Advantages: It was principally due to outstanding strength. The tensile and compressive strength of steel is significantly greater than that of materials like concrete, and the components will have smaller cross-section for the same load; the self-weight of steel is merely 1/3 to 1/5 part of that of concrete structures, which can greatly reduce the requirements of foundation bearing capacity, so it is especially fit for projects on soft soil foundations. And secondly, it is high construction efficiency. More than 80% of parts can be prefabbed in factories by standard method and be assembled on site via bolts or weld, which can bring the construction cycle down for 30%~50% over concrete structures. And thirdly, it is better in anti-earthquake and Green Building. Good toughness of steel means that it can be deformed and absorb energy during an earthquake so its seismic resistance level is higher; In addition, over 90% of steel is recycled, which reduces construction waste.
Disadvantages: The main problem is poor corrosion resistance. Humid environment exposure, such as salt spray on the coast naturally causes rusting, usually followed by anti-corrosion coating maintenance every 5-10 years, which increases the long-term costs. Secondly, its fire resistance is not enough; the strength of steel decreases dramatically when temperature is more than 600℃, fire retardant coating or fire protection cladding should be used to satisfy different building's fire resistance requirement. Besides, the initial cost is higher; the cost of steel procurements and processing for large-span or high-rise building systems are 10%-20% higher that those of ordinary concrete structures, but the total lifecycle cost can be leveled out by adequate and proper long-term maintenance.
