Bridges and culverts for highway traffic, flat slab and girder type ... . ers G3 will be designed to carry the total car load. Each girder may, however, carrj two-thirds of the road roller con-centrations; the full load on the front wheel and one-half of the loadon the two rear wheels. All interior girders on single span bridges should be figured as T-beams. Dead load on girder: Fill, 1 -j X 100X5X32=20.(kh) , A X 150X 5 X 32= 10,000irder (assume 450 lbs. per ft.)=14,400 Total =44,400 Dead load bending moment : M=i 07=4X44,400X33=183,000 ft. lbs. Live Loads—Maximum moments <\ui- to
Bridges and culverts for highway traffic, flat slab and girder type ... . ers G3 will be designed to carry the total car load. Each girder may, however, carrj two-thirds of the road roller con-centrations; the full load on the front wheel and one-half of the loadon the two rear wheels. All interior girders on single span bridges should be figured as T-beams. Dead load on girder: Fill, 1 -j X 100X5X32=20.(kh) , A X 150X 5 X 32= 10,000irder (assume 450 lbs. per ft.)=14,400 Total =44,400 Dead load bending moment : M=i 07=4X44,400X33=183,000 ft. lbs. Live Loads—Maximum moments <\ui- to road roller. We will assume that onl) one road roller will be on the bridge .11 The maximum load on one girder then ma\ be repre- utrated I 1 pounds each, 11 on ccn- The maximum moment will occur with one of the loads 2Q off center of span, a^ shown by Fig. [6. Since the fill is but 15 effect of the fill in dibuting the loads w ill belected in determining the mo-ment 1 mi the girder. H,IOO 53,000 ft. -mi due to electric load by tra<. The maximum moment will occur with one truck at tlu* middle ofthe span, the other truck being off the bridge. (Two cars followingeach other will, for this span, produce practicall) the same momenl asone car. Sec sketch of standard fort) ton car on page 79 The loading for maximummoment will be as shown byFig. 17; where the load givenis that on one girder M = (10,000 X \6yi) — (10,) = ft- lbs- Fig. 17. To this static moment add 2^ for impact for rapidly moving loads,giving a moment of 184,000 foot-pounds. The maximum moment then due to the specified live loads is 184,000fot-pounds. Designing moment : J/„=((2X 183,000)+ (4X184,000)) 12=13,224,000 in. lbs. For the design of T-beams we will use the formula MQ=.S6 Fp bd2=43fooo p bd\ using high elastic limit corrugatedbars. See page 85. Assume d=$2 and £=14, we then have ^/0=i3,224,ooo=43,oooXi4X322X^ from which ^=.0215 ^=.0215X14X32= square inches. We
Size: 2116px × 1181px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectconcrete, bookyear190
