Strain (see also Stress) In modem engineering terms, Strairz is the ratio 'change in length/ original length'. Strength The ability of a material or structure to resist forces or deformations tending to break it. Stress (see also Strain) In modern engineering terms, Stress is the ratio 'applied force1 original cross-sectional area'. Confusingly, until about 1860, the term Strain was generally used instead of stress. Strut (see Col~mm) A member in compression, with load applied (nominally) along the centroidal axis of the member. Suspension Bridge A Bridge formed by suspending between piers Wrought Iron chains or wire ropes (later Steel) and from these a deck. A light and relatively cheap structure, but lacking inherent stiffness. Suspension Girder (see Beanflr~rssedGirder) Smaging (see also Upsetting) The drawing down at the forge, or reducing in size or diameter, of a heated piece of ivrolrgkt Iron. A Stvage is a blacksmith's tool for working rounded parts. Swedish Iron A term generally used in the eighteenth and early nineteenth century to indicate high quality Wrought Iron imported from Sweden. Tempering Heat treatment of medium or high carbon Steel for tool making. Steel heated to cherry red and suddenly cooled or quenched in water or oil is made very hard. Reheating until the surface oxide reaches the desired colour and quenching in water 'lets down' the hardness to the required temper. Tenacity A nineteenth century term for tensile Strength. Tension An action tending to make a body longer (the 'opposite' of Compressiorz),or to stretch it. Tie A member in Tension.
Tied Arch An arch tied between its feet to eliminate horizontal thrust on supporting abutments.
Toughened Cast Iron (see also Cast Iron) A stronger form of Cast Iron first made in the late 1840s by melting with cast iron up to a quarter its weight of Wrought Iron scrap, thus reducing the overall carbon content. Probably not much used. Toughness Resistance to brittle fracture. Treble Best Iron (see also Best, Best Best (BB) Iron) Very high quality Wro~igktIron, superior to 'Best Best' for a given Brand. Truss A skeletal framework in which load is transmitted to supports by compressive and tensile forces in the elements of the framework, rather than by bending. A true truss is fully triangulated.
Trussed Bearnl Girder A compound element in which a B e a d Girder, generally of timber or Cast Iron and working in Bending, is strengthened with Wrought Iron trussing bars working in Tension. Also called a Suspension Girder. Tubular Girder A rivetted box-section Wrought Iron Girder form patented by William Fairbairn in 1846 and widely used in railway Bridge construction. Universal Beam A steel beam with near-parallel flanges, as first rolled in Britain at Lackenby in the late 1950s. Early parallel flanged sections were rolled in Europe from c.1904 and later in the United States by a rather different process and imported to Britain. Upsetting (see also Swaging) Increasing the thickness of a piece of heated Wrought Iron at the forge by jumping up, or repeatedly striking the end of an upright bar on an anvil. Web (see also Flange) In an iron beam or joist, the vertical plate with a Flange at one or both ends. Welsh Iron Relatively expensive Cold-blast Pig Iron from Wales bringing qualities of strength and hardness to a mixture for Cast Iron. \Vet Puddling (see Puddling) White Cast Iron (see Cast Iron) Cast Iron with a low Carbon content, hard and brittle and unsuitable for structural purposes. When fractured cold, shows a granular, greyish surface.