The present invention relates to an improvement in composite columns comprising a core in the form of a steel post contained within a steel tube, said core and said steel tube being intended to coact statically with one another and with concrete cast therebetween.
A large number of different types of composite columns are available commercially in present times. The advantages of composite columns as opposed to purely steel columns reside in the fact that the composite column will often have smaller dimensions in cross-section than the purely steel column, and also a higher fire resistance. The drawbacks with composite columns reside in the necessity of providing expensive devices to ensure that static coaction is achieved between the steel and the concrete, and also the necessity of providing complicated devices at the load-application points, e.g. at each floor structure, so as to ensure that the prevailing load will be distributed truly throughout the whole cross-section of the composite column.
A common type of composite column comprises a steel tube filled with concrete For examples of the type illustrated in the prior art, see references US-A-901,453 and US-A-4,606,167. When a composite column of this kind is erected to pass through several floors or stories of a building, the load from the floor beams can be transferred to the column through connections welded to the steel tube. These connections must be anchored effectively in the concrete in order to ensure that the concrete will also participate in taking up the load applied. This can only be achieved with difficulty. For casting reasons of a technical nature, there is a limit to the number of stories through which such columns can be extended. Consequently, it is more usual to use so-called storey-high columns, i.e. columns which extend vertically through the extent of solely one storey. Such columns are normally provided with robust base and top plates, which enable loads to be distributed between steel and concrete. One advantage with storey-high columns is that the floor beams can be extended continuously over the columns, therewith improving the load bearing capacity of the beams. One drawback with storey-high columns resides in the necessity to fit the beams with complicated devices which will enable the load exerted by an overlying column to be transmitted through the beams without subjecting the beams to compression. Furthermore, erection work is normally slower in the case of storey-high columns than in the case of columns which extend through several stories, because when using storey-high columns, it is necessary to adjust the columns vertically and laterally at each new storey, and to bolt or weld the columns to underlying beams.
An object of the present invention is to provide an improved composite column which eliminates the aforesaid drawbacks of known composite columns. The characteristic features of the inventive column are set forth in the following Claims.
The present invention is manifested in a jointing and position-fixating sleeve which facilitates the work of joining columns together and also guarantees precise positioning of the steel post within the steel tube before and when casting concrete therein. Furthermore, the sleeve provides effective static coaction between the steel post and the steel tube and the concrete cast therebetween. Because of its configuration, the sleeve also forms a support which enables a floor beam to be layed so that it continues over the column, while enabling, at the same time, the steel post of the composite column to project above the plane of the floor beam, for simple and ready connection of the column above, such as to obviate the need of complicated devices on the floor beams for transferring the vertical loads from said column above.
The invention will now be described in more detail with reference to the accompanying drawings, in which
Figs. 1 and 2 illustrate a preferred embodiment of an inventive composite column 1, comprisng a core in the form of a steel post, e.g. a post 2 of cruciform cross-section, and a steel tube 3 which encircles the post. Subsequent to casting concrete between these members, said members are intended to coact statically with one another and with the concrete 4 cast therebetween. The concrete can be cast between said members either in a separate operation, or in conjunction with casting a concrete floor 5 (Fig. 5), or when using concrete for joining in a prefabricated floor structure. The ends of the composite column 1, namely its base end 6 and its top end 7, have mounted thereon a respective jointing and position-fixating sleeve 8 which is operative to achieve said static coaction and which comprises a ring 9 the outer diameter of which is at least slightly smaller than the inner diameter of the steel tube 3, and the inner diameter of which ring 9 is equally as large as or smaller than the inner diameter of the steel tube 3. The ring 9 has extending therefrom a number, preferably 8, of pairs of mutually parallel plates or fingers 10, which extend towards the centre of the ring and which terminate at a given distance therefrom, said plates 10 having an extension in the longitudinal direction of the ring 9 such that the plates, when forming a base ring, will project slightly beyond, e.g. about 10 mm, one outer edge 11 of the ring 9, said outer edge facing outwardly in the fitted position of the ring, whereas the plates 10 extending from the other outer edge 12, which faces inwardly in the fitted position, project much further from said other edge, e.g. about 80-100 mm, so as to enable effective welding of the end edges 14 of the plates 10 in longitudinal and/or transversal abutment with the side walls 13 of the cruciform post 2, by means of a weld 15. The steel tube 3 extends into abutment with respective rings 9 and is secured in position, e.g. by welding. The position of the cruciform post 2 in the steel tube 3 is determined exactly by means of the plates 10 on the base and top rings 9, both before and when casting concrete into the tube.
As will best be seen from Fig. 2, the plates 10 on the jointing and position-fixating sleeve 8 extend mutually parallel in pairs, in a direction towards the centre of the sleeve 8 and the ring 9, at a mutual distance apart which corresponds to the thickness of the legs 16 of the cruciform post 2 used. The plates 10 may be provided with a slot 17, so as to enable the plates 10 to be deformed more redily and to be adapted to a cruciform post 2 of smaller dimensions. The jointing and position-fixating sleeves 8 are fitted into the end parts of the steel tube 9, with the cruciform post 2 fixated by the weld 15 and with plates 10 displaced positionally in the longitudinal direction of the steel tube 3 such as to form a male and a female end where, in the illustrated embodiment, the female end is located at the base end 6 of the column 1 and the male end is located at the top end 7 of said column.
As will be seen more clearly from Figs. 3 and 5, the top end 7 of the cruciform post 2 projects beyond the outer edge 11 of the top ring 9 through a distance which corresponds to the depth of distance from the outer edge 11 of the base ring 9 to the end edge 18 of the cruciform post 2 at the female or base end 6 plus the thickness of the floor 5 to be carried. The plates 10 terminate at the top end 7 of the column 1 flush with the outer edge 11 of the ring, thereby providing a support for the floor beams 19 (Fig. 5). In order to facilitate the erection of an overlying column 1 on an already erected column, the plates 10 mounted on the sleeve 8 which functions as a base ring at the base end 6 of the column 1 project slightly downwrds, beyond the outer edge 11 of the base ring 9, as mentioned above. Because the top ring 9 at the top end 7 of the composite column 1 has a greater diameter in relation to the extension of the cruciform post 2, one or two mutually parallel floor beams 19 can be laid continuously over and supported by the support formed by the top ring 9 on both sides of the cruciform post 2, which increases the load bearing capacity and rigidity of the floor beams 19 while enabling, at the same time, the cruciform post 2 to extend continuously above the floor beams 19 for the purpose of joining the underlying column to the cruciform post of the overlying column and therewith enabling load to be transmitted from the overlying column 1 without requiring the provision of complicated and expensive devices on the beams 19 for transferring the load between the columns.
Described in the following is an exemplifying method of manufacturing an inventive composite column 1. A cruciform post 2 of given dimensions is suspended from an overhead crane or like apparatus, as as to terminate at a given distance from an underlying support surface. A jointing and position-fixating sleeve 8 which forms a base ring and a further sleeve which forms a top ring are pressed onto the ends 6, 7 of the post of cruciform cross-section in a manner to form the aforesaid male and female configurations, whereafter the post 2 is lowered onto the support surface and rolled or rotated so as to enable the plates 10 on the rings 9 to be welded onto the sides 13 of the cruciform post 2. When necessary, the plates 10 can be deformed to coincide with cruciform beams of smaller dimensions, by pressing the plates 10 into abutment with the walls 13 of the post 2 and welding said plates to said walls, this deformation of the plates being facilitated by the aforesaid slots 17. The steel tube 3 is then placed over the cruciform post 2 and welded to the base and top rings. The column 1 can now be erected in position on the building site and filled with concrete, which can either be carried out separately or when casting a concrete floor or when using concrete for joining a prefabricated floor structure.