Learning OutcomesBy the end of this lecture, students will be able to:Recognize different types of structural steel framesRecognize mechanical and geometrical properties of steel elementsIdentify structural elements and its functionIdentify advantages of steel structures

INTRODUCTIONFramed structuresE.g. buildings and bridgesMultistory buildingsConsists of beams and column, either rigidly or with simple connectionWith diagonal bracing to provide stabilityIndustrial buildingLong span truss, lattice girderColumn-free structureBridgesBeams and plate girder or trusses

Steel frame house

Industrial building

High-rise building

Steel stadium

Steel structures in Malaysia

Steel structures in Malaysia

Material Properties of Steel

Steel is an alloy of Iron, Carbon (

Stress-strain curveUltimate tensile strengthYield strength

Yield Strength and Ultimate Tensile Strength

Steel sectionHot rolled - heated up and pushed through rollers that squeeze the metal into a particular profile, depending on the shape of the rollers. Cold formed - are created by the working of sheet steel using stamping, rolling, or presses to deform the sheet into a profileBuilt-up form a shape by welding together different hot-rolled sections

Steel sections

Steel SectionBuilt-up section

STRUCTURAL ELEMENTSMulti-storey frame

Truss and lattice girder

Bracing

Steel Connections | Overview Connections are the glue that holds a steel structure together.

Historically, most major structural failures have been due to some form of connection failure. Connections depend on:

Type of loading Strength and stiffnessEconomyDifficulty or ease of erection

Steel connections have a direct influence on the cost of the framing system.

While a connection may be efficient in the use of material, it may still be very expensive to erect.

Repetitive connection design may save costs.

Bolting is the preferred method of connecting members on the site. Staggered bolt layout allows easier access for tightening with a pneumatic wrench when a connection is all bolted .

High strength bolts may be snug-tightened or slip-critical.

Snug-tightened connections are referred to as bearing connections

Bolts in a slip-critical connection act like clamps holding the plies of the material together.Steel Connections | Bolted Connections

Steel Connections | Bolted Connections

Steel Connections | Bolted Connections

Due to high costs of labor, extensive field -welding is the most expensive component in a steel frame.

Welding should be performed on bare metal.

Shop welding is preferred over field welding.

The weld material should have a higher strength than the pieces being connected.

BCE Place GalleriaToronto . CanadaSantiago Calatrava10Steel Connections | Welded Connections

Weld types define the configuration of the weld and its underlying design approachFillet welds and butt welds are most commonButt welds fall into two categoriesFull penetration the entire member cross-section is weldedPartial penetration just part of the member cross-section is weldedWelding Terminology

Fillet weld is less expensive than butt weldNo special preparationNo backing requiredLess volume of weldPartial penetration groove weld is less expensive than full penetration groove weldLabor represents the majority of the cost associated with weldingWelding Cost Considerations

Steel Connections | Welding vs. Bolting

Advantages:

Eliminates need for punching or drilling.

Simplifies complicated joints.

Disadvantages:

Greater level of skill required for welding than bolting

More expensive than bolting.

Weld inspection is required and is expensive.

Advantages:

Easy method of connecting members on the site.

Field-bolting is cheaper than field-welding.

Disadvantages:

Requires drilling or punching through all plies.

BOLTING

WELDING

Structural ElementsBeams and girders members carrying lateral loads in bending and shearTies members carrying axial loads in tensionStruts, column and stanchions members carrying axial loads in compressions. These members are often subjected to bending as well as compressionTrusses and lattice girders framed members varying lateral loads. These a re composed of struts and tiesPurlins beam members carrying roof sheetingSheeting rails bema members supporting wall claddingBracing diagonal struts and ties that, with columns and roof trusses, form vertical and horizontal trusses to resist wind loads and stabilize the buildingJoints connect members together such as the joints in trusses, beam-to-beam joints and beam-to-column joints. Bases transmit the loads from the columns to the foundations.

STEELWORK COSTS Steelwork construction can be affected by decisions regarding the precise form of element, type of steel used and the method of connection. For large projects, steel can be purchased directly from the mill in the exact lengths required and in the desired grade. The price of individual structural products varies not only with type (hollow sections are generally more expensive than open sections such as I-beams and H-columns) but also within a product range. Small orders is purchased from stockholders. In this case the steel is only available in a limited range of grades, (probably only mild steel). In addition certain sizes of standard section may not be stocked and the sections will only be available in a limited range of lengths.Where higher grades of steel are available they may offer the opportunity for improved efficiency. For instance, high yield steel has a yield strength approximately 25% higher than normal mild steel yet costs only about 10% more.

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Cost breakdown for portal-framed inductrial building

Cost breakdown for portal-framed industrial building

Sheet1

Cost breakdown for portal-framed inductrial building

Hot rolled steel40%

Cold formed steel13%

Fabrication19%

Transport3%

Erection12%

Paint5%

Design and drawing4%

To resize chart data range, drag lower right corner of range.

Chart1

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Cost breakdown for portal-framed inductrial building

Cost breakdown for simple beam and column structures

Sheet1

Cost breakdown for portal-framed inductrial building

Hot rolled steel37%

Cold formed steel5%

Fabrication23%

Transport3%

Erection14%

Paint5%

Design and drawing9%

Project management4%

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Cost breakdown for portal-framed inductrial building

Cost breakdown for high-rise building

Sheet1

Cost breakdown for portal-framed inductrial building

Hot rolled steel48%

Fabrication10%

Transport4%

Erection25%

Paint4%

Design and drawing5%

Project management4%

Advantages of SteelSpeed of execution

Metal decking ready to be laid by hand Edge trims are available to level concrete and prevent over-run The shear studs which provide the key between beam, deck and concrete can be placed by a single operative at 1000 per day Advantages of Steel

Concrete being placed by pumping Services are easily fixed to the underside of the decking Advantages of Steel

Prefabricated stairs can be transported by crane and placed in position to give rapid and safe access for construction workers Cladding units - pre-cast granite faced or curtain walling -can be lifted straight from the lorry and into position to avoid site storage Advantages of Steel

Lightness, Stiffness and Strength Steel structures are generally lighter than other materials. In almost all cases this lower weight leads to lower costs for foundations particularly for sites with poor ground. Smaller columns increase effective floor utilisation and, where longer spans are required, the cost savings between steel and other forms of construction increase considerably. For large column grids in buildings, steel is the only feasible solution.Advantages of Steel

Long span floor systems for office buildings Advantages of Steel

Adaptability of Usage of Steel Frames for RefurbishmentStructural steel provides maximum adaptability for changes in building use, because structural alterations can be accommodated with relative ease. Where additional members are required, connections can be made to the existing frame with minimum disturbance and cost. Advantages of Steel

Quality A steel frame is a factory made, precise product, produced by a stable, well-trained workforce. Only the erection of pre-fabricated members is left for the site - a process which is easily controlled.Advantages of Steel

THANK YOU

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