beam

Table of Contents

Introduction References & Edit History Related Topics

Images

Figure 7: Transverse motion of an initially straight beam, shown at left as an elastic line and at right as a solid of finite section (see text).

Discover

Los Angeles Police Department wanted flyer on Elizabeth Short, aka the "Black Dahlia," who was brutally murdered in January 1947. The FBI supported the Los Angeles Police Department in the case, including by identifying Short through her fingerprints that

America’s 5 Most Notorious Cold Cases (Including One You May Have Thought Was Already Solved)

Queen Elizabeth II addresses at opening of Parliament. (Date unknown on photo, but may be 1958, the first time the opening of Parliament was filmed.)

All 119 References in “We Didn’t Start the Fire,” Explained

German machine gunners occupy a trench during World War I.

Weapons of World War I

Chinese pictograph, calligraphy tablet of Huang Tingjian, a famous calligrapher in Ancient Song Dynasty. The background of Chinese cultural elements.

The World’s 5 Most Commonly Used Writing Systems

Titanic infographic. The 30th anniversary of its discovery is September 1, 2015. SPOTLIGHT VERSION.

Timeline of the Titanic’s Final Hours

Battle of the Alamo from "Texas: An Epitome of Texas History from the Filibustering and Revolutionary Eras to the Independence of the Republic, 1897. Texas Revolution, Texas revolt, Texas independence, Texas history.

6 Wars of Independence

Small, white rat (genus Rattus) on a glass table. (rodent, laboratory, experiment)

Cruel and Unusual Punishments: 15 Types of Torture

beam

architecture

Written and fact-checked by The Editors of Encyclopaedia Britannica

Article History

Related Topics:: cantilever bridge; cantilever; girder; rood beam; stringer

See all related content

beam, in engineering, originally a solid piece of timber, as a beam of a house, a plow, a loom, or a balance. In building construction, a beam is a horizontal member spanning an opening and carrying a load that may be a brick or stone wall above the opening, in which case the beam is often called a lintel (see post-and-lintel system). The load may be a floor or roof in a building, in which case the beam is called a floor joist or a roof joist. In a bridge deck the lightly loaded longitudinal beams are the stringers; the heavier, transverse members are called floor beams.

Large beams carrying the ends of other beams perpendicular to them are usually called girders. Metal girders may be single rolled pieces or, to permit greater stiffness and longer spans, may be built up in the form of an I by rivetting or welding plates and angles. Concrete girders are also widely used.

Beams may be of wood, steel or other metals, reinforced or prestressed concrete, plastics, and even brickwork with steel rods in the bond between bricks. For weight reduction, beams of metal are formed as an I or other shape having a thin vertical web and thicker horizontal flanges where most of the strain appears. See also cantilever.

Figure 1: The position vector x and the velocity vector v of a material point, the body force fdV acting on an element dV of volume, and the surface force TdS acting on an element dS of surface in a Cartesian coordinate system 1, 2, 3 (see text).

truss

building

Written and fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: Mar 11, 2025 • Article History

Key People:: Albert Fink

Related Topics:: hammer-beam roof; flat truss; three-hinged truss; Fink truss; two-hinged truss

See all related content

News •

Newspaper headlines: 'Hundreds feared dead in quake' and Reeves likened to Truss • Mar. 29, 2025, 8:31 AM ET (BBC)

truss, in engineering, a structural member usually fabricated from straight pieces of metal or timber to form a series of triangles lying in a single plane. (A triangle cannot be distorted by stress.)

A truss gives a stable form capable of supporting considerable external load over a large span with the component parts stressed primarily in axial tension or compression. The individual pieces intersect at truss joints, or panel points. The connected pieces forming the top and bottom of the truss are referred to respectively as the top and bottom chords. The sloping and vertical pieces connecting the chords are collectively referred to as the web of the truss.

Trusses were probably first used in primitive lake dwellings during the early Bronze Age, about 2500 bc. The first trusses were built of timber. The Greeks used trusses extensively in roofing, and trusses were used for various construction purposes in the European Middle Ages. Andrea Palladio’s I quattro libri dell’architettura (1570; Four Books on Architecture) contained plans for timber trusses. A major impetus to truss design came in the development of covered bridges in the United States in the early 19th century. Cast iron and wrought iron were succeeded by steel for railroad truss bridges. The two systems most commonly used are the Pratt and the Warren; in the former, the sloping web members are parallel to each other, while, in the latter, they alternate in direction of slope. Trusses are also used in many kinds of machinery, such as cranes and lifts, and in aircraft wings and fuselages.