Plastic panel and structures using the same

1. A barrier comprising:

at least one panel comprising a hollow rotationally molded plastic wall panel for forming part of a sound attenuation barrier, the hollow rotationally molded plastic wall panel having a length greater than a width, a thickness less than the width, a front wall, an opposite back wall and opposed first and second long edge regions, wherein the hollow rotationally molded plastic wall panel comprises a first end and a longitudinally opposite second end, wherein the first long edge region defines a first recessed portion to longitudinally receive and mate with a first longitudinal support structure and wherein the second long edge region defines a second recessed portion to longitudinally receive and mate with a second longitudinal support structure, wherein the first and second recessed portions of the hollow rotationally molded plastic wall panel are generally longitudinally extending; wherein the hollow rotationally molded plastic wall panel comprises a plurality of bridging portions to each form a material bridge between the front wall and the back wall, the plurality of bridging portions being integrally formed with the front wall and the back wall, and the plurality of bridging portions being disposed along the length at spaced positions inward of the first end and the second end;

a vertically extending support structure that is fixed relative to a ground; and

the first and second longitudinal support structures coupled to the vertically extending support structure;

wherein the first and second longitudinal support structures are respectively received in the first recessed portion and the second recessed portion so that the hollow rotationally molded plastic wall panel is supported by the first and second support structures,

wherein a first beam of the first and second longitudinal support structures is fixedly connected to the vertically extending support structure at a lowest beam position and at least a second beam of the first and second longitudinal support structures is fixedly connected to the vertically extending support structure at a position vertically spaced above the lowest beam position to secure the hollow rotationally molded plastic wall panel between the first beam and the second beam.

2. The barrier of claim 1 , wherein each of the plurality of bridging portions comprises a first inwardly projecting portion that extends inwardly from the front wall and a second inwardly projecting portion that extends inwardly from the back wall.

3. The barrier of claim 2 , wherein first and second projecting portions of each of the bridging portions meet and bond with each other at a position toward a middle of an interior of the panel.

4. The barrier of claim 1 , wherein the length of the panel is between about 2 m and about 4 m.

5. The barrier of claim 1 , wherein the thickness of the panel is between about 15 cm and about 25 cm.

6. The barrier of claim 1 , wherein the width of the panel is between about 30 cm and about 100 cm.

7. The barrier of claim 1 , wherein the first and second recessed portions are defined by the hollow rotationally molded plastic wall panel to have a depth and a width, wherein the depth is about half of the width of the first and second recessed portions.

8. The barrier of claim 1 , wherein the hollow rotationally molded plastic wall panel is free of non-moulded longitudinal reinforcing structure.

9. The barrier of claim 1 , wherein the hollow rotationally molded plastic wall panel defines at least one locating recess to allow positioning of the panel in one or more specific positions in relation to cooperating structure on the first or second support structures.

10. The barrier of claim 1 , wherein the hollow rotationally molded plastic wall panel is configured to accommodate movement due to thermal expansion or contraction in a direction of the length or a direction of the width relative to the first and second support structures.

11. The barrier of claim 1 , wherein attenuation of sound through the hollow rotationally molded plastic wall panel is at least about 25 decibels at frequencies between 250 Hz and 5000 Hz.

12. The barrier of claim 1 , wherein the barrier comprises two of the hollow rotationally molded plastic wall panels supported by the first and second longitudinal support structure.

13. The barrier of claim 1 , for use in a sound attenuation barrier near a roadway.

14. The barrier of claim 1 , wherein the first and second recessed portions have substantially the same shape.

15. The barrier of claim 1 , wherein two panels of the at least one panel are positioned end-to end in a line between the first beam and the second beam.

16. The barrier of claim 1 , wherein the first longitudinal support structure is in the form of a first crossbeam and wherein the second longitudinal support structure is in the form of a second crossbeam.

17. The barrier of claim 1 , wherein the first and second recessed portions of the hollow rotationally molded plastic wall panel are approximately u-shaped in cross-section.

18. The barrier of claim 1 , wherein the second beam is clamped to the vertically extending support structure.

19. A method of erecting a barrier, comprising:

erecting a vertically extending support structure that is fixed relative to a ground;

coupling at least two vertically spaced, horizontally extending support beams to the vertically extending support structure; and

positioning at least one panel to be supported in between two of the at least two horizontally extending support beams, the at least one panel comprising a hollow rotationally molded plastic wall panel, the hollow rotationally molded plastic wall panel having a length greater than a width, a thickness less than the width, a front wall, an opposite back wall and opposed first and second long edge regions, wherein the hollow rotationally molded plastic wall panel comprises a first end and a longitudinally opposite second end, wherein the first long edge region defines a first recessed portion to longitudinally receive and mate with a first one of the horizontally extending support beams and wherein the second long edge region defines a second recessed portion to longitudinally receive and mate with a second one of the horizontally extending support beams, wherein the first and second recessed portions of the hollow rotationally molded plastic wall panel are generally longitudinally extending; wherein the hollow rotationally molded plastic wall panel comprises a plurality of bridging portions to each form a material bridge between the front wall and the back wall, the plurality of bridging portions being integrally formed with the front wall and the back wall, and the plurality of bridging portions being disposed along the length at spaced positions inward of the first end and the second end;

wherein the coupling comprises fixedly connecting the first one of the horizontally extending support beams to the vertically extending support structure at a lowest beam position and fixedly connecting the second one of the horizontally extending support beams at a position vertically spaced above the lowest beam position to secure the at least one panel between the first horizontally extending support beam and the second horizontally extending support beam.

20. The method of claim 19 , wherein the coupling and positioning are performed in sequence so that a lower support beam is coupled to the vertically extending support structure, then at least one panel is positioned to rest on the lower support beam, then an upper support beam is coupled to the vertically extending support structure to hold the at least one panel in between the lower support beam and the upper support beam.

21. The method of claim 20 , wherein the positioning comprises positioning two panels of the at least one panel end-to-end in a line between two of the horizontally extending support beams.

22. The method of claim 19 , wherein the first and second recessed portions of the hollow rotationally molded plastic wall panel are approximately u-shaped in cross-section.