# Design of Steel Structures Questions and Answers – Castellated Beams & Lintels

This set of Design of Steel Structures Multiple Choice Questions & Answers (MCQs) focuses on “Castellated Beams & Lintels”.

1. What is castellated beam?
a) beam with no openings in web
b) beam with number of regular openings in web and flange
c) beam with number of regular openings in web
d) beam with number of regular openings in flange

Explanation: A beam with number of regular openings in its web is called castellated beam. A castellated beam is formed by flame cutting a single rolled wide flange beam in a definite predetermined pattern and then rejoining the segments by welding to form a regular pattern of holes in the web.

2. The new rolled section of castellated beam will have depth
a) 50% more than original section
b) 50% less than original section
c) 25% less than original section
d) depth does not change

Explanation: The new rolled section of castellated beam will have depth at least 50% more and its section modulus increases by 2.25 times the original section. This allows the beam to span further than parent rolled section.

3. Castellated beams have ______ shear capacity than original beams
a) shear capacity does not change
b) twice
c) increased
d) reduced

Explanation: Castellated beams have reduced shear capacity. It has reduced shear capacity due to stress concentrations near the openings.

4. Which of the following measures can be taken to improve shear capacity of castellated beams?
a) openings can be made away from neutral axis
b) openings can be made close to neutral axis
c) making cuts in straight manner
d) by not using stiffenings

Explanation: Shear capacity of castellated beams can be improved by making openings close to neutral axis and making cuts in a wavy manner. Stiffening can be provided at load concentrations and reaction points to improve its shear carrying capacity.

5. Which of the following is not an advantage of castellated beam?
a) light in weight
b) can be assembled fast
c) cheaper
d) high fire resistance than original rolled section

Explanation: Castellated beams are light in weight, cheaper, they have relatively high resistance and can be assembled fast at the construction site. They are less fire resistant than normal rolled sections. Castellated beams can very easily be cambered and cranked.
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6. In which of the following cases are castellated beam desirable?
a) when more span to be covered than rolled section
b) when beam subjected to substantial concentrated loads
c) when beam to be used as continuous beam
d) when higher fire resistance than rolled section required

Explanation: The section of castellated beam will have more depth and section modulus than original rolled section. This allows the beam to span further than parent rolled section. Castellated beams may not be desirable when beam is subjected to substantial concentrated loads, or when castellated beam is used as a continuous beam across several supports. Castellated beams are less attractive when very high requirements for fire resistance are required because the fire resistant coating has to be around 20% thicker than for rolled sections in order to obtain the same fire resistance as rolled section.

7. Match the pairs

```   (A) Vierendeel mechanism		  (i) caused by heavy loading and short span
(B) Lateral torsional buckling of web  (ii) caused due to excessive horizontal shear
(C) Rupture of welded joint in web	  (iii) due to excessive deformation across openings in web
(D) Web Buckling			  (iv)caused by large shear```

a) A-i, B-ii, C-iii, D-iv
b) A-iv, B-iii, C-ii, D-i
c) A-iii, B-iv, C-ii, D-i
d) A-i, B-iv, C-iii, D-ii

Explanation: There are number of possible modes of failure for castellated beams. Some of them are as follows: (i) Vierendeel mechanism – occurs due to excessive deformation across one of the openings in web and formation of hinges in corners of castellation, (ii) Lateral torsional buckling of web – caused by large shear at welded joint, (iii) Rupture of welded joint in web – caused due to excessive horizontal shear at welded joint in the web, (iv) Web Buckling – caused by heavy loading and short span of beam, this may be avoided at support by filling firt castellation by welding plate in the hole.

8. What are lintels?
a) beams provided in foundation
b) beams on roof of building
c) columns above openings in wall
d) beams above openings in wall

Explanation: Beams provided above the openings in walls to support masonry that comes in between the opening and slab above are called as lintels. It is desirable that lintel is built flush from both the sides of the walls.

9. _____ section is suitable for small openings and _____ section is suitable for large openings
a) flat, I-section
b) I-section, flat
c) angles, flat
d) angles, angles

Explanation: Flats and plate sections are used for small openings. For openings of moderate dimension, back-to-back angles and inverted T-sections are best options. For large openings, channels, I-sections or built-up sections are preferred. If there is any doubt about lateral support from the wall, I-section with plates can be used.

10. Design of lintel is carried out for
a) weight of slab
c) small portion of masonry load above the opening
d) large portion of masonry load above the opening

Explanation: Design loads for lintels are not well defined because it is not certain as how much load from masonry will come over lintel. It is assumed that after setting of mortar, load from masonry is distributed by arch action. Design of lintel is carried out for small portion of masonry load above the opening.

11. When the slab over lintel is above apex of equilateral triangle formed on lintel, load of masonry is considered as

Explanation: When the slab over lintel is above apex of equilateral triangle formed on lintel, the load of masonry in the triangle thus formed is assumed to act over it. When the design load is from triangular portion of masonry , the maximum moment will be Wl/6, where W = triangular load from masonry and l = effective span of lintel.

12. When the slab over lintel is below apex of equilateral triangle formed on lintel, load of masonry is considered as

Explanation: When the slab over lintel is below apex of equilateral triangle formed on lintel, the load of masonry in the rectangle is considered. The load of masonry in the rectangle is assumed to act over by taking length equal to span of lintel and height equal to clear height of slab above the lintel.

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