Manual of military engineering . If^^ Opposite pn^ 6/. CHAPTER XIV.—BRIDGES. ol of the other forms ; they are, however, unsuitable for aauneven bottom, and extremely difficult to place, excepting byactually carrying them into position. They are usuallyplaced from rafts when working over water, and their legs mustbe weighted. 154. Fig. 3 shows a four-legged trestle ; it is made of two Four-frames similar to two-legged trestles, locked at the transoms, leggedand connected by short ledgers at the feet. One frame must trestles,therefore be made narrower than the other. The inclination of the
Manual of military engineering . If^^ Opposite pn^ 6/. CHAPTER XIV.—BRIDGES. ol of the other forms ; they are, however, unsuitable for aauneven bottom, and extremely difficult to place, excepting byactually carrying them into position. They are usuallyplaced from rafts when working over water, and their legs mustbe weighted. 154. Fig. 3 shows a four-legged trestle ; it is made of two Four-frames similar to two-legged trestles, locked at the transoms, leggedand connected by short ledgers at the feet. One frame must trestles,therefore be made narrower than the other. The inclination of the legs should be such that the breadth of the base on whichthe trestle stands should not be less than half the height. Thelegs must also have an outwards splay of |. Four-legged trestles can be made of fairly light material, andwill stand without bracing. They are consequently usefulfor small bridges of two bays, requiring one central support,and as occasional steadying points in a long bridge of two-legged trestles. When a carp
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