原创 Abercrombie Outlet438

Abercrombie Outlet438

But this ertleps method, besides leading the employer Jnto great expence, is frequently fatal to the undertaker, from the unskilfulness of tbe construction. The beams .which connect its extremities are made abo to support the middle by means of posts which rest on them. Thejr are therefore exposed to a transverse or cross strain, which they are not able Abercrombie Outlet to bear. Their number must therefore be increased, and this increases the load. Some of these cross strains are derived from beams which are pressed very obliquely, and therefore exert a prodigious thrust on their supports. The beams are also greatly weakened by the mortises which are cut in them to re?ceive the tenons of the crossing beams: and thus the whole is exceedingly weak, compared with what it might have been, by a proper disposition of tbe same quantity of timber.he principles from which we are to derive this disposition are the general mechanical principles of carpentry, of which we have given already some ac- count These furnish one general rule: When we. would give the utmost strength possible to a frame of carpentry, every piece should be so disposed that it is subject to no strain but what either pushes or draws it in the direction of its length; and, if we would be indebted to timber alone for the force or strength of the centre, we must rest all on the first of these strains; for when the straining force tends to draw a beam out of its place, it must be held there by a mortise and tenon, which possesses but a very trifling force, or by iron straps and bolts. Cases occur where it may be very difficult to make every strain a thrust, and the best artists admit of ties.; and in?deed where we can admit a tie-beam connecting the two feet of our Abercrombie and Fitch Outlet frame, we need seek no better security. But this Abercrombie may sometimes be very inconvenient. When it is the arch of a bridge that we are to support, such a tie- beam would totally stop the passage of small craft up and down the river. It would often be in the water, and thus exposed to the most fatal accidents by freshes, tec. Interrupted ties, therefore, must be employed, whose joint or meetings must be supported by something analo?gous to the king*posts of roofs. When this is judiciously done, Abercrombie and Fitch the security is abundantly good. But great judg?ment is necessary,