and abutment stakes should be tied to the horizontalcontrol system to meet accuracy requirements.The following is a typical procedure for survey-ing an abutment that is to be at right angles to thecenter line of the bridge. In figure 10-14, thefoundation of a concrete abutment, ABDC, is shownin the plan. AB is the face of the abutment foundation.Establish two convenient points, H and J, near theabutment CD, on the bridge center line. Set a stake atE (station 41 + 37.50)—the station designated on theplan for the abutment face.Set up the transit at E, train on H, match the zeros,and turn 90° angles to locate A and B at the correctdistance from E. Reference the line AB by settingstakes at F and G at the indicated distances from A andB. Set temporary stakes at C and D to mark the othercorners of the foundation.Sometimes the alignment of a bridge is not at rightangles to the center line of the stream or road it crosses.When this occurs, the abutment is askew (other than aright angle) to the center line of the stream or road.Then slight modifications are necessary to stake outan askew abutment.Figure 10-15 shows the plan for an askewnear-side abutment of a railroad bridge over ahighway. The outside line of the foundation is ABCD.The neat line of the face of the abutment is MN. Setstakes to define the direction of MN and ends AD andBC. The stakes P, S, U, R, V, and T are offset from theabutment so they will not be disturbed by foundationexcavating. The general procedure is as follows:Figure 10-14.—Staking a right-angle abutment.Figure 10-15.—Staking an askew abutment.1. Take the dimensions for setting necessary stakesfrom the abutment plans. Set the temporary point O atthe station location indicated.2. With the instrument at O, sight along the centerline of the railroad, turn the skew angle (71°45´), set thepermanent stakes P and R, and set points M and N.3. With the instrument at M, sight R, turn 90°, andset permanent stakes S and T.4. With the instrument at N, sight P, turn 90°, andset permanent stakes U and V.The face of the abutment is defined by P and R.Stakes S, T, U, and V define the face of the end forms.When construction begins, set stakes at A, B, C, andD by measuring from the offset stakes. (These stakesare knocked out as the excavation progresses.)Concrete for the foundation is poured into theexcavation; if forms are needed for the foundation,measure the distances from the reference offset stakes.Set the elevations of the top and bottom of thefoundation from bench marks outside the excavationarea.When the foundation has been poured to grade andhas had a day to set, mark temporary points on the topat M and N by measuring 10 feet plus the distance AM10-17
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