Correct Answer: D. 1.2 N/mm²
Solution:
First, calculate the effective depth (d):
d = Overall Depth - Effective Cover = 300 mm - 50 mm = 250 mm.
Next, calculate the nominal shear stress (τᵥ) using the formula:
τᵥ = Vᵤ / (b * d)
Where Vᵤ = Factored Shear Force = 60 kN = 60,000 N
b = Width = 200 mm
d = Effective Depth = 250 mm
τᵥ = 60,000 / (200 * 250) = 60,000 / 50,000 = 1.2 N/mm².
Correct Answer: A. 60 degrees each
Solution:
Due to the arching action of the masonry above a lintel, the load transferred to the lintel is assumed to be from an equilateral triangle of masonry immediately above it. An equilateral triangle has internal angles of 60 degrees each. Therefore, the angle at either support (end of the lintel) is 60 degrees.
Correct Answer: B. To support the wall above the opening
Solution:
A lintel is a horizontal structural member placed across an opening (like a door or window) in a wall. Its primary function is to carry the load from the masonry or wall structure located directly above the opening and transfer it to the sides, thus preventing the collapse of the wall into the opening.
Correct Answer: D. 1/8 to 1/12 of the span
Solution:
A Jack arch is a flat or minor arch used for its aesthetic appeal and to support loads over small spans. To ensure stability and proper arch action, its rise (the vertical distance between the springing line and the highest point of the intrados) is typically kept small, generally in the range of 1/8 to 1/12 of the span.
Correct Answer: D. All of the above
Solution:
Lintels are often preferred over arches in modern construction for several practical reasons. Arches require significant vertical space (headroom), their outward thrust necessitates strong side supports (abutments), and their curved geometry makes them more complex and time-consuming to construct compared to the simple, horizontal placement of a lintel. Therefore, All of the above are valid reasons for preferring lintels.
Correct Answer: D. Key-stone
Solution:
The Key-stone (or keystone) is the final, central, wedge-shaped stone (voussoir) placed at the apex (crown) of an arch. It locks all the other stones into position, completing the arch and allowing it to bear weight.
Correct Answer: C. 100 mm
Solution:
The bearing for a lintel should be the maximum of the following three values:
1. 10% of the span = 10% of 10,000 mm = 1000 mm
2. Thickness of the lintel = 80 mm
3. A minimum standard value, typically 100 mm to 120 mm.
While 10% of the span is very large, the absolute minimum bearing required to ensure proper load transfer is generally taken as 100 mm. Thus, it is the most appropriate answer among the choices.
Correct Answer: A. Key stone
Solution:
This question is a direct definition. The wedge-shaped stone placed at the very top center (apex) of an arch is called the Key stone. It is the last stone put in place and is critical to the arch's structural integrity.
Correct Answer: A. 1.5 m
Solution:
Flat arches (or Jack arches) are not true arches in terms of structural action and are limited in their load-carrying capacity. They are generally used for aesthetic purposes over small openings. Their practical use is typically limited to spans of up to about 1.5 m.
Correct Answer: B. 4
Solution:
A Tudor arch is a wide, low, pointed arch characteristic of the Tudor period in England. It is a four-centered arch, meaning its shape is constructed from four separate arcs, each with its own center point. Two centers are on the springing line, and two are located below it.
Correct Answer: D. Depth
Solution:
The intrados is the inner curve or surface of an arch, and the extrados is the outer curve. The perpendicular distance measured between these two surfaces is known as the Depth or thickness of the arch.
Correct Answer: B. Haunch
Solution:
The Haunch is the part of an arch located roughly halfway between the springing line (where the arch begins at the support) and the crown (the highest point). It is the section that handles significant stress and thrust within the arch.