Masonry arches: The triangular area between any two adjacent arches and the common tangent to their crowns is termed the…

Introduction / Context:
In multi-arch structures such as viaducts or arcades, specific regions of masonry have established names that relate to structural behavior and detailing. Recognizing these helps in reading drawings and performing quantity take-offs accurately.

Given Data / Assumptions:

• Two adjacent arches share a common superstructure line tangent to their crowns.
• The zone of interest lies externally between the extradoses of the arches and that tangent.
• Conventional arch terminology applies (intrados, extrados, haunch, rise, soffit, spandrel).

Concept / Approach:
The spandrel is the space between the extrados (outer curve) of an arch and the wall or structure carried above. For adjacent arches under a common roadway or stringcourse, the spandrel between them is roughly triangular and bounded above by the line tangent to both crowns. The haunch refers to the zone between the crown and springing along the intrados; the soffit is the underside (intrados) of the arch; rise is the vertical distance from springing to crown—none describe the triangular external wedge between adjacent arches and the crown tangent.

Step-by-Step Solution:
Identify boundary: extrados of adjacent arches and common tangent at crowns.Recall definition: spandrel occupies the space between extrados and superstructure.Match geometry: triangular wedge aligns with spandrel region.Select “Spandrel.”

Verification / Alternative check:
Architectural references depict spandrel masonry filling these wedges to support the roadway or parapet above multi-span arches.

Why Other Options Are Wrong:
Haunch: Intrados-side zone, not the external wedge.Soffit: The underside surface of the arch.Rise: Dimensional term, not a region.Intrados fillet: Not a standard term for this wedge.

Common Pitfalls:
Confusing intrados-side haunch with the outer spandrel; mixing up geometric terms (rise) with spatial regions (spandrel).

Final Answer:
Spandrel.