Corresponding experiments were designed and accomplished to obtain the authentic mechanical response mechanism of pavement under different loading conditions. Replicability and reproducibility of the experiments were discussed in this paper. Meanwhile, the response mechanism for three typical pavement structures was analyzed. Results show that mechanical response test method for pavement structure has characteristics of good replicability, reproducibility, and reliability. The method can also be used as an effective way to investigate the mechanical response of pavement structures. The mechanical states of different pavement materials under the same test condition are quite different. For cement bound granular and asphalt concrete, radial strain changes as alternative compression-tension with obvious mechanical response characteristic. However, the situation is different for cement concrete. The region of pavement that is close to the surface is in compressive state. By contrast, the far region is in tensile state. Top-down cracking of pavement developed from top surface crack may appear when load is too heavy. The working state of pavement can be reflected by utilizing the mechanical response test method. The mechanical response test method is a good reference when calculating mechanical state and determining parameters of pavement material.

The current standards and specifications of China for cement concrete pavements do not take into account the load transfer of transverse cracks in the reinforcement design of continuously reinforced concrete pavements (CRCP), whereas the sensitivity of those factors that influence load transfer has not been comprehensively analyzed. To address these problems, this paper analyzes the load transfer mechanism of transverse cracks and builds a numerical model of CRCP with transverse cracks by using the ABAQUS finite element (FE) software. Following the equivalent area principle, the touching area of the wheel tire is simplified as a rectangular area, whereas the tire load is arranged on the edge of the cracks for the mechanical response of an engineering example. The empirical formulas of Grovetti and Zollinger are used to verify the FE results for load transfer efficiency (LTE), while the effects of reinforcement type, base modulus, longitudinal reinforcement ratio, foundation modulus, and crack width on the bottom stress of the CRC slab are evaluated via a sensitivity analysis. The shear stiffness spring element on both sides of transverse cracks can simulate the load transfer well, and the strain and stress contours of the CRC plate under vehicle load are calculated. This engineering entity has an LTE of 89.73% and an excellent load transfer level. The steel rebar, BFRP, and GFRP have LTEs of 89.73%, 88.11%, and 87.73%, respectively, the strong rigid base, rigid base, and flexible base have LTEs of 92.32%, 89.73%, and 89.47%, respectively, the 8, 16, and 24 mm steel diameters have LTEs of 87.77%, 89.73%, and 92.55%, respectively, the 50, 100, and 150 MPa foundation moduli have LTEs of 89.73%, 91.82%, and 99.04%, respectively, and 0.2, 0.5, and 0.8 mm crack widths have LTEs of 94.40%, 89.73%, and 86.49%, respectively.

Interlayer strain transferring effect of homogeneous or heterogeneous materials is obtained by small-scale interlayer bonding test model to quantitatively evaluate the interlayer bonding of semi-rigid asphalt pavement. The influencing factors are also analyzed. Results show that interlayer strain transferring effect between homogeneous materials is strong. The interlayer contacting is continuous, while the interlayer contacting between heterogeneous materials is discontinuous. Interlayer contacting can be assumed continuous in the structure calculation of homogeneous materials, while Goodman model is recommended for heterogeneous materials. Temperature and load level significantly influence strain transfer between layers. Specifically, with the increase in temperature, interlayer strain value and strain differences of homogeneous or heterogeneous materials become large, and interlayer strain transferring effect becomes poor. As the load level increases, strain transferring effect between homogeneous materials is gradually weakened and not conducive to the combination of interlayer. Meanwhile, strain transferring effects between heterogeneous materials are improved, and cooperation deformation of upper and lower materials occurs easily under compressive stress. Interlayer contacting can be assumed continuous between asphalt or semi-rigid material layers in the structure calculation to ensure that the theoretical model corresponds to the practical situation, while the assumption is semi-continuous or semi-sliding between asphalt and semi-rigid material layers.

This study aimed to elucidate the water-salt transfer mechanism, understand the effect of partition in the subgrade, and establish the relationship between water-salt transfer and salt expansion and thaw collapse in the subgrade. Coupled differential equations of water-heat-salt-stress for embankment of coarse-grained sulfate saline soil were established basing on the theory of seepage and heat conduction in unsaturated soil; considering the influence of water-salt phase change on temperature field, water field, salt field, and stress field; and correcting the established temperature, water, and salt fields that satisfy the engineering characteristics of coarse-grained sulfate saline soil subgrade. Simultaneously, a water-heat-salt-stress four-field coupled numerical model of saline soil subgrade was established by using COMSOL Multi-physics software, and the validity of the established mathematical model was verified by the results of an indoor large-scale coarse particle saline soil freeze-thaw cycle test. The results show that in the freeze-thaw cycle with groundwater recharge, the depth of the low-temperature-sensitive area of gravel sulfate saline soil subgrade is about 45 cm and the location of the geotextile partition should comprehensively consider the influence of regional low temperature on sensitive depth and the strong rise of the capillary water in the subgrade filler. Under the effects of capillarity and temperature, the water and salt in the gravel saline soil subgrade transfer to the cold end, leading to salt accumulation under the geotextile and the strong enrichment of sulfate ion concentration. The geotextile partition in the subgrade can effectively hinder the longitudinal migration path of water and salt, and weaken the transfer of water and salt to the low-temperature-sensitive area, thereby reducing the effect of salt expansion and thaw collapse in the subgrade. In addition, the degree of reduction can reach more than 30%. The obtained calculation model can effectively predict the water-salt transfer mode, thereby providing a theoretical support for the design and construction of coarse-grained sulfate saline soil subgrade.

Traditional vibrating cable methods usually omit the influence of the bending stiffness of anchor threaded rods when measuring the cable force in suspension bridge tunnel-type anchorage, causing a great deviation in the measurement and calculation of the cable force. The cable tension in the anchorage was calculated using the cable-beam composite structure to improve the accuracy of the main cable force. Based on Hamilton's principle and the assumption of cable-beam composite structure, a new measuring method was proposed by using the vibrating matrix equation of the cable-beam composite structure. Then, the matrix was solved using Mathematica. With the Qingjiang Suspension Bridge as a case study, the modified precision of the proposed method was verified by comparing its results with those of the conventional method and the finite element method. Results indicate that using the cable-beam model to calculate the cable force can well describe the relationship among the cable force, the bending stiffness of the threaded rod, and the frequency of the cable. It also reduces the deviation induced by the bending stiffness of the threaded rod, which contributes to obtaining precise results about the actual cable state.

The pier-girder rigid region of continuous rigid-frame bridges with V-shaped piers has a complex spatial stress state because of its special structure and complex boundary condition. However, using the beam-column element model for mechanical analysis in design induces large errors. Therefore, this study analyzes the spatial stress and structural optimization of the pier-girder rigid region of a continuous rigid-frame bridge with V-shaped piers. A solid model of the pier-girder rigid region is established by photoelastic stress experiment and numerical analysis. The stress distribution characteristics of the pier-girder rigid region in the longest cantilevered stage and operational stage are revealed in view of tri-directional normal stress and boundary tangential normal stress, and the stress distribution curve of slice boundary at key positions is drawn. Results show that (1) the experimental values are consistent with the finite element analysis values, and the compressive stress is dominant in the main girder structure, which meets the design requirements of fully prestressed concrete structures; (2) the tensile stress concentration appears around the hole of the diaphragm in the bridge transverse direction, whereas the compressive stress concentration appears at the joints between the top/bottom plates of the box girder and the diaphragm in the bridge longitudinal direction; (3) the consolidation zone between the V-shaped bracing and the vertical pier is the most dangerous area of the structure, where the structural measurements of increasing the reinforcement or using steel fiber reinforced concrete are proposed. An optimization measure for increasing the height of the vertical pier is introduced to present the property of a flexible pier and optimize the mechanical characteristics of the bridge. As the height of the pier increases, the stress gradient of each section of the V-shaped bracing decreases, and the distribution of cross-section stress becomes uniform. When the height of the pier is greater than five times of the girder height at the pier top, the stress gradient of each section of the V-shaped pier is less than 0.6. Herein, the force is reasonable with large safety reserve, which can adapt to the longitudinal displacement of the main girder caused by concrete shrinkage, creep, and temperature change in the later stage.

This study aims to determine the pounding probability of a continuous rigid bridge with high piers and long span at the actual site soil under the action of an earthquake. Finite element models of the bridge are built to analyze separation length. The effect of the actual site soil on seismic wave propagation from the bedrock to the pier and the abutment foundation is considered using DEEPSOIL software. A pounding probability analysis method under multi-support seismic excitations with bedrock peak acceleration as the strength index is proposed. The pounding probability of the continuous rigid bridge with high piers and long span under multi-support seismic excitations is analyzed using the proposed method. Meanwhile, a comparison analysis of the pounding probability results under uniform excitations without considering the influence of the actual site soil is performed. The study indicates that the required width of the expansion joint under uniform excitation is larger than the multi-support excitation with the increase in bedrock peak acceleration. With the increase in the width of expansion joint and the acceleration peak, the probability of pounding at a single abutment and at two abutments under multi-support excitation is gradually less than uniform excitation. Therefore, the actual site soil must be considered when determining the width of the expansion joint of a continuous rigid bridge with high piers and long span.

In order to reasonably analyze the influence of shear deformation of corrugated steel web on the natural vibration frequency of PC continuous box girder bridge with corrugated steel webs, first, the element stiffness matrix of PC box girder bridge with corrugated steel webs is derived by using the energy variation principle. Second, according to the derived element stiffness matrix, the solution program for calculating thenatural frequency of multi-span uniform cross-section PC continuous box girder bridge with corrugated steel webs considering the influence of steel web shearing effect is compiled by MATLAB software. The correctness of the natural vibration frequencies calculated by the MATLA B software is verified by the measured frequency of the constructed bridge and the calculated value by ANSYS 3D FE method. Finally, the influence parameters of the bending vibration frequency of the abovementioned bridge are analyzed. The result shows that (1) The natural frequencies calculated by the proposed program are in good agreement with the measured and FE values of the built bridges. The calculation program has higher precision, the difference of the first 5-order natural frequencies is within 6.01% and 7.32%.(2) The shear defomation effect of corrugated steel webs has great influence on the natural frequency of the subject bridge, while the modification of the shear modulus of corrugated steel webs and the type of corrugated steel webs has little influence on the bending vibration frequency of the bridge, the difference of the first 5-order bending vibration frequencies is within 1.07% and 0.55%, which can be ignored.(3) The dynamic analysis of the subject bridge considering the shear deformation effect can be easily incorporated into the matrix displacement system of the common framed structure, which avoids the complexity of the establishment and solution of the ANSYS FE model, It provides a reference for the calculation and analysis of the bending vibration frequency of the bridge type.

In order to study the precise description and feature quantification of the tunnel lining crack morphology, the paper uses the tunnel lining panoramic image method to rely on the Wujing Expressway Qingyantou Tunnel as the project, and the lining crack image acquired by the tunnel lining expansion image generator to carry out the feature points. Extraction, matching, model recognition, image expansion and splicing processing are used to obtain a comprehensive reflection of the tunnel lining panoramic expansion image. The algorithm is analyzed from the aspects of image enhancement preprocessing, image edge detection, crack feature area interference point removal, crack connection and feature statistics, and the boundary position of the crack is found by the connected area labeling method to determine the spatial position and angular direction of the defect in the image. Using the principle of crack pixel position relationship to calculate the crack length, so as to extract the detailed feature information of the lining crack, develop a tunnel surface lining crack identification evaluation system, which provides a convenient, efficient and comprehensive for tunnel lining crack detection. Comprehensive detection system.

The theoretical analysis of the seismic response of tunnels is still insufficient. The shaking table test is an effective way to study the earthquake resistance of tunnels; because of the complex nonlinear constitutive model of rock soil and the complicated seismic dynamic equation. In the LEBUGUOLAJI tunnel, the similarity ratio is 1:30. A thermal molten mixture of river sand, oil, and fly ash is used as the similar material of the surrounding rock, and gypsum is used as the similar material of the tunnel lining. A strain gauge is symmetrically pasted inside and outside the tunnel model lining to monitor the strain stress, and a structural accelerometer is installed on the tunnel model and shaking table to invert the surrounding rock of the model. The earthquake damage characteristics and engineering shock absorption measures of a shallow-buried double-staggered tunnel are determined using the large shaking table model test. Results show that the surrounding rock of the tunnel model exerts obvious enlargement effect on the input seismic wave, and its frequency spectrum changes. The seismic wave in frequency bands below 15 Hz is strengthened, whereas those in other frequency bands are attenuated. The seismic response of the tunnel is reduced by the confinement effect of rock and soil. On the basis of the similarity ratio of the model test, 45 m can be used as the fortification length of the tunnel entrance. The weak link of the tunnel portal section is the wall angle and the 45° of arch shoulder on the tunnel slope. The seismic damage in the gap section of the tunnel is more serious than that in other parts of the tunnel in the entrance. Thus, the rock and soil volume can be increased at the staggered area to enhance the rock and soil constraints of the site in design. A strong dynamic interaction occurs in the shallow-buried double-hole staggered mountain tunnel under seismic wave action. The seismic response of the tunnel with a large damping structure can be effectively reduced to minimize the damage of the lining strain.

The index system and evaluation method of safety assessment in the operation stage are established to realize the safety risk assessment and management in the operation stage of urban road tunnel. The index scores are obtained from the fuzzy comprehensive evaluation model, and the overall safety risk grade is derived. In view of the index level with an evaluation level greater than or equal to III, special risk assessment is conducted, and safety risk solving measures are introduced. A corresponding safety risk management system platform for urban tunnel operation stage is developed on the basis of the results. The results and application of this study have a certain reference value for managing tunnel informatization based on safety risk management.

Pedestrian safety remains a crucial issue, considering that pedestrian fatalities are increasing faster than motorist fatalities. In 2016, pedestrian fatalities reached nearly 6000 in the United States, which is the highest annual record of pedestrian traffic fatalities in more than two decades. In Louisiana, pedestrian fatalities reached 110 in 2015, nearly 15% of total traffic fatalities. In the same year, the pedestrian fatality rate per 100,000 populations in Louisiana reached a higher level (2.18) than the national average (1.67). While pedestrian crashes most frequently occur in urban areas, the fatal pedestrian crash rate is 1.5 in urban areas and 3.8 in rural areas, and the rural population is only 26.8%. To reduce pedestrian crashes, this paper presents an analysis of Louisiana pedestrian crashes (2006-2015) and investigates the pedestrian safety problem. In addition, the statistical relationship between pedestrian injury severity and contributing factors, including demographics, pedestrian behavior, and the built environment for urban and rural areas, is established using multinomial logit models. Fatal and severe crashes are strongly related to the alcohol or drug use and elderly age of pedestrians, regardless of their urban or rural locations. However, the pedestrian crashes in urban and rural areas have different characteristics. Variables such as pedestrian crossing/entering road away from intersections, walking in the roadway, dark-unlighted conditions, and speed limits greater than 60 mph are significant only in rural areas but not in urban areas. The findings of this study demonstrate some unique characteristics of Louisiana pedestrian crashes, which can help select the targeted countermeasures.