undefined | unit 1 introduction

DSS

Unit – 1

Introduction

Q1) Define steel structures and their types.

A1) Steel shape is a steel shape that is made of structural metal* additives join with every different to hold hundreds and offer complete rigidity. Because of the high electricity grade of metal, this shape is dependable and calls for much less raw substances than different styles of shape like concrete shape and timber shape.

Main structural types

Frame systems: Beams and columns

Grid’s systems: latticed shape or dome

Prestressed systems

Truss systems: Bar or truss members

Arch shape

Arch bridge

Q2) What are the properties of the material required in steel industry?

A2) The houses that want to be taken into consideration with the aid of using designers when specifying metal creation merchandise are:

Strength

Toughness

Ductility

Weldability

Durability.

For design, the mechanical houses are derived from minimal values special withinside the relevant product standard.

Weldability is decided with the aid of using the chemical content material of the alloy, that is ruled with the aid of using limits in the product standard.

Durability depends at the specific alloy type - normal carbon metal, weathering metal or stainless metal.

Q3) Write a short note on Toughness.

A3)

It is withinside the nature of all substances to include some imperfections. In metal those imperfections take the shape of very small cracks.

If the metal is insufficiently tough, the crack can propagate swiftly, without plastic deformation and bring about a brittle fracture.

The danger of brittle fracture will increase with thickness, tensile strain, strain raisers and at less warm temperatures.

The longevity of metal and its cap potential to resist brittle fracture are depending on various of things that have to be taken into consideration on the specification stage.

A handy degree of longevity is the Chirpy V-notch effect take a look at - see photograph at the right. This takes a look at measures the effect strength required to interrupt a small notched specimen, at a special temperature, with the aid of using an unmarried effect blow from a pendulum.

The various product standards specify minimal values of effect strength for distinctive sub-grades of every electricity grade.

Q4) What are the requirements for good weldability of material?

A4)

The following are the essentials of the weldability:

Modulus of elasticity, E = 210,000 N/mm²

Shear modulus, G = E/ [2(1 + ν)] N/mm², regularly taken as 81,000 N/mm²

Poissons ratio, ν = 0.3

Coefficient of thermal expansion, α = 12 x 10-6/°C (withinside the ambient temperature range).

Q5) What are design methods of steel design, enlist them.

A5)

1. Working Stress Method (WSM)

2. Ultimate Load Method (ULM)

3. Limit State Method (LSM).

Q6) Write a short note on LSM.

A6)

In the Limit State Method (aka as Limit State Design), the layout of the shape is taken into consideration for each the serviceability and closing load kingdom.

This is consequently the higher layout philosophy to employ.

The extraordinary restrict states are the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS), for which distinction are made withinside the code SANS10160: five.1.3... These states every have their own minimal degree of reliability - that's colloquially called the Safety Index.

Q7) What are the Restriction in limit state method?

A7) There are 2 sorts of restrict states

Ultimate Limit State: It considers power, overturning, fatigue, sliding etc.

Serviceability Limit State: It considers crack width, deflection, vibration etc.

It makes use of more than one protection elements for the desired protection and serviceability on the closing load and running load respectively through thinking about all restrict states. These are called “partial protection elements”.

Q8) What are the methods of steel design?

A8)

1. Simple Design of Steel Structure

2. Continuous Design of Steel Structure

3. Semi-Continuous Design of Steel Structure

Q9) What are the limitations of LSM?

A9)

The approach of mechanics of substances is restrained to very easy structural factors beneath Neath noticeably easy loading situations.

The structural factors and loading situations allowed, however, are enough to remedy many beneficial engineering troubles.

The idea of elasticity lets in the answer of structural factors of widespread geometry beneath Neath widespread loading situations, in principle.

Analytical answer, however, is restrained to noticeably easy cases.

The answer of elasticity troubles additionally calls for the answer of a device of partial differential equations, that is extensively greater mathematically disturbing than the answer of mechanics of substances troubles, which require at maximum the answer of a normal differential equation.

The finite detail approach is possibly the maximum restrictive and maximum beneficial on the equal time.

Q10) Write short notes on wind velocity.

A10)

(Vz): Design wind velocity is given with the aid of using the equation

Vz= Vb K1 K2 K3

wherein Vz =Design wind speed (m/sec)

Vb= Basic wind velocity in m/sec (Based on Appendix -A of diverse towns in IS 875 –Part three)

Basic wind velocity Vb, relies upon at the place of the building.

Basic wind velocity is primarily based totally on gust speed averaged over a quick time c programming language of three seconds at 10m peak from imply floor degree in an open terrain and for fifty years return period. Vb has 6 values 33, 39,44,47,50 & fifty-five m/sec.

Q11) Elaborate concept of wind load analysis.

A11) Buildings are difficulty to horizontal hundreds because of wind strain appearing at the buildings. Wind load is calculated as in step with IS 875(Part III)-1987.

The horizontal wind pressures act on vertical outside partitions and uncovered location of the buildings.

Some of the strain appearing on uncovered surfaces of structural partitions and columns is directly resisted with the aid of using bending of those members.

The infill partitions act as vertical plate supported at pinnacle and backside with the aid of using ground beams, accordingly shifting the hundreds at slab degree.

The parapet wall is at terrace transfers the wind hundreds to the floor slab with the aid of using cantilever action.

Q12) What are codes used in analysis of loads?

A12) IS: 800: 2007 - Code of Practice for trendy production in Steel

IS: 802 Part 2: 1978 - Code of Practice to be used of Structural Steel in Overhead Transmission Towers-Fabrication, Galvanizing, Inspection and Packing

IS: 806: 1968 - Code of Practice for USE OF Steel Tubes in General Building Construction

IS: 808: 1989 - Dimensions for Hot Rolled Steel Beam, Column, Channel and Angle Sections

IS:814: 2004 - Covered Electrodes for Manual Metal Arc Welding of Carbon and Carbon Manganese Steel Specification

IS:816: 1969 - Code of Practice to be used of Metal Arc Welding for General Construction in Mild Steel.

IS:1161: 1998 - Specification for Steel Tubes for Structural Purposes.

Q13) What are the types of section used in steel structures?

A13) Plastic

Compact

Semi – compact

Slender

Q14) Write note on plastic section.

A14) Cross-sections which could broaden plastic hinges and feature the rotation potential required for failure of the shape with the aid of using formation of plastic mechanism fall beneath Neath this class. The width to thickness ratio of plate factors will be much less than that particular beneath Neath Class 1 (Plastic), in Table 2 of IS 800:2007.

Q15) Give load combination for limit state of collapse as per IS code.

A15)

Load Combination	DL	LL	WL/EL
DL+LL	1.5	1.5	-
DL+WL/EL	0.9/1.5	-	1.5
DL+LL+WL/EL	1.2	1.2	1.2

Q16) Write short note on Semi Compact section.

A16)

Load Combination	DL	LL	WL/EL
DL+LL	1.5	1.5	-
DL+WL/EL	0.9/1.5	-	1.5
DL+LL+WL/EL	1.2	1.2	1.2

Q17) Explain Method of section.

A17) This method can be used when the truss element forces of only a few members are to be found. This method is used by introducing a single straight line cutting through the member whose force wants to be calculated. However, this method has a limit in that the cutting line can pass through a maximum of only 3 members of the truss structure. This restriction is because this method uses the force balances in the x and y direction and the moment balance, which gives us a maximum of 3 equations to find a maximum of 3 unknown truss element forces through which this cut is made. Let us try to find the forces FAB, FBD and FCD in the above example

Q18) Give explanation on semi continuous design of steel structure.

A18)

True semi-non-stop layout is greater complicated than either easy or non-stop layout because the actual joint reaction is greater realistically represented.

Analytical workouts to comply with the actual connection behaviour intently are fantastically worried and mistaken for ordinary layout, as they require the usage of state-of-the-art laptop programs.

Q19) What are the simplified approaches in designs?

A19)

The wind second approach, for unbraced frames. In this procedure, the beam/column joints are assumed to be pinned whilst considering gravity hundreds. However, beneath Neath wind loading they're assumed to be inflexible, which method that lateral hundreds are carried via way of means of body action. A fuller description of the approach may be discovered in reference.

Semi-non-stop layout of braced frames. In this procedure, account of the actual joint behaviour is taken to lessen the bending moments carried out to the beams and to lessen the deflections. Details of the approach may be discovered in reference.

Q20) What is partial safety factors? And what is safety factor?

A20) Partial safety Factor

These are the factors which can applied to the individual input variables. In a design equation to give target reliability without having to carry out the probabilistic calculations.

Safety Factor:

The factor by which the yield stress of a material of a member is divided to arrive at the permissible stress in the material.

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