Quick questions on Structural steel for civil engineering: HSC Engineering Studies Civil Structures

Structural steel is iron-carbon alloy with up to about 0.25 percent carbon plus controlled additions of manganese, silicon and (for higher grades) niobium and vanadium. Australian-made structural steel comes from BlueScope's Port Kembla works (basic-oxygen process, slab caster, hot rolling mill).

The relevant Australian standard is AS/NZS 3679 for hot-rolled sections. The two common grades are:

Australian structural steel sections are designated as:

Members are connected by bolted or welded joints.

The Sydney Harbour Bridge (opened 1932) used about 53,000 tonnes of silicon-manganese structural steel, mostly rolled at Dorman Long in England with smaller quantities from BHP's Newcastle works. Connections are riveted, with around 6 million rivets in the structure. The arch was designed in compression using hand calculations of stress in every member. The choice of high-strength silicon-manganese steel over plain mild steel was driven by the need to keep section sizes within fabrication and transport limits of the day.

Bolted connections allow disassembly but require holes (which reduce member area). Welded connections are continuous but require qualified welders and quality control.

UB (universal beam) is deep and is used in bending. UC (universal column) is roughly square and is used in compression.

Grade 350 has less ductile reserve than grade 250. :::