Accurately identifying the key nodes of the road network and focusing on its management and control is an important means to improve the robustness and invulnerability of the road network. In this paper, a classification and identification method of key nodes in urban road networks based on multi-attribute evaluation and modification was proposed. Firstly, the emergency function guarantee grade of road network nodes was divided by comprehensively considering the importance of road network nodes, the consequences of failure, and the degree of difficulty of recovery. The evaluation indexes were selected according to the local attributes, global attributes, and functional attributes of the road network topology. The spatial distribution patterns of the evaluation indexes of the nodes were analyzed. The dynamic classification method was used to cluster the attributes of the road network nodes, and the TOPSIS method was used to comprehensively evaluate the importance ranking of the road network nodes. Attribute clustering of road network nodes by dynamic classification method (DT) and the TOPSIS method was used to comprehensively evaluate the ranking of the importance of road network nodes. Then, combined with the modification of the comprehensive evaluation and ranking of the importance of the road network nodes, the emergency function support classification results of the road network nodes were obtained. Finally, the method was applied to the road network within the second Ring Road of Beijing. It was compared with the clustering method of self-organizing competitive neural networks. The results show that this method can identify the key nodes of the road network more accurately. The first-grade key nodes are all located at the more important intersections on expressways and trunk roads. The spatial distribution pattern shows a “center-edge” pattern, and the important traffic corridors of the road network show a “five vertical and five horizontal” pattern.

The proper mix ratio of hybrid fiber reinforced concrete and frost resistant concrete as bridge deck pavement materials are needed for optimal design. These are based on both the control of strength and durability and consideration of the environment of the construction site. Without reducing its mechanical properties and durability, 0.7% volume ratio of steel fiber and 0.5% volume ratio imitation steel fiber (treated polypropylene fiber) mixed and prepared as C40 hybrid fiber reinforced concrete. The imitation steel fiber can make up for the fact that steel fiber is easily corroded, rather heavy, higher cost, and difficult to use in construction. C40 frost resistant concrete by the admixture of 0.1% volume ratio Dura fiber to improve the freeze-thaw resistance capacity and reduce shrinkage cracks in an early age. The mechanical properties, impermeability, freeze-thaw resistance has improved greatly compared with ordinary concrete. But its mechanical properties and durability can be somewhat less than hybrid fiber reinforced concrete. Frost resistant concrete has an advantage over hybrid fiber reinforced concrete on workability and simple construction. It is recommended superplasticizer can be used to improve the mechanical properties and frost resistance concrete durability.

The rapid expansion of China’s immersed tunnel construction has resulted in substantial consumption of reinforced concrete and construction energy, thereby generating considerable greenhouse gas (GHG) emissions during the construction stage. Unlike conventional tunnels, immersed tunnels require large cross-sectional dimensions, complicated geological conditions (e.g., varying seabed burial depth and settlement grade requirements), and unique structural parameters, leading to distinct emission characteristics that are currently insufficiently understood. To address this gap, this study aims to quantify construction-stage GHG emissions of immersed-tube segments, identify key influencing factors linking construction parameters and material input with GHG emissions, and develop simplified predictive models for design-stage estimation. A total of 51 immersed-tube segments from three representative cross-sea tunnel projects in China were examined. Under a unified system boundary and functional unit (covering material production and processing, material transportation, and on-site construction energy consumption), the life-cycle assessment (LCA) framework was applied to quantify the construction-stage emissions of each immersed-tube segment. The construction-stage GHG emissions of a single segment range from 1.56 × 10⁴ to 2.71 × 10⁴ t CO₂ eq (mean ≈ 2.40 × 10⁴ t CO₂ eq). Correlation and partial correlation analyses demonstrated that the total mass of construction materials exhibits the strongest correlation with GHG emissions, followed by the element volume, concrete cross-sectional area, settlement grade, and burial depth. The results further indicate that material intensity is the dominant determinant of GHG emissions for immersed tubes, while the effects of seabed and settlement conditions mainly operate through structural scale and material demand. Finally, two linear regression models were developed, and the model based on total material mass provides the most accurate prediction of construction-stage emissions. The immersed-tube volume can be used to estimate approximate GHG emissions at the design stage, whereas the total material mass serves as a better predictor when detailed material input data are available. This study is based on segment-level data from three Chinese projects and focuses on the construction stage; therefore, transferability requires further validation. Material intensity is the dominant determinant, and the total-material-mass model is the most accurate predictor.

The haunched joint with ribbed anchor webs in the concrete-filled double steel tubular (CFDST) structure was proposed in this study. The CFDST column and the steel beam were connected by ribbed webs, which were anchored inside the column and connected to the beam web by the bolted connection, and haunches were welded to shift plastic hinges from the joint core to the beam end. The cyclic loading test was conducted on three beam-to-column joint specimens. Seismic behaviors, including failure modes, strain and stress responses, hysteretic curves, ductility, and energy dissipation capacity, were, respectively, analyzed. Besides, finite element (FE) modeling was validated and was used to further analyze the seismic behavior in consideration of connection constructional details, geometric dimensions, material strength, and axial compression ratios. The parametric investigation shows that besides ribs and haunches, stiffening diaphragms are practicable to connect the double tubes, especially for the high-strength steel beam; beam-to-column bending stiffness ratio per unit length is appropriate to be 0.3–0.5; choosing low strength grade of concrete is allowed to satisfy engineering requirements; the axial compression ratio should be limited within 0.5.