— 227 — 
The \ ertical posts should be strong enough to withstand a working- stress given 
b y Äe equation, ' 
8： 
Wil 
了 
2 
( + t?2 + & C . + d n-i + 誓)， 
Verti ，e U 11 啦 her of tlie tier considered, and S the stress ia the corresponding 
他 ich” dhueiision of tlie vertical posts should be the same as the side of the square 
贫他 tlT 山 0 8ec ti 0n が the inclined posts; so that the diagonal braces may be flush 
Y ‘• le eu tii’e faces of the bents, and be bolted to the verticals without the inter- 
Ventl r OU ^fiUing-pieces. 
prop^ e m ° re elevated tlie bridge, the more important does it become to properly 
t0l ^ tl0ü tlle falsework. The values of W 2 and Af will have to be assumed, or 
s hofü/l Calculafced, before applying the equations. Tlie ofcher quanitias are, or 
Ware い ， ku ° WU * The valueof V may be taken from ten to fifteen pounds per 
t a ]. e le ぞ 00 し unless the situation bo more than ordinarily exposed, when it may be 
ti lß u ^ twent y pounds. One can afford to risk the chance of a hurricane striking 
Gbrid ^ before it is swung. 
Posts Tll V eCti ° US ° f tlie Cftps are S eueralI y ^ade tlie same as those of the inclined 
a nd .• . e ca P3 should be dapped to receive both upper and lower ends of vertical 
b 0 j t ^ lued Posts. The vertical posts should be drift-bolted through the caps, tlie 
Posts T g l0Ug enou g h fco project five or six inches into each post ； and tlie inclined 
p r - e h oul(1 be held in place by wooden splice pieces, one on each side of the bent, 
^rou rl lllg a ' )ove and ^elow the cap, and fastened at each end by a bolt passing 
Verti Y 心 tW0 81 〕 lice P ieces a ud tlie post. This atfcacliinenf; may be used for tho 
Cal 抑也 instead of the drift bolts. 
s plicf° r a(ldlfcl0nal security against slipping a third bolt may be put through the 
thp 4 l)leces and the cap, or cleats may be nailed to tho caps above and below at 
6 0 f eacli inclined post. 
fal 二 ひ ド holes in the timber should be accurately located and bored before the 
tev u 13 ere cted. On this account the bents should be all built after ouo pat- 
Uie va〆 ザ 山 6 P ar ^ s may I>o iiiterchangeble. If the bents be of different heights, 
8 Pikes f “ 的 0 咖ア be effected in the lowest tiers. Bolts are always preferable to 
aiij re conüe ctmg timbers, especially wlieu tlie falsework lias to be taken down 
ere cted for another span. Care should be taken to avoid any unnecessary 
. le in order that it may not be sold at too great a loss after the 
技 13 finished. 
tru 8Ses should be two plank walks on top of tlio lower falsework, exterior to the 
for 如 a runwa y midway between formed of several wooden joists set on edge, 
Purpose of bringing out the material thereon upon timber- trucks. 
ff ow | u g table taken from Carnegie’s ‘‘ Pocket Companion n gives tlie safe 
loa^ s c ^ . istributed loads in pounds for these joists. Tlio safe concentrated central 
n e found by dividing those given in the table by two. 
