Geometric Shapes in Bridge Design

The architectural design of bridges incorporate a number of geometric shapes from which can not only lines of appealing symmetry be achieved, but also immense strength which must of course be fundamental in any design outcome.

The most often used geometric shape in bridge construction is the triangle due to its rigidity. A simple square in pure form does not create a rigid structure, but instead can flex, ultimately creating a rhombus rendering it prone to collapse. However, insert a diagonal cross-beam into a square structure, effectively creating two triangle forms, the square will become rigid and no longer prone to failure.
Another geometric shape frequently used in architectural bridge design is that of the arch (many old bridges use the principal arch design for support). Arches are incredibly strong due to their ability to distribute weight evenly to supporting pillars and change lateral and horizontal forces to vertical ones.

Engineers today, most commonly design the beam type bridge, because their simple structure enables a relatively straightforward build. Beam bridges are used to span shorter distances such as local roads and waterways, using large supports at the edges and a heavy beam across them, which is usually overlayed with metal, boards and a layer of concrete.

However, truss bridges, that are built from a number of connecting elements and stressed using either tension or compression (or both), can be designed using geometric shapes to create amazing structures, spanning lengthy distances in excess of 3,700 metres.