McMaster, John Bach, 1852-1932, Making of America Project · New York, D. Van Nostrand · leaf 91
not be used in every part of a tunnelcentre is the absence of the tie beam,which is certainly a great security againstthe spreading or contracting of the span.Were this tie beam supplied, and it mayeasily be supplied by an iron screw rod,this form of frame would probably, inaddition to the… … 87 diate ribs called scarf or queen post centres, which, as there are no props to beinterfered with, are provided with horizontal tie beams. As these ribs are alsoto be taken apart each time they areshifted, the tie beam is composed of twobeams joined by a scarf joint strenthen-ed by a piece of…
Bridges · Tunneling
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