BUILDING CONSTRUCTION - IV

UNIT - 1Structural Steel Work

Contents

General Principles and terms defined Standard sections

1. Beam joints2. Angles3. Channels 4. Tees5. Bolts6. Rivets7. Welding

INTRODUCTION

Materials generally used are wrought iron, cast iron, and steel.

CAST IRON-only used in compressive members.

WROUGHT IRON-fibrous in nature- resists tensile stresses.

MILD STEEL-suitable for all structural members-equally strong in tension and compression-replaced cast iron and wrought iron.

MANUFACURING PROCESS

The various sections are fabricated from white hot steel by passing it through rolling mills or other machines.

ADVANTAGES

Lightness

High strength and stiffness per weight

Ease of fabrication and

mass production

Fast and easy erection and installation

Economy in transportation and handling

Formwork unneeded

Termite proof and rot proof

DISADVANTAGES

High deformation due to small sizes

of members

Susceptibility to corrosion

Low fire resistance

Buckling due to small sizes of members

Not economical everywhere

ADVANTAGE OF STEEL STRUCTURES OVER R.C.C. AND VISA VERSA

The main advantage of steel frame work over

R.C.C. construction is that in the former case, the fabricated member are

delivered to the site ready for assembly.

Concrete requires no additional fireproofing

treatments and is safer and cheaper.

SHAPES OF STRUCTURAL STEEL

The cross sectional properties of a steel member are identified by its shape.

The various names given to the members of different shapes are Angles ; T-section; I-section; Z-section; Channel; H-section….and so on .

Each shape has its particular use in steel structures.

BARSSHAPES OF STRUCTURAL STEEL

BARS

Used as ties and lateral bindings. If threaded at the ends or looped at

end,used as tension members. Types according to manufacturing

process:1. Cold Rolled Steel Bar2. Hot Rolled Steel Bar3. Galvanized Steel Bar

BARS

Types according to shapes:1. Round bars2. Square bars3. Hexagonal bars4. Flat bars

ROUND BARSBARS

•Used as reinforcement in concrete structures, construction of steel grillage works, etc.•Available in circular cross sections with diameter varying from 5 mm to 25 mm with corresponding weights per metre length as 1.47 N and 37.28 N respectively.

SQUARE BARSBARS

•Used in construction of steel grillage works for windows.•Available in cross sections with sizes varying from 5 mm to 25 mm with corresponding weights per metre length as 1.96 N and 8.07 N respectively.

FLAT BARSBARS

•Used in construction of steel grillage works for windows and gates.•Available in widths varying from 10 mm to 400 mm thicknesses varying from 3 mm to 40 mm .

HEXAGONAL BARSBARS

ANGLE SECTIONSROLLED STEEL SHAPES

ANGLE SECTIONS

Used especially in the construction of steel roof trusses and filler joist floors.

May be of equal or unequal legs.

ANGLE SECTIONS

Equal angle sections available in sections varying from 20 mm X 20 mm X 3 mm to 200 mm X 200 mm X 25 mm with corresponding weights per metre length as 8.83 N and 772 N respectively.

Unequal angle sections available in sections varying from 30 mm X 20 mm X 3 mm to 200 mm X 150 mm X 18 mm with corresponding weights per metre length as 10.79 N and 460 N respectively.

ANGLE SECTIONS

CHANNELSROLLED STEEL SHAPES

CHANNELS

Used as structural members of steel-framed structures.

Consists of web with two equal flanges. The Bureau of Indian Standards has Classified

channel sections as junior channel and medium channel and accordingly, they are designated as I.S.J.C., I.S.L.C., and I.S.M.C. respectively.

Available in sizes varying from 100 mm X 45 mm to 400 mm X 100 mm with corresponding weights per metre length as 56.90 N and 484.61 N respectively.

CHANNELS

CHANNELS

Types:

T-SECTIONSROLLED STEEL SHAPES

T-SECIONS

Widely used as members of steel roof trusses and to form built up sections.

It is designated by overall dimension and thickness.

Available in sizes varying from 20 mm X 20 mm X 3 mm to 150 mm X 150 mm X 10 mm with corresponding weights per metre length as 8.83 N and 223.67 N respectively.

T-SECTIONS

T-SECTIONS

Types:

I-SECTIONSROLLED STEEL SHAPES

I-SECTIONS

These are properly known as the rolled steel joists or beams.

It consist of two flanges connected by a web. It is designed by overall depth, width of the

flange b and weight per meter length. They are available in sizes varying from

75*50mm to 600*210mm. I-sections are used in beams and columns. It is best suited to resist bending moment and

shearing force.

I- SECTION

I-SECTION

Types :

STEEL TUBESSHAPES OF STEEL STRUCTURE

STEEL TUBES

The steel tubes are used as columns and compression members and in some cases it also acts as a tension member in tubular trusses.

The steel tubes are efficient structural sections to be used as compressive members.

Steel tube sections have equal radius of gyration in all directions.

STEEL TUBE SECTION

CONNECTIONS IN STEEL WORK

The various members of a steel framed structure are to be suitably connected for transfer of load.

Following are methods adopted for connecting the members of steel work:1. Bolts2. Rivets3. Welding

BOLTSCONNECIONS IN STEEL WORK

BOLTS

Used when desired to have temporary connections.

May also be adopted when it is difficult to use rivets as connecting members.

Bolts are better suited for tension applications.

Holes are made in members to be connected and dia is kept about 0.50 mm larger than that of external dia of bolt.

BOLTS

BOLTS

BOLTS

Types:

RIVETSCONNECTION IN STEELWORK

RIVETS

A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a

smooth cylindrical shaft with a head on one end.

The end opposite the head is called the tail. On installation the rivet is placed in a

punched or drilled hole, and the tail is upset, or bucked (i.e., deformed), so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place.

RIVETS

Because there is effectively a head on each end of an installed rivet, it can support tension loads (loads parallel to the axis of the shaft); however, it is much more capable of supporting shear loads (loads perpendicular to the axis of the shaft).

Bolts and screws are better suited for tension applications.

RIVETS

Types:

WELDINGCONNECTIONS IN STEEELWORK

WELDING

A welding joint is a point or edge where two or more pieces of metal or plastic are joined together.

They are formed by welding two or more work pieces (metal or plastic) according to a particular geometry.

Five types of joints: butt, corner, edge, lap, and tee.

These configurations may have various configurations at the joint where actual welding can occur.

WELDING

Types:

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