Assumption of Uniformly Distributed Load on a Lintel

To understand why option 'B' is the correct answer, let's first clarify the concept of a lintel and the assumption of a uniformly distributed load.

A lintel is a horizontal structural element typically made of reinforced concrete, steel, or wood, which is placed above an opening in a wall (such as doors or windows) to support the load from the masonry above it. It acts as a beam spanning the opening and transfers the load to the surrounding walls or columns.

When analyzing the behavior of a lintel, engineers often assume a uniformly distributed load. This means that the load is distributed evenly across the entire span of the lintel, rather than being concentrated at specific points.

Key Point: The assumption of a uniformly distributed load simplifies the analysis of the lintel's structural behavior.

Choosing the Correct Height of Masonry Above the Lintel

Now, let's consider the various options provided and determine the correct height of masonry above the lintel.

a) The effective span: This option suggests that the load on the lintel is assumed to be uniformly distributed only for the masonry directly above the lintel's effective span. However, this does not consider the load distribution beyond the effective span.

b) 1.25 times the effective span: This option suggests that the load on the lintel is assumed to be uniformly distributed up to a height of 1.25 times the effective span. In other words, the load is spread evenly over an additional 25% of the effective span.

c) 1.4 times the effective span: This option suggests that the load on the lintel is assumed to be uniformly distributed up to a height of 1.4 times the effective span. Here, the load is spread evenly over an additional 40% of the effective span.

d) 2.4 times the effective span: This option suggests that the load on the lintel is assumed to be uniformly distributed up to a height of 2.4 times the effective span. In this case, the load is spread evenly over an additional 140% of the effective span.

Key Point: The correct height of masonry above the lintel is the one where the load is assumed to be uniformly distributed.

Therefore, option 'B' is the correct answer because it considers a height of 1.25 times the effective span. This assumption allows for a reasonable distribution of load beyond the effective span without excessively increasing the load-bearing capacity of the lintel.

Conclusion

When assuming a uniformly distributed load on a lintel, the correct height of masonry above it is 1.25 times the effective span. This assumption simplifies the analysis of the lintel's structural behavior and provides a reasonable load distribution without overdesigning the lintel.