Beam (architecture)

“ This may be seen from the balances that we call steelyards. When the handle is set as a centre close to the end from which the scale hangs, and the counterpoise is moved along towards the other arm of the beam, shifting from point to point as it goes farther or even reaches the extremity, a small and inferior weight becomes equal to a very heavy object that is being weighed, on account of the equilibrium that is due to the levelling of the beam. ”

“ These closely resemble, and no doubt actually represent, the ends of massive timber beams, which must have connected the colonnade to the wall of the cell in earlier buildings. At the bottom of each is a row of small pendants, known as guttæ, which closely resemble wooden pins, such as would be used to keep a timber beam in place. The panels between the triglyphs are usually as wide as they are high. They are termed metopes and sculpture commonly occupies them. The third division of the entablature, the cornice represents the overhanging eaves of the roof. ”

“ A comparison, for example, of the plans of the Hypostyle Hall at Karnak (Fig. 11, h) and of the Basilica of Constantine (Fig. 58) shows at once a radical difference in constructive principle between the two edifices, and hence a difference of style.
STRUCTURAL PRINCIPLES. All architecture is based on one or more of three fundamental structural principles; that of the lintel, of the arch or vault, and of the truss. The principle of the lintel is that of resistance to transverse strains, and appears in all construction in which a cross-piece or beam rests on two or more vertical supports. ”

“ Nay, even the use of machinery, other than the common rope and pully, for the lifting of weights, is degrading to architecture; the invention of expedients for the raising of enormous stones has always been a characteristic of partly savage or corrupted races. A block of marble not larger than a cart with a couple of oxen could carry, and a cross-beam, with a couple of pulleys, raise, is as large as should generally be used in any building. The employment of large masses is sure to lead to vulgar exhibitions of geometrical arrangement, [127] and to draw away the attention from the sculpture. ”

“ Hence this architecture is called architecture of the beam, or, in more formal language, trabeated architecture. This mode of covering spaces required that in buildings of solid masonry, where stone or marble lintels were employed, the supports should not be very far apart, and this circumstance led to the frequent use of rows of columns. ”

“ Then, placing the beam in a horizontal position, let perfectly straight lines be drawn from one end to the other. So the intervals will be equal in the directions both of the periphery and of the length. Where the lines are drawn along the length, the cutting circles will make intersections, and definite points at the intersections. ”

“ These are in no sense Gothic, but are here given to more clearly explain the principles of roof construction. The common rafters (c.r.) bearing the covering are of light timber, tending to bend under the weight; to prevent this purlins (P.) , stout beams, are placed at suitable intervals, and these are carried at their ends by the roof trusses. The tie-beam (t.b) is the chief beam of the truss. The principal rafters (p.r.) are framed into it and into the heads of the King and Queen posts. In the Queen-post-truss the collar unites the Queen posts; struts and cross-braces complete the structure. ”

“ The thrust must be resisted either by the massiveness of the abutments or by the opposition to it of counter-thrusts from other arches or vaults. Roman builders used the first, Gothic builders the second of these means of resistance. The truss is a framework so composed of several pieces of wood or metal that each shall best resist the particular strain, whether of tension or compression, to which it is subjected, the whole forming a compound beam or arch. It is especially applicable to very wide spans, and is the most characteristic feature of modern construction. ”

“ F is the end of one of the Beams represented in great. G is one of the Pins which travers'd a round Eye, by the help of which the Beam is joyned to the Capital. H is the Cylinder which traverses the excentrical piece I. This Plate relates to pag. 155.
Explication of the Hardest Terms in Architecture.
A Bacus, from ἄβαξ; which signifies a square Trencher: In French it’s called Talloir; it’s that quadrangular Piece commonly accompanied with a Cymatium, and serves instead of a Drip or Corona to the Capital. It supports the nether Face of the Architrave and whole Trabeation. ”

“ A beam ran across over our heads, but not out of reach of our arms and our pickaxes—a beam fast at each end in the ruined wall, with ceiling and flooring all ripped away, and a great gap in the roof above, open to the sky. ”

“ At the turn-table, near the northern extremity of the fifth gallery, two big piles of rubbish had forced their way through from the fifth gallery, and from the looks of the timbers, more was about to come. These beams are solid—eighteen inches square; first, a great beam is laid on the floor, then upright ones, five feet high, stand on it, supporting another horizontal beam, and so on, square above square, like the framework of a window. ”

“ These carved beams, as Choisy points out, are struts rather than ties. If we take one of the columns standing in an angle in the aisles, an impost of marble connects it with the wall to which it is nearest, and a carved wood beam forms a strut to the other wall. The beam across the central bay of secondary order (Fig. 5) forms a rigid strut to the two wider arches (see Fig. 38, where, however, by oversight the beam has been omitted; it is at the springing of narrow arch high above iron tie) . ”

“ Mensch states that "it would take up too much time to prove that the counterfort acts really as a beam." The writer proposes to show in a very short time that it is not a beam. A beam is a part of a structure subject to bending strains caused by transverse loading. ”

“ Up to this beam the lower wall is built of brick set to curve of the timber, from which circumstance it would appear to be a modern insertion. The beam, we may be sure, was straight originally, and the bricks have been fitted to the curve which it subsequently took. Time, no doubt, ate away the lower work of wood, and necessitated the insertion of new materials. The slight curve of the great beam adds, I think, to the interest of the old place, for it is a curve that has grown and was not premeditated; it has grown like the bough of a tree, not from any set human design. ”

“ It is thus nearly one-third larger in the direction across the line of entrance, which gives to every arch, pointed and round, throughout the roof, a different spring from its neighbours.
The vaulting ribs have the simplest of all profiles—that of a chamfered beam. I call it simpler than even that of a square beam; for in barking a log you cheaply get your chamfer, and nobody cares whether the level is alike on each side: but you must take a larger tree, and use much more work to get a square. ”

“ This mode of strengthening a beam by trussing is only adopted in floors, where it is necessary to limit the depth of the truss to that of the beam, to obtain a level surface by means of joists laid across, and supported by, the beam. But it is obvious that much greater strength may be imparted to a [Pg 92] long beam by making it the base of a triangular frame, as is done in roofs, in various manners, when the slanting sides of the triangular frame carry the battens or laths for supporting the tiles or other covering. ”

“ If the young woodworker becomes ambitious enough to think of designing a bridge or large building he can find these figures in any engineers' hand-book. There are so many important factors to be considered that the amateur will do well to go ahead with great caution. Knots and other defects reduce the proportionate strength of large beams greatly, so that it would not be safe to assume that a beam 6 inches square would be 36 times as strong as a piece 1 inch square. ”

“ But the moment that the iron in the least degree takes the place of the stone, and acts by its resistance to crushing, and bears superincumbent weight, or if it acts by its own weight as a counterpoise, and so supersedes the use of pinnacles or buttresses in resisting a lateral thrust, or if, in the form of a rod or girder, it is used to do what wooden beams would have done as well, that instant the building ceases, so far as such applications of metal extend, to be true architecture. ”

“ Paragraph 18 - If the supports, when the beam sits on pegs in the wall, are not one tefach wide and three long, some say that they must be strong enough to support the beam and a half brick and some say that they only need to be strong enough to support the beam. ”

“ But though engineers were, by such experiments and reasonings, enabled to calculate the strength of a given iron beam, and the dimensions of a beam which should bear a given load, it would hardly have occurred to the boldest speculator, a few years ago, to predict that there might be constructed beams nearly 500 feet long, resting merely on their two extremities, of which it could be known beforehand, that they would sustain, without bending or yielding in any perceptible degree, the weight of a railroad train, and the jar of its unchecked motion. ”

“ By far the greater part of the weight of the roof rests directly upon the centre of the tie-beam. The result is that this beam has to be of enormous thickness. The only thing that prevents the building from leaning is the mortise of the tie-beam into the top of the supporting pillar. There are no trusses to prevent leaning, and so it takes but a few years for the building to get out of plumb. ”

“ Some buildings were vaulted in every storey, giving good examples of really fireproof construction; others were fireproof through one or two storeys, and timbered above; and others, again, had timber floors throughout. In secular structures we find trabeated architecture in its truest form—not stone beams, which, when extended beyond very narrow limits, go against the nature of the material, but real beams of wood, used in a thoroughly sensible and constructive manner. ”

“ In most balances the beam rests on steel knife edges; but a maker who has lately obtained celebrity makes his supports of pure rock crystal. The steel edges can be seen with the naked eye; the quartz edges cannot be seen even with a magnifying glass. One writer on this subject thinks that with these perfect crystal edges, with an inflexible girder beam, a short beam giving quick vibrations, and a sensitiveness that can be increased by screwing up the centre of gravity, there can hardly be a practical limit to the smallness of the weight that will turn the beam. ”

“ The beams carrying the floors have air spaces round each end, and to avoid the danger of the wall being pulled down by a falling beam in case the latter should be burnt through, the upper end of the beam is cut away at both ends so that it can fall freely.
Fig. 388.—Solid Blocking carried on Fillets. ”

“ The vividness of the expression of mechanical forces in architecture depends, moreover, upon the kind of materials employed; it is greater in marble than in wood, and less in our modern constructions of steel and glass, where the piers move in single vertical lines from the bottom to the top of the building, than in the old forms, where the upper part of the building is frankly carried by the lower. ”

“ The effect of the partially squared beam is, of course, far more picturesque than that of a completely squared one. The architect, however, need not have been so careful about strength, for if the beams had been only half their diameter they would have been just as effective. The strain on them is by pulling, and not by pushing. Now, as any one can see by trying the experiment with a splinter of wood—say a lucifer-match—an enormous power is required to break it by tearing the ends asunder, while it can be easily broken by pushing them towards each other. ”

“ It has been impossible for modern designers, in their treatment of style, to keep pace with the rapid changes in the structural use of metal in architecture. The roofs of vast span, largely composed of glass, which modern methods of trussing have made possible for railway stations, armories, and exhibition buildings; the immense unencumbered spaces which may be covered by them; the introduction and development, especially in the United States, of the post-and-girder system of construction for high buildings, in which the external walls are a mere screen or filling-in ”

“ The lintel is a beam extending in a right line from one column or wall to another over a vacant space. The floor is a lateral continuation or connexion of beams, by means of a covering of planks. The strength of the lintel, and, in fact, every other elementary part of a building used as a support, can be mathematically determined by the skilful architect. ”

“ The upper parts of all buildings contain timber work to which various terms are applied. And not only in its terminology but actually in its uses it exhibits variety. The main beams are those which are laid upon columns, pilasters, and antae; tie-beams and rafters are found in the framing. Under the roof, if the span is pretty large, are the crossbeams and struts; if it is of moderate extent, only the ridgepole, with the principal rafters extending to the outer edge of the eaves. ”