Ensure smooth, comfortable and safe driving; The traffic volume of the bridge can not only meet the needs at that time, but also take proper care of the future development; For bridges crossing lines or rivers, it is required not to hinder the traffic or navigation under the bridge; For bridges close to cities, villages and towns, the environment and development of bridge head and approach area should also be considered; During the service life, the bridge can ensure daily operation only by routine maintenance and repair.
Safety requires that the safety of the bridge not only includes the safety of vehicles and pedestrians on the bridge, but also includes the safety of the bridge itself. Within the service life of the structure, under various natural conditions and load effects, it is the fundamental requirement for each bridge to have the ability to meet the bearing capacity and maintain an appropriate degree of safety.
Economy requires that, on the premise of applicability and safety, economy is the main factor to measure technology level and make plan selection. Bridge planning should show economic characteristics. With regard to serious bridge projects, it is necessary to compare multiple plans, specifically study the technical feasibility, progressiveness and economic rationality. In this way, the construction cost, construction, technology development and future application of the bridge can be considered as a whole, and a reasonable economic conclusion can be drawn.
Beauty requires that under the premise of applicability, safety and economy, the bridge should have a beautiful appearance as far as possible and be harmonious with the surrounding environment, which is the fundamental requirement for the beauty of the bridge. A reasonable summary of the shape and layout, the transmission of correct expression, and the harmony of the structural style and color with the surrounding environment are the main elements of beauty. In cities and tourist areas, the artistic treatment of bridge buildings can be properly considered, but the flashy and tedious details should not be sought.
