What shape do arches take to effectively resist loads exclusively under compression?

Arches are designed to distribute loads efficiently, and the shape they adopt to resist loads exclusively under compression is known as the funicular shape. This shape is particularly important because it allows the arch to handle vertical loads by ensuring that the material is used only in compression, avoiding tension which could lead to structural failure.

The funicular form occurs naturally under the influence of gravity, as it follows the line of action for the loads applied to it. The curve that results from this optimal form allows for a circular or parabolic profile, minimizing bending stresses that could occur if the arch were to use other shapes.

In contrast, other shapes, such as curvilinear, linear, and polygonal, do not inherently provide the same efficiency in load distribution when subjected to compressive forces. A curvilinear shape might not adequately optimize the compression without introducing tensile forces. Linear shapes, such as simple beams, are subject to bending and would not function as arches effectively. Polygonal shapes could lead to stress concentrations that are detrimental under compressive loading scenarios.

Understanding the characteristics of a funicular shape is crucial for architects and engineers, as it informs the design of structures that must carry loads effectively while maintaining structural integrity.