Fig 1.
Classification system for MS of coastal bridges based on a bottom-up framework.
Table 1.
Material consumption focus for different bridge types in coastal infrastructure projects.
Table 2.
Environmental sustainability impact assessment indicators classification.
Fig 2.
Geographical distribution of Sea-Related bridges in China by structural type.
Caption credit: The four submaps illustrate the spatial distribution of cable-stayed, suspension, arch, and beam bridges along the Chinese coastline, highlighting their geographic density and typological variation.(The base map and administrative boundaries were obtained from the National Platform for Common Geospatial Information Services (Tianditu, https://www.tianditu.gov.cn/; map review No. GS(2024)0650).).
Fig 3.
Basic information and spatial distribution of Sea-Crossing bridges in China.
(The basemap was redrawn by the research team based on UAV photogrammetric data acquired between April 2019 and October 2020 using the DJI Phantom 4 RTK platform. The average flight altitude was approximately 120 m, with a ground sampling distance of 0.03–0.05 m. All imagery was orthorectified and vectorized. The spatial locations and basic attributes of all identified bridges are provided in the Excel file within the S1 File.).
Table 3.
Life cycle greenhouse gas emission factors for coastal bridge construction and operation.
Table 4.
MS calculation results for the 510 coastal bridges along the coast of China (Unit: Million tons).
Fig 4.
Material composition of the total MS in China’s coastal bridge system.
Fig 5.
Inventory distribution and material intensity characteristics of coastal bridges(/km).
(a) Total stock distribution by bridge type; (b) Material stock intensity per kilometer (breakdown by bridge type and material category).
Fig 6.
Boundary of the lifecycle system of coastal bridges.
This diagram outlines the life cycle assessment for coastal bridge construction, covering production of materials, transportation, construction, and the ongoing operation and maintenance. It highlights energy demands, material accumulation, and environmental impacts.
Table 5.
Life cycle inventory for Chinese coastal bridges per kilometer.
Fig 7.
Phase-specific contributions to environmental impacts per km of bridge infrastructure.
(a) Global warming potential (GWP) contributions by phase; (b) Human carcinogenic toxicity contributions by phase; (c) Mineral resource scarcity contributions by phase; (d) Fossil resource scarcity contributions by phase; (e) Freshwater ecotoxicity contributions by phase; (f) Marine ecotoxicity contributions by phase.
Fig 8.
Contribution of raw material production to six environmental impact categories.
(/km) Caption credit: less than 2% is not displayed.
Table 6.
Percentage contributions of steel and cement to global warming potential and resource scarcity.
Table 7.
Hidden operational flows in coastal bridges: Mechanistic drivers and quantified impacts.
Fig 9.
Comparison of material inventory and environmental impact value between sand and steel.