Segmented cold formed joist

Abstract

A joist comprised of at least one cold-formed elongated chord member; a cold-formed web having a plurality of web members and means for securing said web to said chord member.

Description

FIELD OF INVENTION [0001] This invention relates generally to a joist and particularly relates to floor and roof joists for building construction and more particularly to methods for producing concentric top chord bearing cold form joists for composite concrete and non-composite joist conditions for the construction industry. BACKGROUND OF INVENTION [0002] Joists are commonly used in the construction industry to span a distance and provide a surface for a floor, roof or the like. Joists can be comprised of a variety of materials including wood and metal. [0003] Metal or steel joists can be constructed in an open web configuration, which generally consists of spaced apart upper and lower chord members which extend longitudinally thereof and are fastened together by a zig-zag web. Such open web joists are typically manufactured by hot-roll structural sections namely the upper and lower chord members and the webs. The webs typically can be comprised of hot-rolled steel rods, which are ...

AI Technical Summary

Problems solved by technology

It is generally difficult and costly to design steel and concrete composite floors using joists because legislation exists in various jurisdictions which relate to federal safety laws requiring that structural members cannot have objects extending above a structural floor member that will encumber the walking path of a worker.

Generally speaking the details for providing sheer bond capacity between the joist and the concrete in a composite joist are generally expensive to produce in the prior art.

However, the process has become more expensive due to environmental considerations when using dipped tanks containing volatile solvents.

The cold form technology presently has limitation in span lengths for floor and roof members to be widely used.

Unless cold form materials can be used in the thin applications, the use of these materials is cost prohibitive since hot-rolled pre-finished steel coil material typically used in forming comes in at much greater cost than the hot-rolled shapes used for the open web industry as described above.

Furthermore, cold-formed joists presently used only provide limited span lengths and are not very cost efficient to provide for spans greater than 24 feet.

However these provide only limited load capacity due to the nature of the localised connection to the cold-formed joist member.

Although cold-forming provides superior surface finishes and very little dependency on manpower to produce relative to the open web technology, current cold-forming technology does not satisfy the requirements to optimise material use throughout the length of the individual members of the joist.

One of the disadvantages of continuous cold-forming from a single piece of sheet material resides in the fact that material use along the length of the individual members cannot be rationalised or optimised.

Further, material optimisation is limited when cold-forming if the section is constant in weight throughout the length.

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