Reinforced Concrete VS Steel (1) Materials Reinforced Concrete VS Steel

Materials Reinforced Concrete Advantage good resistance to weather & chemical, and good sound and thermal insulation the structure system is more rigid, thus, less severe problem associated with sway deflection, floor vibration, and local column buckling higher fire resistance minimal maintenance is required materials required to make concrete are readily available in the local market, thus no pre-ordering is necessary local contractors are firmly familiar with RC construction can be cast into any versatile shape, thus, allow more flexible design fairly tolerable on last minute changes from Client and Architect waterproofing can be easily applied with different degree of waterproofing can produce a good finished surface, thus, no painting is necessary

Materials Reinforced Concrete Disadvantage general heavier and hence more expensive foundation resulted special care must be taken to ensure esthetic appearance against cracks induced by creeping and shrinkage effects intensive amount of falsework and shuttering are required easily affected by weather condition, this will prolong construction time

Materials Steel Advantage fast construction, weather independent flooring can be cast at the same time where formwork are provided by un-propped corrugated steel decking lightweighted, thus, less expansive foundation can be designed (i.e. shallow foundation.) assembly is simple, since all members can be pre-fabricated prior to delivery to site structure tends to be shallower in structural depth, thus, more space will be provided for service routing with high strength to weigh ratio, suitable for long span construction.

Materials Steel Disadvantage Long pre-ordering and delivery time would be required since majority members are to be import from overseas Early decision on member size & connection details are required so as to allow for ordering and shop drawing preparation. Steel members require special treatment and protection on fire & corrosion. Special surface treatments are needed: Low cost – Sprayed System (Mineral fibre sprayed systems, Vermiculite/gypsum/cement system) External System (Mineral fibre boards/batts, Vermiculite/gypsum boards, Plasterboard) Preformed System Intumescent Coatings Water or Concrete filled structural hollow sections Concrete casings

Materials Steel Disadvantage frequent maintenance is required skilful labors are required for fabrication, erection, and welding large area on site is required for storage of structural member prior to erection sensitive to temperature change and vibration steel members will deflect appreciably under total load, needs pre-cambering fabrication needs heavy plant and crane

(2) Structural Systems Vertical Load Supporting System Lateral Load Supporting System (x & y directions)

Structural Systems Cantilever without back span Columns do not vertically align Too long cantilevers Cantilever from column without back span Heavy loading on long span transfer beam Long Slender Columns

Floor Supporting Systems (3) Structural Forms Floor Supporting Systems

Deflection depends on: Structural Forms (Floor Supporting System) L w Shear α L Moment α L2 Deflection α L4 Deflection depends on: Span Structural Depth Loading Restraints

Structural Forms Different forms of Bracing (Bracing)

Athletic Centre, Sydney, Australia

State Hockey Centre

Irregular Form

Federation Square

(4) Preliminary Member Sizing

Typical service zone requirements

Reinforced Concrete RC beams Typical s /d Typical span Continuous 15 – 20 10 – 15 Up to 10m 10 – 20m Simply supported 12 – 15 8 – 12 Cantilever 5 – 7 7m

Steel Element Typical s /d Typical span Floor beams (UB’s) (include floor slab 15 – 18 Up to 12m Plate girder 10 – 12 Castellated UB’s * 14 – 17 12 – 20m Lattice girders (RSA’s) + 12 – 15 Up to 35m Lattice girders (Tubular) Up to 100m Roof trusses (pitch >20o) 14 – 15 Up to 17m Space Frames 20 – 24 Up to 60m * Avoid if high point loads; increase Ireq by 1.3 + Precamber by L/250

Typical column size

Appendix: Preliminary design charts

Appendix: Preliminary design charts (cont’d)

Appendix: Preliminary design charts (cont’d)

Appendix: Preliminary design charts (cont’d)

Appendix: Preliminary design charts (cont’d)

Appendix: Preliminary design charts (cont’d)

Appendix: Preliminary design charts (cont’d)

(4) References Fuller Moore, Understanding Structures, Boston, WCB/McGraw-Hill, 1999. Institution of Structured Engineers, Manual for the design of reinforced concrete building structures, London, the Institution, 1985. Institution of Structured Engineers, Manual for the design of steelwork building structures, London, the Institution, 1989. Ove Arup & Partners, Structural scheme design guide, London, Arup Research & Development, 1998.