— 1G3 — 
= 19.280 
町扣 stress in the lower portal strut is 
C = (3.104 + 0.408) - 0.408 = 8.399 tons 
u d that in the upper portal strut is 
C， ~ G + p p e== 8.399 + 3.104 — 0.945 = 10.558 tons. 
rpi , 
ie portal stresses have been entered on tlie diagram for the upper lateral 
8 fm. Nexh by referring to Table YI. ami using the column for round sections 
1 e( ‘ Intensity of Working Stress — 7.5 tons,” we can proportion all the lateral 
tlie portal vibration rods as marked on the diagrams, also tlie intermediate 
ra ^ 0u ro( ^ s > which we find will have to be 1 J 7 diameter. 
To proportion the intermediate strut we must add to tlie stress found tlie 
12 on tal component of the initial tension in one vibration rod, which Table YI. 
8h0W8 ^ be 1.25 tons. 
lior 
The 
cosine of the inclination to tlie horizontal is 
功 1836 — 0.84, making tlie bori- 
component 1.25 x 0.84 = 1.05 tons and the total stress on tlie intermediate 
^■ut 2.442 + 1.050 ^ 3.492 tons. 
011su lting Table X. we see tliafc a i f, I-beam 14 f long will have sufficient 
Htt?!'： be well to use a ö" — 11 pound beam, as a 4 f/ beam allows very 
loom foi* the connecting plates to fit between the flanges. 
ac | ( | A x 118 pioportion the portal and lateral struts. Before doing so we must 
in 11 1 s ^ ress already fouiid, tlie longitudinal components of the initial tensions 
^ 10 ro d 8 meeting at one end of tho strut. 
8 tres exam l)】e let us take the second lower lateral strut on which the calculated 
^ Ls Hi 75 tons. The cosine of the angle wliicli the rods make with strut is 
j. 1 ^ ~ 〇以 6. Table VI. gives the initial tensions on a 2y square and a 2 み " round 
8.960 GS ^ eC ^ Ve ^ aS 4.128 and 8.125 tons, the sum of which multiplied by 0.546 is 
) en . も 011 s’ which added to 14.175 makes 18.135 tons for the total stress. The 
as sutJ °| S ) ru t ma y be taken as 18.7 ieet, and the depth of tlie channels may be 
evid t aS ^ inches, even though larger ones might be more economical, for it is 
ticabi。 fr ° m Plate HL that the width of tlie strut should be kept as small as prac- 
. , e * These dimensions make the ratio of length to least diameter about 33, for 
Work) 0ue ^ xe< ^ and oue hinged end, Table IX. gives 8.445 as the intensity of 
re 8 t re ss. Dividing this into 18.180 gives 5.27 square inches as the section 
i n p! lG( 5 corre8 Poucling to two 8.78 pound clianuels. Consulting Carnegie's sections 
Din, er ^' r we that no such channel is rolled, so it will be necessary to em 
P ° y9 P°«nd channels. 
8ec は 011 s 0 f a U tlie other lateral and the portal struts are found in a similar 
diag r : r ’ ai 】d are written both on the diagram of this clmpter and on the principal 
Se ctio^ XIII.), as are also the sections of the portal and lateral rods. The 
s the intermediate struts and vibration rods are marked on the principa- 
ani u P°n the end vertical post. 
