Design of Steel structures


by: nanismart
by using limit statemethod as per IS:800-2007 design will be discussed



ICommon steel structures
 Steel has high strength per unit mass.Hence it is used in constructing large column-free structures.The following are the common steel structures

1.Roof trusses for factories,cinema halls, etc
2.Trussed bents,crane girders,column etc.
3.Roof trusses and columns to cover platforms in railway stations etc.
4.Single or double layer domes for auditoriums,exhibition halls etc.
5.Plate girders and truss bridges for railway and roads
6.Transmission towers for microwave and electric power
7.Water tanks.
8.Chimneys etc, 


 
IIProperties of structural steel
 The properties of steel required fo engineering design may be classified as
i)  Physical properties
ii) Mechanical properties

i) Physical properties: Irrespective of its Grade Physical properties of steel may be taken as given below (clause 2.2.4 of IS 800-2007)

(a) Unit mass of steel ,= 7850 kg/m^3
(b) Modulus of elasticity,E=2.0*10^5 N/mm^2
(c) Poisson's ratio ,u=0.3
(d) Modulus of rigidity,G=0.769*10^5 N/mm^2
(e) Coefficient of thermal expansion , =12*10^-6 / C

ii) Mechanical properties : The following are the important mechanical properties in the design

(a) Yield stress fy,
(b) The tensile or ultimate stress fu
(c) The maximum percentage elongation on a standard guage length 
(d) Notch toughness 
IIIRolled steel sections
 Various types of rolled steel sections manufactured are listed below
 
  i)   Rolled steel I-section 
 ii)   Rolled steel Channel sections
iii)   Rolled steel Angle sections
iv)   Rolled steel Tee sections
 v)   Rolled steel Bars
vi)   Rolled steel Tubes   
vii)  Rolled steel plates
viii) Rolled steel Flates
  ix) Rolled steel sheets and strips 
IVSpecial considerations in steel design
The following special considerations are required in steel design :
 
  1. Size and shape 
  2. Buckling
  3. Minimum Thickness
  4. Connection designs
VLOADS
Various loads expected to act on a structure may be classified as given below

  1. Dead load (DL)
  2. Imposed loads (IL)
  3. Wind loads (WL)
  4. Earthquake loads (EL)
  5. Erection loads (ER)
  6. Accidental loads (AL)
  7. Secondary Effects
 
VIConnections
 The following three tyopes of connections may be made in steel structures:
  1. Riveted 
  2. Bolted 
  3. Welded