STR
598
STR
The force which elastic strings or fibrous bodies, &c.,exert when drawn or compressed in a direction oftheir length, is proportional to the increased or con-tracted space to which they are lengthened or short-ened, ii. 465.
If a beam be supported at' two ends, and a force orweight applied to the middle of it, the deflection ofthe beam or space through which it bends, will be asthe force applied nearly, ii. 465.
If a solid be supported by 4 forces, of which 2 and 2are parallel, then in each pair of parallel forces, oneforce is equal to the other, and its direction contrary,ii. 465.
If instead of the weights i, r., h, as in the last proposi-tion, the points A and d, be supported by two springsag and d h, in the direction ab and DC, parallelto the horizon, and by a prop d f perpendicular toit, and if ad be divided into any two parts A E and E d,then will P. C d = e d. f + e a./; that is, themomentum of power is equal to the sum of themomentum of tension and compression where f isthe tension of the upper spring, or the compression^ ofthe lower, ii. 466.
If a beam be supported by the two ends, and a weightbe applied over the middle section, then will themomentum of power occasioned by the weignt toovercome the resistance of the beam, be equal tohalf the weight multiplied into half the length of thebeam, ii. 466.
If a beam A b be supported in four points a, b, c, d, anda weight w appended to the middle of the part c d,at F, it will carry twice as much as if it were onlysupported by the two middle points c, d, ii. 466.
If a weight w, or any force, act perpendicularly to thelength of a beam supported at the two extremitiesA and b, the strain at the section c, on which theforce acts, will be equal to the rectangle of the twosegments, into the weights divided by the length, thatAC, CB, W ..
is as-, n. 466.
A B
The strain on any section d, of a beam resting on twoprops a and b, occasioned by a second force, appliedperpendicularly upon another section c, is equal tothe rectangle of the two extreme segments into the
weight divided by the length, that is,
A c, d b, wa b
equal to the strain at d, ii. 466.
If a weight be equally diffused throughout any part b cof a beam a d, the strain at either end c of the diffusedpart, is to the strain at the same place from the sameweight being suspended there, as A b + A C, totwice A c, ii. 466.
The strain of a prismatic beam, supported at the twoends a and b, by its own weight, at any section c, isequal to the rectangle of the two segments into theweight of the beam, divided by twice its length, that isAC, BC
2 a b
467.
If a prismatic beam a b, be fixed in a wall at a, thestrain at any section c, d, from its own weight, willbe as the square of the distance b, c, of that sectionfrom the extremity, ii. 467.
To determine the relative strength of a rectangularprismatic beam abcd, projecting horizontally froma wall, supposing the beam to be incompressible at thefulcrum, ii. 467.
To determine the relative strength of a prismaticrectangular beam, projecting horizontally from a wall,supposing it to turn round some intermediate axis inthe section of fracture, ii. 468.
On Galileo’s and Mariotte’s doctrines of resistance,ii. 468.
Tables of Belidor ’s and Buffon’s experiments onstrength of beams, and deductions therefrom, ii. 469.
Mr. Petit and others upon the subject, ii. 473.
To determine the neutral line, ii. 474.
Mr. Banks ’ experiments, ii. 475.
Mr. Tredgold’s do., ii. 475.
Table showing the cohesion of a square inch of diffe-rent woods pulled asunder in a direction perpendicularto the length of the fibres, ii. 475.
Do. in the direction of their length, ii. 476.
Table showing the modulus of elasticity of beams pressedin the direction of their length, ii. 476.
Result of experiments by Rennie, ii. 476.
Table of experiments on the strength of woods supportedat both ends, ii. 476.
Do. supported at one end, ii. 476.
Mr Telford’s experiments on the cohesive force of iron,ii. 477.
Table showing the cohesive force of iron, ii. 477.
Table showing the extension, by a suspended weight,of a wrought-iron bar, 10 feet long, 1 inch square,ii. 477.
Table showing the extension, and permanent set of acast-iron rod 10 feet long, and 1 inch square, drawnin the direction of its length, ii. 477.
Table showing the extensions of cast-iron rods, 10 feetlong, and 1 inch square, deduced from numerousexperiments, and compared with observed compres-sion of bars of the same irons and the same size, castwith them for comparison, ii. 477.
Table showing the compression of a cast-iron bar 10feet long, and 1-inch square, ii. 478.
Table showing the compression of wrought and cast ironbars, 10 feet long, and 1 inch square nearly, ii. 478.
Table showing the average breaking weight of bars, 1inch square, and 3 feet long, ii. 478.
General observations, ii. 478.
Tensile strength of round iron, chain-cable, and ropes,ii. 478.
Transverse strength of a slab of slate from the Penrhynquarries, ii. 478.
Transverse strength of timber, ii. 478.
Results of experiments made with actual weights onmaterials used in the Britannia bridge, January;1848, viz.,
Single bricks of different qualities, ii. 479.
Stretched-out, ii. 479.
Stretcher, ii. 479.
Stretching Course, ii. 480.
Stree, ii. 480.
Striges, ii. 480.
Striking, Sticking, or Running a Mout.ding, ii. 480.
Striking, ii. 480.
Striking a Centre, ii. 480.
String Board, ii. 480.
String Course, ii. 480.
String Piece, ii. 480.
Strix, ii. 480.