Structural element

Abstract

A structural element (1, 20, 30, 40) comprises a web (2) extending between a pair of flanges (3, 4). The areas of particular structural importance are the portions (5, 6) of the web and flanges adjacent to the junction between the web and the flanges. Material is gathered into these structurally important areas of an otherwise thin component. This is achieved by providing a plurality of small ribs (10) to absorb the material in these structurally important areas (5, 6). The ribs (10) are on a pitch of 2 to 8 times the wall thickness t. The pitch is approximately the same as a typical self drilling, self tapping fastener to prevent skating of the fastener, on fixing. The ribs (10) are of a depth of between 1.5 t and 3.0 t, where t is the metal thickness. These parameters ensure that in terms of fixing, the ribs allow a fastening screw to be used and to perform in the same manner as with a flat faced flange or web.

Description

[0001] This is a continuation application of Ser. No. 10 / 983,741 filed Nov. 9, 2004; which in turn is a PCT continuation application of PCT / IE03 / 00067 filed May 12, 2003.INTRODUCTION [0002] The invention relates to structural elements of the type comprising a web extending between a pair of flanges. Such structural elements are generally of roll formed steel section. [0003] A large number of structural elements of this type are known and used widely, for example in building construction. Various complex sections have been developed to provide particular structural performance. Such known sections are however generally inefficient in terms of the amount of material required to achieve a desired structural performance because they are derived from a strip of uniform thickness. Generally the dimensions of the section are altered to achieve desired properties. For example, the width of the flanges may be increased to strengthen the section. However, this has the disadvantage of destabil...

AI Technical Summary

Benefits of technology

The invention provides a structural element with curved stiffening ribs that improve its strength and stability. The ribs are formed at regions of importance along the element's length without reducing the wall thickness. The spacing of the ribs is between 2 to 8 times the wall thickness, and their depth and bend radius are optimized for the element's needs. The element can have flanges that extend from the web, and the ribs can be located in the web, flanges, or both. The technical effects of the invention include improved load-bearing capacity, reduced weight, and improved flexibility.

Problems solved by technology

Such known sections are however generally inefficient in terms of the amount of material required to achieve a desired structural performance because they are derived from a strip of uniform thickness.

However, this has the disadvantage of destabilising the section by moving the centre of rotation of the section (typically a C or sigma section) further away from the centroid of the section.

This increases the need for struts and rotational restraints or a deeper indent in the web in a sigma or zed section which thereby loses the advantage of material saving.

There is also a threshold at which a long slender element becomes ineffective and prone to buckling.

However, this results in higher material costs and the additional cost is not proportional to the improvement in structural properties.

However known sections of this type have the disadvantage that they reduce the effective width of the flange which can be screwed into when fastening cladding or the like to the section.

If the rib is hit by a cladding fastener, the fastener will skate to the bottom of the rib and thereby elongate the hole into which the fastener is held and the fastening is therefore not complete.

With deep ribs conventional fasteners may not be long enough to fasten efficiently at the bottom of the rib leading to potential puncturing of the cladding with an elongate hole.

There is a further problem if the outer part of the web is to be stiffened by a larger rib since such a large rib may prevent the use of normal fasteners in the most advantageous fixing position.

Images