116 



STEEL HIGHWAY BRIDGES. 



CHAP. III. 



BEAM BRIDGES. Beam bridges are made by placing steel I-beams side by side with the 

 ends resting on the abutments. The roadway floor may be made of planks laid transversely on 

 the tops of the beams, or of reinforced concrete. The spacing of the beams depends upon the load 

 to be carried and upon the thickness of the floor planks or floor slabs and varies from 2 to 4 ft. 

 Timber joists should not be spaced more than 2\ ft. centers. A common rule for the thickness 

 of oak floor planks is that the plank shall have at least one and one-half inch in thickness for each 

 foot of spacing of the joists or stringers. The outside beams should be the same size as the inter- 

 mediate beams. It is commonly specified that rolled beams shall have a depth not less than $$ the 

 span. 



Note-.-NumberofRsilmq Posts 

 varies with length of Span. 



v Tar paper - three layers %// with concretes 

 r ~ ' after-jojstsareinp/jce 



L:.t!:;:...j::::;:^K 



ii- 



i ConcreteSlabfithick - Bottom I "oe/ow tops of joists 

 Transverse : D ? ~ ? ' 



ir)3l:-z "'terbet-exhpairof joists- ' 

 {3" Fill ^center r 



three layers after joists are placed ' 



HALF SEC TIONA T ABUTMENT HALF INT SECTION 



Clear 



Curb--* 

 PLAN OF ANGLE RAiuno ON WING WALLS 



lt>Ft 



20" 



28- 



W- 



10 '25 



1542 



1542 



1542 



w_ww_ 



IO'I5 



IMF5 l?>?0-5 WMW 



I5-33 



16V 9 



IIV 



10,000 



?0,.00ff 



V,WU x*\ 



co O 



hote:-Abovf bble is for 3 16ft- rofdwsyFor 

 18 ft 31^^ ft roadways, <sdd one line joists- 



Hote:- This design to be usedonly with 

 concrete substructures shown- 



5CT/W BELOW CWCRETE FLOOR. 



i i *-* r* ? 



snoot . loomM 

 3 ^::n=5^ 



15 TON ENGINE 



Assumed Live Load: - 

 Engines per diagram- 



STANDARD &EAM SPAMS 



Concrete Slab Floor 

 IOWAHI6HWAY COMMISSION. 



FIG. 12. BEAM BRIDGES. 



Standard steel beam bridges with concrete floor as designed by the Iowa Highway Commission 

 are given in Fig. 12 and Fig. 13. The spans vary from 16 ft. to 32 ft. The details are shown in_the 

 cuts. Quantities for beam bridges with angle fence as shown in Fig. 12 are given in Table IX. 



A standard steel beam bridge as designed by the Wisconsin Highway Commission is shown in 

 Fig. 14. Data and quantities for beam spans from 10 ft. to 38 ft. are shown in Table X. 



