Steel structures

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 STRUCTURESHigh 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 erectionThespecific strengthis a material'sstrength (force per unit area at failure)divided by itsdensity. It is also known as thestrength-to-weight ratioorstrength/weight ratio. In fiber or textile applications

STEEL

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

DISADVANTAGES OF USING STEEL IN A STRUCTURESusceptibility to corrosionMaintenance costs / thin-walled structureLoss of strength at elevated temperatureFireproofing costs Susceptibility to bucklingFatigue 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 INDIAWhen 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.

12) A paneljointis a point of connection betweentwoormoremembersofatruss. Alsocallednode.

23) Agirderis a supportbeamused inconstruction.Girders often have anI-beamcross sectionfor strength.

34) APin and Hangerassembly is used to connect twoplate girdersof 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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44) Strings are projections used for supporting the deck of a bridge5) Abridge deckorroad bedis the roadway, or the pedestrian walkway, surface of abridge. It is not to be confused with anydeckof a ship

56) Anexpansion jointormovement jointis an assembly designed to safely absorb theheat-induced expansionand contraction of construction materials, to absorb vibration, to hold parts together, or to allow movement due to ground settlement or earthquakes

67) 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.

78) Mild steel, also calledplain-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 thaniron. Low-carbon steel contains approximately 0.050.3% carbon

9) AnI-beam, also known asH-beam is abeamwith anI- or H-shapedcross-section. The horizontal elements of the I" areflanges, 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 theoryshows that theI-shaped section is a very efficient form for carrying bothbendingandshearloads in the plane of the web

89 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 DetailsBridge type : Suspension type Balanced CantileverTotal span - 2,313.0 ft.Anchor arms of 325ft each sideMain towers are 280ft high above the monoliths and 76 ft apart at the topBridge deck width 71 ft with two footpaths of 15 ft either sideLongest span- 1,500ft. (457.2m)Main span- 1663 ft.Freeboard for river traffic is 8.8 mOther features of the BridgeAll members of the super structure comprise built up riveted sections with a combination of high tensile and mild steelDeck 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 loadsBridge 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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2 3 4 5 More about the BridgeThe 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 JointsThere 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 betweenthem to facilitate rotational movements of the deck.Camber and Traffic clearanceBridge 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. islevel to provide tramway housing channel in between troughing.FoundationThe main tower is founded with single monoliths which are 55.31 x 24.8 m in plan with 21 chambersMonoliths at Calcutta and Howrah side are founded31.41 m and 26.53 m in below ground level respectively.Minimum headroom in carriageway is 5.8 m

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