Types of Spans 



Materials 

 Used 



Clearance 



Deck Spans 

 on Curves 



Spacing of 

 Trusses 

 or Girders 



Skew Ends 



in any of these after tenders have been submitted, will be paid to the Contractor by the 

 Railway Company and viceStersa any decreases in payments for any of these items are 

 to be allowed the Railway Company by the Contractor. 



GENERAL FEATURES 



13. Different types of Spans will be referred to by descriptions and abbreviations 

 as shown in Appendix II. 



14. The Bridge shall be constructed wholly of "Structural Steel for Bridges," 

 except in pier members or where otherwise specified. All materials shall be in accord- 

 ance with the Specifications given in the Appendices relating thereto. 



15. Single track through bridges on tangent track shall have a clear opening not 

 less than that shown in Appendix III. Where track alignment is curved, additional 

 lateral clearance shall be provided to give the same minimum clearance for a car 85 feet 

 long, 14 feet high (above base of rail) and 60 feet centre to centre of trucks, allowance 

 being made for curvature and superelevation in track. 



16. For through bridges carrying two or more tracks on any span, the lateral clear- 

 ance between the centre line of track and the adjacent truss or girder shall be as speci- 

 fied above for single track bridges. 



17A. The distance centre to centre of tracks where there is more than one track, 

 and also the amount of superelevation on the outer rail on curved track, shall be as 

 shown on the Railway Company's drawings. 



17B. Deck Spans on curves shall be set so that at the centre of span the centre 

 line of track is to one side of the centre line of span, one-third of the middle ordinate 

 and at either end of span the centre line of track is to the other side of the centre line of 

 span, two-thirds of the middle ordinate. Deck plate girder spans on curves shall usually 

 be tilted the required amount to take up the full amount of the superelevation in the 

 track. 



18. The distance, centre to centre of trusses or main girders, shall be not less than 

 1/15 of the effective span, and not less than is necessary to prevent overturning under 

 the specified lateral forces. 



19. At the abutment ends of all skew spans the ends of track stringers or girders 

 carrying deck ties shall be square to the track unless a continuous ballasted deck is to 

 be used. 



DECKS 

 Type of Deck 20A. The type of deck shall be as shown on the Railway Company's drawings. 



Timber Decks 21A. Deck ties, preferably not less than 13 feet long, shall be proportioned to carry 



the maximum axle load specified with full impact, distributed over 3 feet of track. 



21B. Details of tie spacing, tie dapping, guard timbers, guard rails, and deck fast- 

 enings, shall be in accordance with the Railway Company's Standard Drawings. 



22. Timber unless otherwise specified shall be Douglas fir, White, Red, or Southern 

 long-leaf pine, and shall be of the grade known as "Merchantable." 



Solid Decks 23. Transverse beams for supporting ballasted decks shall be proportioned for the 



maximum axle load with full impact, distributed longitudinally over 3 feet, or a distance 

 equal to twice the depth from base of rail to top of transverse beams, whichever dimen- 

 sion is the greater, and distributed transversely over 10 feet. 



Floor Iron 24. Unless otherwise specified by the Engineer, hook bolts, guard timber bolts and 



other floor iron shall be supplied by the Contractor and will be paid for at the same rate 

 as for steel in the structure. 



