Design of Steel Structure (General Engineering) (SSC JE)

Stiffener are used to retain or prevent the out of plane deformation of plates.
• Intermediate transverse stiffener increases buckling esistance of web against shear.
• Longitudinal stiffener increase buckling resistance of web against bending.

If any external horizontal force or bending moments acts on column then it is subjected to uplift force. Then to prevent the uplifting of the member, it is fixed at the base with help of bolted connection.

• Uplift forces force is always tensile nature, as the bolt is supposed to resist it. Then in this case pure tensile stress induced in the foundation.

Note–Anchor bolts are provided to check the uplift of bas plate.

Bolted connection are highly susceptible to risk or damage caused by the seismic load. High frequency earthquake bolt hits the connection will lead to its failure due to vibration, lateral thrust, not loosening etc.

• Shear failure, splitting failure, and bearing failure of plate are occurred due to insufficient end distance.

• In bolt joint all similarly placed bolts share the load equally.

Prying Action–Due to the flexibility of the connected plates under tension, an additional force is ind

(i) Tearing of the plate (at an edge)–This failure occurs when the distance between the edge of the plate and rivet holes is not sufficient. This type failure avoided keeping the margin, m = 1.5 d.
(ii) Shearing of rivets–When diameter is less than the required diameter then joint will fail by shearing of rivets.
(iii) Crushing of rivets or plate–In this case joint may fail due to the rivet hole become of an oval shape and hence the joint becomes loose.

Le-chatelier's principle–If a system at equilibrium a subjected to a change of pressure temperature or the number of moles of a component, there will be tendency for a net reaction in the direction that reduces the effect of this change.

• This change counteracts the disturbing influence and returns the system to equilibrium.

• Outside influences the affects physical and chemical equilibrium are change in the concentration or product, change in the volume and pressure of the system.

Stiffeners–
(A) Transverse (stability of vertical) stiffener
• Intermediate transverse stiffener increases buckling resistance of web against shear.
• Spacing of intermediate stiffeners depends on thickness of web.
• Stiffeners used in a plate girder to avoid buckling of web plate.

(B) Longitudinal (horizontal stiffener–
• Longitudinal stiffener increases buckling resistance of web against bending.

The carbon content in high tensile steel is 0.6 to 2.8.

Dead mild steel → 0.15
Low carbon steel → 0.15 - 0.30%
Medium carbon steel → 0.30 - 0.8%
High carbon steel → 0.8 - 1.5 %

Ductility of steel depends upon percentage of carbon when carbon percentage increases then ductility of steel decreases.
Classification of steel based on carbon percentage–
(i) Mild steel ⇒ 0.16% - 0.29%
(ii) Wrought iron ⇒ < 0.15%
(iii) Cast iron ⇒ 2 - 4.5%
(iv) Pig iron ⇒ 3.5 - 4.5%

Steel properties–
Poisson ratio (µ) = 0.3
Modulus of rigidity = 0.769 × 10⁵ N/mm²
Coefficient of thermal expansion = 12 ×10⁻⁶C