■ 67. orneral.—An uniordable river is a difficult obstacle to an advancing army. The enemy, therefore, destroys all possible bridges in the path of advance. It is the Job of engineers to build substitute bridges In the shortest possible time.

■ 68. Speed and Teamwork.—Army engineers should be the fastest bridge builders in the world. They can build fixed and floating bridges quickly because of two things:

a. Their equipment is dpsigned for hasty, rnggptf construction.

b. Their building crews are trained in teamwork and speed.

The second factor depends on the individual engineer soldier. Hundreds oi feet ot bridge must be built in a few hours under difficult conditions; you will be very tired; sometimes you will be under enerr.y fire: you may be cold and wet; or hot and dry. But upon you depends so much that you must overcome all handicaps. An army may be waiting for the products of your toil. You must give all you have in you to do the job on timet

■ 69. Bridge Terms.—Following are some of the common terms used In bridge construction:

a. Abutment.—Shore support of a bridge.

b. Approach.—Roadway leading to the bridge.

c. Balk.—Stringers, or longitudinal load-carrying members. of floating bridge.

d. Bent.—Built-up intermediate support in bridge (see fig. 115)., e. Bracing.—Supporting members connecting adjacent bents to one another or to ground.

f. Cap.—-Top horizontal bearing member of bent.

g. Chess.—Floor planks in floating bridge.

107 69-70

h. End dam.—Plank at abutment Uf bridge, used to hold earth in place behind abutment. (See flg. 114.)

i. Footing.—Piece of wood used beneath supports fcc give added bearing surface on ground. (See flg, 114u)

4. Guard rail.—Flimsy rope or wooden fence on outer edges of bridge to guide foot troops and vehicles.

k. Holdfast.—Anchorage on shore to which bridge cables are fastened.

I. Pile.—Vertical member of bridge, driven into river bed. Several of them may be made into a pile bent.

m. Post.—Vertical member of trestle bent.

7i. Siderail.—Curbing on bridge.

o. Sill.—Horizontal lower bearing member of trestle bent or other support.

p. Span.—Distance between centers of adjacent supports.

q. Stringer.—Longitudinal weight-supporting member of fixed bridge; it carries bridge floor.

r. Sway bracing.—Diagonal bracing on a single bent.

s. Tread.—Additional wearing surface of bridge, running longitudinally.

f. Trestle.—Built-up support, consisting essentially of vertical and horizontal members usually braced by diagonal members.

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