Steel Structures

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 Introduction

 Standard Steel Sections

 Connections

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Introduction

 Ever since steel began to be used in the construction of structures, it has made possible some of the grandest structures both in the past and also in the present day.

 Structural steel is widely used in making:

Bridges

Transmission Towers

Industrial Buildings

Storage Structures……

…… and, Many More.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Golden Gate Bridge, San Francisco

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Howrah Bridge, Kolkata

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Eiffel Tower, Paris

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Olympic Stadium, London

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Inland Steel Building, Chicago

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

An Industrial Shed

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

A Refinery Structure

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

A Railway Platform Shed

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

A Steel Water Tank

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Design Objective

The objective of design is the achievement of an acceptable probability that structures will perform satisfactorily for the intended purpose during the design life.

With an appropriate degree of safety, they should sustain all the loads and deformations, during construction and use and have adequate resistance to certain expected accidental loads and tire.

Structure should be stable and have alternate load paths to prevent disproportionate overall collapse under accidental loading.

All the designs shall confirm to IS 800 : 2007 (Indian

Standard ; General Construction in Steel – Code of

Practice.)

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Advantages of

Steel Structures

 High Strength - about ten times that of concrete.

 Predictable material properties

 Rapid & High Quality Construction.

 Ductile and Robust.

 Good fatigue strength.

 Can be easily repaired and retrofitted.

 Can be easily dismantled and sold as scrap.

 Durable – Long service life.

 Adaptation of prefabrication.

 Higher reliability and safety.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Disadvantages of

Steel Structures

 High Cost of material.

 Skilled workmanship & supervision needed.

 Regular maintenance required.

 Susceptibility to buckling.

 Less resistant to fire attacks.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Structural Steel

 The steel used for structural works shall confirm to IS 2062 : 2011 (Hot Rolled Medium and High

Tensile Structural Steel).

Most Commonly used grade is E-250 (Fe 410).

Following are few important Physical properties of structural steel :

Unit mass of steel, ρ = 7850 kg/m 3

Modulus of elasticity, E = 2.0 x 10 5 N/mm 2

Poisson’s ratio, µ = 0.3

Modulus of rigidity, G = 0.769 x 10 5 N/mm 2

Co-efficient of thermal expansion α.= 12 x 10 -6 / o c

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Standard Steel sections

Different Hot Rolled steel sections are used in combination, or, separately to fulfill the design requirements. These standard sections are:

Indian Standard I – Sections

Indian Standard Angle Sections

Indian Standard Channel Sections

Indian Standard T – Sections

Indian Standard Flats

For the sectional properties, references are:

SP : 6 (1) - 1964 (Reaffirmed 2003)

IS 808 : 1989 (Reaffirmed 2004)

Steel Tables of any standard publication.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

I - section

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

EQUAL ANGLE section

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

UNEQUAL ANGLE section

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

CHANNEL section

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

T - section

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Connections

The different structural components are to be connected together, so as to achieve the final shape of the structure.

The design of connections is having equal importance, as the loads from one component to other are transferred through connections.

Following are the type of connections used in structural steel fabrication:

 Riveted Connections.

 Bolted Connections.

 Welded Connections.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Riveted Connections

 Rivet is a pin having a head on one end, inserted through aligned holes in the pieces to be joined and then hammered on the plain end so as to form a second head.

 Usually rivet is made up of wrought iron or soft steel due to lower hardness which is necessary to have easy deformation during riveting.

 For riveting parts to be joined are first drilled with the help of drilling machine. Clearance is taken into consideration while riveting because by pressing application diameter of rivet is somewhat increased.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

The connection formed by rivets is permanent.

Rivets are widely used in Steel Bridges, trusses, water tanks, silos & boilers.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Advantages of Riveted connections

 Cheaper fabrication cost.

 Low maintenance cost.

 Dissimilar metals can also be joined, even nonmetallic joints are possible with riveted joints.

 Ease of riveting process.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Disadvantages of Riveted connections

 Skilled workers required.

 Leakage may be a problem for this type of joints, but this is overcome by special techniques.

 The process of riveting is noisy.

Due to these disadvantages, rivets are becoming obsolete now a days.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Bolted Connections

 A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Advantages of BOLTED connections

 Noiseless & quick process.

 Only semi-skilled labour required.

 No special equipments needed.

 Cooling period is not required, as in weld or rivets.

 Bolts can be easily disconnected for replacement of damaged parts.

 Reliable under fluctuating stresses.

 No heat damage to the coating on hot dip galvanized or painted structures.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Disadvantages of BOLTED connections

 May be visually unacceptable.

 Deduction for holes is required in calculation of area for tension members, which leads to the use of a larger cross section.

 Bolts may be prone to corrosion if not properly protected.

 Vibrations may lead to loosening of nuts.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Welded Connections

 Welding is a procedure that involves fusing two pieces of steel together by melting a sacrificial

“flux” electrode to two pieces, thereby joining the pieces permanently together.

 The most common type of fillet welding process is

“Arc” welding, or sometime called “stick” welding.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Advantages of WELDED connections

 Welded joints are more rigid than bolted joints.

 Can directly connect pieces without the need for connection plates.

 Welds do not create holes in member (i.e., no need to check fracture on net area)

 Can join odd-shaped pieces together.

 Adaptable to confined spaces and remote locations.

 A high quality weld can often be stronger than the parts to be joined.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Disadvantages of WELDED connections

 Welds are brittle, not ductile like bolted connections.

 Very labor intensive.

 Skilled labor required.

 Quality control is difficult to inspect.

 Potential fire hazard in areas of welding.

 Welding creates a permanent joint, not desirable if parts need to be fixed or replaced later.

 Welding very thin sheets is difficult.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Hey…. Yet Not Over…… Wait….

It’s time for something Yummy……..

But... One has to win them in a …..

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

1. Identify the structure….

It’s – “The Golden Gate Bridge, San Francisco”

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

2.The Indian Standard Code of

Practice used for General

Construction in Steel is…..

IS 800 : 2007

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

3. The Most Commonly used grade of steel in structural work is……

E-250 (Fe 410)

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

4.The unit mass of structural steel is……

7850 kg/m 3

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

5. The most common type of fillet welding process is…..

Arc welding

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

Thanks…….

……. For Your

Attention.

Prof. Sachin Patel (Head, CED) SAMCET, Bhopal

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