Technique for prestressing composite members and related apparatuses

Abstract

Disclosed is a method for increasing and optimizing the structural performance of composite structural member for use as primary load-bearing members through the introduction of prestressing members to the structure. Prestressing may occur by either pre-tensioning or post-tensioning the reinforced polymer structure. The teachings of the present disclosure are useful in constructing structural elements of bridges, buildings, pipes, poles, and other common structural members, including pilings and plywood.

Description

DRAWINGS

The above-mentioned features and objects of the present disclosure will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which:

FIG. 1 shows an embodiment of the process of making one type of composite combining the matrix material and reinforcements to form individual composite lamina, which are rotated, stacked and bonded, or organized by other means know to the art, to produce a composite laminate.

FIG. 2A shows an embodiment of a sectional view of a typical prestressed composite beam with the pre-stressing members placed eccentrically.

FIG. 2B shows an embodiment of a side view of a typical prestressed composite beam that is simply supported on both ends and subject to a dead weight or applied load on the upper surface at the midpoint of the beam.

FIG. 2C shows an embodiment of a stress diagram illustrating the stress distribution on the typical prestressed composite beam as a function of section when the composite prestressed beam is loaded.

FIG. 3 shows an embodiment of a longitudinal cross section of a typical prestressed composite girder showing a method of pre-stressing the girder by affixing a tension retention device at the end of the pre-stressing members.

FIG. 4 shows an embodiment of a perspective view illustrating the process of pre-tensioning the fibers or cables in a typical prestressed composite member by stretching the pre-stressing members on heated drums in a curing chamber while the composite member cures.

FIG. 5 shows a perspective view of an embodiment illustrating the process of pre-tensioning pre-stressing members within a pre-cured composite members.

FIG. 6A shows a cross section of an embodiment of an improved plywood, which is prestressed on two sides.

FIG. 6B shows a perspective view of an embodiment of an improved plywood, which is prestressed.

FIG. 7 shows a perspective view of an embodiment of prestressed composite pilings.

Claims

1. A method of changing the stress profile of a composite member comprising the steps of: (a) providing composite member; and(b) providing at least one prestressing member;wherein the prestressing member is used to prestress the composite member.

2. The method of claim 1, further comprising at least one tension retention device.

3. The method of claim 1, wherein the composite matrix material of the composite member is ceramic, metal, organic or polymer resin such as epoxy, polyurethane, phenolic resin, amino resin, polypropylene, polyethylene, bismaleimide, BMI, polyimide, and polyamide, metal, ceramic or organic compound.

4. The method of claim 1, wherein the at least one reinforcement member of the composite member is carbon, E-glass, S-glass, aramid, kevlar or combinations thereof.

5. The method of claim 1, wherein the prestressing member is either pre-tensioned or post-tensioned.

6. A kit of parts for making a prestressed composite member comprising: (a) an composite matrix material;(b) at least one reinforcement member; and(c) at least one prestressing member;wherein the composite matrix material and the at least one reinforcement member are used to form an composite member;and wherein the prestressing member is designed to prestress the composite member.

7. The kit of claim 6, further comprising at least one tension retention device.

8. A method for reducing construction costs comprising the step of substituting traditional building materials with prestressed composite members.

9. The method of claim 8, wherein costs are reduced through a reduction in the quantity of building materials required for building structures or a reduction in components used to fabricate building materials that are required for building structures

10. The method of claim 8, wherein costs are reduced by selecting building materials with suitable stress profile for an intended application of the building material.

11. An improved plywood-like building material comprising prestressed plywood strengthened by use of a prestressing member, wherein the prestressing member is fixed to the plywood by a laminate, strand, cable, rod, fabric, or cloth on one side, two sides, between the plies of the plywood, or a combination thereof: wherein the plywood-like building material is one of plywood, oriented strand board and other wood based panel and laminated product.

12. The improved plywood-like building material of claim 11, wherein the prestressing member may be made of steel, aluminum or other metal rods or cables; natural fibers, such as flax, kenaf, hemp, or wood; synthetic fibers, such as E-glass, S-glass, aramid, carbon, graphite, silicon carbide, aluminum, boron, ultrahigh molecular weight polyethylene, polybenzoxazile (PBO), nylon, vectran, polybenzimidizole (PBI), vectra, dyneema, certran, and spectra; or other suitable prestressing implements known to those skilled in the art, such as shape memory alloys and materials responsive to changes in temperature, electrical impulse or magnetic field.

13. The improved plywood-like building material of claim 11, wherein the laminate is embedded in epoxy resin.

14. The improved plywood-like building material of claim 11, wherein application of a prestressing member is used to customize the stress profile of the plywood, oriented strand board, or other wood based panel or laminated product.

15. The improved plywood-like building material of claim 11, wherein the prestress is accomplished by pre-tensioning or post-tensioning the prestressing member.

16. A method of reducing construction costs with an improved plywood-like building material comprising the step of treating a plywood-like building material with at least one prestressing member affixed to the plywood, oriented strand board, or wood based panel with a laminate layer: wherein application of the at least one prestressing member to the plywood-like building material modifies the stress profile of the plywood-like building material.

17. The method of claim 16, wherein reduction of costs is accomplished by improving the structural qualities a lower grade of plywood-like building material, wherein the improved lower grade of wood products may be used for building purposes for which unimproved lower grade plywood-like building material would otherwise be unsuited.

18. The method of claim 16, further comprising the step of providing a plurality of improved plywood-like building materials in a plurality of stress profiles, wherein each improved plywood-like building material has a stress profile optimized for at least one specific application.

19. A method of making an improved plywood-like building material comprising the steps of: (a) providing a wooden plywood-like building material;(b) providing a laminating material;(c) providing at least one prestressing member; and(d) treating the plywood-like building material with the laminating material and the at least one prestressing member to form a laminate layer affixed to the plywood-like building material, wherein the laminate contains the at least one prestressing member; andwherein the laminated plywood-like building material exhibits a modified stress profile.

20. The method of claim 19, wherein the laminating material is applied to the plywood-like building material using vacuum assisted resin transfer molding lamination or spray molding.

21. The method of claim 19, wherein the laminating material is applied between the plies of the plywood.

22. An improved composite piling comprising a fiber reinforced piling prestressed with a prestressing member, wherein the prestressing member modifies the stress profile of the composite piling.

23. The improved composite piling of claim 21, wherein the fiber reinforced piling exhibits increased stiffness.