Lightweight low profile floor structure

Abstract

Longitudinal beams span between torque boxes located at each end. The beams attach to the torque boxes to prevent vertical movement or rotation about their horizontal axis, or a fixed end condition. The longitudinal beams cover the width of a platform used to support pallets, and the ends may have wheels for transport of the pallets. The torque box attaches to a moment beam to prevent rotation between the two members about the lateral axis. The torque box has a high strength to transmit all of the moment generated by the end condition through it and into the moment beam. This fixed end condition has the advantages of light weight, low deflection, and low beam depth.

Description

Often in the structural design of a floor structure, or any horizontal surface that requires the ability to sustain vertical loading, it is desirable to maintain a minimum structural thickness. It is also desirable to maintain a low weight for cost and other reasons. These two factors are particularly desirable for transport containers.

SUMMARY OF THE INVENTION

While the present invention has numerous applications, a preferred embodiment is for transport of small containers, for example as described in James Lawrence et al U.S. Pat. No. 6,599,082, incorporated into the present application by this reference, floor of which is designed to carry conventional pallets. Another application is for building construction, in which a floor or roof structure is designed of Reinforced concrete or steel. Greater spans may be achieved because of the reduced stress and deflection inherent in this design.

It is well known that beams with fixed ends deflect less, and have lower stresses than simply supported beams when both beams have the same span and loads. A fixed end condition is typically accomplished in common floor structures by using a single beam over multiple spans or in space frames using moment carrying joints. However, for a platform supported on each end, these are not possible. The present invention spans the distance between end supports without the use of simple beams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a floor structure comprised of longitudinal beams, a, a torque box b, and a moment beam c; and,

FIG. 2 shows a free body diagram of this beam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A set of longitudinal beams which span between torque boxes located at each end, are attached to the torque box in such a way as to prevent vertical movement or rotation about their horizontal (lateral) axis, known in the trade as fixed end condition. Enough longitudinal beams are provided to cover the width of the platform. This platform may be used to support pallets, for example, and the ends may be supported by wheels for easy transport of lading contained on the pallets.

The torque box b is attached to moment beam c in such a way as to prevent rotation between the two members about the lateral axis. The torque box is designed to have a high enough strength to transmit all of the moment generated by the end condition at the end of the longitudinal beam a through the torque box b and into the moment beam c, thereby providing a fixed end condition with the aforementioned structural advantages of light weight and low deflection, while maintaining a low beam depth.

These features are of particular importance for the above mentioned platform to support and transport pallets because of height and weight limitations.

Concerning member sizing and optimization, the relative cross sectional geometric properties of each member of the structure can be calculated to achieve an optimal design.

To determine the properties of the moment beam, first determine the degree of fixity that will result in the lowest maximum stress along the longitudinal beams. FIG. 2 shows a free body diagram of this beam. Because of the constraint of the torque box and moment beam, moment M_a is produced, which acts in the same direction M_b, at beam center, and helps to reduce M_b, thus lowering the bending stress. The critical stress occurs at the location with the highest moment, assuming a beam of uniform cross section, and the sum of these two moments must equal the moment induced by the vertical forces, in this case W*L/8. If both moments are equal, the critical stress (moment) occurs in both places, and is a minimum. Then M_a=M_b=W*L/16. The stiffness of the supporting joint at “A” can be calculated to produce this moment.

Claims

1. A floor structure comprising:

a plurality of longitudinally extending beams;

at least a pair of longitudinally spaced, and transversely spaced torque boxes;

at least one moment beam vertically spaced from said torque boxes, and extending between said transversely spaced torque boxes; and

attachment means attaching said moment beam to said torque boxes.

2. A floor structure according to claim 1 wherein said attachment means comprise plates extending longitudinally and vertically between said moment beam and said transversely spaced torque boxes.

3. A floor structure according to claim 1 comprising a plurality of longitudinally spaced transversely extending supports extending between said longitudinal beams.

4. A floor structure according to claim 3 including a plurality of vertically extending, laterally spaced vertical supports attached to the outermost of said longitudinal beams.

5. A floor structure according to claim 4 including a plurality of vertically extending, laterally spaced, vertical supports attached to the outermost of said longitudinal beams.

6. A floor structure according to claim 5 including a plurality of vertically extending, laterally spaced, vertical supports attached to the outermost of said longitudinal beams.

7. A floor structure according to claim 6 including a plurality of transversely extending, longitudinally spaced upper supports attached to the upper portion of said vertical supports.

8. A floor structure according to claim 6 wherein said upper supports include means for interconnecting opposite ones of said upper transversely extending supports.

9. A floor structure according to claim 8 wherein said upper vertically extending and transversely extending supports are retractable.