. Ingénieur de l'armure. la pression provoquée par les variations de la foun dation des conditions, et de prendre les effets négatifs se whichmight moment directement sous les colonnes ou dans le sidecantilevers. Le béton pour les piles, à l'exception de la col-lonne arbres, est un 1:2 %:5 mélange. Le béton de la col-umns est mieux qu'un 1:2:4 le béton. Barswere ondulé carré utilisé. 26 L'ARMURE [Vol. 2, n° 1 Conception des piliers : les culées sont de l'ordinaire en concreteconstruction massive de poids au-dessus de l'égalité et l'havesufficient largeur de pied pour garder la toe
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. Armour engineer. pressure brought about by variations in the foun-dation conditions, and to take any negative moment whichmight occur directly underneath the columns or in the sidecantilevers. The concrete for the piers, with the exception of the col-umn shafts, is a 1:2% :5 mixture. The concrete for the col-umns is better than a 1:2 :4 concrete. Square corrugated barswere used. 26 THE ARMOUR ENGINEER [Vol. 2, No. 1 Design of Abutments: The abutments are of the ordinary massive plain concreteconstruction of gravity section above the footing and havesufficient width of footing to keep the toe pressure within theallowable limit. Reinforced concrete abutments were not con-sidered because it was expected that this work would be doneduring freezing weather. The abutments were figured forearth pressure (according to Rankines theory) for a live loadsurcharge of 10, 000 pounds per lineal foot of track spread overa width of 13 feet, and for the reaction of the slab span-ning the sidewalk. fB&se. o^/S&i/. Fig. 8. Section of Abutment—Fig. 9. Section of Abutment—?Chicago Avenue Subway Bridge. Church Street Subway Bridge. Fig. 8 is a cross section of the north abutment at theChicago Avenue Subway. This abutment is 21 feet 6 incheshigh from base of rail to bottom of footing, and has a base of14 feet 6 inches, making a ratio of base to the height of .67.The footing has a toe projection of 5 feet, reinforced by 1-inchbars. The step is added to keep the unit sheer low and makeshear reinforcement unnecessary. Fig. 9 is a cross section ofthe north abutment at Church Street, which is on piles. Therows of piles are spaced in such a manner that the load on theextreme front row will never exceed the allowable bearing Jan. 1910] GREIFENHAGBN : EVANSTON TRACK ELEVATION 27 value for the maximum lateral forces, and that the load on therear row will not exceed the bearing for the minimum lateralforces. For average conditions the bearing on all piles ispractically the same. „ As shown by
