Post and lintel (or Post and beam) is a simple architrave where a horizontal member (the lintel—or header) is supported by two vertical posts at either end. This form is commonly used to support the weight of the structure located above the openings in a bearing wall created by windows and doors.
In architecture, a trabeated system or order (from Latin trabs, beam; influenced by trabeatus, clothed in the trabea, a ritual garment) refers to the use of horizontal beams or lintels which are borne up by columns or posts. It is the opposite of the arcuated system, which involves the use of arches.
The trabeated system is a fundamental principle of Neolithic architecture, Ancient Greek architecture and Ancient Egyptian architecture. Other trabeated styles are the Persian, Lycian, nearly all the Indian styles, the Chinese, Japanese and South American styles.
A noteworthy example of a trabeated system is in Volubilis, from the Roman era, where one side of the Decumanus Maximus is lined with trabeated elements, while the opposite side of the roadway is designed in arched style.
In India the style was used originally for wooden constructions, but later the technique was adopted for stone structures for decorative rather than load-bearing purposes.
The biggest disadvantage to a post and lintel construction is the limited weight that can be held up, and the small distances required between the posts. Roman developments of the arch allowed for much larger structures to be constructed.
There are two main force vectors acting upon the post and lintel system: weight carrying compression at the joint between lintel and post, and tension induced by deformation of self-weight and the load above between the posts. The two posts are under compression from the weight of the lintel (or beam) above. The lintel will deform by sagging in the middle because the underside is under tension and the topside is under compression.
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