Under cyclic moving load action, tensile-dominant structures are prone to crack initiation due to cumulative damage effects. The presence of cracks leads to structural stiffness degradation and nonlinear redistribution of dynamic characteristics, thereby compromising str18uctural integrity and service performance. The current research on the dynamic behavior of cracked structures predominantly focuses on transient analysis through high-fidelity finite element models. However, the existing methodologies encounter two critical limitations: computational inefficiency and a trade-off between model fidelity and practicality. Thus, this study presents an innovative analytical framework to investigate the dynamic response of cracked simply supported beams subjected to moving loads. The proposed methodology conceptualizes the cracked beam as a system composed of multiple interconnected sub-beams, each governed by the Euler–Bernoulli beam theory. At crack locations, massless rotational springs are employed to accurately capture the local flexibility induced by these defects. The transfer matrix method is utilized to derive explicit eigenfunctions for the cracked beam system, thereby facilitating the formulation of coupled vehicle–bridge vibration equations through modal superposition. Subsequently, dynamic response analysis is conducted using the Runge–Kutta numerical integration scheme. Extensive numerical simulations reveal the influence of critical parameters—particularly crack depth and location—on the coupled dynamic behavior of the structure subjected to moving loads. The results indicate that at a constant speed, neither crack depth nor position alters the shape of the beam’s vibration curve. The maximum deflection of beams with a 30% crack in the middle span increases by 14.96% compared to those without cracks. Furthermore, crack migration toward the mid-span results in increased mid-span displacement without changing vibration curve topology. For a constant crack depth ratio (γ_i = 0.3), the progressive migration of the crack position from 0.05 L to 0.5 L leads to a 26.4% increase in the mid-span displacement (from 5.3 mm to 6.7 mm). These findings highlight the efficacy of the proposed method in capturing the complex interactions between moving loads and cracked concrete structures, offering valuable insights for structural health monitoring and assessment.

According to vibration characteristics of highway bridge-vehicle coupling, taking a simple supported beam bridge as an example, the scale model test system of vehicle-bridge coupling vibration has been designed and manufactured, including model testing bridge, testing vehicle, traction, braking, limiting device and a data collecting system. Comparison of measured value and theoretical value, the dynamic characteristics of model bridge and testing car have tested efficiency of design and manufacture about model bridge and testing car; Comparison of scale model test results with numerical results of spring mass vibration system and simulation results of LS-DYNA, which verifies the similitude laws of bridgevehicle interaction model text and corrects the reliability of measurement result. The results show the feasibility of model test equipment and the validity of the test results.

Bored pile waste slurry generated during bridge substructure construction exhibits high water content and stable colloidal properties, resulting in difficult solid–liquid separation and severe environmental risks. To improve solid–liquid separation and facilitate efficient disposal, this study systematically investigated the flocculation and dewatering performance of the slurry using three typical flocculants (Anionic polyacrylamide (APAM), cationic polyacrylamide (CPAM), and polymeric aluminum chloride(PAC)) through sedimentation tests, supernatant purification monitoring, particle size analysis, zeta potential measurements, and specific filtration resistance tests. The results show that flocculant type and dosage significantly affect treatment efficiency. Organic flocculants outperform inorganic PAC in both particle aggregation and dewatering improvement. Among them, APAM exhibits a prominent low-dose advantage; at an optimal dosage of 0.2–0.3% (corresponding to a pure reagent dosage of 10–15 mg/L based on wet slurry), it effectively reduces the slurry water content and lowers supernatant suspended solids below the 50 mg/L discharge standard within 80 min. Mechanistically, PAC provides primarily electrostatic neutralization, whereas APAM and CPAM achieve composite flocculation through charge neutralization, adsorption bridging, and sweep capture. Benefiting from efficient low-dose neutralization and long-chain bridging effects, APAM significantly reduces filtration resistance and forms stable flocs. Overall, an APAM dosage of 10–15 mg/L is the optimal scheme for in situ treatment of bored pile waste slurry, providing technical support for the efficient management and controlled disposal of engineering slurry under similar geological conditions.