Quantificationally describing weathering process and characterizing particle breakage are important in predicting the behavior of coarse-grained soil (e.g., weathered granite). In order to comprehensively understand the mechanical properties of weathered granite and provide references for reasonable evaluation of the engineering properties of subgrade filling in mountains, a series of tests—X-ray diffraction, sieving, heavy compaction, large-scale triaxial, and field compaction tests—were carried out in this research. Based on the weathering process parameters (m and r) of in-situ granite samples at two typical sections of weathered granite mountains obtained by using previous grading equation, the mathematical model of weathering process with depth was proposed and the variation laws of weathering process with depth were described. The results show that, with an increase in burying depth of mountain profile (h) of weathered granite, the geological year’s parameter (m) decrease by power function, but the geometric progression constants (r) increase by power function. Some factors affecting the particle breakage properties of compacted weathered granite were evaluated by using relative breakage (B_r). Especially, the effect of field compaction condition (such as thickness of loose paving layer and number of vibratory rolling passes) on particle breakage was analyzed creatively. Through laboratory and field tests, it was found that particle gradation, mineral composition, compaction effect, stress level, and number of rolling passes significantly affected the particle breakage characteristics of weathered granite. Furthermore, it is worthy of attention that the weathered granite in this paper showed obvious particle breakage characteristics under weak compaction effect and at low stress levels and over-compaction could result in a decrease in the degree of compaction of a certain thickness of loose paving layer filled with weathered granite. Findings in this research can provide a theoretical basis for evaluating the physical properties and mechanical behavior of weathered granite as subgrade fillings.

In order to improve the estimation accuracy of bearing capacity of pile foundation, a new forecast method of bearing capacity of pile foundation was proposed on Jeffrey’s noninformative prior using the MCMC (Markov chain Monte Carlo) method of the Bayesian theory. The proposed approach was used to estimate the parameters of Normal distribution. Numerical simulation was used to produce pseudosamples. The parameter estimation of the maximum likelihood method and the Bayesian statistical theory was used to estimate the parameter estimation of the Normal distribution, which has been compared with the theoretical value of the pseudosample of Normal distribution. The result indicates that the forecast model of Normal distribution using the Bayesian method is better than that of the maximum likelihood method, and the performance of the proposed method was improved with increasing of pseudosample number. At last, the proposed method was applied to estimate the parameter of Normal bearing capacity distribution of pile foundation, which shows that the proposed method has a high precision and good applicability.

As the suspension bridge structures become more flexible and the forms of the vehicle load become more diverse, the dynamic coupling problem of the vehicle‐bridge system has become gradually prominent in long‐span suspension bridges, resulting in an increase in accuracy and efficiency requirements for dynamic coupling analysis of the vehicle‐bridge system. Conventional method such as finite element method (FEM) for dynamic coupling analysis of vehicle‐bridge system often requires separate iteration of vehicle system and bridge system, and the contact and coupling interactions between them are used as the link for convergence inspection, which is too computationally intensive and time‐consuming. In addition, the dynamic response of the vehicle‐bridge coupling system obtained by FEM cannot be expressed explicitly, which is not convenient for engineering application. To overcome these drawbacks mentioned above, the backpropagation (BP) neural network technology is proposed to the dynamic coupling analysis of the vehicle‐bridge system of long‐span suspension bridges. Firstly, the BP neural network was used to approximate the dynamic response of the suspension bridge in the vehicle‐bridge coupling system, and the complex finite element analysis results were thus explicitly displayed in the form of a mathematical analytical expression. And then the dynamic response of the suspension bridge under vehicle load was obtained by using a dynamic explicit analysis method. It is shown through a numerical example that, compared with FEM, the proposed method is much more economical to achieve reasonable accuracy when dealing with the dynamic coupling problem of the vehicle‐bridge system. Finally, an engineering case involving a detailed finite element model of a long‐span suspension bridge with a main span of 1688 m is presented to demonstrate the applicability and efficiency under the premise of ensuring the approximation accuracy, which indicates that the proposed method provides a new approach for dynamic coupling analysis of the vehicle‐bridge system of long‐span suspension bridges.

The thin‐walled box girder (T‐WBG) is widely applied in the long‐span bridge structures during the past decades due to its lighter self‐weight and better mechanical properties. The shear lag effect (SLE), an essential aspect of T‐WBG which governs the stress and the deformation, is rather necessary to be revealed properly. The extraordinary issue of T‐WBG analysis nowadays is the SLE impact on its dynamical response to external load. This paper proposes an improved finite element method (FEM) to obtain the realistic vibration characteristics of the T‐WBG considering the SLE by theory analysis and formula derivation. Firstly, based on the classical plate and shell theory as well as beam theory, the T‐WBG was divided into shell subunit for the roof and beam subunit for web and floor, respectively. Secondly, a 3‐order polynomial which is consistent with the experiment results was adopted as the axial‐displacement interpolation function of the roof subunit, whose nodal displacements parameters were also taken as the basic. Thirdly, the nodal displacement parameters of the web subunit and floor subunit were deduced by the basic according to the principle of deflection consistency. It is shown through a numerical example that the proposed method is much more economical to achieve reasonable accuracy than traditional FEM analysis software when dealing with the free vibration problem of the T‐WBG considering the SLE. Besides, it is also observed that the natural frequency values considering the SLE have a trend of decreasing markedly in general, and the influence of SLE on higher‐order frequency is more significant than on the lower one under the boundary condition of cantilever supported, while a contrary effect under the boundary condition of simple supported.

In order to study the transient temperature effect during the construction of a cross-sea bridge off the coast, based on the Hong Kong-Zhuhai-Macao Bridge-Pipe Bridge Crossing Cliff 13-1 Gas Field, a refined analysis was conducted and the prediction of transient temperature gradient and structural response was carried out under the conditions of strong solar radiation and atmospheric convection using the method of combining theoretical research and numerical simulation. Firstly, the partial differential equation of uniform heat flux density on the outer surface of the main girder under the action of solar radiation and atmospheric convection was established. The equation was realized by calculating the solar radiation intensity and the comprehensive heat transfer coefficient, as well as fitting the atmospheric temperature on the outer surface of the main girder, and the equivalent comprehensive temperature at any time on the main girder was obtained. Secondly, a numerical analysis model of the heat conduction of the main girder section was established, and the equivalent comprehensive temperature was input into the numerical model as the temperature field boundary to solve the transient temperature gradient of the section, and the result was verified in comparison with the measured data. Finally, the transient temperature gradient was applied to the girder, and the temperature effect of the main girder during the closing process was also calculated. Construction control measures were also discussed. The research results show that the predicted value of the transient temperature gradient is consistent with the measured value (the maximum deviation is less than 2 °C), and the predicted value is slightly larger than the measured value, which makes the structure safer. During the closing process, the temperature gradient of the main girder has obvious non-linear characteristics: the temperature gradient is relatively high within 0.4 m of the top surface of the roof while tending to zero outside 0.4 m. The best closing time for the main girder is from 21:00 in the evening of the closing day to 6:00 a.m. the next day. For the small angles at both ends of the closure segment during the best closing time, temporary adjustment jacks and temporary counterweights can be adopted to eliminate the small angles at both ends of the closure segment in order to facilitate the welding construction and meet the smoothness requirements of bridge alignment.