Steel structures

SUKHDARSHAN

WHAT ARE STEEL STRUCTURES ? A structure which is made from organised combination of structural STEEL

members designed to carry loads and provide adequate rigidity

Steel structures involve a sub-structure or members in a building made from structural steel.

Some famous steel structures are-

WALT DISNEY CONCERT HALL,US TYNE BRIDGE,UK HOWRAH BRIDGE,INDIA

ELEMENTS IN A STEEL STRUCTURE

Structural member is physically distinguishable part of structure with independent structural function, e.g. member elements,cable,beams,sections etc

ADVANTAGES OF USING STEEL IN STRUCTURES

High strength The high ratio of strength to weight (the strength per unit weight) Excellent ductility and seismic resistance Withstand extensive deformation without failure even under high tensile stress. Elasticity, uniformity of material Predictability of properties, close to design assumption Ease of fabrication and speed of erection

The specific strength is a material's strength (force per unit area at failure) divided by its density. It is also known as the strength-to-weight ratio or strength/weight ratio. In fiber or textile applications

STEEL

MOST IMPORTANT

Steel structures facilitate ease of fabrication and faster erection of structure .Bolts and welding employed for joining .

DISADVANTAGES OF USING STEEL IN A STRUCTURE• Susceptibility to corrosion•Maintenance costs / thin-walled structure• Loss of strength at elevated temperature• Fireproofing costs• Susceptibility to buckling• Fatigue and brittle fracture

Bucling phenomenon

Where & when use steel structures?

1) Long-span structures2)Multi-storey & high-rise buildings3) Buildings of heavy duty plants4)Tower & mast structures5)Portal frames6)Bridges7)Infrastructures8)Deployable structures9)Generalized structures: mechanical

HOWRAH BRIDGE

STEEL MARVEL OF INDIA

When commissioned in 1943, Howrah was the 3rd-longest cantilever bridge in the world

What Is a cantilever bridge?

General Terms1) Rivets are a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end.

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2) A panel joint is a point of connection between two or more members of a truss. Also called node.

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3) A girder is a support beam used in construction. Girders often have an I-beam cross section for strength.

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4) A Pin and Hanger assembly is used to connect two plate girders of bridges. These assemblies are used when the space between two bridge piers is too wide to be spanned by a single set of girders

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4) Strings are projections used for supporting the deck of a bridge

5) A bridge deck or road bed is the roadway, or the pedestrian walkway, surface of a bridge. It is not to be confused with any deck of a ship

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6) An expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of construction materials, to absorb vibration, to hold parts together, or to allow movement due to ground settlement or earthquakes

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7) Movement occurs for many different reasons, including variations in climate or temperature, movement in the frame and movement in the foundations. Articulation joints are tied at specific intervals and sealed with filler.

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8) Mild steel, also called plain-carbon steel, is the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications, more so than iron. Low-carbon steel contains approximately 0.05–0.3% carbon

9) An I-beam, also known as H-beam is a beam with an I- or H-shaped cross-section. The horizontal elements of the “I" are flanges, while the vertical element is termed the "web".The web resists shear forces, while the flanges resist most of the bending moment experienced by the beam. Beam theory shows that the I-shaped section is a very efficient form for carrying both bending and shear loads in the plane of the web

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Construction

TECHNICAL DETAILS1) Official name- Rabindra Setu2) Carries -8 lanes of Strand Road, pedestrians and bicycle path3) Crosses -Hooghly River4) Locale -Howrah and Kolkata5) Maintained by- Kolkata Port Trust6) Designer -Rendel, Palmer and Tritton7) Design -Suspension type Balanced Cantilever 8) Material -Steel(MILD)9) Span-705 m (2,313.0 ft)10) Width -71 ft (21.6 m) with two footpaths of 15 ft (4.6 m) on either side[5]11) Height -82 m (269.0 ft)12) Longest span -1,500 ft (457.2 m)13) Vertical clearance -5.8 m (19.0 ft)14) Clearance below -8.8 m (28.9 ft)15) Construction begin -193616) Construction end -1942

Bridge Details• Bridge type : Suspension type Balanced Cantilever

• Total span - 2,313.0 ft.

• Anchor arms of 325ft each side

• Main towers are 280ft high above the monoliths and 76 ft apart at the top

• Bridge deck width 71 ft with two footpaths of 15 ft either side

• Longest span- 1,500 ft. (457.2 m)

• Main span- 1663 ft.

• Freeboard for river traffic is 8.8 m

• Other features of the Bridge

• All members of the super structure comprise built up riveted sections with a combination of high tensile and mild steel

• Deck hangs from panel points in the lower chord of the main trusses with a series of hangers(39 pairs)

• Road way beyond the tower is supported on ground leaving anchor arm free from deck loads

• Bridge deck comprises 71 ft carriage way and 15 ft footway projecting either side of the trusses and braced by a longitudinal girder.

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More about the Bridge• The deck system consists of cross girders hung between pairs of hangers with

pinned connection.• Six rows of longitudinal stringer girders span between cross girder.• Floor joists supported transversely on top of stringers. They support a continuous pressed steel troughing system. Over which deck concrete is laid out.

• Joint System of Bridge (Expansion Joints)• Longitudinal expansion and lateral sway movement of the deck are taken care of

by expansion and articulation joints.• There are two main expansion joints, one at each interface between the

suspended span and the cantilever arms.• There are expansion joints at the towers and at the interface of steel and

concrete structures at both approach.

• Articulation Joints• There are total 8 articulation joints.• 3 at each of the cantilever arms.• 2 in the suspended portions.• They divide the bridge into segments with vertical pin connection between them to facilitate

rotational movements of the deck. • Camber and Traffic clearance• Bridge deck has longitudinal ruling gradient of 1 in 40 from either endThey are joined by a vertical

curve of radius 4000 ft.• Cross gradient of deck is 1 in 48 between kerbs and central 4.9mtr. is level to provide tramway

housing channel in between troughing. • Foundation• The main tower is founded with single monoliths which are 55.31 x 24.8 m in plan with 21 chambers• Monoliths at Calcutta and Howrah side are founded 31.41 m and 26.53 m in below ground level

respectively.• Minimum headroom in carriageway is 5.8 m

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