—— 245 — 
eÜla ^ n ll Pon it for any length of time. 
Deck BrWge. 一 A bridge in which the passing loads come upon the upper chords or the 
ll ^e nf l S0fthep0sts> 
öeiiectioM. — Motion laterally, or at. right angles to the length, of the piece. It is also used 
e atQ o«nt of motion, ;tnd i：i generally expressed in inches. 
Depth of Truss. — The vertical distance between the centre lines of upper and lower chords . 
Dia S«nal. — A member running obliquely across a panel. In this work till the diagonals 
P the batter braces are tension members. 
• /^^ a » rani of Stresses. - 
016 difl er ti nt, (Plate XIIL) 
- A skeleton drawing of a truss, upon which are written the stresses 
ffervmt members. (Plate XIH.) 
/tj Ajiparatii«. 一 A contrivance for tlirowin^ a derailed vehicle clear of the track 
Wate VI 、 
VI.) 
« Doill> Ie Intersection. — The style of truss where the diagonals cross the posts at the middle 
e ! r as in the bridge shown on Plate I. 
Doi,fe le-rivetejl Lacing. — Lacing in which each bar is connected by two rivets at each. 
ent1 - (Plato II., 10 . } 
Doul * le T «>e. 一 Another name for I-beam. 
örjft Bolt, — A round or square piece of iron, usually from one to tliree feet long, without. 
° r nu t used to connect timbers. 
Dr ift Pin. 一 A. slijrhtly tapering rod of bard steel, used for making rivet Boles coincide. 
Us e is more convenient than advisab]o. (Plate XII” Fig. 14.) 
ßffectiv© Area. — The gross area of a section, Ie3s that lost by rivet or pin holes ； the net 
似执 . 
^ Limit. — That intensity of stress at which the ratio of stress oyer strain commences 
0w a cided change. For wroüght-iron it is from twelve to fifteen tons. 
ecti,1 s-Biii. — A bill of material for a bridge, so arranged as to facilitate tlie finding and 
ClD g of members during erection.' 
® x pansio n Joint. 一 The connection of pedestal to bed -plate, shown on. (Plate II. Fig. 15.) 
^pansion üoiier«. — A set of half a dozen or more turned rods of exactly the same 
i r G er, Placed under the shoe plate at one end of a truss to permit of expansion and con- 
■ ミ 011 . (Plate II., Fig. 16.) 
it x ，3xt ° nsloM ** la <«* 一 . A plate riveted to the end of a strut channel, and projecting beyond 
° ^ erm it of tbe passage of a pin. (Plato II., Fig. 9.) 
Eye . 〜 人 holo in the end of a member to permit of the passage of a pin. 
も e Ear . 一 A bar with an eye at each or one end. 
W 
0| * factor of Safety. 一 The ratio of ultimate load to greatest allowable working- 
Th .^ S ^ rm ^ getting out of favor among engineers, as its use has been somewhat abused. 
Cl suchth 峋 as a factor of safety for a well-proportioned bridge, for each member should 
. ln tensity of working -stress proportionate to the character and amount of work which it 
perform. 
•—人 rope used in erection for raising and lowering weights, 
e^vork. 一 Temporary timber work to support a bridge during erection. 
^»veting. — Kiveting done in tlie field, or during erection. It is the poorest and 
取 こ !) endive kind of riveting. 
h the け 一 ' -^ n end of a strut so firmly connected as to prevent all motion of the strut 
扔 lUn; 
UeighlDorhood of the end. 
S-Plate. — A plate the function of which is to make flush two surfaces. (Plate II.j 
no 
the T** 〜 A s ^nal] ring of iron or piece of pipe placed on a pin in order to keep in position 
加 ）ers coupled thereon. (Plate II., .Fig. 11.) 
a 8tr IXetl レ》 ad. — a : 
Ctureor Portion of a structure. 
load remaining permanently, or for a considerable length of time, upon 
