Design of Steel Structures MCQ Quiz in বাংলা - Objective Question with Answer for Design of Steel Structures - বিনামূল্যে ডাউনলোড করুন [PDF]

Concepts:

As per IS 800:2007:

If

d/t_w < 67ϵ  ; no stiffener is required

85ϵ  <  d/t_w < 200ϵ ; vertical intermediate stiffeners are provided

d/t_w > 200; Horizontal stiffeners are provided.

In all above cases; d is the depth of web and t_w is thickness of web.

Note:

The different type of stiffeners and their function is given below in tabulated form:

Explanation:

As per IS 800: 2007 -

1. The size of normal fillets shall be taken as the minimum weld leg size.
2.  For deep penetration welds, where the depth of penetration beyond the root run is a minimum of 2.4 mm, the size of the fillet should be taken as the minimum leg size plus 2.4 mm.
3. For fillet welds made by semi-automatic or automatic processes, where the depth of penetration is considerably in excess of 2.4 mm, the size shall be taken considering the actual depth of penetration.
4. The size of fillet welds shall not be less than 3 mm.\
5. The minimum size of the weld is based on the  thickness of the thicker plate being connected as shown in the below-tabulated form:

Concept:

(i) For the size of the weld:

Minimum size of weld:

The minimum size of the weld is required to avoid stress concentration in welds.

Maximum size of weld:

Smax = t - 1.5 mm for pointed edge

\(= \frac{{3{\rm{t}}}}{4}\) for rounded edge

Where t is the thickness of the thicker member

The size of welded is limited to ensure uniform stress distribution.

(ii) Length of weld/lap of length

Lp min = 4t or 40 mm (as per WSM)

= 5t or 50 mm (as per LSM)

Concept:

Imperfection Factor: It takes into account, the imperfection that may occur while load transferring, fabrication, or installation.

It depends upon the shape of the column cross-section under consideration, the direction in which buckling can occur, and the fabrication process (hot rolled, welded or cold-formed).

Classification of different sections under different buckling class i.e. a, b, c or d used for the design of axial compression member.

As per IS 800: 2007, Table 7;

∴ The imperfection factor for buckling class b is 0.34

Vertical Deflection limits for industrial buildings as per IS 800:2007 are:

a) For Purlins and Girts subjected to live load/wind load supported on elastic cladding, maximum deflection is limited to span / 150.

b) For Purlins and Girts subjected to live load/wind load supported on Brittle cladding, maximum deflection is limited to span / 180.

Calculation:

∴ Permissible maximum deflection = Span/150 = 4500/150 = 30 mm

Explanation:

As per IS: 800 - 2007

The design value of the effective length factor for various combinations is given below:

Given both ends are fixed

So the Case becomes Restrained in all movements

So effective length = 0.65 × L = 0.65 × 4 = 2.6 m

Explanation:

AS per IS 800(2007) (C- 5.6.1 Dejection)

Explanation:

Shape factor:

The shape factor is defined as the ratio of the fully plastic moment to yield moment of section. Shape factor depend upon cross-section.

Some standard shape factors are as follows:

Permissible stresses in steel structure members:

∴ The permissible bending stress in the slab base of steel columns for all grades of steel is limited to 185. 

Explanation:

As per IS 800:2007, Table 5, Partial safety factors for materials are given as:

(i) When resistance is governed by ultimate stress, γ_m1 = 1.25

(ii) When resistance is governed by yielding, γ_mo = 1.1

(iii) Resistance of member to buckling,γmo = 1.1

(iv) Resistance of connection:

• Bolts-Friction Type or Rivets = 1.25
• Welds = 1.25 (shop fabrications) and 1.5 (Field fabrications)