Final answer:
Open-webbed beams refer to a construction method where beams are arranged in a network of geometric shapes to span across large spaces. This technique was part of the evolution in architecture from simple roof structures to complex vaulting, allowing for greater spans without collapsing walls.
Step-by-step explanation:
Roofs and floors created with open-webbed beams are typically used to describe a construction method that includes structural supports featuring a network of triangular or open geometrical shapes, allowing for a span across large spaces without the need for solid material like stone. This design approach minimizes material use while maintaining strength and is commonly associated with industrial or large-span commercial buildings.
In historical contexts, such as Romanesque or Gothic architecture, the evolution from simple roof structures to more complex vaulting represented significant advancements in the ability to span larger spaces without exerting outward thrust on walls, which could lead to collapse due to the increased load. While the specifics of open-webbed beams are not provided in the information, the overarching discussion about roof and vault construction in historical architectures suggests an evolution towards more sophisticated engineering techniques including the use of open constructions to achieve larger spans.