With the development of all types of new special-shaped arch bridges, the deformation of the pile foundation of special-shaped steel arch bridges has a great influence on the superstructure, and the requirements for it are strict. In addition, the force of the inclined pile group under an earthquake is complicated. In this paper, based on the Zhuhai Jindao Bridge project, the finite element numerical model is established in order to study the dynamic response and parameter influence law of an inclined straight pile group foundation under earthquake action. After a thorough analysis of the results of the simulation, it was found that under the action of an earthquake, the inclination angle of inclined piles has a significant influence on the seismic ability of pile group foundations. When the inclination angle of an inclined pile is 5°, the ability of the inclined pile group foundation to resist deformation can be effectively improved, and the load distribution of the pile top is more reasonable.

This study investigates the evolution of the macro- and micro-scale properties of foamed concrete under different saline environments, including sulfate, chloride, and composite salt conditions. The research focuses on the changes in compressive strength, pore structure, and hydration products of the material. Through full-immersion tests and compressive strength measurements, combined with microstructural characterization techniques such as mercury intrusion porosimetry (MIP) and thermogravimetric analysis (TG), the deterioration mechanisms of foamed concrete under salt attack are systematically explored. The results indicate that Sulfate ions exhibit the most aggressive erosion effect, and the presence of chloride ions can produce a “passivation” effect which partially mitigates the damage caused by sulfate ions. Moreover, increasing the material density and incorporation of mineral admixtures contributes to pore structure refinement, significantly enhancing resistance to salt attack. These findings provide a theoretical basis for the practical application of foamed concrete under a complex salt erosion environment.

Due to their excellent thermal conductivity and sensitivity to temperature changes, special attention should be paid to the influence of temperature on steel-structure bridges. The temperature effect is complex, especially for unstable steel arch bridges with complex structural forms. This paper proposes an approximate method that measures the three-dimensional temperature field of the symmetrical arch rib with the two-dimensional temperature field of multiple sections. In addition, it converts the complex radiant intensity calculation of the special-shaped steel box arch rib into the calculation of numerous planar radiant intensities. It uses the ANSYS Workbench to establish the three-dimensional transient thermal analysis finite element model of the No. 2 steel box arch rib. The influence of seasons and arch rib direction on the temperature field of steel box arch ribs and the stress and deformation of steel box arch ribs under non-linear temperature effects were analyzed. The results show that the temperature changes in different seasons significantly impact the temperature changes in the arch ribs. The change in the azimuth angle of the arch rib has a significant impact on the temperature difference between the web plates on both sides of the arch rib; under the influence of the temperature field at the most unfavorable time in summer and winter, symmetrical stress concentration occurs in the arch foot area. Furthermore, the maximum vertical displacement is 13.9 mm and 10.8 mm, respectively. Finally, when the angle is 40°, the maximum temperature difference between the web plates on both sides is 6.9 °C.

The high-strain direct testing method is a novel technique for dynamic testing of pile bearing capacity, developed as an improvement to the traditional high-strain method. While its theoretical feasibility has been demonstrated through numerical simulations and laboratory experiments, its effectiveness in practical engineering applications remains uncertain. This paper discusses the foundational theory of the high-strain direct testing method, highlighting its clear calculation principles, straightforward process, and advantage of not requiring iterative fitting. The bridge project in Zhuhai, Guangdong Province, China, serves as a case study. An instrumentation layout for concrete-filled piles was designed based on the principles of the high-strain direct testing method, and data processing and analysis programs were developed using Python. Fifteen test piles were selected for field application of the high-strain direct testing method, with detailed analysis conducted on the results from four test piles. The test results were consistent with the soil layer distribution characteristics beneath the four piers of the bridge, validating the feasibility of this method in actual engineering practice. Subsequent static load tests on these four test piles allowed for a comparison with the high-strain direct testing method results, confirming the accuracy and reliability of the high-strain direct testing method for determining the bearing capacity of single piles. Furthermore, this paper identifies sources of error in the application of this method and proposes corresponding improvement measures. As this method directly derives results from instrumented measurements, it is theoretically applicable to piles of any cross-sectional shape and material, provided that enough measurement lines can be successfully arranged along the pile shaft. This capability allows for the real-time estimation of the ultimate bearing capacity during pile driving, thereby enhancing the universality of the high-strain direct dynamic testing method beyond traditional techniques.