Building construction – lintels: For a masonry wall bearing on a lintel, the load above is assumed to disperse and act as a uniformly distributed load on the lintel when the height of wall above the lintel is up to what multiple of the effective span?

Introduction / Context:
Lintels support masonry over openings such as doors and windows. In civil engineering design, the actual load from the masonry above a lintel disperses into the span. For practical analysis and safe detailing, we often convert that dispersed load into an equivalent uniformly distributed load (UDL) when sufficient masonry height is available to spread the load evenly across the lintel span.

Given Data / Assumptions:

• Solid masonry above the lintel without large openings immediately above.
• Standard load dispersion through masonry at roughly 45 degrees (or similar empirical spread).
• We seek the limiting height above which the load on the lintel may be idealized as UDL.

Concept / Approach:

As height of masonry above the lintel increases, arching and load spread reduce load concentration near the jambs. Traditional building practice and many exam standards adopt a rule: if the height of masonry above the lintel is at least about 1.25 times the effective span, the load acting on the lintel can reasonably be treated as a UDL for design purposes. Below this height, a more triangular or trapezoidal pressure distribution may be considered.

Step-by-Step Solution:

Verification / Alternative check:

Many design handbooks use the 1.25 span height as a conservative threshold. If the height is very large compared to the span, the UDL idealization is even more accurate; if much less, a varying load should be assumed.

Why Other Options Are Wrong:

• Equal to span or 1.50×, 2.0×, 2.5×: these values are either less consistent with common practice (span) or overly conservative and not the usual threshold used in preliminary lintel design.

Common Pitfalls:

• Ignoring heavy concentrated loads like beams bearing above the lintel.
• Assuming UDL when height is very small; triangular loading would be more appropriate.

Final Answer:

1.25 times the effective span.