. Ponti e sotterramenti in cemento, sia per ferrovie che per autostrade . Questo può essere necessario per garantire la stabilità e Arill può essere considerato più tardi sotto la testa di carico. Nel progettare le pareti laterali di spandrel a terra che riempiono le regole usuali per trattenere le pareti wilai)ply. La pratica è quella di rendere lo spessore delle pareti di suchwall alla base 40% dell'altezza. Devono essere saldamente fissati o altrimenti fissati all'archmasonrv. 20 COXCRETE PONTI AXD CCUERTS. Vari moduli e come disegnarli. Le forme di Tlie adottate per l'intradosso dei ponti masonryarch sono generalmente circolari, segmentali, ellittiche, o m.
1678 x 1489 px | 28,4 x 25,2 cm | 11,2 x 9,9 inches | 150dpi
Altre informazioni:
Questa immagine potrebbe avere delle imperfezioni perché è storica o di reportage.
. 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.
