Reasons for using steel structures in bridges
Light superstructure; The superstructure of steel bridges is usually lighter than other building materials, which usually leads to smaller foundation and lower cost. In addition, lighter superstructure usually reduces seismic force, which may be a main advantage in high earthquake areas. Future modification and adaptability; Steel bridge components can be strengthened and adjusted if there is a need to address increased live loads, new live loads, road widening or other configuration changes in the future. Other materials do not have the same adaptability, and it is usually necessary to replace the new load or change the configuration, reliability and redundancy; The reliability of steel bridge is realized through redundant design and construction practice. Effective and efficient redundancy can be achieved through system or member level mechanisms using engineering damage tolerance, which can be combined with the inspection interval of the bridge. In addition, the exposed tension elements of in-service steel bridges improve the possibility of damage detection in daily visual inspection, and further improve the safety and reliability.
Large span construction; Steel can span intersections over 500 feet in the form of plate girders, tied arches, suspension bridges, cable-stayed bridges and trusses. Many historical and current examples show that steel is an ideal material for long-span structures. Steel provides the advantages of controlled manufacturing, lighter components and durability for these long-span applications. Railway and transportation applications; Steel bridges are ideal for railway and transportation applications because steel can provide high strength and stiffness as deck beams, through beams or truss bridges. The high strength weight ratio of steel is very suitable for supporting railway live load almost five times that of traditional highway live load. The stiffness characteristics provided by steel bridges can be used to meet more stringent operational requirements for live load deflection and track and transport loads.
In service inspectability; Steel bridges can be visually inspected because bridge inspectors have easy access to all major load-bearing components to effectively evaluate their use. The main load-bearing components are not hidden in the eyes of bridge inspectors, and expensive special equipment or nondestructive testing methods are usually not required to determine their condition. The bridge inspector has access to the main load-bearing components and obtains any physical measurements that may be damaged, providing the evaluator with the necessary data to properly load the structure. Maintainability and repairability; When necessary, the steel bridge can be effectively repaired and continue to be used without complete replacement. Components can be reinforced with additional steel or can be removed and replaced without permanently removing the bridge. Impact and damage of under bridge superelevation vehicles can usually be easily corrected by well-documented thermal straightening technology. The maintenance, repair and repair of steel bridges can usually be carried out under the condition of maintaining all or part of the traffic structurally, while expanding the utility of existing bridges in use.
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