SPECIFICATIONS FOR STEEL HIGHWAY BEIDGES. 37 
FLOOR SYSTEM. 
Floor beams preferably shall be at right angles to the^^^^^^ i o o r 
trusses or maui girders and shall be rigidly connected 
thereto. In general, floor-beam connections shall be 
located above the bottom chord and in riveted work the 
bottom chord lateral system shall engage both the bot- 
tom chord and the floor beam. Floor-beam connections 
to pin-connected trusses preferably shall be above the 
bottom-chord pins, but, if located below, the vertical 
posts shall be extended below the pins to secure rigid 
connections to the floor beams. 
Except in skew bridges end floor beams shall be pro- 53. End floor 
vided on all truss and girder spans. End floor beams ^^™ ' 
preferably shall be designed to permit the use of jacks for 
the future lifting of the superstructure, under which 
condition the specified unit stresses shall not be exceeded 
by more than 50 per cent. 
End floor beams shall be arranged to permit future 
painting of the sides of the beams adjacent to the abut- 
ment back walls. 
Steel stringers preferably shall be riveted between the 54. stringers. 
floor beams, ^\dtn end connections to the floor beam 
webs. 
Wlien end floor beams are not used the end panel ^s. End struts. 
stringers shall be secured in correct locations by end 
struts securely connected to the stringers and to the 
main trusses or girders. The end panel lateral bracing 
shall be rigidly attached to the main trusses or girders 
and shall also be attached to the end struts. Adequate 
provision shall be made for the expansion movement of 
stringers. 
The end connection angles of floor beams and stringers se. End con- 
shall not be less than ^ inch in thickness. When miUed CeSSTnd string- 
ends are required, the thickness of connection angles ^'^^• 
shall be yb" inch greater than for connection angles not 
required to be milled. Except in cases of special end 
floor beam details, end connections for floor beams and 
stringers shall be made with two angles at each end. 
Bracket or shelf angles which may be used to furnish 
support during erection shall not be considered in deter- 
mining the number of rivets required to transmit end 
shears. 
End connection angles shall develop the full depth of 
the webs by having a length as great as the flanges \vill • 
permit. 
In tbe preparation of end connection details special 
care shall be exercised to provide ample clearance for the 
driving of field connection rivets. 
The use of any kind of floor-beam hanger which does 
not prevent all rotation or longitudinal motion of the 
floor beam, will not be permitted. 
