Bridge and Tunnel CentresD. Van Nostrand, 1875 - 106 Seiten |
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Häufige Begriffe und Wortgruppen
abutting angle of repose arc of 60 arch stones arrangement back rib backpieces bolt braces brick bridge centres bridle pieces centre frames centre rib cocket constructed course crown bars cubic foot cubic yard curve cylinder depth direction driven earth equal equation feet firm points folding wedges formulæ friction full centre arch gings give greatest hori horizontal beam horizontal tie beam inches inclined struts intrados laid large span latter leading rib length of arch lower joint middle rib mortar oval patent centres placed points of support pressure principal pieces props rabbeted radii of curvature radius rection resistance rest scarf joint screws segment rib set of laggings shape and span side walls sill soffit soirs spanning the arch springing line strength striking plates STRIKING THE CENTRES sustain thickness tical timbers tion trestles TUNNEL CENTRES upper vertical beams voussoirs Waterloo Bridge weight per cubic wood zontal
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Seite 68 - Where the beams stand square with each other, and the strains are also square with the beams and in the plane of the frame, the common mortise and tenon is the most perfect
Seite 71 - green will, seven cases out of ten, be followed by the fall of the bridge ; but by easing the centring as soon as the arch is keyed in, and continuing this gradual easing till the framing is quite free from the arch, the latter has time to
Seite 9 - in each course abutting end to end by a joint in the direction of the radius of curvature of the arch, and breaking joints with those of the other course.
Seite 69 - firmly in the direction of the thrust, on the solid bottom of the mortise.
Seite 3 - in as brief a manner as the nature of the subject will allow,
Seite 70 - arch will never be so great as to become dangerous even though the supporting frames be removed when the mortar is green. But possibly the best practice lies not far from either of these extremes. It has, indeed, time and again, been amply demonstrated that to leave the centring standing till the mortar has hardened, and then take away all support, the mortar having become
Seite 36 - between them, the joints, especially in the larger and heavier arches, must be secured by pieces of iron placed across them and bolted to the backpieces and struts, to prevent the joints opening in consequence of the bulging at the crown as course after course of stone is laid on the frame.
Seite 56 - The third and fourth systems of arranging the principal pieces, afford an almost unlimited number of designs for centre ribs, which are especially worthy of notice, in that they are applicable to every possible shape and span that can be given to stone arches, and may be constructed with or without intermediate points of support, according as
Seite 95 - case it is the custom in practice to place all the laggings on the ribs before commencing to turn the arch, by which means no small degree of stability is given to the ribs. In tunneling, however, where only a few inches of space remains between the
Seite 27 - is to uphold the voussoirs and transmit the strains it receives as directly as possible to firm points of support, the beams must be so arranged as to do this with the least tendency to change the shape of the rib, by their bending or breaking. The