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The secondary utilization of iron tailings solid waste meets the green development requirements of road construction in the new era. Currently, there is a lack of research on the equivalent confining pressure effect of fiber, the influence of complex stress paths on the mechanical properties of modified soil, and the internal damage in soil based on energy dissipation theory. The effects of different polypropylene fiber content, confining pressure, curing age, and complex stress path on the mechanical properties of fiber cement–modified iron tailings (FCIT) were investigated by triaxial tests and energy angle. Combined with the actual subgrade engineering, the stress path test is set up, and the strength index of the FCIT under different working conditions is obtained. From the thermodynamic point of view, the failure process for the FCIT is further revealed. The results show that: (1) the optimal fiber content of FCITs is 0.75%. At this time, the mechanical properties of FCIT are optimal, the strength is high, and shear failure is not easy. The fiber has the equivalent confining pressure effect, which could provide better shear performance for FCITs so that the FCIT is resistant to collapse in embankment construction; (2) the influence of multislope stress path on the secant modulus of the FCIT is worse than that of a single-slope stress path. The influence of curing age on the secant modulus of these two kinds of stress path is consistent, and the secant modulus of the FCIT at 28-day curing is 1.2 times that at 7-day curing; (3) after 7 and 28-day curing, the dissipation energy of the FCIT was consistent when the fiber content was 1%. Due to the equivalent confining pressure of the fiber, the fiber dissipation energy of the FCIT is not affected by the curing age. The total dissipated energy of the FCIT with a stress path slope of 1.5 is 5–6 times that with a stress path slope of 2.5. The total dissipated energy of the single-slope and multislope stress paths decreases with the increase in curing age. [ABSTRACT FROM AUTHOR]

The accurate installation of long-span arch bridges' arch ribs remains a challenge due to the complex calculations required for cable forces and arch rib displacements, as well as the significant influence of environmental and construction loads. In this study, we propose a practical approach to alignment and error feedback control for long-span arch bridges. Cable forces were optimized using multiple control objectives based on influence matrix principles. The impact of temperature on the next segment to be installed was analyzed using the metastatic GM(1, 1) model and fitting results. Several tunable parameters were employed to account for parameter errors and environmental interference. These parameters were adjusted based on the deviations between practical and theoretical alignments for different arch rib segments, achieving a model output of an offset-free-tracking arch rib structure. This technology was applied to monitor the construction of the Tian'e Longtan Grand Bridge. Compared to conventional alignment control approaches, the proposed method achieved excellent arch ring alignment after the closure of the high-accuracy arch rib and cable release, as well as effective control of cable force uniformity and tower deviation. Field measurement data indicate that the closing deviation of the arch ring is only 3 mm. This study provides a valuable reference for the construction control of long-span arch bridges. [ABSTRACT FROM AUTHOR]

An increase in the nonlinearity of the bridge will lead to a more obvious vehicle–bridge interaction effect and affect the vehicle response and driving comfort as the span increases. This paper establishes a refined finite element model of vehicle–bridge coupling for the 575 m long-span concrete-filled steel tubular arch bridge, Pingnan Third Bridge. Coupling vibration responses under different vehicle speeds, vehicle weights and road conditions of this bridge is analyzed. Then its comfort is assessed according to the comfort criterion. The results show that the vehicle–bridge coupling model has good agreement with the field test. The dynamic response of the bridge within the speed limit has no significant linear relationship with the magnitude of the vehicle speed without considering the pavement class. When the vehicle exceeds the speed limit, the dynamic response increases sharply with the increase in speed. The increase in vehicle weight leads to an increase in the maximum dynamic deflection of the bridge and a decrease in the impact coefficient, but the actual total response of the bridge does not decrease. The worse the road surface condition, the more dramatic the dynamic response of the bridge structure, taking into account the road surface level. [ABSTRACT FROM AUTHOR]