Steel Bridges: Thru Plate Girders - National Model Railroad ...

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© NATIONAL MODEL RAILROAD ASSOCIATION
DATA SHEET
Sheet#:
Title:
Reformated:
Page:
D6c.5
STEEL BRIDGES:
THRU PLATE GIRDERS
October 1999
DATA SHEET
1 of 3
deck plate girder bridge.Such conditions are common in model railroad construction.Thru plate
girder bridges are not as economical as deck plate girder bridges because they require a full
door system (See Data Sheet D6c.2).In multi-track spans,two girders for each track are the
most economical.Generally there is not sufficient clearance between tracks to permit two
girders,hence one heavier girder may be used in the center or in the case of double track
bridges,two outside girders only may be used.In this case,floor beams must be heavier and
only one kind of girder is required.
-- For single track spans,they are approximately the size of deck plate girders
which carry the same load.See Data Sheet D6c.4 for details and typical dimensions.For
double track spans,see the back of this sheet.
-- Clearance between top flanges of the girders should be at least that called for
on NMRA Standards Sheet S8.Spans of moderate length can be used on curved track,but
clearance between flanges of girders should be at least the minimum track center distance for
the curve as given on S8 plus the offset of the curve at the center of the span.
-- consists of the floor beams,one being located at each panel point (See Data Sheet
D6c.2) and a bottom double intersection systemof diagonal angles rigidly connected to the
bottomof stringers at points of intersection.An end floor beam is required or at least a deep
frame.The diagonal angles may be omitted if a solid steel or concrete floor is used which should
be tight against the girders to take the lateral stresses.Top flanges of girders should be stiffened
by knee angles at each floor beam or spaced not over 12'apart in the case of solid floors.
Vertical stiffener angles in pairs,one on each side of the web,are placed about 5'apart·
along the span between the floor beams,dividing each panel into 2 or more parts.Two or more
pairs are used over the bearing plates at the ends,particularly on long spans.At the panel
working points where the floor beams frame into the girders,use one angle on the outside and
two angles on the inside to make connections with the floor beams and knee braces.
-- See Data Sheet D6c.2 for full details.
The dimensions given in the table on the next page are for double track spans having two
outside girders only.In model work if a center girder is desired,it is suggested that one foot be
deducted fromthe depth of the girders listed below for the two outside girders and make the
center girder the full height as given below.Also,if a center girder is used,the depth of the floor
beams would be the same as for a single track bridge.Girder dimensions for single track spans
are approximately the size of those for deck girder bridges which carry the same load and are
given on Data Sheet D6c.4.Bottomlateral bracing angles in all cases are of size given in the
table on page 2.Floor systemdimensions are not repeated on this page as they depend upon
the panel length -- see Data Sheet D6c.2.for details
Size of Girders
Lateral Spacing
Bracing
Floor Systems
TYPICAL DIMENSIONS
Originally
Compiled by:Wells,Ravenscroft
First Issued:
April 1952 (Dc3.4)
GENERAL
Length of Span,Length -- 15 to 120 ft.
Thru plate girder bridges are used when the desired
clearance under the track does not permit the use of a
© NATIONAL MODEL RAILROAD ASSOCIATION
DATA SHEET
Sheet#:
Title:
Page:
D6c.5
STEEL BRIDGES:
THRU PLATE GIRDERS
DATA SHEET
2 of 3
LENGTH
OF SPAN
TYPICAL DIMENSIONS
© NATIONAL MODEL RAILROAD ASSOCIATION
DATA SHEET
Sheet#:
Title:
Page:
D6c.5
STEEL BRIDGES:
THRU PLATE GIRDERS
DATA SHEET
3 of 3
SINGLE TRACK,75'SPAN
DOUBLE TRACK THRU
PLATE GIRDER BRIDGE
116'SCEWED SPAN