Title of Invention	A DOUBLE-LANE,PORTABLE ,STEEL BRIDGE.
Abstract	(a) detachable panels (1) forming load-bearing girders on both sides of the bridge ; (b) bracing frames (6) for holding the formed girders firmly in place ; (c) a plurality of transoms (14) laid across the bottom chords of panels connecting and spacing the main girders apart and at the same time carrying the steel-decked roadway for allowing two-way flow of traffic; (d) a plurality of base plate (11) and bearing assembly provided at both ends of the bridge on which the terminals or ends of the aforesaid girders rest, characterised in that the load-bearing girders are composed of a number of modular units called panels (1) pinned together at ends and placed side to side, if necessary or desired, and the entire structure is reinforced for safety reasons by the addition of chord reinforcements (15) to the top and bottom of each truss.

Title of Invention

A DOUBLE-LANE,PORTABLE ,STEEL BRIDGE.

Abstract

(a) detachable panels (1) forming load-bearing girders on both sides of the bridge ; (b) bracing frames (6) for holding the formed girders firmly in place ; (c) a plurality of transoms (14) laid across the bottom chords of panels connecting and spacing the main girders apart and at the same time carrying the steel-decked roadway for allowing two-way flow of traffic; (d) a plurality of base plate (11) and bearing assembly provided at both ends of the bridge on which the terminals or ends of the aforesaid girders rest, characterised in that the load-bearing girders are composed of a number of modular units called panels (1) pinned together at ends and placed side to side, if necessary or desired, and the entire structure is reinforced for safety reasons by the addition of chord reinforcements (15) to the top and bottom of each truss.

Full Text	2 The present invention relates to a double-lane, portable, steel bridge of unique design. More particularly, this invention pertains to design and construct a simple, through-type bridge, which can be assembled and erected on site as the components can be transpoted easily and can span a void or gap of nearly 270-ft width. So much so, skilled personnel can assemble and erect a double-lane bridge in couple of day's time, a feat not achievable by conventional bridge-building and erection. Need was felt for designing a portable bridge and Indian Army Engineers came up with a functional, but small bridge assembly which could span a void of around 60-ft, and capable of handling single-lane traffic. Such bridges were in demand by various agencies, apart from army, Border Security Forces or similar authorities / agencies, border road authorities, P.W.D. (roads), Indo-Tibetan Border Authorities, and various State Governments, particularly in the North-Eastern States and also in Himachal Pradesh, Uttar Pradesh, Uttarakhand, and the like places having difficult terrain where regular road bridges are extremely difficult to build. After the Indo-China war in 1962, road-building activity was geared up, mainly for speedy troop movement and also to maintain the supply-lines to the strategically important forward areas. Moreover, with the implementation of different development plans to provide people living in remote, difficult to access areas, roads had to be built as a communication link between those people and the administration. In building such roads, numerous voids or gaps had to be bridged. To begin with single lane, portable bridges were found useful. In recent times multispan reployable bridges, as described and claimed in Indian Patent Application SI. No. 191281, have been introduced but the design is relatively complex, apart from being expensive and having time-consuming assembling and dismantling operation. With the passage of time and with the rise in population growth and traffic density, it was noticed that such single-lane bridges were becoming bottlenecks, impeding flow of traffic which was creating a lot of problems. Traffic-jam was becoming a regular feature and hence it had become very important to come out with a double-lane, portable, steel bridge which would avoid the difficulties confronting the single-lane bridge. SBD/DS/mE-l/ PATENT 3 Initially it was believed that escalation of the dimensional parameters of a single-lane bridge could provide the answer. But it was found that simple escalation did not and could not produce a bridge which was structurally sound, stable and capable of withstanding stress and strains of heavy, two-lane traffic. The principle object of this invention is to provide a double-lane, portable, steel bridge capable of providing a satisfactory solution to the problems discused above. A further object of this invention is to provide a ready to assemble or to dismantle a steel bridge which is ideally suited for spanning voids, or chasms in difficult terrain. A still further object of this invention is to provide a double-lane, portable, steel bridge which is structurally stable, sturdy and capable of withstanding stress and strains of heavy, two-lane, up and down traffic. Another object of this invention is to provide a portable steel bridge, in which any one or more of the constituent components can be readily replaced substituted with ease in the event of wear and tear due to atmospheric corrosion, or due to craks or breakage on account of natural causes like earthquake. The foregoing objects are achieved by the present invention which provides for a double-lane, portable, steel bridge which comprises in combination: (a) detachable panels forming load bearing girders on both sides of the bridge; (b) bracing frames for holding the formed girders firmly in place ; 4 (c) a plurality of transoms laid across the bottom chords of panels connecting and spacing the main girders apart and at the same time carrying the steel-decked roadway for allowing two-way flow of traffic; (d) a plurality of base plate and bearing assembly provided at both ends of the bridge on which the terminals or ends of the aforesaid girders rest, characterised in that the load-bearing girders are composed of a number of modular units called panels pinned together at ends and placed side to side, if necessary and/or desired, and the entire structure is reinforced for safety reasons by addition of chord reinforcements to the top and bottom of each truss. The aforesaid panels may be of the following dimensions : heights 1448 or 2137 mm ( 57" or 84") and lengths 3048 or 4572 mm ( lO'-O" or 15'-0"), respectively. Load-bearing capacity of the girders are made to increase by adding extra panels alongside, called herein as "truss", and a row of panel put on top of panels, hereinafter called "storey". These girders are connected crosswise by transoms, which are reinforced steel joists, resting on the bottom chord of panels and carry the roadways superstructure. These transoms are tied to the panel chords by suitable holding means called "transom clamps" and fix the trusses in position at predetermined distances apart. End posts, male and female, are provided for connecting female and male lugs, respectively, at the end panels of each truss of the bridge for distributing the shear forces due to end reaction of the bridge. These end posts attached to the ends of each truss of bridge girder are supported on bearings which rest over base plates placed on the ground at each end of the span. Such base plates are intended to spread the load from the bearings evenly over an area of the ground. 5 Apart from the foregoing, a few other notable features are included in the double-lane bridge of the present invention. For instance, sway braces fabricated from channels are fitted diagonally between the transoms, and vertical braces fabricated from angles are provided along said sway braces. A plurality of ribands of varying lengths are fixed to the steel decks. The steel decks serving as the road surface have serrated, honey-comb or ribbed structure to prevent skidding of vehicles during passage over the bridge. These decks are of varying dimensions and used in varying numbers for completion of the road surface. For instance,four numbers of long and short decks are required per bay and four numbers of end decks are required at each end. Usually all the components of the bridge, including erection equipment and rollers are transported to the bridge site by trucks. The person in charge of erection, the Engineer, commences the work by setting a peg on either side of the void or gap to be bridged to represent the bridge centre-line, and then decide on the bank convenient for launching. The bridge is erected on launching rollers complete with a temporary skeleton cantilever structure, known as "launching nose", fitted at the front. The length of the nose' depends on the width of the span to be bridged. The assembly is then launched across the gap by pushing / pulling on the rollers. All panels pins, bolts and nuts are electro-zinc plated to a coating thickness of around 0.025 mm., followed by chromate passivation to ensure long life under extreme service conditions. 6 Other steel components are sand- or shot-blasted to ensure removal of rust and mill scale. Then the components are given a priming coat, usually a coat of red lead or red oxide-zinc chromet primer. The priming coat is followed by 2 coats of finishing paint to specific customer requirement. Components highly susceptible to corrosion are supplied in hot-dip galvanized conditions. If so desired, the complete bridge may be supplied in galvanized condition and/or coated with special paint like epoxy or polyurethane to ensure prolonged resistance to adverse superincumbent conditions. Usually the material of construction of all the components is steel, preferably high tensile steel. The decks, however, can be made from metal reinforced polymeric materials like polypropylene, polystyrene, high density polyethylene, polyurethane, or copolymers thereof. Although such substitution reduces the overall weight of the bridge and the materials are highly non-reactive, but cost - consideration often discourages the potential users. Trials will shortly be carried out at our end to find a suitable answer to the question of cost-factor involving non-ferrous, polymeric parts. The invention will now be described with reference to the accompanying drawings in which - Fig. 1 is a isometric view of the bridge assembly showing the profile thereof. Fig. 2 is a front sectional view of the transom mounted on girders. Fig. 3 is a front view of the bridge showing the details of fixed end on the left and detail of free end on the right. Fig. 4 shows a profile or isometric view of the panel. Fig. 5 shows a panel pin. 7 Fig. 6 shows a chord bolt Fig. 7 illustrates a clamp transom. Fig. 8 represents a tie plate. Fig. 9 shows a bracing frame. Fig. 10 illustrates a post end pair, male and female. Fig. 11 is for a short chord bolt. Fig. 12 shows a bracing bolt. Fig. 13 shows a bearing assembly. Fig. 14 illustrates a base plate on which the bearing assembly rests. Fig. 15 shows a steel deck with an anti-skid surface design, and Fig. 16 shows a riband (13) to be placed on the deck. Turning next to Fig. 1, it may be observed that panels (1) are joined end to end forming the girders. Each pair of girders are firmly held in place by means of bracing frame (6). The ends of panels are attached to post ends (7), secured by panel pins (2). The bases of the post ends (7) are made to rest on base plate (1 l)carrying a plurality of bearings (10). Four such base plates (11) and bearing (10) assemblies are provided at two ends of the bridge. Steel decks (12) are placed on and secured to transoms (14) which are fixed to the girders by means of clamp transom (4). These decks are held in place without any lateral displacement with the help of holding down bolts. Steel decks are of varying dimensions, namely, long, short and end decks. Accordingly, the ribands are also made of varying lengths, e.g. long, short and end ribands(13) As stated earlier, Fig. 2 shows a sectional view of the transom/ at the end of which there are attached a plurality of panels. The thin middle line in each of these columnar figures represents the central line of each individual panel. 8 In Fig. 3, there has been shown details of fixed and free ends of the bridge assembly which are to be grouted or embedded in ground. The topmost horizontal line on the left denotes the road level and that in the middle denotes the top of the deck. It may be observed that the levels of the road and top of the deck are substantially the same, which ensures a smooth flow of vehicular traffic without any bump or jerk. Figs. 4 to 16 of the drawings show various constituent components of the bridge assembly ; brief narrations of individual components are given below. Pig. 4 showing panel MKII is the basic bridge member, made from The chords at top and bottom of the panel terminate at one end in a male lug and at the other end in a female lug. These male and female lugs enable the panels to be connected end to end with panel pins (2). Holes provided in the top and bottom chords take chord bolts (3) to connect panels together forming multiple storey or to connect Chord-reinforcements to reinforce the trusses. Four transom seatings are provided on the bottom chord to accomodate the transomsCO. l^ In both chords and end verticals, holes are provided for fixing bracing frames (6). The top holes in the end verticals are used for fitting the rakers or tie plates (5). All verticals have a slot above the transom seat to take transom clamps (4). 9 Panel pin shown in Fig. 5 of the drawings is used to connect panels together and is made from special alloy steel of high yield strength, which is usually electro-zinc plated to avoid corrosion. The panel pin is inserted through holes in the male and female lugs in the panels and secured with safety pin or split pin. Chord bolt shown in Fig. 6 of the drawings is a steel bolt, electro-zinc plated to resist corrosion. This is used to connect a panel above or below a panel to form multistorey bridge. The shanks of the bolts are tapered to assist drawing the panels into correct alignment during assembly. In Fig. 7, there is shown a clamp transom (4), which is an articulated fastening means used to hold a transom in its seating on the panel. It connects at the slots in the panel vertical and the transom seat, and is tightened by a vice-handle type of screw. It is to be borne in mind that jacks are not to be placed under a transom held by clamps as the connection is not designed for an upward load. Tie plate illustrated in Fig. 8 of the drawings secures the third truss to the second in triple truss standard width bridges and is a flat steel plate with a hollow conical dowel at each end. It is fixed to the panels and end posts (7) with bracing bolts (9). It is used in the undernoted positions - (i) In a triple truss single storey bridge, between the unoccupied raker holes in the panels at each joint. One tie plate is used on each side of the bridge at each joint, between the front panel verticals. (ii) In a triple truss double storey bridge, in the same holes as in (i) above and, in addition, in the corresponding holes, in the upper storey, between the front-end panel verticals. Tie plates cannot be used on the ends of triple truss where a bracing frame (6) is fitted. (iii) Across the top of end posts in triple truss bridges. 10 In Fig. 9 there is shown a bracing frame, which is a light mild steel i welded frame with a hollow conical dowel at each corner. It is used to brace together panels in multiple truss and storey construction of bridge girders in the following positions :- (i) In a multiple truss single storey bridge, horizontally across the centre of the top chords of the panels. (ii) In double storey bridges, in a similar position, horizontally across the top chords of the panels, and additionally, in a vertical position across the rear verticals of second storey panels. (iii) In double storey bridges, vertically across the front end verticals of the second storey panels in the first bay at the head end of the bridge. Fig. 10 of the drawings is for a pair of post ends, female and male. to An end postymust be attached to each end of every main girder truss to transmit the end reaction of the bridge to the bearing (10). The female end post connects to the male lugs at the ends of the panels; two holes are provided at the top end of the post, the lower one for connecting to the bottom storey panel and the upper one for the second storey panel. Connections are made with panel pins. The bottom end of the post embodies a half round bearing block, which fits over the bearing. A step is fitted to the end post to carry the transom, which has always to be placed outside the end panel vertical at the head of the bridge only when using two transoms per bay. This step in used for jacking, but jacks may also be placed under the transom carried by the end posts, because this is held in position by a hinged bracket. Fig. 11 shows a short chord bolt which is similar in design and finish as chord bolt (3) shown in Fig. 6, except that the overall length is less than (15) the latter. This is used to connect the chord reinforcements/to the;panel chords to chord re-inforced bridges. 11 Bracing bolt shown in Fig. 12 of the drawings is rust proof and is equipped with a special lug on the head to prevent rotation at the time of tightening the nut. This is used for the undernoted purposes :- (i) Attachment of rakers (16) to transoms and panels (1). (ii) Attachment of bracing frames (6) to panels (1). (iii) Attachment of tie plates (5) to panels (1). Fig. 13 of the drawings illustrates bearing assembly which spreads the load of the bridge to the base plate. It is a welded steel assembly carrying a round bar upon which the half round bearing of the end post rests. This bar is divided into three lengths by two stiffeners. In the single truss bridge the end post is arranged to bear on the centre length. In the double truss bridge, two bearings are used, so that each truss rests on the centre length of each bearing. In the triple truss bridge, the inner truss bears as before but the outer trusses bear on the two outer positions of the second bearing. Thus it is seldom necessary to use more than two bearings at each end of every main girder for any bridge. Fig. 14 of the drawings depicts a baseplate(11)which is designed to spread the load from the bearings evenly over an area of ground. It is a welded steel assembly of which the centre forms a sunken platform to accomodate the bearings. One baseplate is adequate for one corner of the bridge, whether the construction is of a single, double or triple truss, but the bearing pressure on the ground must be carefully checked for safety reasons. The bearing (10) as shown in Fig. 13 can move around 229 mm (ca9") longitudinally on the baseplate. For bridges on fixed supports, this movement is largely to assist in erection and also allows for expansion of the bridge. 12 Fig. 15 of the drawings depicts the steel deck over which passes the two way traffic. Hexagonal patterns are usually made on the upper surface of such decks which effectively prevents skidding. Two recesses are made on each side of the deck to allow them to sit snugly on the frames mounted therefor. These decks may be of long, short and end varieties, and 4 numbers of long and short decks are required per bay and 4 numbers of end decks are required at each end. Fig. 16 shows ribands which are fabricated from plates and bolted to decks. These also may be of varying dimensions, e.g. long, short and end ribands. Apart from the foregoing, a few other components play an important role, which are as follows : (a) Raker (5) : This is made from high tensige R.S. channel It connects 'the end of the transom to the top of the inner truss and imparts lateral stability to the truss. Hollow conical dowels are fitted at each end, which serve to draw the panels into correct alignment by engaging the holes in the panel and transom. One raker is used on each side of the bridge at every panel junction point, fastened^ means of bracing bolt (9). (b) Sway braces (not.ghow)-Horizontal sway braces are fabricated from channels and are fitted diagonally between the transoms lending strength and stability to the bridge structure. C) Vertical bracesMsMThese braces are fabricated from angles and are used along with horizontal sway braces. 13 The workability and uniqueness of the portable, double lane bridge were verified after fabricating a prototype of 80' - span bridge as shown in the following example, which is given by way of illustration and not by way of limitation: Example Components of undernoted dimensions / masses were fabricated and assembled to erect an 80' - span, 23' - wide bridge. (i) Panel - 3048 mm (10') long and 1448mm (4'9") high between pin hole centres, weighing 283 kg. (ii) Panel pin - 211 mm (8".3125) in overall length, weighing 2.8 kg., including safety pin. (iii) Chord bolt - 310 mm (12M9) long overall and weighed 3.6 kg. (iv) Transom clamp - weighed 3 kg. (v) Tie plate - weighed 1.5 kg. (vi) Bracingframe - 1244.6 mm (4'1") long and 457.2 (1'6") wide between centres of dowel holes, weighing 18 kg. (vii) Raker - weighed 9 kg. (viii) End posts - male end post weighed 59 kg. and a female end post weighed 66.5 kg. (ix) Short chord bolt - weighed 2.5 kg. (x) Bracing bolt - 20 mm (3/4") dia, and 89 mm (3". 5) long, weighing 0.56 kg. 14 (xi) Bearing - 457 mm (1'6") long, 381 mm (1'3") wide and 97 mm (3".75) high from bottom of base plate to top of the round bar, weighing 31.5 kg. (xii) Base plate - 1400 mm (4'7") longx 900 mm (2'11 3/8") wide x 62 mm (2".5) high from bottom of plate to top of channel, weighing 172 kg. (xiii) Transom - weighed 998 kg. (xiv) Horizontal Sway brace- long-weighed 23 kg. and short-weighed 27.5 kg. (xv) Vertical brace - long, weighed 9.5 kg. and short, weighed 8.5 kg. (xvi) Steel deck - long, weight - 312 kg. short, weight - 285 kg. end, weight - 130 kg. (xvii) Riband - long, weight - 23 kg. short, weight - 21 kg. end, weight - 8 kg. Detailed structural analysis of components / elements of the assembled bridge with Panels of 1448 mm height and 3048 mm long was carried out by 3-dimensional finite element modelling in collaboration with Indian Institute of Technology, Kharagpur, in accordance with the loading norms specified (IRC-6) by Indian Road Congress, and specified loading results were ascertained as shown below: Performance of TD construction under various spans and loading TYPE OF LOADING SPAN IN FEET 60 70 8O 90 10O 110 120 >12O 24R o s - 4OR - - - - 60R s - - - - - - 70R s _ _ _ _ 24RR S s _ _ - _ 24RA s o - - Note: v sign indicates that, the above construction may be safely used for that span under the specified loading. 15 The bridge was equipped with strain gauges and dial gauges before placing test-loads in the form of steel / concrete blocks to simulate Class-24 R loading of "IRC-6" and bridge response was measured to evaluate actual tensile / compressive strain and vertical / axial deflections under symmetric and eccentric loadings as well as their Influence lines'. Extrapolated central deflections and maximum tensile / compressive strains were obtained from 'influence lines' for various combinations of wider spans and loadings. The results are shown below in a tabular form, which are in good agreement with the 3-D analysis referred to above: Extrapolated Deflection from Influence Line for Higer Spans of Double Lane Bridges Span (L)ft Deflection in mm Allowable deflection in mm L/800 Satisfy upto IRC Class Loading 24R 30R 40R 60R 70R 80 10.97 19.58 26.51 36.06 49.2 30.48 40R 90 15.39 27.46 37.18 50.57 69 34.29 30R 100 20.85 37.21 50.38 68.53 93.5 38.1 30R 110 27.43 48.97 66.3 90.18 123.04 41.91 24R 120 35.28 62.98 85.27 115.98 158.25 45.72 24R 130 44.48 79.4 107.5 146.22 199.51 49.53 24R 140 55.09 98.33 133.13 181.08 247.07 53.34 None Dynamic characteristics like natural frequency, resonant frequencies and mode shapes were evaluated by exciting the prototype bridge with a mechanical exciter and the results obtained were found to be satisfactory. Similar structural analysis of assembled Bridge with Panels of 2137 mm (7'-0") height and 3048 mm (10'-0") / 4572 mm (15^0") length was carried out and results ascertained are as per Table : DL-10.1 and DL-15.1 as follows: Table ; DL-10,1 ; The safe unit construction under different spans and loadings Double Lane : 7.35 m width Top and bottom members : ISMC 100 Nose material . : Fe 250 Nose dimension ; 75 X 100 with 47 dia hole Panel Type 10'-0" X 7'-0" Vertical and diagonal members : ISMC 75 Panel material : Fe 410 Heavier panel: Diagonal and vertical members are strengthened by 8 mm plate Span 24R 40R 60R . 70R A 60 SSRH1 DSR1H1 ' DSR2H2 SSHRH3 SSHRH3 13 18 18 23 20 392 425 446 443 403 489 918 1242 867 749 70 SSRH1 DSR1H2 DSHR2K4 DSR1H2 DSR1H1 18 24 25 24 24 456 501 541 547 495 513 944' 1258 ¦ 916 907 80 SSRH2 DSR2H2 TSR2H3 DSR2H2 DSR1H4 23 27 29 26 30 524 591 647 643 583 541 976 1371 958 979 90 DSR1 TSR2H3 TSR3H2 DSR2H3 DSR2H2 22 28 36 33 33 629 724 738 728 663 58S 1034 1392 988 1083 100 DSR1H2 TSR3H1 QSR3H4 TSR3H1 TSR2H2 27 33 37 31 35 711 809 899 874 793 624 1072 1449 1050 1132 '7 m "-1 ft in ffi VO 1-1 X o t^- (V. 00 ON oo vo in O rn rN on m in o ts o m '=1- p-^ ¦^- O m C/f ¦-' ry a r-I P U i~t u ¦"" -i u r™1 "-i H Q Q Q 3H2 r- o 2 o rn CM 00 rn IHF " ! m tn in in R2H1 ON m r-- ON £ 2 oo (N o (V, m o ¦^f " (N CN n~> (N tn f/7 ry i-^ , 4 '-' ¦-" >-' 1- £-, a P Q Q p Pi o R1H2 VO O 432 R1H3 ON oo ON 463 R2H1 oo rn 980 418 2 ON >o 1-I 455 £ 2 CN in 252 581 £ 2 505 702 R2H2 VO "n in -i 934 vo Q >-o P D ?-. Q ¦-' p P ¥~- Q P P P Q p^ o vo "- a oo co r-^ i-ti O ^- o "O fO o i-f m ^r OO to rs m O rri o IT) ¦5- CN VO ^-H c/ P T-H C4 Q P § f-H g 24R CO Q in w p rs ro 1375 1240 a1 p o o o o (-> p, CM in i-i Span 24R 40R 60R 70R A 180 DDR1H1 38 1455 1349 TDR2H1 49 1690 1971 TDR3H1 55 3735 2346 TDR2 43 1791 1481 TDR3 39 1717 1577 190 DDR2H1 33 1582 1510 TDR3H1 46 1830 2474 TDR3 39 1937 1563 TDR2H1 52 1784 1730 200 DDR2H1 40 1665 1546 QDR3H1 47 2137 2630 . TDR3 44 2039 1621 TDR3H1 49 1926 3913 210 TDR2HI 39 1969 1698 QDR3H1 53 2243 2677 TDR3 48 2141 1678 TDR3H1 55 2021 2080 220 TDR2H2 44 2080 1749 QDR4H2 54 2426 2754 TDR3H2 53 2278 1752 QDR3H1 53 2348 2663 230 TDR3H1 42 2212 1799 QDR4H2 59 2535 2813 QDR4H1 52 2511 2797 240 TDR3H1 48 2307 1851 QDR4H1 58 2619 2889 Note : Read each row as designation. Live load displacement in mm. Dead weight in kN, Max.support reaction(DL+LL) in kN oo Table : DL-15.1 : The safe unit construction under different spans and loadings Double Lane : 7.35 m width Top and bottom members : ISMC 125 Nose material : Fe 250 Nose dimension : 100 X 125 with 57 diahole Panel Type 15'-0" X 7r-0rr Vertical and diagonal members : ISMC 100 Panel material :Fe410 Heavier panel: Diagonal and vertical members are strengthened by 8 mm plate Span 24R 40R 60R 70R. A 60 SS 20 349 473 SSRH1 19 374 892 DSR1H1 19 415 1228 SSRH1 19 400 849 SSRH1 17 374 729 75 SSRH1 14 467 518 SSHRH3 29 481 932 DSR2H2 23 552 1338 SSRH2 29 504 889 SSRH2 26 471 879 90 SSRH1 23 559 555 DSR2H2 27 658 1004 DSR2H3 35 668 1350 DSR2H1 28 688 966 DSR1H2 TO 628 1052 105 SSRH4 28 663 601 DSR2H4 37 779 1057 TSR3H3 37 888 1429 DSR2H3 36 820 1017 DSR2H3 36 774 1101 120 DSR2H1 26 862 696 TSR3H3 40 1009 1167 QSR4H3 42 1136 1536 TSR3H2 40 1047 1126 TSR3H2 39 995 1184 -vD Span 24R 40R 60R 70R A 135 DSHR2 QSR4H4 DDR1H1 QSR4H2 QSR4H3 30 40 43 41 41 986 1290 1096 1312 1271 1029 1315 1411 1264 1294 150 TSHR3 QSHR4H3 DDR1H4 QSHR4H2 QSHR4H2 29 45 51 43 44 1253 1466 1272 1513 1447 1174 1390 1612 1344 1392 165 TSHR3.H3 DDR1H4 DDR2H2 DDR1H3 DDR1H2 35 49 57 47 51 1420 1392 1411 1445 1354 1241 1533 1786 1322 1319 180 QSHR4H3 DDR2H3 TDR2H3 DDR2H3 DDR2H3 35 54 57 50 50 1748 1554 1801 1633 1554 1481 1S23 2279 1433 1653 195 DDR2H2 TDR3H1 TDR2H3 40 55 52 1660 1954 1944 1593 2376 1972 210 TDR2H2 TDR3H4 42 54 2059 2186 1797 2226 225 TDHR3H4 34 i 2401 1967 Note : Read each row as designation, Live load displacement in mm, Dead weight in k.N, Max,support reaction(DL+LL) in kN 21 Advantages of the portable bridge of this invention : The bridge of the present invention offers a number of advantages as noted below: i) It is built in accordance with modular, pre-engineered design. ii) It is easy to fabricate and quick to assemble. It can even be built manually with minimum number of tools and tackles. iii) It is easy to transport to remote sites in dismantled condition only to be assembled and launched to span the chasms or voids. iv) This ensures unrestricted flow of traffic in both directions, and v) Such a bridge can be dismantled and redeployed to a new site, if and when necessary. While the invention has been described in detail and with reference to the specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without deviating or departing from the spirit and scope of the invention. Thus the disclosure contained herein includes within its ambit the obvious equivalents and substitutes as well. Having described the invention in detail with particular reference to the accompanying drawings and also to the illustrative example given above, it will now be more specifically defined by means of claims appended hereafter. 22. We claim: 1. A double-lane, portable steel bridge which comprises in combination: (a) detachable panels (1) forming load-bearing girders on both sides of the bridge ; (b) bracing frames (6) for holding the formed girders firmly in place ; (c) a plurality of transoms (14) laid across the bottom chords of panels connecting and spacing the main girders apart and at the same time carrying the steel-decked roadway for allowing two-way flow of traffic; (d) a plurality of base plate (11) and bearing assembly provided at both ends of the bridge on which the terminals or ends of the aforesaid girders rest, characterised in that the load-bearing girders are composed of a number of modular units called panels (1) pinned together at ends and placed side to side, if necessary or desired, and the entire structure is reinforced for safety reasons by the addition of chord reinforcements (15) to the top and bottom of each truss. 2. A steel bridge as claimed in Claim 1, wherein load - bearing capacity of the girders are increased by adding extra panels alongside called truss and row of panel put on top of panels called storey. 3. A steel bridge as claimed in Claims 1 and 2, wherein the said girders are connected in a crosswise manner by transoms (14), resting on the bottom chord of the panels and carrying the roadways superstructure. 4. A steel bridge as claimed in Claim 3, wherein the said transoms are tied to the panel chords by suitable holding means called "transom clamps", and fix the trusses in position at predetermined distances apart. SRD/DS/FILE-1/PATE1IT 23 5. A steel bridge as claimed in Claims 1 to 4, wherein end posts, male and female, are provided for being connected to the female and male lugs at the ends of the panels of each truss of the bridge for distributing the shear forces due to the end reaction of the bridge. 6. A steel bridge as claimed in Claim 5, wherein the said end posts attached to the ends of each truss of bridge girder are supported on bearings which rest over base plates placed on the ground at each end of the span and intended to spread the load from the bearings evenly over an area of the ground. 7. A steel bridge as claimed in Claims 1 to 6, wherein sway braces fabricated from channels are fitted diagonally between the said transoms. 8. A steel bridge as claimed in Claims 1 to 7, wherein vertical braces are provided along the said sway braces. 9. A steel bridge as claimed in Claims 1 to 8, wherein a plurality of ribands of varying lengths are provided at the foot of the said truss, which in trun are fixed to the steel decks. 10. A steel bridge as claimed in any of the precefding claims, wherein said steel decks are of varying dimensions having serrated or honey-comb surface structure to prevent skidding, and a plurality thereof is needed for completion of the road surface. 11. A steel bridge as claimed in Claim 10, wherein four numbers of long and short decks are required per bay, and four numbers of end decks at each end. 12. A steel bridge as claimed in Claims 1 to 11, wherein the erection of a bridge is preceded by setting a peg on each side of the gap or void to be bridged to represent the bridge centre line. 24 13. A steel bridge as claimed in Claim 12, wherein the bridge is erected on launching rollers complete with a temporary skeleton cantilever sturcture known as "launching nose", fitted at the front, and the entire bridge assembly is then launched across the gap by pushing pulling on the rollers. 14. A double-lane, portable steel bridge, substantially as hereinbefore described with particular reference to the accompanying drawings and the illustrative Example given before. (a) detachable panels (1) forming load-bearing girders on both sides of the bridge ; (b) bracing frames (6) for holding the formed girders firmly in place ; (c) a plurality of transoms (14) laid across the bottom chords of panels connecting and spacing the main girders apart and at the same time carrying the steel-decked roadway for allowing two-way flow of traffic; (d) a plurality of base plate (11) and bearing assembly provided at both ends of the bridge on which the terminals or ends of the aforesaid girders rest, characterised in that the load-bearing girders are composed of a number of modular units called panels (1) pinned together at ends and placed side to side, if necessary or desired, and the entire structure is reinforced for safety reasons by the addition of chord reinforcements (15) to the top and bottom of each truss.

Full Text

2
The present invention relates to a double-lane, portable, steel bridge of unique design. More particularly, this invention pertains to design and construct a simple, through-type bridge, which can be assembled and erected on site as the components can be transpoted easily and can span a void or gap of nearly 270-ft width. So much so, skilled personnel can assemble and erect a double-lane bridge in couple of day's time, a feat not achievable by conventional bridge-building and erection.
Need was felt for designing a portable bridge and Indian Army Engineers came up with a functional, but small bridge assembly which could span a void of around 60-ft, and capable of handling single-lane traffic. Such bridges were in demand by various agencies, apart from army, Border Security Forces or similar authorities / agencies, border road authorities, P.W.D. (roads), Indo-Tibetan Border Authorities, and various State Governments, particularly in the North-Eastern States and also in Himachal Pradesh, Uttar Pradesh, Uttarakhand, and the like places having difficult terrain where regular road bridges are extremely difficult to build.
After the Indo-China war in 1962, road-building activity was geared up, mainly for speedy troop movement and also to maintain the supply-lines to the strategically important forward areas. Moreover, with the implementation of different development plans to provide people living in remote, difficult to access areas, roads had to be built as a communication link between those people and the administration. In building such roads, numerous voids or gaps had to be bridged. To begin with single lane, portable bridges were found useful.
In recent times multispan reployable bridges, as described and claimed in Indian Patent Application SI. No. 191281, have been introduced but the design is relatively complex, apart from being expensive and having time-consuming assembling and dismantling operation.
With the passage of time and with the rise in population growth and traffic density, it was noticed that such single-lane bridges were becoming bottlenecks, impeding flow of traffic which was creating a lot of problems. Traffic-jam was becoming a regular feature and hence it had become very important to come out with a double-lane, portable, steel bridge which would avoid the difficulties confronting the single-lane bridge.
SBD/DS/mE-l/ PATENT

3
Initially it was believed that escalation of the dimensional parameters of a single-lane bridge could provide the answer. But it was found that simple escalation did not and could not produce a bridge which was structurally sound, stable and capable of withstanding stress and strains of heavy, two-lane traffic.
The principle object of this invention is to provide a double-lane, portable, steel bridge capable of providing a satisfactory solution to the problems discused above.
A further object of this invention is to provide a ready to assemble or to dismantle a steel bridge which is ideally suited for spanning voids, or chasms in difficult terrain.
A still further object of this invention is to provide a double-lane, portable, steel bridge which is structurally stable, sturdy and capable of withstanding stress and strains of heavy, two-lane, up and down traffic.
Another object of this invention is to provide a portable steel bridge, in which any one or more of the constituent components can be readily replaced substituted with ease in the event of wear and tear due to atmospheric corrosion, or due to craks or breakage on account of natural causes like earthquake.
The foregoing objects are achieved by the present invention which provides for a double-lane, portable, steel bridge which comprises in combination:
(a) detachable panels forming load bearing girders on both sides of the
bridge;
(b) bracing frames for holding the formed girders firmly in place ;

4
(c) a plurality of transoms laid across the bottom chords of panels
connecting and spacing the main girders apart and at the same
time carrying the steel-decked roadway for allowing two-way flow of
traffic;
(d) a plurality of base plate and bearing assembly provided at both ends
of the bridge on which the terminals or ends of the aforesaid girders
rest,
characterised in that the load-bearing girders are composed of a number of modular units called panels pinned together at ends and placed side to side, if necessary and/or desired, and the entire structure is reinforced for safety reasons by addition of chord reinforcements to the top and bottom of each truss.
The aforesaid panels may be of the following dimensions : heights 1448 or 2137 mm ( 57" or 84") and lengths 3048 or 4572 mm ( lO'-O" or 15'-0"), respectively.
Load-bearing capacity of the girders are made to increase by adding extra panels alongside, called herein as "truss", and a row of panel put on top of panels, hereinafter called "storey".
These girders are connected crosswise by transoms, which are reinforced steel joists, resting on the bottom chord of panels and carry the roadways superstructure. These transoms are tied to the panel chords by suitable holding means called "transom clamps" and fix the trusses in position at predetermined distances apart.
End posts, male and female, are provided for connecting female and male lugs, respectively, at the end panels of each truss of the bridge for distributing the shear forces due to end reaction of the bridge. These end posts attached to the ends of each truss of bridge girder are supported on bearings which rest over base plates placed on the ground at each end of the span. Such base plates are intended to spread the load from the bearings evenly over an area of the ground.

5
Apart from the foregoing, a few other notable features are included in the double-lane bridge of the present invention. For instance, sway braces fabricated from channels are fitted diagonally between the transoms, and vertical braces fabricated from angles are provided along said sway braces.
A plurality of ribands of varying lengths are fixed to the steel decks.
The steel decks serving as the road surface have serrated, honey-comb or ribbed structure to prevent skidding of vehicles during passage over the bridge. These decks are of varying dimensions and used in varying numbers for completion of the road surface. For instance,four numbers of long and short decks are required per bay and four numbers of end decks are required at each end.
Usually all the components of the bridge, including erection equipment and rollers are transported to the bridge site by trucks. The person in charge of erection, the Engineer, commences the work by setting a peg on either side of the void or gap to be bridged to represent the bridge centre-line, and then decide on the bank convenient for launching.
The bridge is erected on launching rollers complete with a temporary skeleton cantilever structure, known as "launching nose", fitted at the front. The length of the *nose' depends on the width of the span to be bridged. The assembly is then launched across the gap by pushing / pulling on the rollers.
All panels pins, bolts and nuts are electro-zinc plated to a coating thickness of around 0.025 mm., followed by chromate passivation to ensure long life under extreme service conditions.

6
Other steel components are sand- or shot-blasted to ensure removal of rust and mill scale. Then the components are given a priming coat, usually a coat of red lead or red oxide-zinc chromet primer. The priming coat is followed by 2 coats of finishing paint to specific customer requirement.
Components highly susceptible to corrosion are supplied in hot-dip galvanized conditions. If so desired, the complete bridge may be supplied in galvanized condition and/or coated with special paint like epoxy or polyurethane to ensure prolonged resistance to adverse superincumbent conditions.
Usually the material of construction of all the components is steel, preferably high tensile steel. The decks, however, can be made from metal reinforced polymeric materials like polypropylene, polystyrene, high density polyethylene, polyurethane, or copolymers thereof. Although such substitution reduces the overall weight of the bridge and the materials are highly non-reactive, but cost - consideration often discourages the potential users. Trials will shortly be carried out at our end to find a suitable answer to the question of cost-factor involving non-ferrous, polymeric parts.
The invention will now be described with reference to the accompanying drawings in which -
Fig. 1 is a isometric view of the bridge assembly showing the profile
thereof.
Fig. 2 is a front sectional view of the transom mounted on girders. Fig. 3 is a front view of the bridge showing the details of fixed end
on the left and detail of free end on the right. Fig. 4 shows a profile or isometric view of the panel. Fig. 5 shows a panel pin.

7
Fig. 6 shows a chord bolt
Fig. 7 illustrates a clamp transom.
Fig. 8 represents a tie plate.
Fig. 9 shows a bracing frame.
Fig. 10 illustrates a post end pair, male and female.
Fig. 11 is for a short chord bolt.
Fig. 12 shows a bracing bolt.
Fig. 13 shows a bearing assembly.
Fig. 14 illustrates a base plate on which the bearing assembly rests.
Fig. 15 shows a steel deck with an anti-skid surface design, and

Fig. 16 shows a riband (13) to be placed on the deck.
Turning next to Fig. 1, it may be observed that panels (1) are joined end to end forming the girders. Each pair of girders are firmly held in place by means of bracing frame (6). The ends of panels are attached to post ends (7), secured by panel pins (2). The bases of the post ends (7) are made to rest on base plate (1 l)carrying a plurality of bearings (10). Four such base plates (11)
and bearing (10) assemblies are provided at two ends of the bridge. Steel decks
(12) are placed on and secured to transoms (14) which are fixed to the girders by
means of clamp transom (4). These decks are held in place without any lateral displacement with the help of holding down bolts. Steel decks are of varying dimensions, namely, long, short and end decks. Accordingly, the ribands are also made of varying lengths, e.g. long, short and end ribands(13)
As stated earlier, Fig. 2 shows a sectional view of the transom/ at the end of which there are attached a plurality of panels. The thin middle line in each of these columnar figures represents the central line of each individual panel.

8
In Fig. 3, there has been shown details of fixed and free ends of the bridge assembly which are to be grouted or embedded in ground. The topmost horizontal line on the left denotes the road level and that in the middle denotes the top of the deck. It may be observed that the levels of the road and top of the deck are substantially the same, which ensures a smooth flow of vehicular traffic without any bump or jerk.
Figs. 4 to 16 of the drawings show various constituent components of the bridge assembly ; brief narrations of individual components are given below.
Pig. 4 showing panel MKII is the basic bridge member, made from The chords at top and bottom of the panel terminate at one end in a male lug and at the other end in a female lug. These male and female lugs enable the panels to be connected end to end with panel pins (2).
Holes provided in the top and bottom chords take chord bolts (3) to connect panels together forming multiple storey or to connect Chord-reinforcements to reinforce the trusses.
Four transom seatings are provided on the bottom chord to accomodate the transomsCO*. l^
In both chords and end verticals, holes are provided for fixing bracing frames (6). The top holes in the end verticals are used for fitting the rakers or tie plates (5). All verticals have a slot above the transom seat to take transom clamps (4).

9
Panel pin shown in Fig. 5 of the drawings is used to connect panels together and is made from special alloy steel of high yield strength, which is usually electro-zinc plated to avoid corrosion. The panel pin is inserted through holes in the male and female lugs in the panels and secured with safety pin or split pin.
Chord bolt shown in Fig. 6 of the drawings is a steel bolt, electro-zinc plated to resist corrosion. This is used to connect a panel above or below a panel to form multistorey bridge. The shanks of the bolts are tapered to assist drawing the panels into correct alignment during assembly.
In Fig. 7, there is shown a clamp transom (4), which is an articulated fastening means used to hold a transom in its seating on the panel. It connects at the slots in the panel vertical and the transom seat, and is tightened by a vice-handle type of screw. It is to be borne in mind that jacks are not to be placed under a transom held by clamps as the connection is not designed for an upward load.
Tie plate illustrated in Fig. 8 of the drawings secures the third truss to the second in triple truss standard width bridges and is a flat steel plate with a hollow conical dowel at each end. It is fixed to the panels and end posts (7) with bracing bolts (9). It is used in the undernoted positions -
(i) In a triple truss single storey bridge, between the unoccupied raker holes in the panels at each joint. One tie plate is used on each side of the bridge at each joint, between the front panel verticals.
(ii) In a triple truss double storey bridge, in the same holes as in (i) above and, in addition, in the corresponding holes, in the upper storey, between the front-end panel verticals. Tie plates cannot be used on the ends of triple truss where a bracing frame (6) is fitted.
(iii) Across the top of end posts in triple truss bridges.

10
In Fig. 9 there is shown a bracing frame, which is a light mild steel
i welded frame with a hollow conical dowel at each corner. It is used to brace
together panels in multiple truss and storey construction of bridge girders in the following positions :-
(i) In a multiple truss single storey bridge, horizontally across the centre of the top chords of the panels.
(ii) In double storey bridges, in a similar position, horizontally across the top chords of the panels, and additionally, in a vertical position across the rear verticals of second storey panels.
(iii) In double storey bridges, vertically across the front end verticals of the second storey panels in the first bay at the head end of the bridge.
Fig. 10 of the drawings is for a pair of post ends, female and male.
to
An end postymust be attached to each end of every main girder truss to transmit the end reaction of the bridge to the bearing (10). The female end post connects to the male lugs at the ends of the panels; two holes are provided at the top end of the post, the lower one for connecting to the bottom storey panel and the upper one for the second storey panel. Connections are made with panel pins. The bottom end of the post embodies a half round bearing block, which fits over the bearing. A step is fitted to the end post to carry the transom, which has always to be placed outside the end panel vertical at the head of the bridge only when using two transoms per bay. This step in used for jacking, but jacks may also be placed under the transom carried by the end posts, because this is held in position by a hinged bracket.
Fig. 11 shows a short chord bolt which is similar in design and finish as chord bolt (3) shown in Fig. 6, except that the overall length is less than
(15)
the latter. This is used to connect the chord reinforcements/to the;panel chords to chord re-inforced bridges.

11
Bracing bolt shown in Fig. 12 of the drawings is rust proof and is equipped with a special lug on the head to prevent rotation at the time of tightening the nut. This is used for the undernoted purposes :-
(i) Attachment of rakers (16) to transoms and panels (1).
(ii) Attachment of bracing frames (6) to panels (1). (iii) Attachment of tie plates (5) to panels (1).
Fig. 13 of the drawings illustrates bearing assembly which spreads the load of the bridge to the base plate. It is a welded steel assembly carrying a round bar upon which the half round bearing of the end post rests. This bar is divided into three lengths by two stiffeners. In the single truss bridge the end post is arranged to bear on the centre length. In the double truss bridge, two bearings are used, so that each truss rests on the centre length of each bearing. In the triple truss bridge, the inner truss bears as before but the outer trusses bear on the two outer positions of the second bearing. Thus it is seldom necessary to use more than two bearings at each end of every main girder for any bridge.

Fig. 14 of the drawings depicts a baseplate(11)which is designed to
spread the load from the bearings evenly over an area of ground. It is a welded steel assembly of which the centre forms a sunken platform to accomodate the bearings. One baseplate is adequate for one corner of the bridge, whether the construction is of a single, double or triple truss, but the bearing pressure on the ground must be carefully checked for safety reasons.
The bearing (10) as shown in Fig. 13 can move around 229 mm (ca9") longitudinally on the baseplate. For bridges on fixed supports, this movement is largely to assist in erection and also allows for expansion of the bridge.

12
Fig. 15 of the drawings depicts the steel deck over which passes the two way traffic. Hexagonal patterns are usually made on the upper surface of such decks which effectively prevents skidding. Two recesses are made on each side of the deck to allow them to sit snugly on the frames mounted therefor. These decks may be of long, short and end varieties, and 4 numbers of long and short decks are required per bay and 4 numbers of end decks are required at each end.
Fig. 16 shows ribands which are fabricated from plates and bolted to decks. These also may be of varying dimensions, e.g. long, short and end ribands.
Apart from the foregoing, a few other components play an important role, which are as follows :

(a) Raker (5) : This is made from high tensige R.S. channel It connects
'the end of the transom to the top of the inner truss and imparts lateral stability
to the truss. Hollow conical dowels are fitted at each end, which serve to draw the panels into correct alignment by engaging the holes in the panel and transom. One raker is used on each side of the bridge at every panel junction point, fastened^ means of bracing bolt (9).
(b) Sway braces (not.ghow*)-Horizontal sway braces are fabricated from channels and
are fitted diagonally between the transoms lending strength and stability to the
bridge structure.
C) Vertical bracesMsMThese braces are fabricated from angles and are used along with horizontal sway braces.

13
The workability and uniqueness of the portable, double lane bridge were verified after fabricating a prototype of 80' - span bridge as shown in the following example, which is given by way of illustration and not by way of
limitation:
Example
Components of undernoted dimensions / masses were fabricated and assembled to erect an 80' - span, 23' - wide bridge.
(i) Panel - 3048 mm (10') long and 1448mm (4'9") high
between pin hole centres, weighing 283 kg.
(ii) Panel pin - 211 mm (8".3125) in overall length, weighing
2.8 kg., including safety pin.
(iii) Chord bolt - 310 mm (12M9) long overall and weighed
3.6 kg.
(iv) Transom clamp - weighed 3 kg.
(v) Tie plate - weighed 1.5 kg.
(vi) Bracingframe - 1244.6 mm (4'1") long and 457.2 (1'6") wide
between centres of dowel holes, weighing 18 kg.
(vii) Raker - weighed 9 kg.
(viii) End posts - male end post weighed 59 kg. and a female end
post weighed 66.5 kg.
(ix) Short chord bolt - weighed 2.5 kg.
(x) Bracing bolt - 20 mm (3/4") dia, and 89 mm (3". 5) long,
weighing 0.56 kg.

14
(xi) Bearing - 457 mm (1'6") long, 381 mm (1'3") wide and
97 mm (3".75) high from bottom of base plate to top of the round bar, weighing 31.5 kg.
(xii) Base plate - 1400 mm (4'7") longx 900 mm (2'11 3/8") wide x
62 mm (2".5) high from bottom of plate to top of channel, weighing 172 kg.
(xiii) Transom - weighed 998 kg.
(xiv) Horizontal Sway brace- long-weighed 23 kg. and short-weighed 27.5 kg.
(xv) Vertical brace - long, weighed 9.5 kg. and short, weighed 8.5 kg.
(xvi) Steel deck - long, weight - 312 kg.
short, weight - 285 kg. end, weight - 130 kg.
(xvii) Riband - long, weight - 23 kg.
short, weight - 21 kg. end, weight - 8 kg.
Detailed structural analysis of components / elements of the assembled bridge with Panels of 1448 mm height and 3048 mm long was carried out by 3-dimensional finite element modelling in collaboration with Indian Institute of Technology, Kharagpur, in accordance with the loading norms specified (IRC-6) by Indian Road Congress, and specified loading results were ascertained as shown below: Performance of TD construction under various spans and loading

TYPE OF LOADING SPAN IN FEET

60 70 8O 90 10O 110 120 >12O
24R o s -
4OR - - - -
60R s - - - - - -
70R s _ _ _ _
24RR S s _ _ - _
24RA s o - -
Note: v sign indicates that, the above construction may be safely used for that span under the specified loading.

15
The bridge was equipped with strain gauges and dial gauges before placing test-loads in the form of steel / concrete blocks to simulate Class-24 R loading of "IRC-6" and bridge response was measured to evaluate actual tensile / compressive strain and vertical / axial deflections under symmetric and eccentric loadings as well as their Influence lines'. Extrapolated central deflections and maximum tensile / compressive strains were obtained from 'influence lines' for various combinations of wider spans and loadings. The results are shown below in a tabular form, which are in good agreement with the 3-D analysis referred to above:
Extrapolated Deflection from Influence Line for Higer Spans of Double Lane Bridges

Span (L)ft Deflection in mm Allowable deflection in mm L/800 Satisfy upto

IRC Class Loading

24R 30R 40R 60R 70R

80 10.97 19.58 26.51 36.06 49.2 30.48 40R
90 15.39 27.46 37.18 50.57 69 34.29 30R
100 20.85 37.21 50.38 68.53 93.5 38.1 30R
110 27.43 48.97 66.3 90.18 123.04 41.91 24R
120 35.28 62.98 85.27 115.98 158.25 45.72 24R
130 44.48 79.4 107.5 146.22 199.51 49.53 24R
140 55.09 98.33 133.13 181.08 247.07 53.34 None
Dynamic characteristics like natural frequency, resonant frequencies and mode shapes were evaluated by exciting the prototype bridge with a mechanical exciter and the results obtained were found to be satisfactory.
Similar structural analysis of assembled Bridge with Panels of 2137 mm (7'-0") height and 3048 mm (10'-0") / 4572 mm (15^0") length was carried out and results ascertained are as per Table : DL-10.1 and DL-15.1 as follows:

Table ; DL-10,1 ; The safe unit construction under different spans and loadings

Double Lane : 7.35 m width
Top and bottom members : ISMC 100
Nose material . : Fe 250
Nose dimension ; 75 X 100 with 47 dia hole

Panel Type 10'-0" X 7'-0"
Vertical and diagonal members : ISMC 75
Panel material : Fe 410
Heavier panel: Diagonal and vertical members are strengthened by 8 mm plate

Span 24R 40R 60R . 70R A
60 SSRH1 DSR1H1 ' DSR2H2 SSHRH3 SSHRH3
13 18 18 23 20
392 425 446 443 403
489 918 1242 867 749
70 SSRH1 DSR1H2 DSHR2K4 DSR1H2 DSR1H1
18 24 25 24 24
456 501 541 547 495
513 944' 1258 ¦ 916 907
80 SSRH2 DSR2H2 TSR2H3 DSR2H2 DSR1H4
23 27 29 26 30
524 591 647 643 583
541 976 1371 958 979
90 DSR1 TSR2H3 TSR3H2 DSR2H3 DSR2H2
22 28 36 33 33
629 724 738 728 663
58S 1034 1392 988 1083
100 DSR1H2 TSR3H1 QSR3H4 TSR3H1 TSR2H2
27 33 37 31 35
711 809 899 874 793
624 1072 1449 1050 1132

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Span 24R 40R 60R 70R A
180 DDR1H1
38 1455 1349 TDR2H1 49 1690 1971 TDR3H1
55 3735 2346 TDR2 43 1791 1481 TDR3 39
1717 1577
190 DDR2H1
33 1582 1510 TDR3H1 46 1830 2474 TDR3 39
1937 1563 TDR2H1 52 1784 1730
200 DDR2H1 40
1665 1546 QDR3H1
47 2137 2630 . TDR3
44 2039 1621 TDR3H1
49 1926 3913
210 TDR2HI 39 1969 1698 QDR3H1
53 2243 2677 TDR3 48 2141 1678 TDR3H1
55 2021 2080
220 TDR2H2
44 2080 1749 QDR4H2
54 2426 2754 TDR3H2
53 2278 1752 QDR3H1
53 2348 2663
230 TDR3H1
42 2212 1799 QDR4H2
59 2535 2813 QDR4H1
52 2511 2797
240 TDR3H1 48 2307 1851 QDR4H1 58 2619 2889
Note : Read each row as designation. Live load displacement in mm. Dead weight in kN, Max.support reaction(DL+LL) in kN

oo

Table : DL-15.1 : The safe unit construction under different spans and loadings

Double Lane : 7.35 m width
Top and bottom members : ISMC 125
Nose material : Fe 250
Nose dimension : 100 X 125 with 57 diahole

Panel Type 15'-0" X 7r-0rr
Vertical and diagonal members : ISMC 100
Panel material :Fe410
Heavier panel: Diagonal and vertical members are strengthened by 8 mm plate

Span 24R 40R 60R 70R. A
60 SS 20
349 473 SSRH1 19 374 892 DSR1H1
19 415 1228 SSRH1 19 400 849 SSRH1 17 374 729
75 SSRH1 14 467 518 SSHRH3 29 481 932 DSR2H2
23 552 1338 SSRH2 29 504 889 SSRH2 26 471 879
90 SSRH1 23 559 555 DSR2H2 27 658 1004 DSR2H3 35 668 1350 DSR2H1 28 688 966 DSR1H2
TO
628
1052
105 SSRH4 28 663 601 DSR2H4 37 779 1057 TSR3H3 37 888 1429 DSR2H3 36 820 1017 DSR2H3 36 774 1101
120 DSR2H1 26 862 696 TSR3H3 40 1009 1167 QSR4H3 42 1136 1536 TSR3H2 40 1047 1126 TSR3H2 39 995 1184

-vD

Span 24R 40R 60R 70R A
135 DSHR2 QSR4H4 DDR1H1 QSR4H2 QSR4H3
30 40 43 41 41
986 1290 1096 1312 1271
1029 1315 1411 1264 1294
150 TSHR3 QSHR4H3 DDR1H4 QSHR4H2 QSHR4H2
29 45 51 43 44
1253 1466 1272 1513 1447
1174 1390 1612 1344 1392
165 TSHR3.H3 DDR1H4 DDR2H2 DDR1H3 DDR1H2
35 49 57 47 51
1420 1392 1411 1445 1354
1241 1533 1786 1322 1319
180 QSHR4H3 DDR2H3 TDR2H3 DDR2H3 DDR2H3
35 54 57 50 50
1748 1554 1801 1633 1554
1481 1S23 2279 1433 1653
195 DDR2H2 TDR3H1 TDR2H3
40 55 52
1660 1954 1944
1593 2376 1972
210 TDR2H2 TDR3H4
42 54
2059 2186
1797 2226
225 TDHR3H4
34 i
2401
1967
Note : Read each row as designation, Live load displacement in mm, Dead weight in k.N, Max,support reaction(DL+LL) in kN

21
Advantages of the portable bridge of this invention :
The bridge of the present invention offers a number of advantages as noted below:
i) It is built in accordance with modular, pre-engineered design.
ii) It is easy to fabricate and quick to assemble. It can even be built manually with minimum number of tools and tackles.
iii) It is easy to transport to remote sites in dismantled condition only to be assembled and launched to span the chasms or voids.
iv) This ensures unrestricted flow of traffic in both directions, and
v) Such a bridge can be dismantled and redeployed to a new site, if and when necessary.
While the invention has been described in detail and with reference to the specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without deviating or departing from the spirit and scope of the invention. Thus the disclosure contained herein includes within its ambit the obvious equivalents and substitutes as well.
Having described the invention in detail with particular reference to the accompanying drawings and also to the illustrative example given above, it will now be more specifically defined by means of claims appended hereafter.

22.
We claim:
1. A double-lane, portable steel bridge which comprises in
combination:
(a) detachable panels (1) forming load-bearing girders on both sides
of the bridge ;
(b) bracing frames (6) for holding the formed girders firmly in place ;
(c) a plurality of transoms (14) laid across the bottom chords of panels
connecting and spacing the main girders apart and at the same
time carrying the steel-decked roadway for allowing two-way flow
of traffic;
(d) a plurality of base plate (11) and bearing assembly provided at
both ends of the bridge on which the terminals or ends of the
aforesaid girders rest,
characterised in that the load-bearing girders are composed of a number of modular units called panels (1) pinned together at ends and placed side to side, if necessary or desired, and the entire structure is reinforced for safety reasons by the addition of chord reinforcements (15) to the top and bottom of each truss.
2. A steel bridge as claimed in Claim 1, wherein load - bearing
capacity of the girders are increased by adding extra panels alongside
called truss and row of panel put on top of panels called storey.
3. A steel bridge as claimed in Claims 1 and 2, wherein the said
girders are connected in a crosswise manner by transoms (14), resting
on the bottom chord of the panels and carrying the roadways
superstructure.
4. A steel bridge as claimed in Claim 3, wherein the said transoms
are tied to the panel chords by suitable holding means called "transom
clamps", and fix the trusses in position at predetermined distances apart.
SRD/DS/FILE-1/PATE1IT

23
5. A steel bridge as claimed in Claims 1 to 4, wherein end posts, male
and female, are provided for being connected to the female and male lugs
at the ends of the panels of each truss of the bridge for distributing the
shear forces due to the end reaction of the bridge.
6. A steel bridge as claimed in Claim 5, wherein the said end posts
attached to the ends of each truss of bridge girder are supported on
bearings which rest over base plates placed on the ground at each end of
the span and intended to spread the load from the bearings evenly over
an area of the ground.
7. A steel bridge as claimed in Claims 1 to 6, wherein sway braces
fabricated from channels are fitted diagonally between the said
transoms.
8. A steel bridge as claimed in Claims 1 to 7, wherein vertical braces
are provided along the said sway braces.
9. A steel bridge as claimed in Claims 1 to 8, wherein a plurality of
ribands of varying lengths are provided at the foot of the said truss,
which in trun are fixed to the steel decks.
10. A steel bridge as claimed in any of the precefding claims, wherein
said steel decks are of varying dimensions having serrated or honey-comb
surface structure to prevent skidding, and a plurality thereof is needed for
completion of the road surface.
11. A steel bridge as claimed in Claim 10, wherein four numbers of
long and short decks are required per bay, and four numbers of end
decks at each end.
12. A steel bridge as claimed in Claims 1 to 11, wherein the erection
of a bridge is preceded by setting a peg on each side of the gap or void to
be bridged to represent the bridge centre line.

24
13. A steel bridge as claimed in Claim 12, wherein the bridge is
erected on launching rollers complete with a temporary skeleton
cantilever sturcture known as "launching nose", fitted at the front, and
the entire bridge assembly is then launched across the gap by pushing
pulling on the rollers.
14. A double-lane, portable steel bridge, substantially as hereinbefore
described with particular reference to the accompanying drawings and
the illustrative Example given before.
(a) detachable panels (1) forming load-bearing girders on both sides
of the bridge ;
(b) bracing frames (6) for holding the formed girders firmly in place ;
(c) a plurality of transoms (14) laid across the bottom chords of panels
connecting and spacing the main girders apart and at the same
time carrying the steel-decked roadway for allowing two-way flow
of traffic;
(d) a plurality of base plate (11) and bearing assembly provided at
both ends of the bridge on which the terminals or ends of the
aforesaid girders rest,
characterised in that the load-bearing girders are composed of a number of modular units called panels (1) pinned together at ends and placed side to side, if necessary or desired, and the entire structure is reinforced for safety reasons by the addition of chord reinforcements (15) to the top and bottom of each truss.

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Patent Number

201699

Indian Patent Application Number

00017/KOL/2003

PG Journal Number

6/2007

Publication Date

09-Feb-2007

Grant Date

09-Feb-2007

Date of Filing

16-Jan-2003

Name of Patentee

GARDEN REACH SHIPBUILDERS AND ENGINEERS LIMITED

Applicant Address

AN INDIAN COMPANY OF 43/46 GARDEN REACH ROAD KOLKATA-700024

Inventors:

#	Inventor's Name	Inventor's Address
1	NIRMAL BANERJEE	AN INDIAN COMPANY OF 43/46 GARDEN REACH ROAD KOLKATA-700024

PCT International Classification Number

E 01B 15/133

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA