4 oTES ON PLATE-GIRDER Dl 



function of the depth, loading, unit stresses, and many 

 other things. 



PKnr.i.i MS 



la. Skrtrh the rroas-ection of a platr pinl.-r wit!) :m<l without 

 and write the name of each i-.-u-t <.;, th, -k.-trhes. 



1 Sk.-t.-h the plan of single-track railroad <!<. k pl.-itr 

 and write the names of the various parts on the sketc -h. 



1 Skrtrh the plan of single-track railroad through pl.-it.- irinlrr 

 bridge, and write the names of the various parts in the sketch. 



ART. 2. REQUIRED AREA OF CROSS SECTION FOR THE 



FLANGES 



The plate girder is a built-up structure, and may be made 

 with a variety of cross-sect ion- depending on the require- 

 ments of the case. The forms of cross-section im.M fre- 

 quently used are those of a, 6 and c of Fig. '2. 



M Pfah 



a 5 



TIG. 2. 



The object of these forms being to take advantage of 

 the known law of stress distribution in flexure. 



The relation between the moment of the outer forces 

 and inner stresses for homogeneous bodies subject to flexure 

 is given from the formula 



