[Steel-Treadway Bridge M2]
[From the U.S. Government Publishing Office, www.gpo.gov]

Ill DEPARTMENT TECHNICAL MANUAL
NON-CIRCULATING
STEEL-TREADWAY
4
BRIDGE M2
WAR DEPARTMENT
9 MAY 1944


Document Reserve
NTSU LIBRARY
I
WAR DEPARTMENT	TECHNICAL	MANUAL
T M 5-272
This manual supersedes TM 5-272, 10 July 1942, and TB 5-272-1, 26 January 1944
STEEL-TREADWAY
BRIDGE M2
WAR DEPARTMENT •	9 MAY 19 44
United States Government Printing Office Washington : 1944
WAR DEPARTMENT, Washington 25, D. C., 9 May 1944.
TM 5-272, Steel-Treadway Bridge M2, is published for the information and guidance of all concerned.
[A. G. 300.7 (27 Mar 44).]
By order of the Secretary of War:
G. C. MARSHALL,
Chief of Staff. Official:
J. A. ULIO,
Major General,
The Adjutant General.
Distribution:
As prescribed in paragraph 9a, FM 21-6; Armies (10) ; Corps (10) ; D 17 (10) ; R 17 (15) Bn 17 (15) ; I Bn 5 (15) ; AAF Schs (10) ; Engr RTC (100) ; Engr Unit Tng Cen (100) ; Com Z (Engr Hq) (10) ; Com Z Sections (Engr Hq) (10).
IBn 5: T/O 5-215, Armored Engr Bn.
For explanation of symbols see FM 21-6.
II
CONTENTS
Paragraph Page
SECTION I.	GENERAL.
Purpose__________________________________________ 1	1
Design___________________________________________ 2	1
Capacity_________________________________________ 3	5
Size of working party required___________________ 4	5
Estimated times for construction_._______________ 5	5
Composition and assignment of equipment__________ 6	5
SECTION IL	DESCRIPTION AND USE OF EQUIPMENT.
Pneumatic float__________________________________ 7	8
Saddle___________________________________________ 8	9
Steel treadway_________________________________   9	11
Treadway-connecting pin_______________________   10	11
Treadway-spacing hook--------------------------- 11	15
Treadway wedges________________________________  12	15
Anchors_________________________________________ 13	15
Trestle_________________________________________ 14	15
Trestle-bracing equipment_______________________ 15	16
Treadway adaptor________________________________ 16	17
Outboard motor and motor bracket________________ 17	17
Tools and accessories___________________________ 18	17
Portable air compressor_________________________ 19	17
Motorized air compressor________________________ 20	19
Truck crane_____________________________________ 21	19
Power utility boat______________________________ 22	19
Blackout markers________________________________ 23	21
SECTION III.	TRANSPORTATION.
General_________________________________________ 24	24
Treadway truck__________________________________ 25	24
Contents of truck loads_________________________ 26	25
Operation of treadway truck_____________________ 27	26
SECTION IV.	SELECTION AND PREPARATION OF BRIDGE SITES.
Reconnaissance__________________________________ 28	30
Site requirements_______________________________ 29	30
Preparation of site_____________________________ 30	30
Lay-out of site_________________________________ 31	30
SECTION V.	WORKING PARTY.
Organization of working party------------------- 32	34
Duties of construction details__________________ 33	34
in
Paragraph Page
SECTION VI. CONSTRUCTION.
Methods of construction_________________________ 34	42
Advantages of different methods of construction_	35	42
Anchorage of bridge_____________________________ 36	43
Shore connections_______________________________ 37	47
Alinement of bridge_____________________________ 38	54
Dismantling bridge______________________________ 39	54
Use of trestle equipment________________________ 40	54
Expedient use of equipment______________________ 41	54
Use of drawspan_________________________________ 42	56
SECTION VII. RAFTS.
Ferry set_______________________________________ 43	57
Construction of rafts__.________________________	44	57
Capacity---------------------------------------- 45	58
Ferry sites ____________________________________ 46	60
Ferry party------------,------------------------	47	60
Rigging arrangement----------------------------- 48	61
Loading and unloading rafts_____________________ 49	61
Methods of propulsion___________________________ 50	61
SECTION VIII. TRAFFIC CONTROL AND MAINTENANCE OF BRIDGE.
Bridge guard------------------------------------ 51	64
Traffic control--------------------------------- 52	64
Traffic capacity________________________________ 53	64
Maintenance of bridge___________________________ 54	64
Blackout delineation____________________________ 55	65
Protection against air attack___________________ 56	65
Protection against debris_______________________ 57	68
Precautions during floods_______________________ 58	68
Maintenance of equipage_________________________ 59	68
IV
(This manual supersedes TM 5-272, 10 July 191,2; and TB 5-272-1, 26 January 191,1,.)
SECTION I
GENERAL
1. PURPOSE. This manual describes the steel-treadway bridge M2 (fig. 1) which furnishes a rapid means of stream crossing for medium tanks and other heavy vehicles.
Figure 1. Tanks crossing steel-treadway floating bridge M2.
2. DESIGN. The treadway bridge can be built of floating spans, fixed spans, or a combination of both.
a.	Floating bridge (fig. 2). (1) The roadway of the bridge consists of two tracks of continuous-beam-action steel treadways formed of 12-foot lengths connected rigidly at each joint by two treadway pins. The treadways are supported by pneumatic pontons spaced 12 feet center to center, lhe pontons consist of saddles carried upon pneumatic floats. Shore connections are made by resting the end treadways upon abutment sills on the banks or by using one or more trestle spans.
(2)	The type shore connections used depends upon how close to the banks the shoreward pontons can be placed, the slope of the banks, and the bearing quality of the soil close to the water’s edge. Trestles require firm foundations and take considerable time to erect and should be used only when shore supports for the end treadways cannot be employed.
b.	Fixed bridges (fig. 3). Short-span fixed bridges employing one or two lengths of treadway for each track and supported on abutments can be built without intermediate supports. Bridges employing three or more
1
2
BLUNT-END TREADWAY WEDGE	TREADWAY	HOOK-END TREADWAY WEDGE '
/ \ \
| I
_ o o_____
? < Q_ ui
/	I	tLtVAIIUN I
.	FLOAT ROPE GIRDLE	TREADWAY-CONNECTING PINS
ABUTMENT	\	\	ABUTMENT
SILL	\ ROPE HALTER TREADWAY	SADDLE TREADWAY-SPACING HOOK	SILL
I	\ V \	/	\	i ____
APPROACH TREADWAY
I
PLAN Figure 2. Steel-treadway floating bridge M2.
- 12-0"—
-3-9'1*
ELEVATION Figure 3. Steel-treadway fixed bridge M2.
TRESTLE SHOE7
/ TRESTLE TRANSOM' APPROACH TREADWAY
HOOK-END TREADWAY WEDGE \
PLAN
TRESTLE COLUMN	/TRESTLE - BRACING	TREADWAY-CONNECTING	BRACING STRUT
\	/ CLAMP	PINS.	XU /
BLUNT-END	KC.
TREADWAY WEDGE	H STEEL TREADWAY /	\
BRACING STRUT	HOLDFAST^”
III) X	TREADWAY-SPACING
-a'*	X	unnkQ	^======s^.
\ \ STRUT SHOE \
APPROACH TREADWAY
3
/STRUT SHOE	TRESTLE TRANSOM	- IN. CABLE TO TRESTLE SHOE
^^===^1111 X	/ /TREADWAY ADAPTER	/
VEHICLE	WEIGHT CLASS - TONS	STEEL TREADWAY BRIDGE M-2										
		FLOATING (2)						FIXED				
		CAPACITY IN TONS POSTED ON BRIDGE										
		40		46	46			18	35	46	60	
		MAXIMUM STREAM VELOCITY IN FEET PER SECOND						MAXIMUM SPAN IN FEET				
		7		5	3			40	26	23	18	
Truck, 2'/2-T, w/8-T tlr. Truck, 4-T, cargo (same as distributor, water) Truck, 4-T, ponton Truck, 4-T, w/155-mm How., carr., Ml Crane, trk.-mtd. (Engr.) Crane, trk.-mtd., w/crane attachments tlr. Tank, light, M2A4 Truck, 4-T, cargo, w/8-T tlr. Truck, wrecking, C-l (AC) Tank, light, M3 Truck, 6-T, cargo Truck, 6-T, bridge Truck, 6-T, w/90-mm AA gun, Ml Truck, 6-T, w/3-in. AA gun, M2A2 Truck, 6-T, w/distributor, bituminous, 1,250-gal. Tank, light, M5 Tractor, D-7, w/dozer Motor carriage, M8 Tractor-trk, 6-T, w/semi-tlr., wrecking, C2 Truck, 7'/i-T, cargo & prime mover Tank, light, 18-T	17 13 13 16 12 15 12 20 16 14 18 19 23 22 23 16 15 16 26 21 18					1							
						Date; 1 Jan. 1944 Vehicle ratings based on 4-inch minimum freeboard at upstream end of float; 45,000 P.S.I. maximum stress for steel in bending.						
												
							LEGEND |	| SAFE m UNSAFE W/=WITH					
												
Tank, medium, M2A1	21											
Tractor-trk, 7’/2-T w/semi-tlr., fuel service, F-l (AC)	26											
Truck, 6-T, w/16-T tlr.	31											
Truck, 7'/2-T, w/155-mm gun, carr., M2 & M3 Truck, 7'/2-T, w/8-in. gun, carr., M2, transporter, Ml		28 34											
Truck, 6-T, w/20-T tlr. Tractor-trk, 5 to 6-T, w/20-T semi-tlr. Truck, 7'/2-T, w/20-T tlr.	37 32 39											
Motor carriage, M7 Tractor, D-8 w/dozer Motor carriage, Ml 2 Motor carriage, MIO Tank, medium, M3 Tank, medium. M4	24 22 27 29 33							1				
Tank, assault. T-l 4	46											
Tank, heavy, M6	60											
NOTES
(T) Unable to pass because of gap between treadways.
(5) Normal construction, with one pair of treadways per float.
(3) Vehicle on centerline of deck. Maximum speed—3 M.P.H.
Table I. Capacity of steel-treadway floating and fixed bridges
4
lengths of treadway for each track require trestles as intermediate supports to carry heavier loads.
3.	CAPACITY. a. Table I gives the posted and vehicle capacities of the steel-treadway floating and fixed bridges M2.
b. Multi-wheel trailers can cross the M2 bridge, provided their weight class does not exceed the posted capacity of the bridge and timbers are placed on the treadway-spacing hooks between the treadways. Two 4- by 12-inch timbers, 14 feet or greater in length, placed side by side, give a 24-inch roadway between treadways. The timbers are connected end to end by nailing 2- by 6-inch by 6-foot timbers over the joints.
4.	SIZE OF WORKING PARTY REQUIRED. The steel treadway bridge normally is constructed by a company of armored engineers using the equipment of and assisted by the treadway bridge company. See paragraph 32 for organization of working party.
5.	ESTIMATED TIMES FOR CONSTRUCTION. Table II gives estimated times for construction of various lengths of steel-treadway floating bridges.
Table II. Estimated times for construction of steel-treadway floating bridges
Length of bridge (in feet)	Number of floats	Construction time (in hours)	
		Daylight	Blackout
216		18	2	3
432	•		36	3	4^
648		54	4	6
864		72	5	71/ ‘ /2
The above estimates for daylight construction assume 45 minutes for initial adjustments, 3 minutes per float, and 20 minutes for final adjustments. They do not provide for work on approaches other than that done by abutment details simultaneously with bridge construction or for preliminary clearing which may be necessary at construction sites.
6.	COMPOSITION AND ASSIGNMENT OF EQUIPMENT, a. Bridge set. One unit of steel-treadway bridge equipage provides 864 feet of floating bridge. The bridge can be built to this length entirely by floating spans or by a combination of fixed and floating spans. When fixed spans are used exclusively the maximum length depends upon the spans of the 24 available trestles (see table I). Table III gives the component parts of the steel-treadway bridge set.
b. Basis of issue. One unit of steel-treadway bridge is issued per engineer treadway bridge company.
583586°—44---2
5
Table III. M2 steel-treadway floating bridge set
Item
Quantity
Adaptor, treadway, steel........................................
Anchor, kedge, 100-lb...........................................
Bag, canvas, paddle, 9-paddle-capacity..........................
Binder, load, lever-type, heavy-duty............................
Block, snatch, steel-shell, iron-sheave, graphite-bronze-bushed, for manila rope:
%-in. rope, 6-in. shell....................................
%-in. rope, 7-in. shell....................................
Box, sign, interior-illuminated, electric, 4- by 15-in., message. . Bracket, stern-attachment, 22-hp outboard-motor, pneumaticfloat, 18-ton, Ml...............................................
Bracket, auxiliary trestle, 25-ton..............................
Chain, log, w/hook and ring, %-in. by 10-ft.....................
Clamp, column-bracing (trestle-bracing), 25-ton.................
Clip, wire-rope, steel, galvanized:
%-in.......................................................
%-in......................................................
Float, pneumatic, with emergency kit, 18-ton, w/carrying case, Ml.........................................................
Grip, cable, %-in., wire-rope...................................
Hammer, machinists, ball-pein, type L, class 1, handled, 1%-lb. Hoist, chain, ratchet, 1%- to 3-ton, 2 hoists w/spares per chest.......................................................sets. .
Holdfast, complete w/9 pickets..................................
Hook, boat, ball point, 10-ft...................................
Hook, treadway-spacing..........................................
Hose, pneumatic, braided, w/couplings, %-in.-dia., 50-ft........
Lamp, electric, debris patrol and rescue boat...................
Lantern, electric, portable, hand, dry-cell, 6-volt.............
Marker, luminous (radioactive), type II, 1%-in., bolt-back. . . . Paddle, boat, single-blade, 5-ft., single.......................
Picket, steel, 1%-in. by 3-ft...................................
Pin, lifting, trestle, 25-ton...................................
Pin, treadway, steel............................................
Pin assembly, strut-shoe, complete..............................
Rope, manila, 3-strand: %-in.......................................................feet.	.
%-in..................................................feet.	.
1-in..................................................feet.	.
Rope, wire, steel-cast, galvanized, fiber-core, regular-lay:
6 by 19	stranding	%-in.	rope........................feet.	.
6 by 19	stranding	%-in.	rope........................feet.	.
Saddle, steel-treadway, knockdown, Ml (pneumatic float, 18-ton, Ml).........................................................
Shoe, bracing-strut.............................................
Sledge, blacksmith’s, double-faced, class II, handled, 12-lb. . . . Snap, harness, round-eye, %-in., rubber-finish..................
Strut, bracing (trestle-bracing), pipe, standard-black, 2 %-in.
by 22-ft......................................................
24
80
16
36
8
8
8
8
12
72
20
360
160
98
32
24
20
12
36
144
20
3
3
240
144
144
24
72
8
2.800
8,400
14,400
3,000
2,000
72
8
12
300
8
6
Table 111. M2 steel-treadway floating bridge set—Continued
Item
Quantity
Tool, aligning, treadway....................................
Treadway, steel, complete with 2 pins, w/I-beam lok open type flooring, Ml, 45%-in., 12-ft...........................
Trestle, complete wo/hoist, steel, 2 5-ton..................
Wedge, treadway: Blunt-end...................................................
Hook-end................................................
Wrench, adjustable, crescent type, single-end, 1%-in. jaw opening 10 in. long.........................................
8
144
24
8
8
36
7
SECTION II
DESCRIPTION AND USE OF EQUIPMENT
7. PNEUMATIC FLOAT, a. The 18-ton pneumatic float (fig. 4) is 8 feet 3 inches wide, 33 feet long, and 33 inches deep. It is made of rubberized canvas tubing and consists of an outer tube, a floor, and a removable center tube. Each tube is 33 inches in diameter. The float weighs approximately 975 pounds and has a maximum displacement of 35,500 pounds when the voids between the center and outer tubes are filled with water. Deflated, it is rolled and packed in a carrying case 4 feet long and 3 feet 9 inches in diameter. Included in each case is an emergency repair kit.
Figure 4. Eighteen-ton pneumatic float. {Length, 33 feet; diameter of tubing, 33 inches.)
b. The ends of the float are turned up to lessen the effect of currents pushing against it. D-rings (fig. 4) attached to the outside of the float support the rope girdle running completely around it. At each end a rope halter for anchoring the float (fig. 5) is spliced to the girdle. Straps attached to D-rings on the outer side of the outer tube fasten the saddle to the float. Straps attached to D-rings on the inner side of the outer tube hold the center tube in place. The removable center tube adds rigidity and buoyancy to the float when it is submerged.
c. Bulkheads divide the outer tube into 12 and the center tube into four
8
INFLATION VALVES
— ROPE GIRDLE
•-- ROPE HALTER
air compartments, each having a separate inflation valve. Using two four-hose manifolds and the 105-cfm motorized air compressor, the float can be inflated in about 5 minutes. The air pressure in the float should be maintained at 2 psi, at which pressure the air chambers are firm but yield to pressure applied by the heel of the hand. Additional pressure adds nothing to buoyancy and damages the float. Changes in temperature should be anticipated. To maintain proper pressure air must be released as the temperature rises or added as the temperature drops. Air pressure should be checked regularly. Deflate floats by removing valve caps and allowing air to escape. Draw out the remaining air with the inflation-deflation manifold to make the float easier to pack in small space.
Figure 5. Bottom of pneumatic float.
8. SADDLE, a. The load on the bridge and the weight of the treadways are transmitted to the floats by a knockdown saddle (figs. 6 and 7(7)) which consists of two saddle beams surmounting eight bearing plates. The beams transmit the load to the float through the bearing plates. The completed saddle assembly weighs 2,200 pounds.
b. There are six interior bearing plates (fig. 7@) and two end ones (fig. 7@). They are constructed of %-inch plywood. Each plate can be carried by two men.
c. Each saddle beam (fig. 7@) consists of two 6-inch wide flange steel beams, weighing 15.5 pounds per linear foot, joined together at the center
9
ROPE HALTER SPLICED TO ROPE GIRDLE
THIMBU —
of the float by engaging with a pin the female end of one section with the male end of another to form a hinged joint. The hinge action of the beam under load is limited by a butt joint on the upper part of the connection. Hinged to the outer end of each beam are two 3-inch channels which transmit the load through the end bearing plates to the upturned ends of the floats. When the saddle is assembled, a removable pin hinges the channels to the web of the wide-flange beams; when knocked down, the pin is removed and the channels are retracted to fit between the flanges on each side of the web.
d. The saddle beams are held in place on the saddle by a sliding clip (figs. 7@ and 8). One section of the clip is attached rigidly to the bearing plate; the other section is movable. To assemble, the movable section of each clip is driven open, the saddle beam is set in place against the fixed section, all bearing plates are oriented alike, and the movable section of each clip is driven home with a hammer. To disassemble it, the movable sections are driven away from the beam.
e. Another method employed to hold the saddle beams in place is by a spring-actuated catch. The catches are located on the bearing plates approximately in the same place as the sliding clips. The catches are provided with a handle for manual operation. To assemble the complete saddle the catches are opened manually, the saddle beam is set in place between the spacer lugs, and the catch allowed to close under the compression of the spring. To dismantle, the catches are opened manually and the beams are removed.
Figure 6. Saddle on pneumatic float.
10
INTERIOR BEARING PLATE
- TREADWAY RETAINER
END BEARING PLATE
f. On top of the saddle beams are treadway retainers (figs. 7@ and 13) which hold the treadways in place. In assembly these retainers are driven over the lower flange of the treadway and pinned into place (fig. 8). There are four treadway retainers on each side of the middle of the saddle beam. To secure the treadways alternate treadway retainers are used beginning with the one on the downstream end of the saddle beam (fig. 10). The treadway retainers are placed so the treadways in position are offset 6 inches downstream on the pontons. They are locked in place with a safetypin.
9.	STEEL TREADWAY, a. The roadway of the bridge consists of parallel treadways. The narrowest vehicle the bridge will accommodate is the %-ton, 4x4 truck. The treadways will accommodate a vehicle 124 inches wide (outside clearance of tires or tracks), allowing 3 inches clearance at each curb.
b.	The steel treadway (fig. 9) weighs 2,350 pounds and has an effective length of 12 feet and a clear track width of 45% inches. It consists of two parallel steel channel beams tied together laterally by I-beams, channels, and pipe sleeves. It has a road surface of I-beam-lok flooring. At one end the main channels are blunt; at the other end, integral tapered engaging plates with hook ends provide an interlocking connection with the adjacent treadway. At the blunt end are two pipe sleeves running through holes in the webs of the treadway channels; at the hook end there is one hole and a notch in the engaging plates. Two treadway-connecting pins connect the blunt end of one treadway rigidly to the hook end of another treadway to form a continuous beam. Connection is made by inserting one treadway-connecting pin through the inner pipe sleeve in the blunt end of one treadway and the notches in the hook end of the other; the second pin is inserted through the outer pipe sleeve in the blunt end and the holes in the hook end.
c.	A drill-rod curb (fig. 9) of 1%-inch diameter steel is welded to the inner edges of the top flanges of the main channels to prevent tracked vehicles climbing out of the roadway. Three U-shaped eyes are welded to the outside of each main channel. The outer eyes are for the treadway-spacing hooks which space parallel treadways laterally; the middle eye is at the balance point and is used in handling the treadway when loading or unloading it from a truck. Directly above the middle eye a pear-shaped lifting hook hole is cut into the main channels. This accommodates the hook of the treadway-lifting chain of the treadway truck.
d.	The treadways are so placed across the saddles on the floats (fig. 10) that their flanges are engaged by the treadway retainers on the saddle beams.
10.	TREADWAY-CONNECTING PIN. Treadway-connecting pins are used to connect treadways longitudinally and to connect wedges at the ends of the bridge. The treadway-connecting pin (fig. 9) is 2% inches in diameter, 4 feet 6% inches long, and weighs 65 pounds. It has a handle at the blunt end and a hole at the tapered end to accommodate a safetypin (fig. 9).
11
nWn	n H n ~FPl f n	n H n	n 1 6n
Figure 7. Knockdown saddle.
---------------------------	BOTTOM VIEW
(3) END BEARING PLATE	@ INTERIOR BEARING PLATE	@ CENTER CONNECTION
SADDLE-RFAMS
SECTI^^-^^ Pl N
°	I butU^topvS^
jB , Z-p	■ xx_,	j o i nt'"-*_
/	(2) ELEVATION-ASSEMBLED SADDLE /	\
SADDLE	/	\	FEMALE^
\ \ / \ ■/////,
H^~1TJTD • UJ l^u	LI J 
\ J /	/
SADDLE \	/	/
BEAM .	‘	/
/	SPACING-HOOK
<>P^	/	EYE
:	X^X	TREADWAY
P	''P-'?x-.' Pp;,py/ x' X	RETAINER
*S<	x'	x' x^X TREADWAY-
P.	V\p xx X^	XZ XXX	RETAINER
P.	\ Ps=P s	P'^PP*'" STOP
^ARING^^^EAmNG- ------
PLATES	PLATE	P/ xX \
STIFFENER	\	SADDLE
CLIP
Figure 8. Assembly of treadways on saddle.
x-^	r^1-1-'—n ,.
X 3“	1 dia.x	—T
I P 6*	*1 A	TREADWAY-SPACING HOOK
I i C~^2r6)	SAFETYPIN H--------- 4-65"------«H
\	F /	hole '■'<	L
\ (ENLARGED) /	2|"D|a/
' •	TREADWAY-CONNECTING PIN
-___LIFTING-HOOK HOLE
CONNECTING-PIN	'r
HOLES	''z=,
LL R0D CURB
SPACING-HOOK |'"'\	IZ
l._______451"_____h	EYES I \	C
2	LIFTING-HOOK	? - JJ
Ot	»O--r	EYE
....................... I
11'111-14-4 15"	I
I	CONNECTING-PIN
_J	  1	hole
CROSS SECTION
Figure 9. Steel treadway, with treadway-spacing hook, treadway-connecting pin, and sajetypin.
583580°- -44- —3
13
TREADWAY
TDPAnu/Av	OFFSET DOWNSTREAM
SADDLE BEAM	TREADWAY	TREADWAY	e. _.T
\	\	6"—/	FLOAT
\	TREADWAY \	CENTER LINE j j CENTER LINE	/	/
\	RETAINERS \	0F	i between	/	/
end	\	AlNtKS \	FLOAT I TREADWAYS	/	INTERIOR	/
BEARING	\	\\	\	I ।	/	BEARING	/
PLATE	\	•><	/	PLATE	/
\	\	\\	\ h*--45x"-*+<—3'-3>!->+*-45-5-*H /	/	/
\ \ \vT ~Ti L..J/ /	/
\	\________X^X^ fe&FFFFR■ JT=I=I=FI=HE1	/	/
. p ifX- p P
"P's.	<7 J ~
/ -*-----------< -------------------- 33-0" ----———^-----------------------
or\oc rioni c	CUR RENT.	/	\
ROPE GIRDLE	X.	------/	R0PE HALTER
HALTER SPLICED TO GIRDLE '
Figure 10. Steel treadways in position on pneumatic ponton.
14
11.	TREADWAY-SPACING HOOK. The treadway-spacing hook (fig. 9) keeps treadways spaced parallel. It is a 1-inch diameter steel bar, 3 feet 1% inches long, with a 4-inch bend at each end, and it weighs 10 pounds. It is fitted into spacer eyes welded to the web of the treadway channel beam and when in place fixes the distance between the inside faces of the inner curbs at 3 feet 3 inches (fig. 10).
12.	TREADWAY WEDGES. Treadway wedges are used on the ends of the steel-treadway bridge to facilitate the movement of vehicles on and off it. The wedges are of two types. Hook-end wedges (fig. 11®) are connected at the engaging-plate end of the treadway. This wedge has the same type of wearing surface as the treadway itself. Blunt-end wedges (fig. 11®) are connected at the blunt end of the treadway. This type wedge has a steelplate deck. The hook-end wedge has one hole in its sides for one treadwayconnecting pin and the blunt-end wedge has two holes for two pins.
® Blunt-end wedge.	® Hook-end wedge.
Figure 11. Treadway wedges.
13.	ANCHORS. The bridge has 100-pound kedge anchors to secure it against currents and wind. Two hundred feet of 1-inch manila rope is provided for each anchor.
14.	TRESTLE. The trestle of the steel-treadway bridge equipment (fig. 12) is the same as that of the heavy ponton bridge. It consists of a transom, two columns, and two trestle-column shoes.
a. Transom. The transom consists of a tubular-steel truss section. Each end of the transom is open so the trestle column can be inserted from the side. Two metal clamps hold together the jaws of this opening. At the ends of each transom are three sets of pinholes. Two pins on chains are at-
15
tached to each end of the transom. The lower end of the ratchet chain hoist is attached to one pin inserted in the outermost set of pinholes. The second pin is inserted through one or the other of the remaining sets of holes and through one of the holes in the trestle column, securing the trestles to the column.
b. Columns. The column is a steel tube 5 inches in diameter with a vertical row of holes throughout its length. It has a chain-hoist supporting bracket to support the upper end of the chain hoist when the hoist is used to adjust the transom. The bracket can be attached to the column at any convenient height by an inserted pin attached to the bracket with a chain.
Figure 12. Assembled trestle.
c. Shoes. The trestle-column shoes, 30 inches square, are made of steel. The trestle column is fitted into a sleeve in the center.
d. Ratchet chain hoists. Two ratchet chain hoists of fi/2- to 3-ton capacity are used to adjust the height of the transom. The hoist has a 12-foot chain which can be attached so only a single strand takes the load, giving a capacity of iy> tons; or, it can be doubled so that two strands take the load, giving the 3-ton capacity, required when treadways are in place.
15. TRESTLE-BRACING EQUIPMENT. Trestle bracing is used to
16
RATCHET CHAIN HOIST -— (CONNECTS TO GIVE 3-TON CAPACITY)
-15'-6’ -
DETACHABLE CHAINHOIST SUPPORTING -BRACKET
NOTE:
CHAIN-HOIST SUPPORTING BRACKET CAN BE MOUNTED TO SUIT HEIGHT CONDITIONS
-5" TRESTLE COLUMN

\TRANSOM PINS
^■TRESTLE transom
TRESTLE ' COLUMN SHOE
increase the stability of trestle spans subjected to heavy traffic. The trestlebracing equipment is composed of the following parts:
Bracing struts.
Bracing-strut shoes.
Bracing-strut shoe pins.
Column-bracing clamps.
All of the above parts are described in C 1, TM 5—273.
16.	TREADWAY ADAPTOR. There is a treadway adaptor (fig. 13) for each trestle. It consists of a 5-inch channel on which the treadways bear. The under surface of this channel has four semicircular bent plates with protruding lips which are bent around the tube of the trestle transom by a hammer to secure it in place. The upper surface has six tread way retainers similar to those on the saddles; however, they are spaced so they will accommodate either the 45^/2-inch or the old type 33-inch width steel treadways.
17.	OUTBOARD MOTOR AND MOTOR BRACKET, a. The treadway bridge company has six 22-hp. outboard motors which can be used to propel either single pneumatic pontons or pneumatic ponton rafts.
b. Each bridge set has eight stern attachment brackets (fig. 14) for mounting an outboard motor on the pneumatic ponton. The bracket is fastened to the saddle and can be lifted so the motor clears the water when not in use.
18.	TOOLS AND ACCESSORIES. Each bridge set has the following tools and accessories:
a.	Heavy-duty load binders and log chains to add stability to truck loads in transit.
b.	Steel snatch blocks for miscellaneous rigging.
c.	Wire-rope clips for wire rope.
d.	Cable grips for handling wire rope.
e.	Holdfasts to anchor light loads.
f.	Manila rope, 1-inch for anchor lines, 3^-inch for bridle lines, and t^-inch for miscellaneous rigging. The 200-foot anchor lines and the 80-foot bridle lines with harness snap are made in the field.
g.	Wire rope and % inch in diameter for anchor cables and guy lines, h. Treadway alining tools for alining treadways.
i.	Adjustable crescent-type wrenches, sledges, and ball-pein hammers for miscellaneous use.
j.	Paddles and boat hooks for handling pneumatic pontons.
k.	Lamps and lanterns for night construction.
19.	PORTABLE AIR COMPRESSOR. Gasoline-engine-driven, port-
17
TREADWAYS IN PLACE ON TRESTLE
Figure 13. Treadway adaptor.
4.
RETAINFR TRranmv	TREADWAY RETAINERS	TREADWAY RETAINERS TREADWAY RETAINER ADAPTER
REJ™oER TREADWAY RETAINER	USED FOR 33-INCH—*-	USED FOR 45|-INCH—AND HOUSING	CHANNEL
STOP RETAINER HOUSING	TREADWAYS	TREADWAYS	\	/
/	. ',X-	fl /
7	(Yij ;	u u	'	7
{_______________ ]■	TRANSOM ADAPTER-ELEVATION	U
/	, /f ___________________________________________ k J
ADAPTER CHANNEL	-giir,,	o»!—-------Lio ----i'oi i--------'■! II ''"x?	U
I i.T^|-1 /	Lj----------LJ--------------
T X. y	SHAPE
-*--------------------12-10"-----------------»-	TO FIT PIPE
AT ASSEMBLY
SraTLARGEBo’>B	TRANSOM ADAPTER —PLAN	S(eJlarg*o)A
in	h—45f—*t-—±—“f—h	m
18
able air compressors (fig. 15) of 16-cfm capacity are issued to the treadway bridge company for use in maintaining proper air pressure in the pneumatic floats in a bridge. In an emergency these compressors can be used to inflate the floats during construction. However, their limited capacity makes inflation relatively slow.
20.	MOTORIZED AIR COMPRESSOR. Motorized air compressors (fig. 16) having a capacity of 105 cfm are issued to the treadway bridge company for inflating pneumatic pontons during the construction of a bridge. Using two four-hose manifolds this air compressor will inflate a float in about 5 minutes.
Figure 14. Outboard motor and bracket mounted on pneumatic ponton.
21.	TRUCK CRANE. The truck crane (fig. 17) which is issued to the treadway bridge company is mounted on a 6 x 6 truck. This crane formerly was mounted on a 4 x 4 truck. Both a truck driver and* a crane operator are essential, since one man cannot control both crane and truck. Treadways can be placed individually by the crane when necessary. However, the crane cannot handle the treadways in pairs as can the treadway truck (par. 27). The truck crane is useful when the bridge must be installed at a point where river banks are high and steep. Under such conditions pneumatic pontons are assembled on the bank and lowered into the water by crane.
22.	POWER UTILITY BOAT. The power utility boat (fig. 18) issued to the treadway bridge company, is used to push bridge parts from assembly sites to the bridge site, to push rafts, and for general utility work during bridge construction.
19
Figure 15. Portable air compressor.
Figure 16. Motorized air compressor.
20
a. Boat. The hull is made of molded plywood which is strong and light and without seams. It has a rope fender and a carrying rail. Equipment includes towing bits, bow and stern lights, a mounted searchlight, a fire extinguisher, anchors, life preservers, spare parts, and tools. It has the follow-
ing characteristics:
Length, over-all--------------------------------- 18 feet.
Width, maximum-----------------------------------6 feet	9 inches.
Depth, maximum-----------------------------------2 feet	6 inches.
Weight, including engine and accessories_________ 1,800 pounds.
Maximum allowable load___________________________ 4,000	pounds.
Figure 17. Truck crane.
b.	Engine. The boat is powered with a 57-hp. marine engine equipped with a governor that keeps it operating at a safe and economical speed and allows it to develop its full power for towing or pushing. It has the standard marine type propeller drive with forward, neutral, and reverse gears.
c.	Transportation. The boat is carried on a two-wheel pole type utility trailer, type IV, from which it can be launched directly into the water.
d.	Precautions. The following precautions must be observed in using the powerboat:
(1)	Care must be exercised in launching to avoid damaging the hull.
(2)	Shallow places and snags should be approached at slow speeds.
(3)	Avoid crossing anchor and guy lines and heavily weeded water areas because the propeller becomes entangled easily.
(4)	When passing over a line disengage the clutch, stop the propeller, and allow the boat to drift over the line.
23.	BLACKOUT MARKERS. Blackout markers are provided for delineating bridges during blackout. They may also be used advantageously for delineating location of stock piles and personnel. The following types are included in the bridge set:
583586°—44---4
21
a.	Radioactive luminous marker type II (fig. 19(T)). This is circular, l3/± inches in diameter. The front surface is luminous. The back surface has an integral bolt and nut for attachment.
b.	Interior-illuminated sign box (fig. 19(2)). This is rectangular, with a 4- by 15-inch front face hinged so paper signs may be readily inserted. It is illuminated by a battery, controlled by a pull-push switch on the front of the box. A folding shield is attached to the box.
22
SEARCH LIGHT
STERN LIGHT SOCKET
STERN TOW BITS
BILGE PUMP
• BOW TOW BIT
ROPE FENDER
HAND RAIL
AFT BUMPER -
STEERING LEVER
SPRAY RAIL
Figure 18. Power utility boat.
® Radioactive luminous marker type II.
© Interior illuminated sign box.
Figure 19. Blackout markers.
23
SECTION III
TRANSPORTATION
24.	GENERAL. The steel-treadway bridge equipment is transported in 36 treadway trucks and 14 2^/2-ton cargo trucks. Each treadway truck carries sufficient equipment for 24 feet of floating bridge. Spare parts and trestle equipment are carried in the 21%>-ton trucks.
25.	TREADWAY TRUCK, a. Truck and crane. The treadway truck (fig. 20) is a special 6-ton, 6x6 cargo truck with a crane operated by four hydraulic cylinders powered by the truck engine. The crane is
Figure 20. Treadway truck.
operated from a platform at the front of the cargo body. Two long upper cylinders control the boom of the crane and two short lower cylinders act as boosters when the boom is extended. The maximum capacity of the crane with all four cylinders operating is 8,000 pounds. The unit has a fairlead and a snatchblock at the rear so treadways may be lowered beyond the reach of the boom. The snatchblock is attached to the boom, and the winch cable mounted on the front of the truck is threaded back through the fairlead and snatchblock.
b. Treadway-handling chains. Each truck has a set of treadwayhandling chains (fig. 21) attached by stirrups to the boom of the hydraulic
24
crane. The two outer long chains are the sling chains. Each sling chain has a grab link and a grab hook, the use of which permits the chain to be adjusted to any desired length. Treadway slings, used to handle treadways except during loading or unloading from the truck, are linked to the grab link on each sling chain. A pair of treadway hooks is attached to the ends of the treadway slings. The treadway hooks fit over the flanges and the drill-rod curbs of treadways, or through the lifting holes in the sides of the treadways. A cross chain is linked between the sling chains. Suspended from the cross chain are two pairs of treadway hoisting hooks; the outside pair is on seven-link chains and the inside pair on one-link chains. The treadway-hoisting hooks are used in pairs, two outside and then two inside hooks, to load and unload two treadways at a time from the bridge truck.
CROSS CHAIN
GRAB HOOK
INSIDE TREADWAYHOISTING HOOK
OUTSIDE TREADWAY HOISTING HOOK
TREADWAY
GRAB LINK
TREAD’ SLING
TREADWAY HOOK
Figure 21. Treadway handling chains.
c. Air compressor. Each truck is equipped with a 24-cfm air compressor for emergency use.
26. CONTENTS OF TRUCK LOADS, a. Treadway trucks. For transportation, the treadways are placed on their sides in the bed of the truck. The parts of the saddles are placed as shown in figure 22. The floats are placed side by side on the truck bed, behind the treadways. Other equipment is placed where convenient. Each treadway truck contains the following equipment:
4 treadways.
2 knockdown saddles.
25
2 pneumatic floats.
4 treadway spacing hooks.
9 treadway connecting pins (1 spare).
2 anchors and anchor lines.
4 paddles.
4 75-foot guy lines.
FLOATS
SADDLE BEAMS
NOTE: LOAD CONSISTS OF EQUIPMENT FOR CONSTRUCTION OF 24 FT. OF BRIDGE
4 TREADWAYS
2 FLOATS
2 SADDLES
2 ANCHORS
Figure 22. Loaded treadway truck.
b. 2% -ton trucks. The following equipment is carried in the 2%-ton trucks:
Trestles.
Trestle-bracing equipment.
Extra pneumatic floats.
Treadway adaptors.
Blackout markers.
Outboard motors and brackets.
Boat hooks.
Manila rope.
Wire rope.
Pneumatic float repair kits.
Treadway wedges.
Portable air compressors.
Ratchet chain hoists.
Tools and accessories.
27. OPERATION OF TREADWAY TRUCK, a. Unloading. The pneumatic floats are pushed off the end of the truck. Saddles, spacing hooks,
26
/ TREADWAY	/
___H SADDLE BEARING PLATE
TREADWAY.
connecting pins, anchors and anchor lines, paddles, and guy lines are manhandled off the truck. The treadways are unloaded in pairs. Treadwayhoisting hooks are fastened into the lifting-hook eyes of the treadways. The inside hoisting hooks are attached to the inner treadways. The inner pair of treadways then are lifted out of the truck by the hydraulic crane (fig. 23®) and set upon the ground. The hooks are unfastened and the treadways are pushed over so that they lie horizontally with treads up. Treadway-spacing hooks then are placed in their appropriate places (see par. 11), sling chains are attached, and the treadways are ready to be placed on a float. The second outer pair of treadways is unloaded by using the outside pair of treadway-hoisting hooks. To avoid the outer treadways piling on each other, the sling chains are attached while the treadways are on edge, and the truck boom is used to put them in a horizontal position.
b.	Loading. For loading, the sequence is reversed. The treadways on the ground are raised on their sides and the treadway-hoisting hooks are attached as in a above. The treadways are placed in the truck with their hook ends to the rear, the floorings of the inner pair face-to-face, and the floorings of the outer pair facing away from the center of the truck. The floats are loaded by fastening the sling chains to any convenient strap on the carrying case and lifting them into the truck with the hydraulic crane. All other parts are manhandled onto the truck.
c.	Handling treadways in pairs. The treadway hooks of both treadway slings are fastened on the flanges or through the lifting hook holes of the treadway as shown in figure 23®. A treadway truck can handle only one pair of treadways at a time.
d.	Handling treadways connected longitudinally. The treadway hooks of two treadway slings are fastened on the flanges of the treadways as shown in figure 23®. When this type of chain arrangement is used, both treadway slings are connected by the grab links to both main slings, rather than to a single main sling as when handling treadways in pairs. A treadway truck can handle two or three treadways connected longitudinally.
27
(T) Treadways being unloaded from truck.
Figure 23. Operation of treadway truck. •
28
UPPER CYLINDER
- FAIRLEAD
LOWER CYLINDER
@ Handling treadways in pairs.
@ Handling treadways connected longitudinally.
Figure 23. Operation of treadway truck—Continued.
29
SECTION IV
SELECTION AND PREPARATION OF BRIDGE SITES
28.	RECONNAISSANCE, a. The bridge site must be reconnoitered prior to construction so plans may be formulated and equipment operators instructed as to disposition of vehicles at assembly sites. The following technical data should be obtained:
(1)	Width, velocity, and depth of stream.
(2)	Character and shape of banks.
(3)	Rise and fall of stream.
(4)	Location of approaches to assembly sites.
(5)	Location and approach of tributary streams.
(6)	Location of main current.
(7)	Location of motor park for treadway trucks.
b.	For detailed information on bridge reconnaissance, see FM 5-6 and FM 5-10.
29.	SITE REQUIREMENTS. The following site requirements are desirable:
a.	Proximity to road net over which equipage can be moved.
b.	Approaches requiring little preparation.
c.	Current less than 10 feet per second.
d.	Banks less than 3 feet high and firm enough to support vehicles.
e.	Current parallel to banks.
f.	Stream bottom free of snags, sand bars, and large rocks.
g.	Stream bottom in which anchors will hold.
30.	PREPARATION OF SITE. The amount of preparation required prior to erection depends upon the site. Brush and trees must be cleared from assembly sites. Approach roads must be cleared and made passable. A straight approach at least 30 yards long must be prepared for entrance onto the bridge. Whenever tactical conditions permit it is desirable to complete site preparation before bridge construction commences.
31.	LAY-OUT OF SITE. A suggested site lay-out for bridges constructed by parts from far shore to near shore, using three assembly sites (see pars. 34 and 35), is shown in figure 24. Figures 25 and 26 give suggested site lay-outs for alternative methods of construction.
30
31
FAR SHORE
CURRENT
PART ASSEMBLY SITE
' -1'
25 YD. MIN.
TO MOTOR PARK
I 25 YD MIN. i 25 YD. MIN.	50 YD. MIN.	50 YD. MIN.	50 YD. MIN.
h----------------------------$--------------------------->
ASSEMBLY SITE	ASSEMBLY SITE	ASSEMBLY SITE
A
CONTROL POINT phone to motor park for equipment
Figure 24. Site lay-out for bridge constructed bv parts from far shore to near shore, using three assembly sites.
LEGEND________
• uninflated float fl* INFLATED FLOAT C ) PNEUMATIC PONTON
PNEUMATIC PONTON y- WITH TREADWAYS HB> TREADWAY TRUCK E3 AIR COMPRESSOR IL QsA°°tE
POWER BOAT
FAR SHORE
32
_	o	o
<	h-	tz S_	at
2 5 § o< = 2
«	2	2	-	<
Q	£	=!	y	y<	>	£	o
Z	5	a	!?	5S	$	S	“
u 3^5 Sh- go "a
Ou. >	<	<	Q (j	7;	lu
z ^	=>	13 x <	£	>
LU	= LU LU LU ►—	UJ ex	Q	5-
। z z z z >	<*	p
Z3=:Q_a.> i— <	 a.
_____50 YD- M1N-___ I ________50 YD. MIN.___	50 YD. MIN.	I 50 YD, MIN, ASSEMBLY SITE |	ASSEMBLY SITE	I ASSEMBLY SITE
I FAR SHORE RAFT SITE
- ':
X
CONTROL POINT phones to motor park for equipment
Ugure 2.5. Site lay-out lor bridge construction by individual pontons from near shore to jar shore, using three assembly sites.
CURRENT
CENTER LINE OF BRIDGE
I
LEGEND_________
UNINFLATED FLOAT INFLATED FLOAT PNEUMATIC PONTON PNEUMATIC PONTON WITH TREADWAYS I TREADWAY TRUCK AIR COMPRESSOR
SADDLE
POWER BOAT
FAR SHORE
CURRENT
25 YD. MIN. |	25 YD. MIN.	50 YD. MIN.	[	50 YD. MIN.	I 50 YD. MIN.	>
---------......-..-....................... —..»|<.	.................4*.......---------------*“ PART TREADWAY PLACING SITE.SADDLE ASSEMBLY SITE , FLOAT INFLATION SITE
ASSEMBLY
SITE
25 YD, MIN. Jl
TO MOTOR PARK 1
33
CONTROL POINT phones to motor park for equipment
Figure 26. Site lay-out for bridge construction by parts from far shore to near shore, using one assembly site.
SECTION V
WORKING PARTY
32.	ORGANIZATION OF WORKING PARTY. The working party is under the direction of the bridge officer who normally is from an armored engineer company. He is assisted as required by officers from both his company and the treadway bridge company supplying the equipment for the bridge. Personnel required for the construction normally is supplied by the constructing company assisted by noncommissioned officers, truck drivers, and assistant truck drivers of the treadway bridge company. Table IV gives a suggested organization of the working party for constructing bridges from three assembly sites as shown in figure 24. When fewer or more assembly sites are used, the organization of the working party must be adjusted accordingly. Table IV does not include personnel for approach roads, security, and debris-control details, or for controlling the movement of treadway trucks from motor park to assembly sites and for operating field telephones.
33.	DUTIES OF CONSTRUCTION DETAILS. The duties of the construction details are as follows:
a.	Unloading detail (1 noncommissioned officer and 8 enlisted men). Two men climb on each truck as it approaches the float-inflation site and unload floats. The six men who remain on the ground roll floats to floatinflation site near the water, truck moves to saddle-assembly site, and men on truck pass saddle beams, bearing plates, treadway pins, anchors, anchor lines, float guy lines, and paddles to men on ground, who carry them as close to stream as possible. All equipment must be stacked in its proper stock pile.
b.	Float-inflation detail (1 noncommissioned officer and 9 enlisted men). (1) The float-inflation detail includes the air compressor operator. Six additional men can be added to help carry the floats. The detail—
(a)	Unrolls and spreads out floats.
(6)	Inflates floats to a pressure of 2 psi (see par. 7c).
(c)	Launches floats by carrying them into the water.
(d)	Turns over floats to two-man crew of ponton-handling detail.
(e)	Stacks float carrying cases and emergency repair kits.
34
Table IV.—Organization oj working party
Personnel
------------------;------------------Total personnel
Bridge Company	Construction Company AT . r
Details	Equipment per detail	umber of
--	-___________ ------- details--------------------
Noncom-	| Noncom-	Noncommissioned Enlisted men missioned Enlisted men	missioned I Enlisted men
officers I	i officers	officers
Unloading.............................................. 1	................. 8	3	3	24
Float-inflation...... 1 air compressor................. 1	]................ 8	3	3	27
Saddle-assembly...... (4 hammers...... . ........1	j ......................... g	3	3	%
[4 treadway pins per float.J
Treadway placing..... 2 sledge hammers................. I	................. 4	3	3	12
Truck drivers and assist- 12 bridge trucks..................... 24	.................. 3 ..................... 72
ant drivers.
Ponton-handling........p	75-fl. rope and I paddle per 1.................................................. 1 20 J ]	20
°	(.	man.	J
12	alining tools.........]
2 sledge hammers................. 1	.................. 6	1	1	6
2	12-ft planks..........I
{4	picks.................'
8 shovels.................
Logs for dead men, cables, cable ►................. 1	12	1	1	12
clips, and wrenches for guy lines.	,
Far-shore-abutment*...............do...................................... 1	12	1	1	12
Powerboat............ 1 powerboat............................... 1	........ 2	2 ............... 6
_____________________I__________________________i__________________I________L____________________________________
Total..............16	215
Bridge company.....13	77
Constructing company. . 3 138
*A bulldozer with operator is attached to these details when required.
35
(2) When floats are launched from steep high banks, they are placed in the water by a truck crane (see par. 21). The saddle may be placed on the float (see e below) before launching, the assembled ponton being fitted with a rope sling so it can be readily handled by the truck crane. Treadways can be placed in the normal manner (see <1 below) with the unloading treadway truck held in place by a preventer line to a winch on another truck, by the truck crane, or by the winch cable of the treadway truck running through the fairlead and a snatch block (par. 25a) at the rear of the truck.
c. Saddle-assembly detail (1 noncommissioned officer and 8 enlisted men).	(1) Two men carry and place each bearing plate on floats which are
delivered by ponton-handling detail (e (2 I below ). Bearing plates are placed in the following order:
(a)	First pair of interior bearing plates is placed over inflation valves of center tube.
Figure 27. Saddle-assembly detail placing saddle on float.
(b)	Second pair of interior plates is placed inside first pair.
(c)	Third pair of interior plates is placed one on each flank of the first pair.
(d)	Two end-bearing plates are placed.
(2)	Four men carry and fit each saddle beam in place under stationary section of saddle-beam clip. Beams are placed in the following order:
(a)	Riverward upstream beam (with female fittings).
(6)	Shoreward upstream beam (with female fittings).
(c)	Riverward downstream beam (with male fittings).
(d)	Shoreward downstream beam (with male fittings).
(3)	Four men drive movable section of saddle-beam clips into place with hammers; four men lash assembled saddle to float with the straps attached to D-rings of float (fig. 27).
36
(4)	Four treadway pins are placed on the assembled pneumatic ponton which is turned over to two-man crew of ponton-handling detail. Two pins are inserted at treadway-placing site (d(6) below) and two at either partassembly site (e(5) below) or bridge site (g(4) (a) 2 below).
d.	Treadway-placing detail (1 noncommissioned officer and 4 enlisted men). (1) Treadway-placing detail—
(1)	Directs placing of treadway truck in its proper place at treadway-placing site. Truck stops far enough back from edge of bank so treadways can be placed on ground between back of truck and edge of water.
(2)	Connects treadway hooks (see par. 27c) to one pair of treadways and guides treadways as they are lifted from truck and placed on ground.
Figure 28. Treadway-placing detail guiding treadways onto pneumatic ponton.
(3)	Disconnects tread way hooks and pushes inner treadways over so they fall flat. Uses treadway slings and truck boom to place outer treadways flat.
(4)	Connects hooks of treadway slings through pear-shaped holes in sides of treadways and, as treadways are lifted off the ground, inserts treadway spacing hooks. Detail then guides treadways into position on pneumatic ponton (fig. 28). Treadways must be centered and balanced on pontons or assembly may overturn, and alined longitudinally so they will fit in bridge.
(5)	Drives treadway retainers on saddles into place over flanges of treadways (fig. 8) and inserts pins.
(6)	Inserts a treadway pin through inner holes of blunt end of each treadway and turns over assembled part to two-man crew of ponton-handling detail.
37
e.	Ponton-handling detail (1 noncommissioned officer and 20 enlisted men). Noncommissioned officer and 6 men remain at part-assembl\ site. Remaining 14 men are divided into two-man crews which are dispatched to float-inflation sites as required. Each crew secures a float as it is launched by float-inflation detail. Crew stays with float until it arrives at part-assembly site. Each two-man crew—
(1)	Attaches guy lines to floats and picks up two paddles.
(2)	Paddles or pulls float along shore to saddle-assembly site.
(3)	Assists saddle-assembly detail as needed and, when saddle has been attached, places anchors as required on float and paddles or pulls it along shore to treadway-placing site.
(4)	Assists treadway-placing detail as needed and, when treadways have been placed, paddles or pulls float along shore to part-assembly site. Powerboats are used if sites are far apart.
(5)	Assists six-man crew at part-assembly site in connecting together two assembled pneumatic pontons. Blunt ends of one pair of treadways are inserted between engaging plates of hook ends of other pair. Pins already in place in blunt ends (d(6) above) fit into notch of hook ends of second pair of treadways. A second pair of pins then is driven through holes of hook-end treadways and outer holes of blunt-end treadways to fasten treadway rigidly.
(6)	Assisted by powerboat crew, joins crew of other pneumatic ponton in attaching powerboat to assembled part. One crew goes in powerboat and delivers part to bridge-assembly detail. It assists in incorporating part into bridge, and returns to float-inflation site in powerboat. Meanwhile other crew returns to float-inflation site, picks up float, and repeats procedure.
(7)	When bridge is built by method of individual pontons powerboat picks up assembled pontons at treadway-placing site. Ponton-handling crews remain with ponton until it is assembled into bridge. This method eliminates work at part-assembly site.
f.	Truck drivers and assistants (24 enlisted men per site). (1) Truck is moved as directed from motor park to assembly site where floats, saddles, and small parts are unloaded.
(2)	Truck is moved to treadway-placing site as directed.
(3)	Directed by treadway-placing detail, truck is backed into proper place (par. d(l) above) at treadway-placing site.
(4)	Assistant driver operates truck boom, and driver moves truck while boom is operated as directed by noncommissioned officer of treadway-placing detail.
(5)	Truck is returned to motor park.
g.	Bridge-assembly detail (1 noncommissioned officer and 6 enlisted men). The bridge-assembly detail—
(1)	Receives from ponton-handling crews first four assembled pneumatic pontons constructed at part-assembly site. Connects pontons into four-ponton raft as described in e(5) above.
38
(2)	Receives a pair of overhanging tread ways from a treadway truck and installs them at one end of raft.
(3)	After raft is loaded with men and equipment of far-shore abutment detail, crosses stream on raft pushed by powerboat.
(4)	(a) When bridge is built from far shore to near shore, remains on far-shore raft and receives parts delivered by powerboat. Parts must approach bridge with hook ends of treadways toward far shore (see par. 34d). Parts are incorporated into bridge as follows:
1.	Four men of detail pull part into bridge proper by guy lines; other two men guide ends of treadways together (fig. 29).
Figure 29. Part being incorporated into bridges.
2.	Minor adjustments are made with treadway-alining tools, and treadway pins are inserted and driven through treadway holes with sledge hammers as described in e(5) above. Before connection is made, 3- by 12-inch planks about 12 feet long are laid parallel to and outside of treadways to provide a platform for men inserting treadway pins (fig. 30).
(b)	When bridge is built from near shore to far shore, detail remains on near shore and receives parts from ponton-handling crews. It connects parts together in manner described in (a) above. A pair of overhanging treadways first must be connected to shoreward end of first ponton part received.
39
h.	Near-shore abutment detail (1 noncommissioned officer and 12 enlisted men). The near-shore abutment detail—
(1)	Prepares abutment as described in paragraph 37. Erects trestles, when used.
(2)	Prepares holes for and places deadmen as required (see par. 36). When bridge is built from far shore to near shore, deadmen farthest from center line are prepared first; when bridge is built from near shore to far shore, deadmen nearest to center line are prepared first.
(3)	Secures shore guy lines and anchor cables, when used, to deadmen and tightens them after bridge is in final position.
(4)	Improves approaches as required.
Figure 30. Treadway-connecting pins being inserted.
i.	Far-shore abutment detail (1 noncommissioned officer and 12 enlisted men). The far-shore abutment detail—
(1)	Crosses on far-shore raft and secures raft to shore.
(2)	Prepares abutment; erects trestles, when used.
(3)	Prepares holes for and places deadmen as required (see par. 36). When bridge is built from far shore to near shore, deadmen nearest to center line are prepared first; when bridge is built from near shore to far shore, deadmen farthest from center line are prepared first.
(4)	Secures shore guy lines and anchor cables, when used, to deadmen and tightens them after bridge is in final position.
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j.	Powerboat detail (6 enlisted men). Powerboat detail is divided into two crews, each consisting of an operator and two men. It acts as follows:
(1)	Launches two powerboats directly from trailer (see par. 22c).
(2)	Strings upstream anchor cable, when used.
(3)	Uses boats to push far-shore raft from assembly site across stream.
(4)	Uses boats as required to push parts from part-assembly site to bridge, laying upstream anchors or attaching bridle lines to upstream anchor cable by pushing part upstream and then backing downstream to bridge. Downstream anchors or bridle lines and anchor cable are left off until bridge is completed.
(4)	Acts as rescue patrol as required during bridge construction.
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SECTION VI
CONSTRUCTION
34.	METHODS OF CONSTRUCTION, a. The steel-treadway bridge can be constructed by the following methods:
(1)	Direction of construction, (a) From far to near shore.
(6)	From near to far shore.
(c)	From both shores.
(d)	From neither shore; pontons pinned together but not initially tied into either shore.
(2)	Method of assembly, (a) By two-ponton parts.
(6) By individual pontons.
b.	The assembly sites may be downstream or upstream from the bridge site, or both. The location and number of the assembly sites depend upon the location and number of adequate cleared spaces with a road net leading to them, and on the number of troops available. Assembly sites downstream generally are better, for with powerboats it is easier to maneuver parts to the bridge against the current.
c.	The method of bridge construction depends upon length of bridge, bank conditions, current, conditions of approach roads, and the number of troops available.
d.	Regardless of whether the bridge is built from either shore or from both shores simultaneously, a far-shore raft consisting of four pneumatic pontons with five pairs of treadways—one pair overhanging for connection to the shore—is always built first. The raft is connected to the far shore with the hook ends of the treadways shoreward. The raft serves as part of the bridge and also is used to cross the far-shore abutment detail with bulldozers, air compressors to operate pneumatic tools, and treadway trucks as needed in preparing the far-shore abutment and approach.
35. ADVANTAGES OF DIFFERENT METHODS OF CONSTRUCTION. The advantages of the different methods of construction are as follows:
a. Direction of construction. (1) From far to near shore, (a) Near-shore approach can be used as part-assembly site.
(5) Shore guy lines first placed lead to far shore and do not interfere with movement of pontons to bridge.
(c) Any delay incident to preparation of near-shore approach is eliminated.
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(d) Final adjustments and final pinning are completed at near shore where mechanical aids are more readily available.
(2)	From near to far shore, (a) Parts can be towed along the shore into position at the bridge.
(6)	Since all work except that on far-shore approach is done on near shore, supervision of erection is easier.
(c)	Any delay incident to preparation of the far-shore approach is eliminated.
(3)	From both shores. This method is advantageous only when a long bridge is built. Bridge-assembly details work from both shores. Final pinning is made by placing a treadway truck on near-shore section, attaching a tow chain from it to far-shore section, and pulling sections together. Both sections must be free to float from their respective banks during final pinning. This method should be used only when personnel are available for more than three assembly sites, for one bridge-assembly detail can pin parts together as fast as three sites can furnish them.
(4)	From neither shore. This method is advantageous when approaches at both banks require considerable preparation. Parts are pinned together as in construction from near shore, except first ponton is anchored instead of being attached to shore. Successive parts are pinned to it. When one approach is ready, a part consisting of two or more pontons is attached to shore and floating section previously pinned together is propelled to it. This method should not be used in currents over 3 feet per second, in the building of long bridges, or when winds make bridge alignment difficult.
b. Method of assembly. (1) By two-ponton parts, (a) Parts are more stable and safer to handle.
(6)	Parts can be pinned together before either abutment is prepared.
(c)	Powerboats have fewer parts to push into place.	#
(d)	It is easier to attach powerboats to two-ponton parts.
(2) By individual pontons, (a) All pinning is done at bridge, eliminating part-assembly site.
(b)	Alignment of treadway-connecting-pin holes is easier.
(c)	In streams having shoals, rocks, or other obstructions, individual pontons are easier to propel to bridge.
36. ANCHORAGE OF BRIDGE, a. Methods. (1) The method of anchoring the steel-treadway bridge depends upon current, width of stream, and type of stream bottom. The following methods of anchorage can be used:
(a)	Guy lines.
(b)	Anchors.
(c)	Anchors and guy lines.
(d)	Anchor cable and bridle lines, and guy lines.
(2) Table V lists the positions of anchors, guy lines, and bridle lines for
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the various methods. Regardless of the method used, short guy lines are used on both sides at each end of the bridge to prevent movement caused by starting or stopping of heavy vehicles.
b. Anchorage by guy lines. Guy lines are %-inch wire ropes. They are attached on the shore to deadmen or natural holdfasts, and on the bridge to the lifting-hook eyes of the treadways. Both ends are secured by wire-
NOTE: IN CURRENTS UNDER I FT. PER.SEC.
C-L. DEADMAN	USE GUY LINES AT EVERY STH. FLOAT
ON UPSTREAM AND DOWNSTREAM SIDES
Figure 31. Bridge anchored by guy lines.
rope clips. The lines are tightened with ratchet chain hoists which are removed as soon as the lines are at the proper tension. Guy lines hold the bridge in place during construction as well as after completion. They can be used alone to anchor bridges in currents less than 3 feet per second, as shown in figure 31. In stronger currents, they are used in conjunction with anchor cables and bridle lines (e below) or anchors (d below).
c. Anchorage by anchors. Bridges may be anchored by anchors
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/GUY LINES (£-IN. WIRE ROPE) / ATTACHED TO TREADWAYS AT
EVERY 6TH. FLOAT ON UPSTREAM SIDE
GUY LINES (-^-IN. WIRE ROPE)\ ATTACHED TO TREADWAYS AT
EVERY 6TH. FLOAT ON DOWNSTREAM SIDE
CURRENT
1-3FT PER SEC. /
alone as shown in figure 32. This method of anchorage should not be used in currents over 3 feet per second. Anchor lines can be attached to either of the following:
(1) Rope halter of float. A bowline on a bight is tied on the anchor line about 15 feet from the thimble of the rope halter and the line is threaded through the thimble and back through the bight. Then the free end is brought back to the treadway for lashing as shown in figure 35. The anchor
NOTE: IN CURRENTS UNDER I FT. PER. SEC.
USE ANCHOR LINES ON EVERY OTHER
i	FLOAT ON UPSTREAM SIDE AND ON
tis DEADMAN	EVERY 4TH. FLOAT ON DOWNSTREAM
SIDE
Figure 32. Bridge anchored by anchors.
line must pay off from the top of the coil of rope as the anchor is dropped. Ropes must not be fastened to the saddle as a strong pull tends to submerge the float and pull the saddle apart.
(2) Lifting-hook eye of treadway. The anchor is placed so the rope will pass between two floats and hence not chafe the float or tend to submerge it. The anchor rope is passed under the upstream treadway through a hook
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V-----------H
\ ANCHOR LINE
(I—IN. MANILA ROPE)
------------H
------------A
CURRENT ---------
1-3 FT PER SEO. , f---------------
eye on the upstream side of the downstream treadway and tied to a hook eye on the downstream side of the upstream treadway as shown in figure 36.
d. Anchorage by anchors and guy lines. This method of anchorage is shown in figure 33. Anchors are attached as described in c (1) or (2) above, and guy lines as described in b above.
e. Anchorage by anchor cables, bridle lines, and guy lines. This method of anchorage is shown in figure 34. Anchor cables are %-inch wire
NOTE1 IN CURRENTS UNDER 3 FT. PER.SEC.
USE ANCHOR LINES ON EVERY OTHER
FLOAT ON UPSTREAM SIDE AND ON
Ua DEADMAN	EVERY 4TH. FLOAT ON DOWNSTREAM
SIDE
Figure 33. Bridge anchored by anchors and guy lines.
ropes extended from one shore to the other and fastened to deadmen or natural holdfasts 50 feet upstream and downstream from the center line of the bridge. Bridle lines are ^-inch manila rope 80 feet long with a harness snap at one end. The snap is fastened to the anchor cable and the other end of the line is tied to the rope halter of the floats. Guy lines are attached as described in b above.
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7~ LINES <^-IN. WIRE ROPE) ---ATTACHED TO TREADWAYS AT
----- EVERY 6TH. FLOAT ON
-------- UPSTREAM SIDE
---V---------------)
____\ ANCHOR LINE
(l-IN. MANILA ROPE)
GUY LINE (-j-IN. WIRE ROPE) ATTACHED TO TREADWAY AT '
EVERY I0TH. FLOAT ON
DOWNSTREAM SIDE —
CURRENT --------
-<--------
OVER 3FT PER SEC. h-----------------
37. SHORE CONNECTIONS. a. General. (1) The traffic capacity of a bridge cannot be greater than its approaches. Often it takes as long to build approaches as it does to build the bridge. Abutments must be solidly constructed to withstand the impact and weight of the heaviest vehicles, and erosion by rainfall or stream action. Abutment sills must be
NOTE; IN CURRENTS UNDER 3 FT. PER.SEC.
USE BRIDLE LINES ON EVERY OTHER
1 rMTAHMAM	FLOAT ON UPSTREAM SIDE AND ON
DEADMAN
EVERY 4 TH. FLOAT ON DOWNSTREAM
SIDE
Figure 34. Bridge anchored by bridle lines and guy lines.
used at both ends of the bridge. Any available dressed lumber built up to a sufficient height, or rough lumber adzed on its upper surface, may be used. However, the sill must consist of at least 6- by 8-inch by 12-foot lumber, and it must support both treadways. Sills are firmly fastened by pickets and protected by riprap against the possibility of wave action wearing away the soil on the banks.
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7 GUY LINES (|-IN. WIRE ROPE) ATTACHED TO TREADWAYS AT
EVERY 6TH. FLOAT ON UPSTREAM SIDE
______ ANCHOR CABLE
(f-IN. WIRE ROPE)
\	BRIDLE LINE
'\/(|-IN. MANILA ROPE)
GUY LINE (|-IN. WIRE ROPE) ATTACHED TO TREADWAY AT
EVERY IOTH FLOAT ON
DOWNSTREAM SIDE
^CURRENT
OVER 3 FT. PER SEC.
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Table V. Methods of anchorage
i	-	;	---------------------------------------------------------
n	Anchors	Guy lines	Bridle lines
*^Ure	Method	Current ,--------------------------------------------------------------------------
Wo.	(fps)	।------------
Upstream	Downstream	Upstream	Downstream	Upstream	Downstream
(0—1................................ One every One every ..............................
31 Guy lines 1.........J	eighth float.	eighth float.
1~3................................ One every Oneevery ...............................
I	sixth float.	sixth float.
0—1...... One every One every ..............................................
32	Anchors 1	J	second float. fourth float.
11—3...... One every One every ......................................................
I	float.	fourth	float.
(0-3......... Oneevery	Oneevery Oneevery Oneevery ....................................
33	: Anchors and guy lines. .