Last Updated On 11th August 2022
1. Which IS code is used for the design of steel structures?
IS 800-2007: General construction in steel – code of practice.
2. What is fatigue and in which situations it is important?
Reversal of stresses due to repeated loading is called fatigue. It is important in case of bridges, crane girders and platform carrying vibrating machines etc.
3. What should be the minimum thickness of steel sections used for design and construction?
IS 800-2007 specifies no limit on minimum thickness requirement of steel sections but however a minimum thickness of 6 mm for main members and 5 mm for secondary members must be used in steel design and construction. The minimum thickness is required for better performance under adverse environmental conditions. In addition to that, steel in contact with water and soil and those subjected to alternative wetting and drying, an additional thickness of 1.5 mm should be provided.
4. Explain limit state design method.
In the limit state design of structures, all conditions are taken into account that makes the structure unfit for use, means it considers all the relevant conditions pertaining to limit states of strength and serviceability.
The strength limit states are based on load carrying capacity of the structure wgich includes buckling. Fatigue, fracture etc. Serviceability limit states are based on performance of the structure under the actual application of service loads and includes deflection, vibration, corrosion, Ponding etc.
5. What are the advantages of limit state design?
Advantages of limit state design are:
- This method recognizes that design parameters are variants.
- This method logically deals with the fact that there exists always a possibility of variations in loads and material properties.
- This method gives different weightages to different materials and loads.
6. What do you mean by design load in LSM?
The design load in Limit state method (LSM) of design is obtained by multiplying the working load (called as characteristic load) with a partial factor of safety and the resulting load is called as factored load or the design load. Different loads (i.e. live load, earthquake load, dead load, wind load etc.) are then combined under the most severe but realistic conditions.
7. What is design strength?
The design strength of the material is obtained by dividing the characteristic strength of the material by a suitable partial factor of safety. The design strength of each material must be such that the most severe combination of design loads must not cause failure and it must also be ensured that the structure is stable against overturning, sway etc.
8. What is the difference between factor of safety and partial safety factors?
Factor of safety is defined combindly for the material properties and uncertainties in loads while partial safety factors are defined separately.
Factor of safety is derived from experience only and underestimated the properties of materials and forces but partial safety factors are derived using probabilistic approach for most unfavourable conditions for material properties and forces.
9. Define riveting connections?
Riveting is a method of joining together pieces of metal by inserting ductile metal pins called rivets into holes of pieces to be connected and forming a head at the end of the rivet to prevent each metal piece from coming out.
9. What are the disadvantages of riveting connections?
Following are the disadvantages:
- Removing poorly installed rivets is costly
- Inspection of connection is a skilled work.
- It is associated with high level of noise pollution.
- Labour cost is high.
11. What are the advantages of bolted connection over riveting connection?
Advantages of bolted connections over rigid connections are following:
- Bolted connections facilitate faster erection of structure.
- Semiskilled labours can easily do the bolting connections work whereas riveting connection required skilled labours.
- Bolted connection is more economical than riveted connection because cost skilled labour is reduced as well as equipment costs are also very less.
12. What does grade (or class) like 4.6 of a bolt imply?
Bolts are classes as grade x.y
Where x represents 1/100th of the nominal tensile strength and y represents the ratio of yield stress to ultimate stress.
For example – a bolt of grade 4.6 implies the ultimate strength of the bolt is 400 N/mm2 and yield strength is 0.6 x 400 = 240 N/mm2
13. What are the classification of Bolts based on method of load transfer?
On the basis of load transfer in the connection, bolts may be classified as:
a. Bearing type
b. Friction grip type
Unfinished (black) bolts and finished bolts are bearing type since they transfer shear force from one member to other member by bearing, whereas HSFG bolts belong to friction grip type since they transfer shear by friction.
14. What is the difference between pitch of the bolt and gauge?
Pitch of the bolt – it is the centre to centre spacing of bolts in a row, measured in the direction of load.
Gauge – it is the distance between the two consecutive bolts of adjacent rows and is measured at right angle to the direction of load.
15. What are the different types of Riveted/Bolted connection?
A. Lap Connections
in lap connection the connected members to be overlap each other. the load in a lap connection has an eccentricity and thus causes bending on the riveted connection.
B. Butt Connections
In butt connection, the connected members are placed end to end, cover plates are provided one or both sides of main plate. in double cover connection, no eccentricity of load, Hence double cover butt connection is free from bending effect.