Title:
ORTHOTROPIC TRAILER
United States Patent 3856344


Abstract:
A highway trailer has a relatively low-weight, high-strength load-support bed which includes a pair of longitudinally extending, parallel, inverted T-beams, and a series of side-by-side transverse compound channel members, or pans, welded to the vertical webs of the T-beams in an orthotropic design. Preferably, each pan is substantially J-shaped in cross-section, and comprises a load-supporting horizontal top flange, a horizontal bottom flange, and a vertical web between the top and bottom flanges. The bottom flange and vertical web of each pan are slotted so the bottom of each top flange rests on the top edge of the T-beams. The top flanges are welded together to provide a continuous unitary deck surface extending the length of the T-beams. The top flange, bottom flange, and web of each pan are welded to the T-beams to provide shear continuity between the top deck flanges and the T-beams. A row of spaced apart longitudinal depressions are formed in each top flange to add stiffness to the top deck flanges.



Inventors:
LOEBER F
Application Number:
05/341874
Publication Date:
12/24/1974
Filing Date:
03/16/1973
Assignee:
AMERON INC,US
Primary Class:
Other Classes:
52/674, 105/422, 280/789
International Classes:
B62D25/20; B62D33/02; B62D53/08; (IPC1-7): B62D33/02
Field of Search:
296/28M,28F 280
View Patent Images:
US Patent References:
3049198Building structures1962-08-14Dobbins et al.
2812192Truck trailer frame1957-11-05Cole
2773718Floor construction with integral cross-sills1956-12-11Bohlen
2494404Trailer1950-01-10Nixon
2056137Freight car floor1936-09-29Idoine
1991484Truck body construction1935-02-19Ball



Foreign References:
GB771298A1957-03-27
AU108279A
Primary Examiner:
Sheridan, Robert G.
Assistant Examiner:
Paperner, Leslie J.
Attorney, Agent or Firm:
Christie, Parker & Hale
Parent Case Data:


CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of my application Ser. No. 221,608, filed Jan. 28, 1972, now abandoned.
Claims:
I claim

1. In a highway trailer, a load-support bed including a pair of spaced apart and generally parallel, rigid, elongated open-section metal beams each having at least a vertical web and a bottom flange, and a series of rigid, elongated open-section load-support members each being made of metal and shaped to provide a top flange, a bottom flange below the top flange, and a web integral with and extending between the top flange and the bottom flange, the series of load-support members being mounted on the beams in a side-by-side relation with the bottom of each top flange being in substantially continuous contact with the top of each beam and being rigidly bonded to each beam, the web and the botton flange of each load-support member also being rigidly bonded to each beam, the top flanges of the load-support members being rigidly bonded together to form a continuous rigid panel extending lengthwise relative to the beams for providing a load-supporting deck and also serving as a compression flange for the vertical webs of the beams and a tension flange for the webs of the load-support members to form a stiff, unitary load-support bed of orthotropic design.

2. Apparatus according to claim 1 including a series of spaced apart depressions formed in each top flange to stiffen the top flanges.

3. Apparatus according to claim 1 in which each beam is inverted T-shaped in cross-section and including slotted openings in the web and bottom flange of each load-support member to permit the vertical web of each beam to fit into the slotted openings, with the top edge of the vertical web of each inverted T-shaped beam continuously supporting the bottom surface of each top flange.

4. Apparatus according to claim 1 in which the web and bottom flange of each load-supporting member is bonded to both sides of the vertical flange of each beam

5. Apparatus according to claim 1 including a series of spaced apart openings formed in the web of each load-supporting member.

6. Apparatus according to claim 1 including several stiffening members for providing additional stiffness at longitudinally spaced apart points in the bed, each stiffening member being rigidly secured between a pair of adjacent loadsupport members and shaped so it cooperates with at least one of the load-support members to form a closed-section beam extending parallel to the load-support members.

7. Apparatus according to claim 1 in which the load-support members are made of work hardening steel.

8. In a highway trailer, a load-support bed including a pair of spaced apart rigid, elongated open-section metal beams, a series of rigid, elongated open-section load-support members each being made of metal and shaped to provide a substantially planar top flange, a bottom flange below the top flange, and a web integral with and extending between the top flange and the bottom flange, the series of load-support members being mounted on the beams in a side-by-side relation with the bottom of each flange being bonded to each beam, the web and bottom flange of each load-support member also being bonded to each beam, and the top flanges of the load-support members being bonded together to form a continuous rigid load-supporting deck panel extending lengthwise relative to the beams, and several stiffening beams mounted on the open-section beams for providing additional stiffness at longitudinally spaced apart locations in the trailer bed, each stiffening member being disposed between a pair of adjacent load-support members and having a load-supporting top flange, and a web transverse to the top flange, the top flange of each stiffening beam being in the same plane as the top flanges of the adjacent load-support members, and including means bonding the top flange of each stiffening beam to the top flange of its adjacent load-support members, the bottom flange of at least one adjacent load-support member being bonded to the web portion of the stiffening beam so that said one adjacent load-support member and the stiffening beam cooperate to form a transverse closedsection beam, the entire composite structure forming a stiff, unitary load-support bed of orthotropic design.

9. Apparatus according to claim 8 including a series of spaced apart openings extending through the web of the stiffening member.

10. In a highway trailer, a load-support bed including a pair of spaced apart and generally parallel, rigid, elongated open-section beams which are inverted T-shaped in cross-section and define a vertical web and a bottom flange, the open-section beams being made of a material having a Young's modulus on the order of that of steel, and a series of rigid, elongated open-section load-support members each being made of a material having a Young's modulus on the order of that of steel and being shaped to provide a top flange, a bottom flange below the top flange, a web integral with and extending between the top flange and the bottom flange, and a series of spaced apart depressions formed in each top flange to stiffen the top flanges, each load-support member having slotted openings in the web and bottom flange thereof, the series of load-support members being mounted on the beams in a side-by-side relation with the vertical web of each beam fitting into the slotted openings of the load-support members, and the bottom of each top flange being in substantially continuous contact with the top edge of the vertical web of each beam, the bottom of each top flange being bonded to the web of each beam, the web and bottom flange of each load-support member being bonded to each beam, and the top flanges of the load-support members being bonded to each other to form a continuous, rigid panel extending lengthwise relative to the beams for providing a load-supporting deck and also serving as a compression flange for the vertical webs of the beams and a tension flange for the webs of the load-support members to form a stiff, unitary load-support bed of orthotropic design.

11. Apparatus according to claim 10 in which the web and bottom flange of each load-support member is bonded to both sides of the vertical web of each open-section beam.

12. Apparatus according to claim 10 including a series of spaced apart openings formed in the web of each load-support member.

13. Apparatus according to claim 10 including several stiffening members mounted on the open-section beams for providing additional stiffness at longitudinally spaced apart points in the bed, each stiffening member being rigidly secured between a pair of adjacent load-support members and being shaped so it cooperates with at least one of its adjacent load-support members to form a closed-section beam extending parallel to the load-support members.

14. Apparatus according to claim 13 in which each stiffening member has a load-supporting top flange, and a web transverse to the top flange, the top flange of each stiffening member being in the same plane as the top flanges of its adjacent load-support members, and including means bonding the top flange of each stiffening member to the top flanges of its adjacent load-support members, the bottom flange of at least one adjacent load-support member being bonded to the web portion of the stiffening member so that said one adjacent load-support member and stiffening member cooperate to form a transverse closed-section beam.

15. Apparatus according to claim 14 including a series of spaced apart openings extending through the web of the stiffening member.

Description:
BACKGROUND OF THE INVENTION

This invention relates to highway trailers, and more particularly to a relatively low-weight and high-strength trailer bed.

All states have laws which limit axle loads imposed by vehicles using public highways and streets. Thus, there is a strong economic incentive for truck and trailer manufacturers and companies shipping cargo on fleets of trucks to minimize tare weights of the vehicles so as to maximize pay loads. Substantial economic advantages are gained by reducing the tare weight of trucks carrying maximum pay loads during a large percentage of their total mileage.

Besides the increased pay load resulting from highway tractors and trailers of reduced weight, a low-weight vehicle also produces lower running costs in the form of less maintenance, increased tire life, and an overall increase in fuel economy.

Thus, a trailer having a weight reduction of 1,500 lbs. to 2,000 lbs, can produce substantial cost savings, which can be in the neighborhood of several hundred dollars per week.

SUMMARY OF THE INVENTION

This invention provides a highway trailer having a load-support bed of orthotropic design which is extremely low in weight and easily fabricated from a few similar parts.

Briefly, the trailer bed includes a pair of spaced apart, elongated, rigid open-section beams, and a series of rigid, open-section load-support members rigidly secured to the beams in an orthotropic design to provide a unitary deck for the trailer bed. Each load-support member includes a horizontal top flange, a bottom flange spaced below the top flange, and a vertical web integral with and extending between the top and bottom flanges. The load-support members are mounted on the open-section beams in a side-by-side relation, with the bottom of each top flange resting on the top of each beam. The top flanges of the load-support members are rigidly secured together to form a substantially continuous unitary deck panel extending lengthwise relative to the beams. The top flange, bottom flange, and web of each load-support member are rigidly secured to the open-section beams to provide "shear continuity," i.e., continuous load-carrying capacity uninterrupted by elastic losses, between the open-section beams and the continuous deck panel formed by the top flanges. Moreover, the orthotropic design of the trailer bed enables the continuous deck panel to act as both a compressive member and a tensile member capable of resisting bending in two mutually perpendicular directions. That is, the deck panel acts as the compressive flange of the longitudinal open-section beams to resist bending about a transverse axis through the load-support bed, and also acts as the tensile flange of the vertical webs of the load-support members to resist bending about a longitudinal axis through the load-support bed.

The trailer bed provided by this invention is relatively low in weight and high in strength because of the shear continuity between the structural components of the bed and the ability of the integral deck panel to resist bending in two directions.

In a preferred form of the invention, a series of laterally spaced apart depressions are formed in each top flange. The depressions provide additional stiffness for the top flanges of the load-support members, thereby increasing the ability of the deck panel to carry planar compressive loading.

Additional strength also is provided by several closed-section stiffening members rigidly secured between certain load support members in the bed.

Thus, the trailer bed has high strength and low weight, which makes it possible to carry pay loads of increased weight, thereby providing substantial cost savings for companies shipping cargo on public highways and streets. Moreover, the design of the bed lends itself to fabrication from only a few similar parts, which provides substantial cost savings for trailer manufacturers.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be more fully understood by referring to the following detailed description and the accompanying drawings in which:

FIG. 1 is a fragmentary perspective view showing a highway trailer;

FIG. 1A is an elevation view, partly in section, taken on line 1A--1A of FIG. 1;

FIG. 2 is a fragmentary perspective view showing a loadsupport member from which the bed of the trailer is constructed;

FIG. 3 is a fragmentary plan elevation view taken on line 3--3 of FIG. 2;

FIG. 4 is a fragmentary plan elevation view taken on line 4--4 of FIG. 3;

FIG. 5 is a sectional elevation view taken on line 5--5 of FIG. 4;

FIG. 6 is a fragmentary sectional elevation view taken on line 6--6 of FIG. 3;

FIG. 7 is a fragmentary elevation view showing the construction of the longitudinal T-beams which support the load-support members;

FIG. 8 is a fragmentary plan elevation view taken on line 8--8 of FIG. 7;

FIG. 9A is a fragmentary sectional elevation view taken on line 9A--9A of FIG. 8;

FIG. 9B is a fragmentary sectional elevation view taken on line 9B--9B of FIG. 8;

FIG. 9C is a fragmentary sectional elevation view taken on line 9C--9C of FIG. 8;

FIG. 9D is a fragmentary sectional elevation view taken on line 9D--9D of FIG. 8;

FIG. 10 is an enlarged sectional elevation view showing means for stiffening the load-support members;

FIG. 11 is a fragmentary sectional elevation view taken on line 11--11 of FIG. 10;

FIG. 12 is a fragmentary sectional elevation view showing means for welding the load-support members to the T-beams; and

FIG. 13 is a fragmentary sectional elevation view taken on line 13--13 of FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, a highway trailer 20 is supported on a conventional rear running gear 22. Preferably, the weight of the running gear is reduced by using forged disk aluminum wheels 24. During use of the trailer, a king pin 25 (see FIG. 7) at the front of the trailer is connected to a conventional highway tractor (not shown).

Trailer 20 has a high-strength, low-weight load supporting bed 26 of orthotropic design. The bed includes a pair of longitudinally extending, parallel open-section inverted T-beams 28, each T-beam having a vertical web 30 and a horizontal bottom flange 32. The T-beams comprise the main load-carrying structural members of the trailer bed.

A series of side-by-side elongated transverse load-support members or pans 34 are mounted on the top edges of webs 30 of the T-beams. The pans are open-section members rigidly secured to the T-beams in an orthotropic design. Each pan is formed from sheet metal to provide a substantially J-shaped cross-sectional configuration which includes a vertically extending web 36, and a relatively wide, downwardly opening top channel having a flat, horizontal top flange 38 integral with the top edge of web 36 and a downwardly turned marginal lip 40 at the remote edge of top flange 38. Each pan also includes a relatively narrow, upwardly opening bottom channel having a flat horizontal bottom flange 42 integral with the bottom edge of web 36. Bottom flange 42 extends away from web 30 in a direction opposite that of upper flange 38. An upwardly turned marginal lip 44 extends along the remote edge of bottom flange 42.

A pair of laterally spaced apart, parallel, slotted openings 46 are formed in web 36, bottom flange 42, and lip 44. A separate pair of laterally spaced apart and parallel slotted openings 48 are formed in lip 40. Each slot 46 is aligned longitudinally with a respective one of slots 48 so that each pan can slip over webs 30 of the T-beams, with the bottoms of top flanges 38 resting on the top edges of webs 30.

Thus, top flanges 38 of the adjacent pans provide a continuous deck panel extending the length of the T-beams.

As shown best in FIG. 1 the pans are mounted on T-beams 28 so that lip 40 of each top flange 38 abuts against the top portion of the web of the neighboring pan continuously for the width of the trailer bed. The abutting portions of the adjacent pans are rigidly bonded together by stitch-welding 50 (see FIGS. 1, 8 and 12) so the top flanges provide a rigid load-supporting unitary deck panel. Preferably, each weld 50 is about 11/2 inches wide, and has a naturally V-shaped configuration which substantially prevents fatigue or localized stress occurring in the weld as a result of loads on the deck panel. The purpose of the welds at 50 is to interconnect top flanges 38 so they form the equivalent of a continuous, rigid load-supporting deck panel. It is critical to the orthotropic design of the load-support bed to maintain the structural continuity of the top flanges. For example, certain methods of bolting the top flanges together would be unacceptable, if they would produce elastic losses at the joints which, in turn, would prevent the top flanges from acting as a continuous, rigid flange.

As shown in FIG. 12, the bottom of each top flange 38 is rigidly bonded by stitch-welding 50a to both sides of each T-beam web 30. This rigid connection provides "shear continuity" between the top deck panel and the webs of the main load-carrying T-beams. "Shear continuity" between structural members is defined herein as the capability of maintaining load-carrying ability with stiffness, uniterrupted by elastic losses, between component structural members such that the resulting composite structure has stiffness, or rigidity, equal to that of the basic structural members. For example, the load-carrying top flanges 38 rest on the tops of T-beam webs 30, and are rigidly bonded thereto as an integral unit. This provides shear continuity between flanges 38 and webs 30. On the other hand, shear continuity between these members would be destroyed if (1) the top flanges were bolted to the webs 30 in a manner which would result in elastic losses at the joints, (2) the load-supporting plane of the top flanges is spaced apart from webs 30, or not bonded to the webs, or (3) a material such as aluminum or wood having a substantially lower Young's modulus than that of the steel top flanges and webs is interposed between the top flanges and the webs. In the latter instance, loading on the trailer bed would cause the material of lower modulus to develop shear between the deck panel and the T-beam webs which would absorb energy and therefore would prevent the transmission or continuity of shear between the load-supporting deck panel and the T-beams. In the trailer bed this invention, the T-beams, pans, and other transverse members between the pans are made of steel or other structural metal having a modulus equivalent to that of steel, i.e., in the neighborhood of 30 × 106 psi.

Referring to FIGS. 12 and 13, the vertical web 36 of each pan is rigidly bonded by stitch-welding 50b to each side of each T-beam web 30. This rigid connection provides shear continuity between top deck panel flanges 38 and webs 36.

Bottom flange 42 of each pan is rigidly bonded by stitch-welding 50c to each side of each T-beam web 30. This rigid connection provides shear continuity between webs 36 and bottom flanges 42.

The structural integrity of load-support bed 26 enables the continuous deck panel to act as both a compressive member and a tensile member capable of resisting bending in two mutually perpendicular directions. For example, the deck panel acts as the compressive flange of the longitudinal T-beams to resist bending about a transverse axis through the load-support bed, and it also acts as the tensile flange of the vertical webs of the pans to resist bending about a longitudinal axis through the load-support bed. Moreover, bottom flanges 42 also have compressive and tensile continuity under loads imposed on the load-support bed.

Referring to FIGS. 1 and 1A, a pair of elongated side channel members or rub rails 52, each having a substantially C-shaped cross-sectional configuration, are fitted over the ends of pans 34. Preferably, the rub rails are formed from 10-gauge sheet metal, and may take a variety of suitable shapes for fitting over the ends of the channel members to protect them from impact damage and abrasion. FIG. 1A shows a typical rub rail configuration which includes an upwardly turned, diagonally extending top flange 52a and a substantially horizontally extending and inwardly projecting bottom flange 52b which is turned back on itself to provide a channel which makes a tight friction fit over the ends of the pans. Rub rail 52 is the main support member for a variety of auxiliary load supporting equipment such as load hooks 53a (see FIG. 1A), cargo winches 53b, stake pockets 53c, reflectors 53d, running lights 53e, and the like. The rub rail is also welded in place so it can serve as the top flange of the trailer deck panel.

The detailed construction of pans 34 is understood best by referring to FIGS. 3-6. The pans are formed from 14-gauge sheet steel, preferably carbon steel capable of work-hardening. The pans are preferably 8 feet long, with each pan being continuous for the width of the trailer bed. Top flange 38 is preferably 101/2 inches wide, web 36 is preferably 4 inches deep, and bottom flange 42 is preferably 13/4 inches wide. Each return lip 40 and 44 is about three-fourth inch in depth. The bending of the sheet steel to form the substantially J-shaped configuration work-hardens the steel and thereby increases its physical strength.

A series of laterally spaced apart, parallel, longitudinally extending and downwardly projecting elongated depressions or dimples 54 are formed in top flange 38 of each pan. Depressions 54 are continuous for most of the width of the top flange, and are substantially V-shaped in cross-section, as viewed in FIG. 6. Each depression is about three-eighth inch deep. The depressions are uniformly spaced apart, except that depressions are omitted in those portions of the top flange supported by vertical webs 30 of the T-beams.

During use of trailer bed 26, loads carried on the bed put top flanges 38 in compression. When the trailer bed carries heavy loads, particularly loads which maximize the pay load capacity of the vehicle, there is a natural tendency for the top flanges to buckle or sag. However, the T-beams directly support the continuous load-carrying deck panel provided by the top flanges, and thereby act as transverse stiffening members to keep the top flanges in a common load-supporting plane, thereby resisting the tendency of the flanges to buckle. The working of the steel to form depressions 54 work-hardens the steel to provide additional strength for the top flanges, which increases their ability to stay in a flat plane resisting the tendency to buckle. The work-hardening of the steel increases the strength of the pans to such a degree that additional transverse stiffening members, such as additional T-beams, or closed-section beams, are not needed to prevent buckling of the pans. Thus, a substantial savings of weight results from the use of the high-strength, work-hardened pans.

A series of laterally spaced apart lightening holes 56 are punched through web 36 of each pan. As shown best in FIGS. 3 and 4, each lightening hole preferably is aligned longitudinally with a respective one of the depressions 54. The holes are punched so that the metal surrounding each hole bends away from the plane of web 36 to form a circular flange or lip 58 bordering the hole. The bending of the steel during forming of the holes work-hardens the steel to provide additional strength for the web of each pan. Moreover, the lightening holes produce a considerable weight reduction for the pans.

During use of the trailer bed, loads on the bed put bottom flanges 42 in tension. Bottom flanges 42 provide transverse beam strength for the trailer bed when the bed is subjected to heavy loading. The strength of the bottom flanges 42 is enhanced by return lip 44 which stiffens the edge of each bottom flange to prevent it from deforming under loading. Each bottom flange also includes several laterally spaced apart drain holes 60.

The presently preferred J-shaped configuration of the pans is shown in the drawings. The pans also can be substantially C-shaped (i.e., by turning bottom flange 42 in an opposite direction) without departing from the scope of the invention. The J-shaped configuration is preferred because it is easier to fabricate.

The geometry of the pans also can be varied to increase the capacity for localized loading. For example, changes such as (a) depth increase, (b) increase in the width of bottom flange 42, (c) decrease in the width of top flange 38, (d) increase in metal thickness, and (e) increase in the density of depressions 54 can be made to increase the capacity of the pans for given localized loading situations. Consideration of the above changes together with attendant fabrication advantages can yield an optimum cost/weight profile to suit a given application.

The detailed construction of the trailer bed lower support structure is best understood by referring to FIGS. 7 and 8. The front of the trailer is supported independently of the tractor on a conventional telescoping landing gear 62. A series of spaced apart lightening holes 64 are punched through web 30 of each T-beam rearward of the landing gear. Holes 64 serve substantially the same purpose as holes 56 in the pans. Each lightening hole 64 is formed by bending the metal surrounding it away from the plane of flange 30 to work-harden the steel and thereby provide additional strength for the T-beams. Moreover, each lightening hole 64 provides a substantial weight savings.

As shown best in FIG. 8, the vertical dimension of each T-beam web 30 is relatively narrow at the front end of the trailer, tapering wider toward the load-bearing intermediate portion of the trailer, and tapering narrower toward the end of the trailer. Two series of holes 64 are formed in the wide intermediate portion of web 30, with a single series of the holes being formed in the narrower front and rear portions of the web. Alternatively, a single series of wider holes 65 (shown in FIG. 1) may be formed in webs 30, although it is preferred to use a large number of smaller holes, as shown in FIG. 7, because the additional working of the steel provides greater work-hardening and therefore a stronger structural member.

Each bottom flange 32 of the T-beams is fabricated from alloy steel and bent at several longitudinally spaced points to conform to the lower edge contour of web 30. The two members are then welded together continuously to provide shear continuity between web 30 and flange 32. Preferably, web 30 is sheared out of 10-gauge sheet steel, preferably a type of carbon steel capable of work-hardening.

As shown best in FIG. 8, the front portions of flanges 32 are interconnected by a continuous flat, horizontally disposed plate section 66. The plate section supports a king pin mounting bracket assembly 67.

FIGS. 9A through 9D, 10, and 11 show the detailed construction of the trailer bed, including means for providing additional stiffness for the bed. The front of the trailer bed includes a rearwardly opening, substantially C-shaped elongated transverse channel member 68 extending the width of the bed. Channel member 68 is slotted in a manner identical to pans 34 so the channel member fits over webs 30 of the T-beams. The top flange, bottom flange, and web of member 68 are welded to T-beam flange 30 in a manner similar to that of pans 34 to maintain the desired shear continuity.

Referring to FIG. 9A, additional stiffness in the area of king pin 25 is provided by a vertical stiffening plate 70 extending laterally between vertical webs 30 of the T-beams. The top edge of the plate is stitch-welded to the bottom edge of web 36 of a pan forward of king pin 25. The bottom of plate 70 is stitch-welded to the top of horizontal plate section 66. An identical vertical stiffening plate 72 is spaced rearwardly from plate 70 and rigidly secured between webs 30 of the T-beams at a point behind king pin 25. Stiffening plates 70 and 72 stiffen the bed in the area of the king pin which is subjected to substantial stress when the trailer is hitched and pulled by a tractor.

FIG. 9B shows means for providing additional stiffness for the trailer bed on both sides of landing gear 62. A narrow, vertically extending transverse, elongated stiffening channel 74 is sandwiched between a pair of pans 34. Stiffening channel 74 extends the width of the trailer bed and is located forward of the landing gear. An identical stiffening channel 76 is sandwiched between a pair of pans to the rear of the landing gear.

As shown best in FIGS. 10 and 11, each stiffening channel has an intermediate portion 77 which includes a vertical web 78, and a downwardly opening top channel which includes a horizontal top flange 80 integral with the top edge of web 78 and continuous for the width of the trailer bed, and a downwardly turned marginal lip 82 along the remote edge of top flange 80. The stiffening channels also include an upwardly opening bottom channel having a horizontal bottom flange 84 integral with the bottom edge of web 78, and an upwardly turned marginal lip 86 extending along the remote edge of bottom flange 84. Top and bottom flanges 80 and 84 extend in the same direction from the plane of web 78 to form a substantially C-shaped configuration when the intermediate portion of the stiffening channel is viewed in transverse cross-section.

As shown best in FIG. 11, top flange 80 is continuous for the entire width of the trailer bed. Top flange 80 is welded to the top flanges of the adjacent pans 34 to maintain the desired structural integrity of the deck panel. The bottom of top flange 80 is welded to the top of T-beam webs 30 to maintain the desired shear continuity.

The intermediate portion of each stiffening channel is continuous between webs 30, and is supported at its bottom by a pair of horizontal support plates 88 welded to the inner vertical side walls of webs 30. Stitch-welds 90 (see FIG. 10) rigidly secure the bottom of each intermediate portion 77 to support plates 88. Support plates 88 prevent fatigue failure of the connection of vertical web 78 to main web 30.

Each stiffening channel also has a pair of outer portions 91 each including a vertical web 92 extending downwardly from the edge of top flange 80 in the same plane as vertical web 78. Each web 92 is separated from web 78 by a respective slotted opening 94 which receives a web 30 of a respective T-beam. Webs 92 are welded to the sides of webs 30 to maintain the desired shear continuity.

Several vertically spaced apart and horizontally extending series of lightening holes 96 are formed through vertical web 78 of each stiffening channel. A single row of laterally spaced apart lightening holes 98 are formed through outer vertical webs 92 of the stiffening channels. The purpose of holes 96 and 98 is identical to that of the lightening holes 56 in the pans, i.e., they reduce weight and provide added strength because of the work-hardening of the steel surrounding the holes.

As shown best in FIGS. 9B and 10, stiffening channel 74 cooperates with web 36 and bottom flange 42 of the pan to its rear to form the equivalent of an elongated closed-section transverse stiffening beam extending the width of the trailer bed at a point forward of landing gear 62. Stiffening member 76 forms an identical closed-section stiffening beam rearward of the landing gear. Each closed-section stiffening beam is formed by rigidly securing the top of web 78 to upper lip 40 of the neighboring pan forward of the stiffening channel by stitch-welds 100. Stitch-welds 102 rigidly secure the rear face of web 78 to bottom lip 44 of the neighboring pan rearward of the stiffening channel. Stitch-welds 104 rigidly secure upper lip 82 of the stiffening channel to the top of the web 36 of the neighboring pan to the rear of the stiffening channel. The closed-section stiffening beams provide additional physical strength in the areas of the trailer bed which are subjected to heavy loading when the trailer rests on landing gear 62.

FIG. 9C shows means for stiffening the trailer bed to withstand heavy loading above rear running gear 22. A stiffening channel 106 (identical in construction to channels 74 and 76) is rigidly secured between a pair of adjacent pans, in a manner identical to that described above for stiffening channels 74, 76, to form a closed-section stiffening beam above a spring hanger 108 forward of the front set of wheels. A second identical stiffening channel 110 is identically welded between a pair of pans above an intermediate spring hanger 112 to form a closed-section stiffening beam between the front and rear set of wheels.

FIG. 9D shows the detailed construction of the rear of trailer bed 26. A substantially C-shaped transverse channel member 114 spans the width of the trailer bed at the rear of the trailer. A substantially J-shaped transverse channel member 116 rigidly connects the forward or free end of rear channel member 114 to the rearwardmost pan 34 of the trailer bed. Channel member 116 is slotted so it fits over webs 30 of the T-beams, with its top flange acting as part of the deck surface. Channel member 116 is welded to web 30, its neighboring pan 24, and channel 114 in a manner identical to that described above for pans 24 to provide the desired shear continuity.

The equivalent of a closed-section beam stiffens the rear of the trailer bed above a rear spring hanger 118. The rear stiffening beam includes a substantially Z-shaped transverse channel member 120 extending laterally between the vertical webs of the T-beams. Channel member 120 has a top flange rigidly secured to the bottom edge of channel member 114, and a bottom flange rigidly secured to the inner portions of flanges 32 of the T-beams. An upright diagonally upwardly extending plate 122 extends between a bottom flange 123 of channel member 120 and a downwardly extending lip 124 at the front of rear channel 114. Plate 122 has several series of vertically spaced apart and horizontally extending rows of lightening holes 125 formed through it to work-harden the metal for strengthening the plate sufficiently to provide additional strength for the rear of the trailer. Channel member 120 is so constructed to allow for protecting flush mounting of lights, signals and license plates.

The trailer bed deck panel may have a variety of surfaces to resist abrasion and the like from loads carried on the deck. The deck surface can be a coating (not shown) of epoxy, urethane, or similar material loaded with abrasive material such as sand, carborundum dust, or like media. Alternatively, the deck can be covered with plywood (not shown) treated to withstand abuse, weather conditions, and so forth. As a further alternative, the deck can have a non-skid tape (not shown) applied selectively over critical portions.

The structural members of the load-supporting bed are made of work-hardening steel. Preferably, a medium strength steel such as high manganese/silicon steel, is used as the initial material. The rolling, bending, and dimpling of the steel work-hardens it to such an extent that the members are of high strength steel when work-hardening is completed. The structural members of the bed are better able to take heavier loads and resist dents and the like because of the work-hardening. Moreover the use of medium strength work-hardening steel as the starting material provides substantial cost savings when compared with the use of high strength carbon steel.

Thus, highway trailer 20 has relatively high strength and low weight because of the work-hardened open-section transverse structural members of orthotropic design which are low in weight and have good physical strength. Moreover, the pans of the trailer bed are supported on only a pair of longitudinal open-section beams which are themselves low in weight and work-hardened to provide good physical strength. Thus, the need for a large number of structural members to support the compound channel members is eliminated, which provides a substantial savings in weight.

An additional weight savings is provided by the welded unitary construction of the bed, which eliminates the need for cross-ties or other similar means for rigidly holding the deck-forming structural members in place.

The trailer also exhibits greater stiffness than conventional designs. The open-section pans are supported by the T-beams so that top flanges 38 of the pans provide the equivalent of a stiff orthotropic deck panel which resists bending in longitudinal and transverse directions. Thus, the continuous deck plate provided by top flanges 38 acts as a combination compression flange-tension flange which reduces substantially the structural members required to support loads without buckling, which also is a factor in the reduced weight of the trailer bed. The orthotropic design provides good stiffness vertically and laterally, while remaining torsionally flexible. Thus, the trailer is able to carry maximum pay loads, and yet is flexible enough in torsion to resist the tendency to buckle under heavy loads and prevent shock from being transferred to the load.

The trailer also is relatively inexpensive to fabricate because it is manufactured from a few similar parts.