Strut

“ The particular case of the above for which α is very small is a curve of sines of small amplitude, and the result in this case has been applied to the problem of the buckling of struts under thrust. When the strut, of length L′, is maintained upright at its lower end, and loaded at its upper end, it is simply contracted, unless L′2W > 1/4π2EI, for the lower end corresponds to a point at which the tangent is vertical on an elastica for which the line of inflections is also vertical, and thus the length must be half of one bay (fig. 25, a) . ”

“ If the applied load is not strictly axial, if the strut is not initially straight, if it is subject to any deflexion by transverse forces, or if the modulus of elasticity is not uniform over each cross- section — then loads smaller than the limit which causes instability will produce a certain deflexion which increases with increase of load, and will give rise to a uniformly varying stress of the kind illustrated in figs. ”

“ Fig. 120.
[Pg 100] The line E, D, on the diagram represents a tie-rod, which by the construction of this truss would naturally tend to stiffen the structure by supporting the center of the tie-beam.
Wire, nuts, and washers are supplied (where the student makes a whole model) to make the tie-strut.
The student in writing out notes will make two sketches of trusses he may have observed on shop visits. The buildings visited almost all have trussed roofs, either wood or iron. ”

“ Suppose in the first place that the ends are free to rock. The value of the load which causes instability will be found by considering what force P applied to each end would suffice to hold an originally straight strut in a bent state, supposing it to have received a small amount of elastic curvature in any way. ”

“ The struts and Z principal rafters are usually of T section, the - - Iron tensional members being rods or Hat bars., 00, s Flat plates and bolts or rivets are used to form the connexions between the members, and a means is provided in the tie-rod for tightening up the truss should any of the members “ give ” slightly under their load. Large trusses for very wide spans are specially designed for their work and may be of many different types of design. ”

“ The more it bends, the more powerful its thrust upon the inner surface of the walls in which it has its bearing. It is this pressure upon the interior surface that tends to thrust the wall outwards. But if, as in this case, in order to relieve the bearing of the beams, struts of wood have been put underneath (Fig. 12) , this effect of thrust is all the more sensible because the arm of the lever is longer. You do not quite understand, I see. A sketch will make it clear to you. Let A be the section of the wall, or, if you will, its thickness. ”

“ For fuselage struts, where the chief consideration is stiffness, to resist the bending strain produced by inequalities of wiring, fittings, etc., it may actually give better results, being slightly more rigid than silver spruce—at least that is the writer’s experience of it. ”

“ Jointing Beams to Posts and Struts.—The usual methods of forming joints between beams, posts, struts, and braces as used in the construction of gantries, stagings, jetties, bridges, etc., are illustrated by Figs. ”

“ A panel is one of any number of equal parts into which the truss of a bridge is divided by means of the posts or rods. This second truss is called the queen-post truss; here also the full black lines are in compression and the dotted lines are in tension. As you will notice in this truss, which is also the case in the flanged girder, the top part of the truss and the top flange are always in compression; so the lower chord is always in tension, as the lower flange in the flanged girders. ”

“ In Fig. 118 is shown a method that is sometimes used in the construction of trusses. A truss is that part of a roof which supports the purlines, rafters and sheathing. A roof is the covering or upper enclosure of a building with the frame work by which it is supported. It may be of almost any shape. A light roof is usually of moderate span, without trusses, the rafters being supported by the walls or partitions of the building. A heavy roof is employed for wider spans, [Pg 96] and the rafters are then supported by the purlines and trusses. ”

“ The beam or girder. 2. The framed truss. 3. The arch. 4. The suspension bridge.
The most ordinary form which we see in this country, and the one most generally used for the purpose of railway bridges, is the framed truss, and that is the one the development of which it is our purpose to show.
The one point to be carefully studied in all bridge construction is economy—that is, to get as much strength with as little material as possible; in other words, the maximum amount of strength with the minimum amount of material. ”

“ Figs. 160 to 194 give diagram sketches of a few out of the many forms of open, or truss, girders which have been adopted for large spans. There are many types from which to make a selection, each one possessing its own special features and [Pg 151] advocates. In working out the details of any, or all of them, there are some points which should always be kept in mind when deciding the distribution of material in the main booms. ”

“ Even the great alarm bell on the roof must have felt the force of the wind, for the rope rose and fell slightly, as though the bell were moved a little from time to time, and the limber rope fell on the oak floor with a hard and hollow sound. ”

“ In all structures exposed to wind, if the resisting moments of the ordinary materials of construction, such as masonry, partitions, floors and connexions, are not sufficient to resist the moment of distortion due to wind pressure, taken in any direction on any part of the structure, ad- ditional bracing shall be introduced sufficient to make up the differ- ence in the moments. ”

“ H. T. Crofton, an able pontist, who sent me his notes on bridges, asking me to cull from them whatever information my own research had missed. A hobby is the only altruism.
[113] Springing. The plane of demarcation between the ring and the abutment is called the “springing” of an arch. A “ring” is the compressed arc of materials known as archstones or voussoirs; and the “springing” marks the place where a ring starts out on its upward curve from a pier or from an abutment. ”

“ An undermotion of this kind is illustrated at Fig. 96. The spring is fixed at A, and a wire hook connects the spring with the quadrant at B. It will easily be seen that as the stave lifts, the direction of the pull of the spring is gradually moved over the centre of the quadrant at C. If the stave were lifted until the spring was in a direct line from A to C, the pull on the stave would be nil, as all the force would be exerted on the fulcrum. ”

“ In the extant cross the four flat faces of the upper part of the shaft gradually die off into the round surface of the lower part, giving a semicircular line of intersection, which is emphasised by a roll moulding, forming a continuation of the mouldings on the four square angles. The four flat surfaces exhibit a great variety of human and animal forms, with zoomorphic ornament and abstract plaits. ”

“ I claim, 1st, The within described novel construction of a truss for a wall building machine, the same consisting in the pyramidal framing, A B B, the horizontal timbers, D D, uprights. E F, holding-down bolts G J, and inclined braces, I H, combined and arranged substantially as and for the purpose herein set forth.
2d, Also in such truss firmly securing the timbers, D D, to the pyramidal framing, A B B, by enlarging and bolting, or equivalent fastenings, at the points of contact, in addition to the truss work before described, substantially as and for the purpose herein specified. ”

“ The drawbacks to any form of springing are the rapid wear of the hinges or joints by which the wheel is connected to the springs and the springs to the rigid portion of the frame, and the bouncing effect that is set up by the uncontrolled movement of the springs. ”

“ We have a system of levers to do our walking with, and they act precisely as do all levers. One leg is a lever to pry the body over the other leg, and the latter becomes a pendulum and swings back by force of gravity. ”

“ An advantage of the first importance is evidently secured if the rods of the pendulum, of which the building is conceived to be composed, have sufficient elasticity to be considerably distorted without rupture and to again recover their original position. ”

“ Passing by the fact that it is evidently safer to span a swelling river by a bridge of wide, rather than of several narrow arches, three powers or forces act on the row of stones or bricks forming the arch. There is first the force that would carry the stone downward—that is, the force of its own weight and of anything that might be placed upon it. ”

“ On taking the field, two trusses of 36 pounds each to every five men, at the end of eight days to be refreshed by one truss, and at the end of eight days more to be refreshed again by the same quantity. At the end of twenty-four days the whole to be removed, and an entire new bedding to be given, and refreshed as before, viz. two trusses for every five men. ”

“ In the article Block it has been mentioned, that a block is commonly bound with a ring, or wreath, formed of a piece of rope, called the strop; the eye of the strop, therefore, is that part by which it is fastened, or suspended, to any particular place upon the sails, yards, or rigging, the eye whereof is represented by fig. 37, plate II. The eye is sometimes formed by fastening the two ends of the strop together with a short line, so as to bind round a mast, yard, or boom, as occasion requires. ”

“ A very strong chain is hooked, one end to the body of the stump, or its principal root, and the other to the axle-tree. The power of horses or oxen is then applied to the loose end of the rope above-mentioned, and as they draw, rotary motion is communicated, through the smallest wheel, to the axle-tree, on which, as the chain hooked to the stump winds up, the stump itself is gradually disengaged from the earth in which it grew. ”

“ When a belt connects two pulleys whose respective planes of revolution are at an angle one to the other, it is necessary that the centre line of the length of the belt shall approach the pulley in the plane of the pulley’s revolution, which is sufficient irrespective of the line of motion of the belt when receding from the pulley. ”

“ The heads of the opposite uprights are held together by ropes, but in practice in this country6 it has been found that, under the immense pressure exerted upon the plank sides by the earth firmly rammed in the interior, the ropes are so liable to stretch, and to break, that it is advisable to use iron rods or bars in this position also. When ropes are used, the distance between the side planks is measured by gauge rods, and the ropes tightened when requisite to preserve the proper breadth of wall. ”

“ But the thickness of her yards, with the canvas rolled up on them, the thickness of the masts, too, the spread of the tops, the complicated gear of shroud, backstay, and running rigging—all offered resistance enough to the dark and living gale that was bellowing right over the stern to put something of the speed of an arrow into the keel of the fabric. ”

“ But on their flanks, where is the slope of the shoulder-like pediment, the arches vanish, and a wedge-shaped frieze takes their place, tapering outwards, in order to allow the columns to be carried to the extremity of the pediment; and here, where the heights of the shafts are so fast shortened, they are set thicker; five shafts, or rather four and a capital, above, to four of the arcade below, giving twenty-one intervals instead of nineteen. ”

“ A load contains 36 trusses. The term is also used generally of a supporting frame or structure, especially in the construction of a roof or a bridge. It is thus used as the name of a surgical appliance, a belt with an elastic spring keeping in place a pad used as a support in cases of hernia (q.v.) ”

“ An elastic spring is set in vibration by the thrust of the tooth of a cog-wheel: the first swing is the greatest, and each of the others is less than the preceding one (see Fig. 26) .
[59]
After several vibrations of this sort (without the spring coming to rest) let another thrust be given by the tooth; the next swing will again be a maximum one, and so on. ”

“ These are the diagonal bracings, or the rods provided to resist the action of the wind: they are strong enough to resist any strain that can be brought to bear against them, and are fitted with screwed connections and couplings, so that they can be adjusted with the greatest accuracy. ”

“ For thin webs in which the free breadth is greater than one hundred and twenty times the thickness, the diagonal compressive stress may be completely ignored, and the thickness determined with reference to the diagonal tension stress only. ”

“ It rests upon a heavy framework that is carried on the shoulders of one hundred and eight bearers. Thick transverse poles have heavy padded ropes run fore and aft between them, so that the shoulders of the bearers may not be galled. On the high framework is a structure like a little house, ten feet long, six feet high and five feet broad. ”

“ The fabric to be fluted and puffed is drawn between a pair of rollers moved by a crank, the rollers, where they approach each other, having flutes or grooves so arranged as by their pressure on the fabric as it passes between them to make the fluting and to flatten it. ”