. Betonbrücken und Sekten, sowohl für Eisenbahnen als auch für Autobahnen. Dies kann notwendig sein, um die Stabilität zu sichern, und Avill wird später unter der Leitung der Lasting in Betracht gezogen. Bei der Gestaltung der Seite spandrel Wände zu retainearth Füllen der üblichen Regeln für die Stützmauern Willai)ply. Die Praxis ist, die Dicke der Wände an der Basis 40% der Höhe zu machen. Sie sollten fest eingedüst oder anderweitig an der Erzmasonrv befestigt werden. 20 COXCRETE-BRÜCKEN AXD-CCUERTS. Verschiedene Formen und wie man sie zeichnet. Tlie-Formen für die Intrados von Masonryarch Brücken angenommen sind in der Regel kreisförmig, segmental, elliptisch, oder m
1678 x 1489 px | 28,4 x 25,2 cm | 11,2 x 9,9 inches | 150dpi
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. Concrete bridges and culverts, for both railroads and highways . This may be necessary to secure stabilityand Avill be considered later under the head of load-ing. In designing the side spandrel walls to retainearth filling the usual rules for retaining walls willai)ply. Practice is to make the thickness of suchwalls at the base 40% of the height. They shouhlbe firmly doweled or otherwise secured to the archmasonrv. 20 COXCRETE BRIDGES AXD CCUERTS. Various Forms and How to Draw Them. Tlie forms adopted for the intrados of masonryarch bridges are generally circular, segmental, elliptical, or multi-centered. These four types canbe reduced to two. circular and elliptical, for the seg-mental arch is merely a segment of a circle, and themulti-centered arch is merely an approximate ellipse.The two general forms are, therefore, the circu-lar and the elliptical.Methods of drawingthe ellipse and themulti-centered curveare as follows: Ellipse. Let AD and CD )e the semi-major and semi-minor axes of an ellipse at right ^ angles to each other. Draw circular arcs. Fig. 1 with radii AD and CD, respectively. From i)ointswhere a common radius intersects the two circulararcs, draw vertical and horizontal ordinates. The in-tersection of these ordinates gives points on the ellipse. Multi-Centered Arch—Three Centers. These curves are sometimes called 1)asket-liandledarches. The method of drawing a three-centered PLAIX COXCRETF. ARCH BRIDGES. 21 •^ arili is as follows :Let AD and CDbe the semi-majorand semi-minoraxes, respectively, of a true ellipse.The form of thetrue ellipse is firstd r a w n by themethod givenabove. This isshown in Figure 2by the full line.The approximateform is theno drawn as follows :Assume any two ecpal distances CB and AE lessthan half of the semi-minor axis. Join BE and bisectthe line BE at F. Through F draw a perpendicu-lar to BE. intersecting the line CD at 0. The twojioints 0 and E will be centers of two circular arcswhich will form an approximate ellipse.