— 250 — 
Thermal Stresa. — A stress causyl by variation m temperature. 
Thread. — The spiral part of a screw or nu+. 
T ： aroi«gU Bridge. —— A bridge with overliead bracing. 
Tie. — A tension member ； generally refers to a main truss. A sleeper. 
Timber Truclc, — A small, strong wooden frame» with an iron roller set entirely below the 
upper surface. It is used in l)ridge erection for moving large timbers and heavy weights along" 
runway. (Plate XII., Fig. 7.) 
Tonga. — Part of a riveting outfit ； used for holding and carrying heated rivets. (Plate XU 
Fig. 18.) 
Truck ； Stringer. — See stringer. 
Track Tie. — A sleeper. 
Transverse Ctm&poiieiit. — A component in a transverse direction ； generally intended 
a component perpendicular to the planes of the trusses. 
Truss. — An assemblage of tension and compression members so arranged as to transit 
loads from intermediate points to the ends. 
Trussing« 一 A poor substitute for lacing or latticing. (Plate II., Fi^. 13.) 
Turn Buckle, — Similar to a sleeve nut, and for the same purpose. The sides are op eI1 » s ° 
that a crowbar may be inserted for tlie purpose of screwing up. Turn buckles are used for larg er 
bars or rods thn.n are sleeve nuts. (Plato II., Fig. 5.) 
Ultimate streiigtu. 一 The greatest load that a, portion of material can bear. 
Uniform lioad. — A 10.1 cl so distributed over an entire structure, tliat equal lengths 
where receive equal portions. 
ir-init. 一 A piece of iron, in the shape of the letter it, througli which passes the threaded e 11 '^ 
of a rod, and which affords a bearing for the nut, with room to screw up tKe latter. Its use 
not permissible in first-class bridge construction. 
Upper liaise work. — The falsework that lies above the level erf tlie lower chords. 
Upset 1211 cl. 一 An end of a rod or bar enlixr^od far tlie cutting thereon af a screw-thread* 
Verbatim, — Word for word. 
Vibration Rod. •一 A tension member for vertical or portal sway bracing. (Plate I.) 
Washer. 一 A piece of cast or wrought iron to distribute the pressure of a bolt-head or ntr 七 
over timber. (Plate II., Fig. 7.) 
Web. — The portion of a truss or beam between tlie flanges. Its office is. principally 切 
resist shear. (Plate II., Fig. 15.) 
Welded Headit. — Heads first worked into ^lapc, then welded on the bars. 
Wlilpjil© Truss. 一 See Linville truss. 
Wind sitakea. — Cracks in timber caused by the wind while the, tree was living-. 
Woikiug-Ora wing*. — Drawings containing all the measurements necessary for ㈨ 形 一 
truction. 
Working-Stresa. — The stress, usually the greatest stress, to which a. piece of material 运 ゴ 
sliould bö subjected. Sometimes incorrectly 6131 ployed, for intöusity of working-stress* 
Wrench. — A tool for screwing up nuts. . (Plate XII., Fig. 15.) 
Yen. — A Japanese paper dollar of fluctuating value 
