional lateral earth pressure is basically the same as the Boussinesq solution, but the vertical additional earth pressure is larger than the Boussinesq solution. This study suggests the use of the Boussinesq solution with multiple lanes and standard vehicles as the additional load caused by vehicle when designing the retaining wall (especially heavy duty road retaining wall).

This study summarized the application field of machine learning to explore the basic seismic thinking of machine learning methods used for bridges. The development and actuality of bridge seismic analysis theories and technology were briefly reviewed, particularly in relation to the field of civil engineering. This study introduced the concept of machine learning, summarized its key factors and current software platforms, and illustrated the common methods and representative algorithms of machine learning using simple examples. First, the normal types of simply supported and continuous girder bridges, which are used for highway bridges with small and medium spans in China, were summarized. The earthquake damage phenomena had been observed for bridge types during the Wenchuan earthquake. Data from these phenomena were assessed, including the damage grade divisions of piers, bearings, shear keys, and abutments. Second, a series of seismic performance tests had been conducted by international and domestic academics for bearings, shear keys, piers, and abutments. These tests were summarized in this study to obtain the constitutive relationships for seismic analysis and determine the seismic design parameters of bridge components (including foundations). Finally, an overall analysis methodology based on machine learning was introduced into the bridge seismic analysis. This methodology explained that machine learning for bridge seismic tasks had two aspects. The first was the collection of considerable bridge design data and set up data sets, and the second was data reduction, including raw data processing and debugging or developing a reasonable machine learning algorithm model. This study also discussed the shortcomings of existing performance-based probabilistic seismic design and evaluation methods that are currently used in analyzing bridges in China. Results indicated the potential future major concerns for bridge seismic analysis technology. The establishment of computational simulations based on artificial intelligence method was also recommended. In addition, the mutual integration between disciplines and mutual communication among different professionals were advocated in this study.

Three 36-year-old beams are taken as research objects to estimate the fluctuation scale θ of structural dimensions and material property parameters of reinforced concrete structure in service. First, the protective layer thickness C_d and the concrete compressive strength f_c of service bridge component are measured, and the ordinary kriging method is used to interpolate the measured data and gather effective data. Second, the θ values of C_d and f_c are estimated by two methods, namely autocorrelation function (ACF) and semivariogram function (SVF). Thereafter, the spatial distribution of R of each corroded steel bar is studied on the basis of measured values of the pitting factor R at different positions of 246 corroded steel bars. On the basis of one-dimensional random field theory, each beam is discretized into several small elements. According to the fluctuation scale obtained by different estimation methods, the random variables are transformed into spatial correlation variables, and the parameters of each discrete element are obtained. Then the bending capacity of each discrete beam element and the corresponding whole beam are obtained on the basis of the value of parameters of each discrete element. Finally, the two estimation methods are compared and analyzed by comparing the theoretical moment value and the bearing capacity test results of the corroded beams. Results show that the mean values of θ of f_c and C_d obtained by the SVF method are 2.242 and 2.467, respectively, which are larger than that obtained by the ACF method. Moreover, the fluctuation intensity of concrete compressive strength is smaller with an increase of θ value, and no firm correlation is identified between the spatial distributions of each pit on the surface of a corroded steel reinforcement. The bending moments of three beams from the SVF method are in better agreement with the experimental values than those predicted from the ACF method. In addition, the average relative error of the theoretical bending moment value of all beams based on the SVF estimation is 6.52%, which is 33.19% lower than that obtained by ACF method. Therefore, the SVF method is more effective in describing the spatial properties of material and geometrical parameters compared with the ACF method.

This study aimed to comprehensively analyze the effects of the thickness of a super toughness concrete (STC) layer, the thickness of diaphragms, and the spacing of stud shear connectors on the fatigue property of a lightweight composite bridge deck. A multi-parameter analysis was performed on a steel-STC lightweight composite deck to facilitate its fatigue design. Based on a real bridge, a serial local finite element model was built to calculate the fatigue stress range of the typical fatigue-prone cracking details of the steel bridge deck under different combinations of the three parameters. On the basis of the FE analysis, the nominal stress of each fatigue-prone detail was obtained, and the following observations were obtained. First, the lightweight composite bridge deck structure could strongly enhance the local stiffness of the steel bridge deck, but its contribution to the global stiffness of the bridge deck is limited. Second, increasing the STC layer thickness from 45 mm to 60 mm could further reduce the fatigue stress range of fatigue-prone details in the steel deck. Third, increasing the thickness of the floor beams could improve the cracking details at the U-rib-to-diaphragm connection and butt weld at the U-rib lower edge, and the stress range reduction is about 20%-29%. Fourth, reducing the spacing of the stud shear connectors could obviously decrease the stress range of the U-rib-diaphragm welded joints and the arc cutouts in floor beams, and the stress range decreases by 22.01%-27.96%.

Determination of the optimal bridge scheme is crucial in the preliminary design stage of bridge construction, and the scientific decision results directly affect the construction and implementation of the whole project. At present, the determination of bridge schemes in mountainous areas is mainly based on empirical judgment, and few theoretical methods can be adopted. Therefore, a comprehensive evaluation model was built for mountainous bridge type scheme by the basic AHP theory, grey relational analysis, and TOPSIS. The model comprehensively considered the various factors affecting the selection of bridge type from the aspects of economy, technology, and society, and 12 evaluation indexes were selected to build a comprehensive evaluation system for the bridge type scheme in mountainous areas. Weight vector of valuation indexes of bridge type was calculated by AHP to reduce the influence of human subjective factors. Then, a weighted grey correlation coefficient decision matrix was constructed by fuzzy mathematics theory and grey correlation analysis, and the relative closeness coefficient between the alternative schemes and the Grey correlation ideal solution was calculated by TOPSIS. Finally, the optimal bridge type scheme was determined based on the relative closeness coefficient. The evaluation model was used to judge three alternative bridge type schemes (A₁-A₃) of a highway in the mountainous area of Pu'an County, Guizhou Province. The relative closeness coefficients of continuous PC T beam bridge (A₁), PC continuous rigid frame bridge (A₂), and PC dwarf-tower cable-stayed bridge (A₃) were respectively 0.597 7, 0.315 6, and 0.400 3, indicating the first scheme is the best optimized bridge type. Thus, the first bridge scheme was applied to actual bridge construction and achieved good economic and social values. The results show that the evaluation model provides a feasible theoretical method for the decision-making of mountain bridge type.

The spatial characteristic of a freight transportation connection network can provide a basis for regional logistics planning and freight transportation organization. The theory of spatial rescaling is introduced for the method of developing a freight transportation connection network to effectively extract the complex interrelations in intercity freight transportation connections. This approach is conducted by applying Geographic Information System (GIS) spatial analysis technology on the spatial organization process and hierarchical structure of a system to explore the dynamic features of a freight transportation connection network. Yunnan province is used as an example. Then, the correlational analysis method and complex network are used to optimize a spatial organization to strengthen transportation connection and improve network stability to conduct a comprehensive evaluation of the transportation factors. Results indicate that (1) spatial organization of a freight transportation connection network is a complex process that involves geographic concentration and preferential attachment interactions, and the control power of key nodes will transfer to the secondary nodes with a decrease of its hierarchy, causing a balance in the spatial differentiation of urban functions; (2) the scale, grade, and accessibility of transportation infrastructure have a weak effect on the intercity freight connections, and spatial organization optimization improves transportation capacity; and (3) the enhancement of survivability of key nodes in the core network will achieve the goals that balance the network connectivity and improve the stability of freight system preferentially.

This study aims to investigate retroreflectivity sheeting matching and design of highway warning piles. The effects of relevant parameters on the nocturnal guidance for a change in horizontal alignment of highway-side warning pile are studied and discussed by using real vehicle tests. We consider the two forms of warning piles that are commonly used on national highways. The first is the red and white warning piles, which is used for warning function of access spots; and the second is the yellow and black warning piles, which is used for the induction function of highway side profile. Deceleration spots before the vehicle enters the bend and the smoothness of the deceleration process are considered identification indicators on the basis of the real vehicle test. We obtain optimal quantities of retroreflectivity sheeting matching and design of highway warning piles using mathematical statistics method and correlation analysis. We also propose a corresponding low-cost solution considering the low budget of low-class highways.

The adjustment of transport structure is a major decision made by the CPC(Communist Party of China) Central Committee with General Secretary Xi Jinping as the core. This decision is an important link to reduce air pollution and achieve environmental protection. Promoting the "road to railways" for cargo transportation, reducing the amount of road freight, and increasing the amount of railway freight transportation are vital for preventing and controlling air pollution in the Beijing-Tianjin-Hebei region and accelerating the construction of a modernized and integrated transportation system. On the basis of the analysis of the status quo of freight transportation in the Beijing-Tianjin-Hebei region, this article presents an understanding of the structure adjustment of such freight transportation and proposes optimization strategies.

An approximate model can be used to replace the real model to reduce the computing time and guarantee the feasibility of optimization. However, the approximate model must meet the required accuracy. The higher the accuracy of the approximate model, the higher the reliability of optimization results. In this study, a finite element model for the 40% offset impact of minibus was established, with the thickness of 10 plates in the front of the car body as the design variable and peak acceleration of B pillar lower end, the total mass, and the intrusion volume of dashboard beam, steering column hole, and clutch pedal as the response values. We obtained 70 sample points by the Latin hypercube experimental design method and built approximate models of design variables and the response. Then, we compared the relative error scatter, mean relative error, and decision coefficient of the response surface approximate model, radial basis function network approximate model, kriging approximate model, and orthogonal polynomial approximate model. Results show that the prediction accuracy of the response surface approximate model and radial basis function network approximate model in the peak acceleration of B pillar lower end and the intrusion volume of the steering column hole and clutch pedal does not meet the requirement. The orthogonal polynomial approximate model has a high prediction accuracy in total mass, but its prediction accuracy in other responses does not meet the requirement. In addition, all three approximate models are obviously influenced by the linear relationship between the response and the variables. The kriging approximate model meets the required prediction accuracy of the four responses and is less affected by the linear relationship. Thus, the kriging approximate model is suitable to replace the original model. Then, particle swarm optimization can be performed to optimize the kriging approximate model. This study shows that the kriging approximate model has high fitting precision, and the optimization results reach the expected aim.

Urban agglomeration is becoming an important form of urbanization in China. The national Urbanization Plan (2014-2020) proposes that urban agglomeration is an urgent priority, and short- and long-term plans should be developed. A suitable method of estimating and evaluating the carbon emissions of the road network in urban agglomeration-oriented transportation planning is needed. For measuring and evaluating the carbon emission of road network, suitable methods that use the basic data of different sources are lacking. With data on fuel sales, vehicle ownership, transportation planning modeling, and urban population, methods of calculating the carbon emission based on vehicle kilometers of travel (VKT) were designed in this work. Three methods based on fuel sales data, vehicle ownership, and transportation planning modeling were designed for current VKT estimation. As for the future, two VKT prediction methods were designed that are separately based on transportation planning modeling and the urban population. A method of calculating carbon emissions was designed based on the estimation and prediction of VKT. Then, the data sources, advantages, limitations, and the reflected subject of the methods were compared. With a comprehensive application of these methods, we established a method of calculating the carbon emissions of urban agglomeration-oriented transportation planning; this method is sensitive to traffic parameters. Then, a case study was used as an example of the road network transportation planning of Chengdu-Chongqing city agglomeration to demonstrate the application of the method. The results of the case analysis can prove that under the current existing data, the carbon emission of transportation in urban agglomeration could be calculated and quantitatively analyzed with the comprehensive application of these methods, thereby possibly providing support for transportation decision-making.