Composite load bearing structure

Abstract

A composite load bearing member is provided comprising an elongated inner structural member and a thick polymeric composite outer member. An apparatus for producing the composite load bearing member is provided including devices for suspending the inner structural member within a mold cavity prior to and during injection of the polymeric composite outer member. A method of using the apparatus to produce the composite load bearing member is provided.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention is generally directed toward composite load bearing structures and an apparatus and process for manufacturing composite load bearing structures. In particular, the present invention is directed toward a composite load bearing structure having an inner strengthening member. Most specifically, the present invention is directed toward a durable, long-lasting, economic alternative to traditional load bearing structures.[0003]2. Background Information[0004]The selection and use of materials and configurations in load bearing structures has become increasingly challenging in recent times due in part to advances in technology and the continuous development of new and better materials. Correspondingly, considerations and expectations involved in such a selection has grown as well, including such traditional considerations as strength and stiffness, but also including demands for more durable, long-lasting,...

AI Technical Summary

Benefits of technology

[0027]The present invention provides many advantages over traditional support members, particularly railroad ties and marine timbers, as well as prior art composite load bearing members. Importantly, the present invention can be engineered to provide performance characteristics on par with those of traditional wood members. That is, the strength and stiffness characteristics of wood railroad ties or marine timbers may be easily replicated through the joint action of the internal structural member and the polymeric composite outer member. Thus, the present invention provides a structural member that may be placed in close proximity to traditional wood members, while maintaining substantially equivalent loading on each, a requirement of which concrete, steel, and aggregate members are incapable. At the same time, the overall density of the member of the present invention can be engineered to be much more similar to that of a solid wood member than that of the prior art. Therefore, the present invention provides a structural member similar in weight and performance characteristics to traditional wood members so as to be handled, transported, and installed using existing or traditional methods, including providing the capability of being lifted and maneuvered manually by two people, another requirement that steel, concrete, and aggregate members are not capable of fulfilling.

[0028]Moreover, the present invention provides a composite member for use as a railroad tie allowing the traditional method of attaching a rail thereto. Rails have long been attached to traditional wood railroad ties by embedding spikes into the railroad tie itself. The head of the spike has an elongated edge that overlaps a lower portion of a rail, entrapping the rail against the tie as the spike is driven into the tie. Embodiments of the present invention allow for such a railroad spike to be driven deeply into the composite member, potentially embedding into the inner structural member itself. Optionally, voids may be intentionally placed in the inner member where railroad spikes are intended to be driven such that a railroad spike does not penetrate the internal structure but remains embedded into the polymeric composite portion of the load bearing member. Thus, in contrast to steel, concrete, or aggregate based members, the present invention allows use of traditional methods of rail attachment.

[0029]In addition to incorporating the advantages of traditional wood structural members,

Problems solved by technology

The selection and use of materials and configurations in load bearing structures has become increasingly challenging in recent times due in part to advances in technology and the continuous development of new and better materials.

Despite these more recent demands, traditional structural members are still predominant in many current industrial sectors for various reasons, including the fact that the current state of the art has not been able to provide a product that adequately meets these existing demands.

However, the use of conventional wood railroad ties have a number of disadvantages associated therewith as well.

First and foremost, despite their predictability, wood ties must be replaced every few years making such use somewhat expensive over a long period of time.

However, the typical preservatives currently used to treat wood ties are either prone to leaching and dissipating from the wood into the surrounding environment and/or are hazardous in nature.

For instance, borate products are known for their ability to preserve wood when used as a fungicide and pesticide; however, it is also well known that the borate treatments tend to leach out of treated wood very quickly, particularly along crevices or checks in the surface of the wood itself.

In addition, creosote is currently used as a surface treatment to wood railroad ties and utility poles to preserve the wood and prevent deterioration due to insects; however, creosote is a known carcinogen, harmful to humans and animals.

In fact, the Environmental Protection Agency considered banning creosote in 1987, but the agency allowed its continued use because of the lack of suitable alternatives.

Additionally, a number of lawsuits have been filed in recent years relating to the detrimental effects of creosote usage.

Therefore, it is clearly undesirable not only to manufacture such railroad ties, but also to have such railroad ties in use and finally, to dispose of such ties as well.

In an effort to provide a railroad tie with increased longevity, railroad ties of varying material composition have developed over the years; however, none of them have had great success in replacing wood ties because of the various drawbacks associated with their respective use.

Steel ties, for instance, have realized only limited use due to a number of factors.

First, although steel is a strong, stiff material (with similar properties to wood), steel's susceptibility to rusting makes it an unattractive alternative.

Additionally, the use of steel ties is also associated with a high noise level during use.

Finally, the use of steel ties also does not facilitate the typical system of attaching rails to ties through the use of railroad tie spikes.

Therefore, steel railroad ties have emerged as an unattractive option to traditional wood ties.

Concrete ties are significantly more expensive than wood ties.

That is, since concrete is significantly heavier than wood, such ties are not able to be handled, transported, or installed using existing processes and equipment.

Furthermore, the use of concrete ties requires much more complex rail fastening systems, again increasing the cost of installation.

The use of such reinforcement potentially short-circuiting the aforementioned train locating system as well.

Because of this difference, when concrete ties are mixed into sections with existing wood ties, uneven loading occurs, resulting in significantly shorter lifespan of the surrounding wood ties.

For this reason, entire sections of railroad ties must be replaced when rep

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