WO1985004207A1

WO1985004207A1 - A beam web for a composite beam

Info

Publication number: WO1985004207A1
Application number: PCT/SE1985/000103
Authority: WO
Inventors: Lars Stalin
Original assignee: Lars Stalin
Priority date: 1984-03-16
Filing date: 1985-03-08
Publication date: 1985-09-26
Also published as: SE8401475L; AU4065385A; SE8401475D0; EP0208687A1

Abstract

A beam web for a so-called composite beam with longitudinal flanges (1, 2) of one material, such as wood, consists of web rods (3) of another material, for example metal. The web rods (3) extend between the flanges (1, 2) and are anchored in them, as well as being disposed in zig-zag formation. According to the invention, the beam web includes connecting rods (4-6) extending in the longitudinal direction of the beam and being of the same material as the web rods (3). At least one connecting rod (4) interconnects, and is fixedly anchored in, the web rods (3) in the neutral plane of the beam. Furthermore, the web is suitably provided with connecting rods (5, 6) in the transitional zones between the web rods (3) and the flanges (1, 2).

Description

A BEAM WEB FOR A COMPOSITE BEAM

TECHNICAL FIELD

The present invention relates to a beam web for a so-called composite beam, which is designed in such a manner as to comprise a beam web including a number of web rods extending between both flanges of the beam. BACKGROUND ART

Swedish Patent Specification No. 7610600-4 describes a beam of the type intimated by way of introduction. This beam is designed in such a manner that both flanges of the beam are manufactured of wood and are composed of two separate parts which are glued together. In the joining region between these two parts, there are disposed V-shaped grooves directed towards one another, in which the web of the beam, which comprises a zig-zag-bent wire or rod, is anchored before the beam flanges are glued together.

The concept forming the basis of the above-outlined con- struction is that it should be possible to realise a beam which combines light weight, low cost and a high degree of strength in relation thereto.

In practice, the construction acording to the above-mentioned Swedish Patent has proved to be unsatisfactory in many different respects. As a rule, the straight rods constituting the beam web have been dimensioned in such a manner as to take into account only the tensile and compression stresses which prevail in the beam web when the beam is placed under loading. On the other hand, no account has been taken of the buckling forces which occur in every second of the rods included in the beam web, which has resulted in the fact that these have buckled long before the beam has been placed under fully extended loading in its entirety. The result is that the material, primarily in the flanges of the beam, has not been utilised to an optimum extent.

As a result of the buckling which occurred in the rods in the beam web, the anchorage of the rods in the beam flanges has, furthermore, become weakened or destroyed in such a manner that the strength of the beam has been reduced and its sagging effect increased. This phenomenon has become particularly manifest in such cases where the beam is manufactured with flanges of wood, since the ability of the wooden material to accommodate compression forces in the border zone between the flanges and the web of the beam is highly limited. PROBLEM STRUCTURE

Thus, the object of the present invention is to realise a beam web of the type mentioned by way of introduction, the beam web being designed in such a manner as to obviate the above-mentioned disadvantages inherent in prior Art constructions. SOLUTION

This object is attained, according to the present invention, by means of a beam web which comprises a number of web rods extending between the flanges of the beam and being characterised in that the web rods are interconnected by the intermediary of one or more connecting rods extending in the longitudinal direction of the beam.

One particularly important embodiment of the present invention is characterised in that a connecting rod is disposed in the neutral plane of the beam.

An alternative, or supplementary, embodiment of the present invention which is particularly intended to obviate the problems which have prevailed in the border region between the flanges of the beam and its web, is characterised in that the connecting rods are disposed in transitional zones between the web rods and the flanges of the beam.

In order to attain fully satisfactory function, it also applies, according to the present invention, that the connecting rods must be fixedly connected to the web rods, for example by welding. DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying Drawings, and discussion relating thereto. In the accompanying Drawings:

Fig. 1 is a side elevation of a composite beam designed with a beam web according to the present invention;

Fig. 2 is a section taken along the section marking A-A in Fig. 1; Figs. 3a-c are cross-sections through alternative embodiments of the present invention, the cross-sections following the section markings B-B in Fig. 1 and illustrating the region marked by the reference D; and

Figs. 4a-c are a cross-section of alternative embodiments, the cross-section following the section marking C-C in Fig. 1 and illustrating the region marked by the reference E. DESCRIPTION OF PREFERRED EMBODIMENT

The beam illustrated in Fig. 1 is a so-called composite beam, which entails that it consists of more than one material type. Thus, the flanges 1 and 2 of the beam are manufactured of wood, plastics or concrete, or possibly also of other materials. Both of the beam flanges 1 and 2 are interconnected by means of a beam web which consists of a number of solid metal rods, or web rods 3 which may be of circular or rectangular cross-sectional configuration. The web rods may make angles with the flanges of in the region of between 10 and 90 degrees. Furthermore, the web rods may have relatively slight cross-sectional surface areas and may still be of "uniform strength" with the beam flanges, if account is taken only of the tensile and compression stresses occurring in the web rods when the beam is placed under load. Greatly siirplified, the above-disclosed dimensioning of the web rods may be considered as optimal, but does not meet the demands which must, in practice, be placed on the beam web. The reason for this is that the web rods which are recumbent while under pressure loading are often buckled, so that their pressure absorption capacity is greatly reduced. The consequence of this may, on many occasions, be a failure of the beam in its entirety, or at least an unacceptably high degree of sagging of the beam. According to the present invention, there is disposed, in the neutral plane of the beam - as a rule approximately vertically in the centre of the beam - a horizontal or longitudinal connecting rod 4 which, for example by welding or equivalent means for fixed retention, is fixedly anchored in the web rods. Hereby, the centre points of the web rods which are placed under pressure loading, will be stayed so as to prevent any possible buckling of the web rods, since any such buckling motion would, because of the connecting rods, be transmitted to the web rods which are placed under tensile stress. Since these are subjected to tensile stress, they will fix and prevent any longitudinal shifting of the connecting rods.

DESCRIPTION OF ALTERNATIVE EMBODIMENTS

In one practical embodiment of the present invention, several designs of the connecting rods may be employed, as intimated in Figs. 2 and 3. In Figs. 2 and 3a, a circular connecting rod is used, this being place in between the web rods. In the embodiments according to Figs. 3b and 3c, double-connecting rods are used, and these may be of both rectangular and circular cross-section, and be anchored on the sides of the web rods.

By the employment of the above-described connecting rods, the height of the beam web may be more than doubled, with reference to the capacity to withstand buckling forces in the web rods, without any necessity of increasing the material amount included in the web. Naturally, this also entails that the strength of the beam will be considerably greatened in relation to the amount of material included therein. On loading of the beam illustrated in Fig. 1, the regions of connection between the web rods 3 and the beam flanges 1 and 2 will also be subjected to heavy loading, and in particular pressure loadings on beam flanges 1 and 2 which are manufactured of wood may be specially problematical. The reason for this is that the wood material is not capable of taking up any greater degree of loading of this type. Thus, deformations in the wood material may easily occur, such deformations greatly increasing the sagging effect to which the beam is exposed at a certain specific loading. Consequently, according to the present invention, there may be employed one or more connecting rods 5 and 6, respectively, in the region adjacent the beam flanges 1 and 2, i.e. in the transitional zones of the web rods, between the web rods and the beam flanges. As will be apparent from Figs. 4a-c, these connecting rods 5 and 6 may, in a manner which is analogous with that described for the connecting rod 4, be designed both as double and single rods, and with both circular and rectangular cross-section.

The details shown by broken lines in Figs. 4a-c intimate that the connecting rods 5 and 6 may also be placed interiorly within the material in the beam flanges 1 and 2.

The connecting rods 5 and 6 placed in the border zones between the web and flanges of the beam may, in analogy with that described above, be fixedly welded or, in any other appropriate manner, be fixed and rigidly anchored in the web rods. The present invention may be modified without departing from the spirit and scope of the appended Claims.

Claims

1. A beam web for a so-called composite beam, the beam web including a number of web rods (3) extending between the flanges (1, 2) of the beam, cha racte r i sed i n tha t the web rods (3) are interconnected by the intermediary of one or more connecting rods (4-6) extending in the longitudinal direction of the beam.

2. The beam web as recited in claim 1, cha r ac te ri s ed in that a connecting rod (4) is disposed in the neutral plane of the beam.

3. The beam web as recited in claim 1 or 2, character i sed i n tha t connecting rods (5, 6) are disposed in transitional zones between the flanges (1, 2) and the web rods (3) of the beam.

4. The beam web as recited in any one of the preceding claims, character i sed in that the connecting rods (4-6) are rigidly connected to the web rods (3), for example by welding.