STEEL HIGHWAY BRIDGES. 



CHAP. III. 



TABLE IV. 

 REINFORCEMENT FOR REINFORCED CONCRETE FLOOR SLABS. 



The reinforcement given in this table is to be used at the bottom of slabs figured as simple 

 supported, and at the top and bottom of slabs figured as continuous or partially continuous over 

 the supports. Longitudinal reinforcement ^ in. round or square bars spaced two feet centers. 



The Illinois Highway Commission for stringer spacings of about 25 ft. uses a concrete sub- 

 floor 4 in. thick, with a 4 in. concrete wearing surface, or a 3 in. creosoted timber block wearing 

 surface. The concrete sub-floor, 4 in. thick, is reinforced on the under side with in. square bars, 

 spaced 6 in. centers and centers I in. above lower edge. Transverse reinforcement consists of 

 f in. square bars spaced 12 in. centers. The concrete is specified as 1-2-3^ mix, and is designed 

 for a stress of 800 Ib. per sq. in. 



The West Virginia Highway Commission specifies 1-2-4 concrete and a minimum thickness 

 of slab of 5 in. to the center of the tension reinforcement. 



The Ohio Highway Commission specifies concrete slabs for different stringer spacings as 

 follows: 5 in. slab for 2 ft. spacing; 6 in. slab for 3 ft. spacing; 6 in. slab for 4 ft. spacing. 



Specifications for highway bridges of the state of Nebraska specify slabs made of concrete of 

 a 1-2-4 mix, 6 in. thick reinforced with in. round bars spaced 6 in. centers. The bottom of the 

 concrete to be i inch below top of joists. 



The standard reinforced concrete floor used by the Michigan Highway Commission is shown 

 in Fig. 8. The slab is 6| in. thick at the center and 6 in. thick at the curb. The details of the 

 floor are shown in the cut. 



Buckle Plates. Buckle plates are made by "dishing" flat plates as in Table 55, Part II. 

 The width of the buckle W or length L, varies from 2 ft. 6 in. to 5 ft. 6 in. The buckles may be 

 turned with the greater dimension in either dimension of the plate. Several buckles may be put 

 in one plate, all of which must be of the same size and be symmetrically placed. Buckle plates 

 are made i in., fV in., | in. and ^ in. thick. Buckle plates should be firmly bolted or riveted 

 around the edges with a maximum spacing of 6 inches, and should be supported transversely 

 between the buckles. The process of buckling distorts the plates and an extra width should be 

 ordered, and the plate should be trimmed after the process is complete. The buckle plates are 

 usually supported on the tops of the stringers, but may be fastened to the bottoms of the stringers. 

 The space above the buckles is filled with concrete which carries the wearing surface. Buckle 

 plates are now seldom used except for special floors and heavy floors where the weight of a rein- 

 forced concrete floor would be too great, or where it is necessary to cut down the clearance. 



