Beams and their types. In building construction a beam is a horizontal member spanning an opening and carrying a load that may be a brick or stonewall above the opening

In building construction a beam is a horizontal member spanning an opening and carrying a load that may be a brick or stonewall above the opening. 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. Joists – of timber, steel, or reinforced concrete – are laid in a parallel series across abutting girders or a bearing wall, to which they are attached, usually by metal supports called joist anchors.

The ends of the joists are grooved so that they are leveled with the load-bearing elements to provide a smooth horizontal. Before the floor is laid above additional strength may be given in the form of bridging anchors – diagonal braces between the horizontal beams.

Large beams carrying the ends of other beams perpendicular to them are usually called girders. Metal girders may be single rolled pieces to provide greater stiffness and longer spans. 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. Timber is easier to cut and transport. Apart from its inferior durability, it is also a more appropriate material because timber has a tensile strength along the grain to match its compressive strength. With stone there was only one possibility – the use of metal reinforcement at the bottom to improve the tensile strength.

Iron beams became structurally important elements only in the late 18th century with the widespread introduction of cast iron. Reinforced concrete became a highly versatile structural material, since the strength of the concrete, the overall geometry of the element, and the quantity and placement of the reinforcement rods were all under the designer's control.

Дата добавления: 2015-07-20