Abstract:
An autorack rail road car has an underframe having a main deck, and a rack mounted to the underframe. The rack supports one or more decks above the main deck, and also supports, or defines, an enclosure that protects the automobiles carried as lading. One way to prolong the life of the rack is to delay corrosion. Corrosion may start in locations that are difficult to clean, or that have not been cleaned prior to painting. Autorack upper decks may use longitudinally extending stringers. A stringer of closed section may be less prone to facilitating early corrosion, and may be less prone to drip rust-filled water on automobiles carried as lading. In some embodiments the stringer may be placed at a slope discontinuity in the lading deck, and may overlap that slope discontinuity.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to the field of railroad freight cars, and, in particular to the field of railroad freight cars for carrying automotive vehicles, this kind of car being referred to in the industry as an “autorack” car. 
       BACKGROUND 
       [0002]    Modern autorack cars, which is to say autorack cars built since about 1975 for carrying automobiles, trucks or other vehicles in a multiple deck arrangement, have typically had the structure of a flat car underframe covered by a surface defining a main deck for supporting automotive vehicles. Most typically an upstanding elevated-deck supporting framework is mounted to the underframe. Since about 1975 the framework has usually been enclosed within, or used also to support a barn-like housing structure, which may be referred to as a closure system. Closure systems may include side screens, roof, and end closures, typically in the form of movable doors, the better to discourage thieves and vandals. This superstructure is typically referred to collectively as the “rack” of the autorack. Most typically the framework structure includes a series of vertical posts spaced along the sides of the car, with diagonal bracing or shear web panels between the posts, as may be, and one or two additional decks spaced upwardly from the main deck, and upon which respective second and third layers of automotive vehicles may be transported. That is, the rack may be a bi-level rack (i.e., a single elevated deck spaced upwardly above the main deck of the underframe) or a tri-level rack (two upper decks rather than one). The cars tend to be as tall as permitted under the applicable AAR plate clearance diagrams, for this car type, mainly Plate ‘J’ and Plate ‘K’, with maximum heights above Top of Rail or 19′-0″ and 20′-3″ respectively. The housing may tend to have gable ends and bridge plates that are movable to an extended position to span the gap between adjacent cars during loading and unloading. Those end closures, when open, permit circus loading of the cars, i.e., sequential loading of the automotive vehicles by driving in one end, and out the other on arrival. Although other kinds of end closures are known, most typically radial arm doors are mounted at the ends and are movable between open and closed positions to govern loading and unloading of the cars. The racks are typically replaced twice during the economic life of the autorack car underframe. That is, the old rack is removed from the underframe and replaced with a new set of racks. 
         [0003]    Dirt and corrosion tend to be problematic in autorack service. First, replacement of the rack superstructure, or merely the deck thereof, is not an inexpensive process. The life-limiting feature of a rack may be corrosion. Rusting of the racks is problematic in two ways. First, rust is a problem for the integrity of the racks themselves. Second, and possibly more important, it is generally undesirable for the racks to drip rusty, or dirty, water on brand-new automobiles being carried as lading. Efforts have been made to limit entry of moisture in to autorack cars. Nonetheless, prevention of the onset of corrosion typically remains desirable. One of the ways to avoid early corrosion is to keep the racks clean, and to reduce the number of locations at which moisture and other contaminants may collect. 
         [0004]    In manufacturing, welding soot may tend to collect in every crevice. An approach to this problem is to blast the structure with pneumatically conveyed shot prior to painting. However, the shot blasting process may be imperfect, and it is also desirable that the shot itself not collect in poorly accessible locations in the structure. If not removed the shot may tend to promote poor coating coverage and subsequent corrosion. 
       SUMMARY OF THE INVENTION 
       [0005]    In an aspect of the invention there is an autorack rail road car deck assembly for mounting to a framework of a rack of an autorack car, said autorack car having a lengthwise rolling direction, and a direction cross-wise to the rolling direction. The deck assembly has at least a first decking member for mounting in a position supported by said framework. The decking member has undulations, the undulations being oriented cross-wise. There is at least a first stringer, the first stringer being oriented lengthwise. The first stinger has a hollow cross-section of closed periphery. 
         [0006]    In another feature of that aspect of the invention, the first stringer has capped ends. In a further feature the first stringer is made of a roll-formed section. In still another feature the roll-formed section has ends butt-welded together. In a further feature the roll-formed section has first and second legs that are roll-formed inwardly to lie next against each other, and an external weld is formed along a seam where the two legs meet. In yet another feature the first stringer includes at least a first member and a second member, the first and second members co-operating to form respective first and second portions of the closed periphery of the hollow cross-section. In a yet further feature, the first member defines an open-section member having opposed first and second longitudinally running margins, and the second member defines a closure plate welded across the margins to close the section. 
         [0007]    In another feature, the stringer is substantially triangular in cross-section. In still another feature the first decking assembly has an upper surface over which wheeled vehicles may be conducted, and an opposed underside facing downwardly, and the first stringer is mounted on the underside of the first decking assembly. In yet still another feature the first decking assembly includes the first stringer and a second stringer, and the first and second stringers are mounted to the deck member in a lengthwise-running, cross-wise spaced-apart symmetrical arrangement. In again another feature the undulations of the first decking member define corrugations, the corrugations being oriented cross-wise, and the stringer is mounted to an underside thereof, the stringer running square to the corrugations. In still another feature the closed periphery includes a first portion for placement in mating engagement with the first decking member, and the first portion of the closed periphery includes a first part and a second part, there being slope discontinuity as between the first part and the second part. In yet another feature the first and second parts co-operate to form a reflex angle in the profile. 
         [0008]    In again another feature the first deck member defines a roadway over which to conduct wheeled vehicles in the lengthwise direction. There are at least first and second stringers. The first deck member has a central portion and first and second side margins, the first and second side margins running lengthwise along the central portion. The first and second side margins each meeting the central portion at respective first and second slope changes in the first decking member in the cross-wise direction. The first stringer under-girds the first slope change of the first decking member. In still another further feature the central portion of the deck member is crowned. The side margins meet the central portion at respective first and second transitions. The first and second side margins are mated to the central portion such that the side margins extend in a common, substantially horizontal plane. The first and second stringers overlap the first and second transitions, respectively. In yet another feature each of the first and second stringers has a first portion having a reflex angle formed therein to mate with the transition associated therewith. 
         [0009]    These and other aspects and features of the invention may be understood with reference to the description which follows, and with the aid of the illustrations. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0010]    The description is accompanied by a set of illustrative Figures in which: 
           [0011]      FIG. 1   a  is a general arrangement, side view of an autorack railroad car according to an aspect of the invention; 
           [0012]      FIG. 1   b  is an end view of the autorack railroad car of  FIG. 1   a;    
           [0013]      FIG. 1   c  is an isometric view of the autorack railroad freight car of  FIG. 1   a  without trucks; with housing side panels and roof panels removed to show internal structure, and with the end portions of the mid-level deck removed; 
           [0014]      FIG. 1   d  is a perspective view, from below, of one half of the autorack railroad car structure of  FIG. 1   c;    
           [0015]      FIG. 2   a  is an isometric view of a section of deck for use in an autorack railroad car such as that of  FIGS. 1   a ,  1   b ,  1   c  and  1   d;    
           [0016]      FIG. 2   b  is a half end view of one half of the section of deck of  FIG. 2   a;    
           [0017]      FIG. 2   c  is a half sectional view taken on “ 2   c - 2   c ” of the section of deck of  FIG. 2   a;    
           [0018]      FIG. 2   d  is a side view showing a detail of the deck assembly of  FIG. 2   a;    
           [0019]      FIG. 2   e  is an upwardly looking view of the detail of  FIG. 2   d;    
           [0020]      FIG. 3   a  is an isometric view of a stringer of the deck assembly of  FIG. 2   a;    
           [0021]      FIG. 3   b  shows an end view of the stringer of  FIG. 3   a;    
           [0022]      FIG. 3   c  shows an alternative stringer to that of  FIG. 3   a;    
           [0023]      FIG. 3   d  shows a further alternative stringer to that of  FIG. 3   a;    
           [0024]      FIG. 3   e  shows an alternative stringer to that of  FIG. 3   a ; and 
           [0025]      FIG. 3   f  shows a further alternative stringer to that of  FIG. 3   a.    
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples, of particular embodiments of the principles, aspects or features of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the description, like parts are marked throughout the specification and the drawings with the same respective reference numerals. The drawings may be taken as being to scale unless noted otherwise. 
         [0027]    The terminology used in this specification is thought to be consistent with the customary and ordinary meanings of those terms as they would be understood by a person of ordinary skill in the rail road industry in North America. The Applicant expressly excludes all interpretations that are inconsistent with this specification, and, in particular, expressly excludes any interpretation of the claims or the language used in this specification such as may be made in the USPTO, or in any other Patent Office, other than those interpretations for which express support can be demonstrated in this specification or in objective evidence of record, (for example, earlier publications by persons not employed by the USPTO or any other Patent Office), demonstrating how the terms are used and understood by persons of ordinary skill in the art, or by way of expert evidence of a person or persons of at least 10 years&#39; experience in the rail road industry in North America or in other former territories of the British Empire and Commonwealth. 
         [0028]    In terms of general orientation and directional nomenclature, for rail road cars described herein the longitudinal or lengthwise direction is defined as being coincident with the rolling direction of the rail road car, or rail road car unit, when located on tangent (that is, straight) track. In the case of a rail road car having a center sill, be it a stub sill or a straight-through center sill, the longitudinal direction is parallel to the center sill, and parallel to the top chords and side sills, as may be. Unless otherwise noted, vertical, or upward and downward, are terms that use top of rail, TOR, as a datum. In the context of the car as a whole, the terms cross-wise, lateral, or laterally outboard, or transverse, or transversely outboard refer to a distance or orientation relative to the longitudinal centerline of the railroad car, or car unit, or of the centerline of a centerplate at a truck center. The term “longitudinally inboard”, or “longitudinally outboard” is a distance taken relative to a mid-span lateral section of the car, or car unit. The commonly used engineering terms “proud”, “flush” and “shy” may be used herein to denote items that, respectively, protrude beyond an adjacent element, are level with an adjacent element, or do not extend as far as an adjacent element, the terms corresponding conceptually to the conditions of “greater than”, “equal to” and “less than”. The directions correspond generally to a Cartesian frame of reference in which the x-direction is longitudinal, the y-direction is lateral, and the z-direction is vertical. Pitching motion is angular motion of a railcar unit about a horizontal axis perpendicular to the longitudinal direction. Yawing is angular motion about a vertical axis. Roll is angular motion about the longitudinal axis. Given that the rail road car described herein may tend to have both longitudinal and transverse axes of symmetry, a description of one half of the car may generally also be intended to describe the other half as well, allowing for differences between right hand and left hand parts. In this description, if used, the abbreviation kpsi stands for thousands of pounds per square inch. 
         [0029]    In this discussion it may by understood that persons of ordinary skill in the art are familiar with the Rules and Standards of the Association of American Railroads (the AAR), which govern interchange service in North America. This specification or the accompanying illustrations may refer to standards of the Association of American Railroads (AAR), such as to AAR plate sizes. To the extent necessary or appropriate, those references are to be interpreted in a manner consistent with the Rules and Standards as extant on the earliest of the date of filing of this application or the date of priority of the earliest application from which this application claims priority, as if they formed part of this specification on that date. 
         [0030]    Also for the purposes of the present discussion, it may be taken as a default that the structure of the car is of all-welded mild steel fabrication except as otherwise shown in the illustrations or indicated in the text. This need not necessarily be the case. Other materials, such as aluminum or stainless steel might be used. The rack structure may also be taken as being of steel fabrication, although, again, aluminum or stainless steel might be used, and the side web panels or side screen panels of the car, which may be made of mild steel, stainless steel, or aluminum might also be made from plastic composite material, which may be reinforced composite. 
         [0031]    In  FIGS. 1   a - 1   d , an autorack rail road car is shown generally as  20 . It has an underframe, or underframe assembly, indicated generally as  22 , that is carried upon railroad car trucks  24  for rolling motion in a longitudinal or lengthwise direction along railroad tracks. Underframe  22  is surmounted by an enclosure system which may have the form of an overspanning housing structure indicated generally as  26 , and which may be referred to as “the rack” of the car. The ends of housing structure  26  are open to permit loading and unloading of automotive vehicles. Ingress and egress of those vehicles is governed by a pair of end closures,  28 , such as may be radial arm doors or multiply-folding movable between open and closed positions. 
         [0032]    Underframe  22  has a center sill  30 . Center sill  30  is a “straight through” center sill that runs substantially entire length of the car between first and second ends  32 ,  34  at which strikers  36  are mounted. The main deck  40  extends to either side of the center sill to the sides of the car at side sills  42 ,  44 . The term “straight through” is used in distinction to stub center sills such as used in, e.g., grain cars, where the center sill at each end of the car is truncated inboard of the center plate to leave a “stub”, namely the center plate and draft sill assembly. In a straight through center sill, the center sill extends from one truck center to the other. The outboard portions of the center sill may be identified as the draft sills  38  in which the draft gear and couplers are mounted. Draft sills  38  are extensions of center sill  30  that extend longitudinally outboard of (and often include) the truck center to the striker  36 . 
         [0033]    Side sills  42 ,  44  run lengthwise along either side of underframe assembly  22 , and are structurally connected to center sill  30  by an array of laterally extending structural members  46  which may include cross-bearers  48  and cross-ties (not shown). A cross-bearer is a beam having a first end connected to the center sill at a connection that is intended to be capable of transmitting a bending moment, such that the cross-bearer is also a cantilever that has its root, or built-in end at the center sill. The second end or distal end or transversely outboard end of each cross-bearer is connected to the associated side sill running along that side of the car. The side sills are themselves beams, typically of hollow or open section, formed with an upper flange, a lower flange, and a medial portion that functions as a web to carry shear between the upper and lower flanges. Side sills may sometimes have a somewhat C-shaped section, with the open part of the C facing toward the center sill and the webs of the cross-bearer and cross-ties extending into the C and forming a connection. 
         [0034]    Main deck  40  typically extends across the car from side sill to side sill and from end to end of the car, and provides a driving pathway for wheeled vehicles, i.e., the lading for this kind of car. Main deck  40  is supported by side sills  42 ,  44 , center sill  30 , cross-bearers  48  and such cross-ties as may be, and may form the top flange of one or more of them. In the example illustrated, for example, main deck  40  forms, or is substantially flush with the top cover plate (i.e., top flange) of center sill  30 , over most or all of its length e.g., excluding draft sills  38 . The main deck may also form the top flange of the cross-bearers  46  and cross-ties (if any). The main deck is open at the ends (i.e., the curbs defined by the side sills only run along the sides) such that wheeled vehicles may be end-loaded. 
         [0035]    Looking at the framework of the rack structure  26 , the rack structure  26  includes an array, or a series, of upstanding posts  50 . That are spaced along the left and right hand sides of the car, i.e., along, and standing upwardly of, side sills  42  and  44  respectively. There is an end framing structure, indicated as  52 , that extends upwardly from the ends of the end sill, and which defines the shape of the gable end. Next inboard is “the first post”, an upright side post  54  that runs between the side sill and the top chord at the station of the first lateral cross-members. Next inboard are posts  56 , mounted at the ends of the first lateral frame (i.e., outboard of the truck center), and posts  58 , mounted near the ends of the second lateral frame member inboard of the truck center. Posts  60  are mounted further inboard at the ends of the respective cross-bearers  46  that extend laterally of central portion  48  of center sill  30 . Diagonal shear bracing  61 ,  62  is mounted between main posts  58  and next longitudinally inboard posts  60 . Longitudinally running left and right top chords  64  run along, and tie together, the tops of all of posts  54 ,  56 ,  58 , and  60  as may be. The roof structure  66  is mounted atop top chords  64  and restrains them in the lateral direction, and provides a lateral shear connection between the left and right hand side walls  67 ,  68  of the car. This framework and the stringer form a truss structure that cooperates with the truss structure of the sidewall posts. The framework may support one or more elevated decks, such as a second or mid-level deck  70 , and a third or upper deck  72 . The structure may include sidewall screens of sidewall panels  74  that are mounted between the various posts and that may tend to act as shear panels between those posts and between side sills  42 ,  44  and the respective top chords  64 . 
         [0036]    When the replaceable rack structure of posts and braces and top chords is in place, the high longitudinal members act as chords of a truss more than 10 ft. distant from the side sills. This deep truss structure provides the car with the resistance to vertical bending required when carrying lading in service. As noted above, the underframe is intended to define, and to be, permanent structure of the autorack car, whereas the racks may have roughly one third the life of the underframe. That is, the underframe may be provided with a first set of racks when new, and then with a further two sets of replacement racks during the car&#39;s lifetime. 
         [0037]    The rack structure of the elevated deck or decks includes a set of deck panels, or deck panel assemblies, of which a representative one is shown in  FIG. 2   a  as deck panel assembly  80 . Other than as noted, assembly  80  is symmetrical about the longitudinal vertical (i.e., x-z) centerline plane of the rack, and spans the open space between the left and right hand sidewall support structure of car  20 . It may also be noted that deck panel assembly  80  may be manufactured in different lengths, and a set of deck panels  80  is installed to define a full length deck of car  20 , be it deck  70  or deck  72 . As may be appreciated, each of deck panels  80  may be replaced as an individual module if damaged or corroded, or in need of replacement or repair for whatever reason. Deck panel assembly  80  includes a main, or first, decking panel  82 , first and second, (or left and right) side beams or rails  84 ,  86 , first and second, or left and right, upper longitudinally running members  88 ,  90 ; a vehicle placement securement fitting, or fitting array  92 , hinge fittings  94 ,  96 , and first and second, or left and right hand, longitudinally extending underside stringers  100 ,  102 . 
         [0038]    Main decking panel  82  may include a central portion  104  and left and right hand edge or margin portions  106 ,  108 . Main decking panel  82  may have an upper surface  112  which defines a roadway, or pathway, or track  114  over which wheeled vehicles may be conducted in the lengthwise direction (or x-direction) in the normal procedure of loading and unloading vehicles in autorack cars. Main decking panel  82  may also have an underside, or downwardly facing surface  116  that faces toward the next lower deck, be it the middle deck (in the case of an upper decking panel) or the rail road car main deck  40  of underframe  22 . As installed, main decking panel is spaced upwardly from the next lower deck by a distance commensurate with the carrying of another layer of vehicles on the deck therebelow. Main decking panel  82  may have an undulating form, with up-and-down undulations in the vertical direction made to increase its effective depth of section and therefore its second moment of area for resistance to bending. The undulations may run cross-wise, namely in the lateral, transverse, left-to-right, or y-direction. The undulations run in the direction generally cross-wise to the lengthwise running direction of main decking panel  82  generally, and also of pathway  114 . The undulations may have the form of corrugations  118 . 
         [0039]    Central portion  104  may be formed as a single section, or may be formed by welding two left and right halves together. In that context, the left and right halves may be identical, but reversed and welded together along a central seam. Central portion  104  may be formed on a curvature such that it has an arcuate crown  120 , of which the crest is at, and runs along, the longitudinally running centerline. The downwardly and outwardly sloped margins or edges of central portion  104  meet, and are joined to, left and right hand margin portions  106 ,  108 . The junction of these components may be formed by welding. Margin portions  106  and  108  are oriented horizontally. That is, if decking panel  82  is placed on a flat surface, margin portions  106  and  108  will lie in a common horizontal plane, which central portion  104  deviates convexly arcuately away from that plane. 
         [0040]    Side beams, or rails,  84 ,  86  run in the lengthwise direction along margin portions  106 ,  108 . Each side beam  84 ,  86  has a first leg  122  that extends substantially horizontally, a second leg  124  that extends substantially vertically, and a roll-formed lower flange  126  which is located distant from first leg  122 . In this way first leg  122  functions as an upper flange, and second leg  124  functions as a vertical shear web. The distal portion of first leg  122  that is most distant from second leg  124  overlaps, and is welded to, a respective one of margin portion  106  or  108 . The corrugations of margins  106 ,  108  extend downwardly of first leg  122 . The ends of portions  106 ,  108  terminate inboard well clear of second leg  124 , and are offset laterally inboard relative to flange  126 , such that a water drip falling straight down from an open corrugation end would drop clear of flange  126 . 
         [0041]    Longitudinally running members  88  and  90  are mounted to the upwardly facing surfaces of the corrugations, symmetrically to either side of the centerline of crown  120 . Members  88  and  90  may have the form of open structural section members, and in one form may be inverted channels or top-hat sections with the toes of the legs mated to surfaces  112  of the successive corrugations. Members  88  and  90  may function as upper, longitudinal flanges of deck panel assembly  80 . They may also function as upstanding guideways, or curbs, for wheeled vehicles being conducted along deck panel assembly  80 . To the extent that the open section faces downward, and is self-draining, it is not a place where moisture, dirt, or other material may tend to collect. 
         [0042]    Securement fitting  92  may have the form of a locking rail spaced laterally outboard from member  90 . Securement fittings may be placed on both sides of the centerline of deck panel assembly  80 , however, in the embodiment shown only a single securement fitting rail is shown, it being a non-symmetrical feature of an otherwise symmetrical assembly. The apertures formed in the inboard upstanding leg of securement fitting  92  provide engagement points for wheel lock-down apparatus, or chocks, used to prevent motion of wheeled vehicle lading during operation of railcar  20 . 
         [0043]    Hinge fittings  94  and  96  may mate with corresponding hinge fitting of adjacently placed movable decks or bridge plates, as may be. Mounting bracket assemblies  98  define the mounting interfaces at which deck panel assembly  80  is connected to the side post array, and thus suspending in an overhead spanning position relative to any lower deck or decks. 
         [0044]    Underside stringers  100  and  102  may be mounted to the underside, or downwardly facing surface  116  of the successive corrugations of main decking panel  82 . They may be placed laterally outboard of respective upper longitudinally running members  88 ,  90 . They may be placed laterally closer to side beams  84 ,  86  than to members  88 ,  90 . Each may be placed adjacent to a respective slope discontinuity  128  at the junction of central portion  104  and each of side portions  106  and  108 . Underside stringers  100 ,  102  may each be placed to overlap slope discontinuity  128 , thereby to provide reinforcement at what might otherwise be a location of weakness in the panel. 
         [0045]    Mounting bracket assemblies  98  may include fittings such as mounting plates  130 , which may be substantially rectangular and which may define a mounting foot of deck panel assembly  80 . They may have pre-bored holes that locate on the upright posts, as may be. Diagonal reinforcement, or braces, or load spreading members  132 ,  134  may be positioned with one end rooted to plate  130 , and a distant end attached to main decking panel  82  or to one of underside stringers  100 ,  102 . 
         [0046]    In the past, stringers for autorack decks have been made with an L-shaped piece of steel, and angle iron, installed with its toes upward, mounted to the underside of the deck sheet. When thus mounted, the stringer forms a trough that may be liable to collect dirt and debris, particularly during the shot blast process prior to painting where the trough may tend to function as a shot trap. When debris or other material of this nature remains in the trough, it subsequently may be a rust initiation site, and may cause or hasten premature rusting of the rack. Further, where rusting occurs, and there is moisture in the car, whether from collection of rain or snow, dripping of automobiles when loaded, or from condensation overnight, the rusty water may drip on the automobiles carried as lading within the autorack, thus potentially ruining their finish. Shot that collects from the blast process, as well as dust, dirt and debris from ordinary usage, should be removed. It is a painstaking task. The process may be difficult due to either lack of access or poor access. It is generally desirable to need to spend less time cleaning after blast, and to deliver a cleaner product. By replacing the L-shaped stringer with a closed section, the trough is covered. A closed stringer prevents shot, dust, and dirt from being collected, greatly simplifying cleaning. This may tend to discourage or prevent the collection of debris therein. This in turn may reduce or eliminate the need for cleaning, and may reduce or delay the onset of rusting of the stringer. Having a closed stringer may tend to prevent it from trapping dirt, and hence to reduce the need for regular cleaning, or to allow longer intervals between cleaning. Having a cleaner autorack may tend to allow them to deliver automobiles with less dirtying and damage. 
         [0047]    Several embodiments of a closed stringer are shown and described herein. This includes typical L-channels with closure plates welded either on top or inside; a roll-formed profile with continuously welded seam; and standard hollow structural sections. 
         [0048]    In  FIG. 3   a  a stringer, be it  100  or  102 , is shown as  140 . Stringer  140  runs the length of deck panel assembly  80 . As may be noted stringer  140  has an external wall section  142  that defines a periphery, that is, when oriented as installed, closed at the top side as at  144 , such that water may not tend to collect in stringer  140 , and such that blast shot may also tend not to collect. The periphery may be closed all-around such that the section is a closed hollow structural section. The external wall  142  includes not only the top side or part or portion, but another portion  146  that forms the remainder or balance of the closed section. Further aiding in closing the section, stringer  140  may be closed at its ends, as, for example, by end caps  138  such as may be welded or otherwise fixed in place. 
         [0049]    The closed section may have a multitude of different possible forms. It may be substantially circular, or square, or rectangular, or D-shaped. In the examples shown it may be substantially three-sided or triangular. The sides or parts, or portions need not be planar, i.e., linear as viewed in section. However many sides there are, and whether those sides be straight or not, the upper part may provide a surface, or seat, such as at  148  for mating engagement with the underside of main decking panel  82 . In the embodiment illustrated in  FIGS. 3   a  and  3   b , top side  144  has a kinked or dog-legged, or gull-winged, or reflex angle shape, there being first and second parts  150  and  152  of top side  144 , parts  150  and  152  meeting at an internal angle that exceeds 180 degrees, the angle and shape being suited to seat next to, to accommodate, or to conform to, the slope change, or slope discontinuity, at the transition or junction between central portion  110  and one or the other of margin portions  106 ,  108  of main decking panel  82 . Top side  144  need not be horizontal, but may be on a slant, such that it may not be the “top” of stringer  144 , but may be the uppermost side thereof. In the example of  FIGS. 3   a  and  3   b , parts  150  and  152  may be substantially planar. The end portions, or legs  154 ,  156  of parts  150  and  152  may be roll formed such that they curl inwardly next adjacent to each other. Where the radii of the back of legs  154 ,  156  come together, a fillet weld is formed along stringer  140  as indicated at  136 . The fillet weld may lie shy of (i.e., below), or flush with the planes of parts  150  and  152  so as not to impede mounting of stringer  140  next to the transition of main decking panel  82 . As can be seen, in this embodiment top side  144  overlaps the slope change discontinuity in main decking panel  82 . In this embodiment, in which stringer  140  is substantially triangular in section, top side  144  may be the long side, and the other two sides are identified as second side  158  and third side  160 . Second and third sides  158  and  160  may meet at a right-angled corner. Any or all of the vertices of the section may be radiused, as indicated. 
         [0050]    In other embodiments, top side  144  need not be kinked or dog-legged, but may be straight as viewed in section (such that top side  144  is planar), or may follow an arc such as may correspond to main decking member  82  and the slope change therein. Further, stringer  140  need not be placed at, or overlap the slope change discontinuity in main decking panel  82 , or at the junction of the margins of portion  104  with  106  or  108  as may be. Stringer  140  could be placed to either side of that junction, either undergirding portion  104  or either of portions  106  and  108 . 
         [0051]    While stringer  140  may be made of a roll-formed section with re-entrant legs, as shown in  FIGS. 3   a  and  3   b , it may also be formed as a roll-formed section  162  in which toes  166 ,  168  are butt-welded together, as in  FIG. 3   c ; or may be a seamless steel section  170  as shown in  FIG. 3   d , which may have sides corresponding to those described above. 
         [0052]    In the alternative of  FIG. 3   e , stringer  140  may have the form of a two (or more) part section  170 , in which there is a structural member  172  which has a hollow or formed structural section, but in which that section is open. A second portion  174 , which may be a cap plate, is welded across toes  176 ,  178  of member  172 , thus forming a closed section. As may be understood, this is done prior to mounting of stringer  140  to main decking panel  82 , such that the section is closed prior to welding, shot blasting and painting. Although structural member  174  may be a channel or other multi-sided or circular or other form, in  FIG. 3   e  it may have the form of an angle iron  180  having first and second legs  182 ,  184  corresponding generally to sides  158  and  160 , above. Structural member  172  may have the a form generally corresponding to first part  144 , including any kink or dog leg to facilitate mating engagement with main decking section  82 , as may be. Structural member  172  may extend slightly beyond the tips of the toes of legs  182 ,  184 , those tips abutting the back side of member  172 , with appropriate fillet welds being made. Member  172  need not be of the same thickness of material as member  174 . In one embodiment it may be somewhat thinner. On assembly, the margins of member  172  are welded to the downwardly facing surface of main decking member  82 . 
         [0053]    In this alternative, the uppermost side defined by structural member  172  extends beyond the tips of the open section of structural member  174 . In the further alternative of  FIG. 3   f  there is a two-part section  190  that includes a first member  192 , it being an open hollow formed structural member, such as a channel or angle iron, having spaced apart toes  194 ,  196 . However the spanning, or closing member, identified as plate  198 , is welded to the inside of toes  194 ,  196 . Plate  198  may be shy of a tangent line drawn across toes  194 ,  196  by some distance h 198 . Plate  198  may be flat, i.e., planar. Section  190  may be welded to the underside of main decking sheet  82  and accommodate a discontinuity in curvature, or an asperity in structure within the space provided by h 198 . In this circumstance, toes  194 ,  196  are welded to the downwardly facing surface of main decking sheet  82 . As before, section  190  may be substantially triangular, and it is understood that section  190  is provided as a complete, pre-fabricated closed section. 
         [0054]    Any closed-section stringer would provide the advantages of this feature. An open-section design that had the opening at the bottom would provide some of this feature&#39;s advantages, but not completely. 
         [0055]    Various embodiments have been described in detail. Since changes in and or additions to the above-described examples may be made without departing from the nature, spirit or scope of the invention, the invention is not to be limited to those details.