Design of Steel Structure

1. Design of steel structure
Module-1
By: Prof. Arpan Patel
Loads & Loading Standard

2. Different types of Loads on a
structure
 Different types of loads can cause stress,
displacement, deformation on a structure; which
results in structural problems and even structural
failure. Determining the total load acting on a
structure is very important and complex.
 The structure should be designed in a way that it
should be enough strong to bear any type of load at
any time that they are likely to face during their
lifecycle.
 So, the estimation of total load act on the structure or
the total load that is likely to be acted on the
structure in future is accurately calculated and same

3.  The different types of loads acting on a structure are broadly
classified into following two types
1. Vertical loads and
2. Horizontal loads


4. Vertical Loads:
Vertical loads are further classified into following types:
Dead Loads:
These loads are permanent loads which are carried to the structure
throughout their lifespan. Dead loads are also called as stationary loads.
These loads occur mainly due to the self-weight of the structural members,
fittings, fixed partitions, fixed equipment, etc.

5. Calculation or Determination of dead loads
on a structure:
Material Unit Weight of Material
Plain Cement Concrete [PCC] 24 kN/m3
Reinforced Cement Concrete [RCC] 25kN/m3
Steel 78.5KN/m3
Brick Masonry, cement plaster 20 kN/m3
Stone Masonry 24 kN/m3
Wood 8KN/m3
Floor Finish 0.6-1.2KN/m3

6. Live Loads
 As the name itself resembling that these type of loads are real-
time loads. Live loads are also called as imposed or sudden
loads. Live loads changes with respect to time. This type of
loading may come and go. For example, At one moment the
room may be empty hence the live load is zero. If the same
room is packed with the people, then the live load intensity will
vary considerably. The live load includes the weight of
furniture, people occupying the floor, etc.

7. Calculation or Determination of dead loads on a structure:
Live loads are considered and added to the total load acting on a member at
the time of designing of the building. Some of the common live load values
used in the design of buildings are tabulated below:
Types of floors Minimum Live load KN/m2
Floors in houses, hospital wards,
dormitories
2.0
Office floors other than entrance
halls
2.5 & 4.0
2.5 when separate storage facility
provided, otherwise 4.0
Shops, educational buildings,
assembly buildings, restaurants
4.0
Banking halls, office entrance halls 3.0
office floors for storage, assembly
floor space without seating, public
rooms in hotels, dance halls, waiting
halls
5.0

8. Types of floors Minimum Live load KN/m2
Ware houses, workshops, factories Light wt loads- 5.0
Medium - 7.5
Heavy - 10.0
Garages 4.0-7.5
Stairs, landings, balconies and
corridors for floors but not liable to
overcrowding
3.0
Flat slabs, sloped roofs Access provided - 1.5
Access not provided - 0.75
Stairs, landings, balconies and
corridors for floors liable to
overcrowding
5.0

9. Snow loads:
This type of loads is considered only on the structure which receives
snowfall during monsoon. Snow loads are calculated by the
projections made by snow at different parts of the structure, The
amount of snow load depends on the height of building, size &
shape of the roof, the location of building whether it’s on the slope or
not, the frequency of snow etc. The more details about snow loads
are clearly mentioned IS 875 (part 4) – 1987.

10. Calculation or Determination of Snow loads
on a structure:
The minimum snow load on any area above ground
or roof area which is subjected to snow
accumulation is obtained by the expression
S= μS0
Where,
S = Design snow load
μ = Shape coefficient
S0 = Ground snow load.

11. Horizontal Loads:
Wind loads:
This types of loads are considered in design if the height of the
building is more than 15m. Wind loads are occurred due to the
horizontal load caused by the wind. As an increase in using lighter
materials in the construction, wind load for a building should be
considered. The structure should be strong enough with the heavy
dead weights and anchored to the ground to resist this wind load. If
not, the building may blow away. Wind load acts horizontally towards
roofs, walls and create

12. Calculation or Determination of wind loads on a structure:
Wind loads are considered in design if the height of the building
is more than 15m. The intensity of wind load depends upon the
velocity of wind, size, and height of the building.
To calculate the design wind pressure or a total load of wind on
a building the following expression is used
Pz = 0.6 Vz
2
Where Pz Is in N/m2 at height Z and Vz is in m/sec.
Up to the height of 30m, the wind pressure is considered to act
uniformly. Above 30m the wind pressure may increases.
In order to calculate the Vz the following expression is used
Vz = k1k2k3Vb
Where
k1 = Risk coefficient
k2 = Coefficient based on terrain, height and structure size|
k3 = Topography factor

13. Earthquake loads:
These type of loads causes movement of the foundation of structures.
Earthquake forces are internal forces that developed on the structure
because of ground movements.
Three mutually perpendicular forces act on the structure during an
earthquake, two horizontal forces which acts in opposite direction and
one vertical force due to the weight of the structure. As vertical force
doesn’t affect much during earthquake whereas two opposite horizontal
forces results in movement of the building during an earthquake. These
two horizontal direction forces are considered in the design.

14. Advantages & Disadvantages
Advantages
 High comp. & tensile strength per unit weight hence low
 construction weight, saves space
 Good aesthetic view
 Good quality and durability
 Very high speed of construction
 Reusability and scrap value – env. Friendly
 Better solution to cover large span and tall structures
Disadvantages
 Highcost – Initial
 Corrosion
 Low fire resistance