Bailey Bridge Manual [PDF]

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TWL BAILEY TYPE PORTABLE STEEL BRIDGE



GENERAL DESCRIPTION TWL Bailey type Portable Steel Bridge has been designed on Unit Construction principle. Panel is the basic unit of a Bridge [3.048M(10’) long and 1.448M(4’-9”) high between pin hole centres]. Its weight is 286 Kgs. The Panels are manufactured from High Tensile Steel for strength and lightness and are assembled with accessories to suit the length of the bridge in multiples of 10 feet upto 200 feet. Rows of Panels form the main two girders of the bridge. The two main girders are connected by transoms which carry the Bridge Roadway. The load carrying capacity of the bridge can be increased by adding extra Panels, alongside (Truss) and/or on top of the original Panels (Storey). Capacity can be further increased by putting Chord Reinforcement on top and bottom of Panels. The Bridge is classified by the number of trusses and storeys which form its main girders. There are several possible combinations of truss-storey e.g. single-single, double-single, triple-single, double-double, triple-double etc. The types of construction are simply abbreviated as S.S., D.S., T.S., D.D., T.D. etc. The various types of construction mentioned above can be further reinforced by Chord Reinforcements at the top and bottom of each truss. The constructions which are reinforced are abbreviated as S.S.R., D.S.R., T.S.R., D.D.R. etc. (Fig.1).



Fig.1 – DIFFERENT FORMS OF CONSTRUCTION OF GIRDERS FOR TWL BRIDGES



Page 1 of 19



TWL BAILEY TYPE PORTABLE STEEL BRIDGE The girders are connected crosswise by Transom. These are made up of high tensile Rolled Steel Joists which rest on the bottom chord of Panels and carry the road superstructure. Transoms are clamped with the Panels by Transom Clamps and position the trusses at the required distances apart. The girders are also connected by two diagonal braces, called Sway Braces, at each Panel bay. Across the Transom runs the “Unit Bridge Steel Deck”. The ends of each truss of bridge girders are attached with the End Posts. These are placed on bearings which rest on Base Plates placed on the ground at each end of the span. The Base Plates are intended to spread the load from the Bearings evenly over an area. The arrangements of the basic components of a Double Single Reinforced (DSR) construction bridge is shown in Fig.2. Component details including illustration are furnished in subsequent pages.



Fig.2 – TWL BAILEY TYPE PORTABLE STEEL BRIDGES – GENERAL DESCRIPTION All parts are fully interchangeable. This is ensured by use of Jigs / Fixtures / inspection gauges at all stages of manufacture. Erection of these bridges is fairly simple. No skilled labour is required. Supervision by an experienced and trained Engineer is adequate. The heaviest component can be handled manually by six persons.



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TWL BAILEY TYPE PORTABLE STEEL BRIDGE ROADWAY WIDTH The TWL Portable Steel Bridges are classified according to the width of the roadway. Currently, Titagarh Wagons Limited manufactures bridges with two sizes of roadway. Nomenclature



Width of roadways



Distance between the inside edges of the inner most trusses



Standard Width (SW)



3.277 M (10’-9”)



3.76 M (12’-4”)



Extra Wide (EW)



4.250 M (13’-11”)



4.775 M (15’-8”)



Fig.3 – TYPICAL ELEVATION & PLAN OF TWL BAILEY TYPE PORTABLE STEEL BRIDGE SECTION AT A-A



Fig.4 – TYPICAL CROSS SECTION THROUGH EXTRA-WIDE TWL BAILEY TYPE PORTABLE STEEL BRIDGE TRIPLE SINGLE CONSTRUCTION



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TWL BAILEY TYPE PORTABLE STEEL BRIDGE SECTION AT A-A



Fig.5 – TYPICAL CROSS SECTION THROUGH STANDARD WIDTH TWL BAILEY TYPE PORTABLE STEEL BRIDGE DOUBLE SINGLE REINFORCED CONSTRUCTION



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TWL BAILEY TYPE PORTABLE STEEL BRIDGE MULTI SPAN BRIDGE Bailey Type Portable Steel Bridges can be constructed with Single Span upto a maximum of 200 ft (60.94M). Larger gaps can be spanned by constructing TWL bridges over intermediate piers either as a Continuous Span Bridge or as Broken Span Bridge. Continuous Span Bridge The spans are supported on intermediate piers using specially designed Distribution Beams on Bearings.



Compared to Broken Span Bridge, continuous Span Bridge is economical to construct. However, this has the following constraint – If any intermediate pier / end abutment sinks afterwards, bridge girders may stretch beyond permissible limits. Further, should an end span be shorter than the adjacent intermediate span, the End Posts tend to lift off their bearing when a heavy load passes over the intermediate span. Broken Span Bridge This is essentially single span bridges connected by special type of Junction Posts, Junction Links etc. to accommodate change in slope between two spans in case of sinking of pier / end abutment. During launching the junctions are locked using special components, which are removed on completion for erections. The additional gap created due to placement of junction post is filled by End Deck Unit.



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TWL BAILEY TYPE PORTABLE STEEL BRIDGE DESCRIPTION OF MAJOR COMPONENTS OF TWL BAILEY TYPE PORTABLE STEEL BRIDGE PANEL – BB-1 The Panel is the basic member of the Bailey type bridge, constructed from high tensile steel with all welded joints. One end of the top and bottom Chord of the Panel is fitted with forged male lug and the other end is fitted with female lug. These male and female lugs enable the Panels to be connected end to end by using Panel Pins. There are 4 nos. Transom seatings on the bottom chord on which Transom will rest. The bottom chord also has two slot holes into which Sway Braces are fitted with pins. Holes are provided in the top chords and in end verticals for fixing Bracing Frames. The top holes in the end verticals are also used for fitting the Rakers or Tie Plates. There are slots in all the verticals for fixing with Transom Clamps. The Panel is 3.048 M (10’) long and 1.448 M (4’9”) high between pin-hole centres. The top and bottom chords have holes to take Chord Bolts to connect Panels together for multiple storey or to connect Chord reinforcement to Panel for Chord Reinforced Trusses.



It weighs : 286 Kg. RAKER – TBB-3A The Raker is made from steel rolled channels with hollow conical dowels fitted at each end. It is fitted between top of inner truss and the end of the Transom by using its dowel in the top hole of Panel vertical so that the Panel is in correct alignment. It also gives lateral stability to the truss. Each end of the bridge at every Panel junction point, one Raker is used. It is fastened with two Bracing bolts.



It weighs : 9.25 Kg. Page 6 of 19



TWL BAILEY TYPE PORTABLE STEEL BRIDGE BRACING BOLT – BB-11 It is electro-zinc plated mild steel bolt. Special lug is fitted with the bolt head and a combination of nut and washer. The bolt is used for securing (a) Raker to the Panel & Transoms, (b) Bracing Frames to the Panel and (c) Tie Plates to the Panel.



SWAY BRACE – BB-15



It weighs : 0.47 Kg.



This is a combination of a mild steel rod, hinged at the centre and a Turn Bukcle for adjustment. This is used as a diagonal bracing on the underside of the bridge and is connected to the opposite ends of the two inner Panels in a bay. The adjustable Turn Buckle can be rotated by the tail of one of the erection spanner. It is designed in such a way that when it is screwed up tight with both ends of the rod against the sliding block gauge, the Sway Brace is properly tensioned. A nut is also provided on one of the Sway Brace rods, which may be tightened up against the Turn Buckle to act as a lock nut. In every bay of bridge two Sway Bracings are required.



PANEL PIN – BB-4



It weighs : 28.6 Kg.



Panel Pin is made from special alloy steel of high yield strength and impact value. It is electro-zinc plated to resist corrosion. Used to connect Panels or Chord Reinforcement together.



CHORD BOLT – BB-9



It weighs : 2.71 Kg.



Chord bolt is used to connect a Panel above and below to form multi-storeyed bridges. The bolt is made from mild steel and is finished electro-zinc plated to resist corrosion. The taper shanks of the Chord Bolts help to draw the Panels into correct alignment during assembly.



It weighs : 3.5 Kg. Page 7 of 19



TWL BAILEY TYPE PORTABLE STEEL BRIDGE BRACING FRAME – TBB-2A A Bracing Frame is made from mild steel, welded construction, provided with hollow conical dowels at each corner. It is used to connect Panels together in multiple truss and storey construction of bridge girders, at different location horizontally and vertically. It is 1.244 M (4’1”) long and 0.457M (1’-6”) wide.



It weighs : 17.9 Kg. TRANSOM CLAMP – TBB-6 This is mild steel fabricated assembly consisting of an arm fitted with hinge bar, a vice type screw and a clamping bolt for tightening the transom in position on the Panels. The nose type arm is inserted into rectangular slot in the Panel vertical.



SHORT CHORD BOLT – TBB-9A



It weighs : 3.2 Kg.



This is identical to BB-9 except it is short in overall length. It is made from M.S. and electro-zinc plated to resist corrosion. These are used for connecting Chord Reinforcement to the Panel Chords for Chord Reinforced Bridge.



CHORD REINFORCEMENT – BB-150



It weighs : 2.63 Kg.



It is identical to the bottom Chord of Bailey Panel. Like the Panels, male lug and female eye plates are provided at the ends of the Chord. Like the Panels, there are Chord bolt sockets, Bracing Frame and Sway Brace attachment points. The Chord sockets are positioned on the opposite face of the Bracing Frame holes. When the Panel is reinforced, the heads of the Chord bolts are housed inside the Chord. This gives an uninterrupted Chord Reinforcement surface. So, when the Chord Reinforcement is attached to the bottom Chord of the Panels it helps launching and when attached to the top chord of Panel, the attachment allows bracing frame without interference.



It weighs : 90 Kg. Page 8 of 19



TWL BAILEY TYPE PORTABLE STEEL BRIDGE BEARING – BB-19 The bearing is a fabricated assembly carrying a round bar upon which the half round bearing of the end post rests. This bar is divided into three lengths. For single truss bridge, the end post is rested on the centre length. For double truss bridge, two bearings are used so that each truss rests on the centre of each bearing. For triple truss bridge, the inner truss rests on the centre on one bearing and the other trusses rest on the two outer positions of the second bearing. So, it is not necessary to use more than two bearings at each end of main girder for a bridge.



It weighs : 35 Kg. BASE PLATE – TBB-1031 The Base Plate is designed to spread the load from the bearings evenly over an area of ground. It is a fabricated steel assembly. There is a sunken platform at the centre of the assembly to take the bearings. Two Base Plates are required on either end of the bridge, whether it is single, double or triple truss construction. For correct positioning of the centre line of the trusses certain numbers (1,2 & 3) are embossed on the edge of the Base Plates. The Bearing can be moved 229 mm longitudinally on the Base Plate. This movement provides flexibility during erection.



STANDARD STEEL DECK TRANSOM – TBB-1061



It weighs : 155 Kg.



High tensile steel joists are used to fabricate Transoms. Dowel holes are provided at the ends, which locate dowels on the Transom seat at the bottom Chord of Panel. Transoms are held in position with Transom Clamp. There are Raker-block and stopper-block on the Transom top flange to prevent longitudinal and lateral slip of decking member and for fixing Deck Units to the Transom.



It weighs : 268 Kg. Page 9 of 19



TWL BAILEY TYPE PORTABLE STEEL BRIDGE STEEL DECK CLAMP UNIT (MOD) – TBB-1114 It is an assembly of high tensile Tee bolt, M.S. Plain Washer, Spring Washer and Hex Nut, used for fixing Steel Deck Units to the Transoms. Positioning the Tee Bolt in the saddle on the Transom, the Steel Deck is then positioned so that the Tee Bolt protrudes through the cut in the Deck. The Deck Unit is then locked in position with Plate Washer, Spring Washer and Nut.



It weighs : 0.32 Kg. POST END FEMALE – BB-62 POST END MALE – BB-63 The End Posts are fitted to both the ends of each truss of main girder. These transmit the end reaction of the bridge to the Bearing. Post End Female connects to the male end of the Panel whereas the Post End Male connects to the female end of the Panel. Each Post End has two holes at the top, the upper one for connecting the 2nd Storey Panel and the lower one for connecting bottom Storey Panel top chord. The hole at the bottom end of End Post connects to the bottom chord of bottom Storey Panel. The Posts also have a half-round bearing block at the bottom, which rests on Bearing. A step with locator at the lower end locates Transom. A hinged bracket has been provided to lock the Transom. The step is also the place for placing Jack for lifting the bridge during final placement on Bearing at the end of launching.



Post End Female weighs : 65 Kg. Post End Male weighs : 60 Kg. Page 10 of 19



TWL BAILEY TYPE PORTABLE STEEL BRIDGE STEEL DECK UNITS STEEL DECK UNIT (LONG) – TBB-1105 STEEL DECK UNIT (SHORT) – TBB-1106 The Steel Deck Units are fabricated from channels of high tensile steel and M.S. chequered plates. Two Deck Units are used instead of one full by length of 3.048M to avoid rattling under moving load due to any gap between Deck and middle Transom of a bay length. Each Deck Unit is positively fixed with the saddle welded on Transom by Steel Deck Clamp Unit. Stoppers provided on the Transom locate the Deck Unit. The chequered top plate of Decks provide better wheel grip.



< Steel Deck Unit (Long) weighs : 362 Kg.



< Steel Deck Unit (Short) weighs : 344 Kg.



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TWL BAILEY TYPE PORTABLE STEEL BRIDGE END STEEL DECK UNIT (LONG) – TBB-1107 END STEEL DECK UNIT (SHORT) – TBB-1108 END STEEL DECK RETAINER – TBB-1098 The End Steel Deck Units connect the roadway with bridge deck. Design of the Decks are similar to the other Deck Units except that their lengths are shortened. End Steel Deck Retainer is fitted at either end of a bridge. It provides additional positional stability to End Decks.



End Steel Deck Unit (Long)



End Steel Deck Unit (Short) < End Steel Deck Unit (Long) weighs : 213 Kg. < End Steel Deck Unit (Short) weighs : 143 Kg.



End Steel Deck Retainer End Steel Deck Retainer weighs : 85 Kg.