FRAME CONSTRUCTION OF A CONNECTOR BEAM

Abstract: Frame structure of a connector beam (1, 2, 3) which is intended for use along with concrete (4) in plate (6) connection points (L) of plate sets or the like as a binding and primary structure comprising a main beam structure (1), bottom surface (2), which functions during concrete (4) casting as at least part of the formwork surface, and binding units (3) which secure the adhesion of concrete (4) and the main beam structure (1). According to the invention, the said bottom surface (2) is connected to the said main beam structure (1) by the said binding units (3) in a way that the lower surface (2) is essentially separate from the main beam structure (1), wherein the connector beam (1, 2, 3, 4) as a result from concrete (4) casting has a concrete layer (4) in between the said main beam structure (1) and the said bottom surface (2).

Description: Frame construction of a connector beam The subject matter of the invention is the frame construction of a connector beam which is intended for use along with concrete as a binding and primary structure in plate connection points of plate sets or the like, comprising a main beam structure, a bottom surface which functions during concrete casting as at least part of the formwork surface, and binding units which secure the adhesion of concrete and the main beam structure. Connector beams of the said type manufactured of steel and concrete are used e.g. to form the frame of a prefabricated building, in which case they, fixed to rest on vertical columns, function as the primary horizontal structures of intermediate and/or primary floors. In comparison with conventional concrete or reinforced concrete structures, connector beams of the said type have the advantage of the capability to achieve essentially lower structures. In comparison with steel structures, they have the advantage of essentially better fire resistance. Steel, which has favourable strength, has significantly decreased strength during temperature rise in a fire situation. Therefore, in connection with primary steel structures of this kind, special attention should be paid on the fire shielding of their visible parts. A connector beam of steel and concrete is previously known e.g. from Finnish Patent Application No. 900985. In the connector beam presented in the said publica¬ tion, the frame structure is made of steel and com- prises a beam with two web parts, one edge of which forms a horizontal cantilever flange part extending outwards. The web parts are fixed at an angle to the flange part and the web parts are fixed adjacent to each other in an inclined position towards each other. The web parts are connected at the edges closest to each other by the horizontal upper part and at the edges of the web parts farther from each other which are connected to the cantilever flange parts by a plate welded to the web parts. In addition, holes have been perforated near the upper edges or in the horizontal upper part of the web parts for filling with concrete the space limited by the upper part of the web parts, the web parts and the plate functioning as the bottom. In the edges of the holes, cantilevers have been formed projecting from the level of the web parts or the upper part to secure the adhesion effect of concrete and steel. The frame structure presented above or corresponding frame structures of prior art are characterized in that the primary beam of the frame structure, such as a steel beam or a corresponding steel profile, forms at least a part of the external surface of the connec¬ tor beam resulting from concrete casting. Because the strength of steel is significantly decreased by a rise in temperature, the visible parts of a steel beam or a corresponding structure must be protected from fire. Fire shielding is provided by the kind of structures presented, either by covering the visible part of the cantilever flange or the like with a fireproof plate, insulator, paint, or spray. For aesthetic reasons, the said fire shielding must often be also covered by a so-called counter ceiling. In addition to the fire shielding measures mentioned above, the construction according to Finnish Patent Application No.900985 requires also several operations of different kinds such as moulding or working, welding, and perforating the plate material, etc. The purpose of the frame structure according to the present invention is to produce a decisive improvement to the disadvantages presented above and thus to raise the level of technology in the field. To fulfil this purpose, the method according to the invention is characterized in that the bottom surface is connected to the main beam structure by binding units in a way that the bottom surface is essentially separate from the said main beam structure, wherein the connector beam resulting from concrete casting has a concrete layer in between the main beam structure and the said bottom surface. The most important advantages of the frame structure according to the invention are the simplicity of installation, casting and other corresponding opera- tions connected with its use and the fire resistance feature of the connector beam formed thereby, because it is possible according to the invention to arrange the said main beam structure to remain completely within concrete thus being surrounded on all sides by concrete which has better fire resistance. Further¬ more, it is simple to manufacture a frame structure according to the invention e.g. at an engineering workshop, because e.g. standardized steel beams or the like can be used as the main beam structure. Thus the pre-elevating of the frame structure to compensate for detrimental deflection can often be arranged in the easiest way by treating the said bottom surface only. By the beam structure according to the invention, also considerable savings of steel material are gained as compared with conventional beam structures. In the following explanation, the invention is il¬ lustrated in detail by referring to the attached drawings wherein Figure 1 illustrates the perspective image of a frame structure according to the invention in the connecting point, Figure 2 illustrates a cross section of a connector beam formed by a frame structure according to Fig. 1, Figure 3 illustrates the frame structure of Fig. 2 as seen from direction A, Figure 4 illustrates a cross section of an edge beam formed by a frame structure according to the invention, Figure 5 illustrates the frame structure in Fig. 4 as seen from direction B, Figure 6 illustrates the cross section of an alternative frame structure according to the invention, Figure 7 illustrates the frame structure of Fig. 6 as seen from direction C, Figure 8 illustrates the perspective image of an alternative frame structure according to the invention, situated in the connection point, Figure 9 illustrates the cross section of a connect¬ or beam formed by a frame structure according to Fig. 8, and Figure 10 illustrates the frame structure of Fig. 9 as seen from direction D. The frame structure 1, 2, 3 in the connection point L of plates 6 according to the invention comprises a main beam structure which in the presented appli¬ cation consists of one main beam 1, bottom surface 2 which in connection with concrete casting functions as at least part of the formwork surface, and binding units 3 for securing the adhesion of concrete 4 and main beam 1. In the applications presented in Figs. 1 to 10, the said bottom surface 2 is arranged to extend at least on one side of connector beam 1, 2, 3, 4 over the said connection point L, wherein a side surface 2a has been fixed on the corresponding side of bottom surface 2 which side surface contacts plate 6 connec¬ ted to connection point L. The said bottom surface 2 and the adjacent side surface/surfaces 2a are in the applications presented in Figs. 1 to 10 fixed under the bottom surface 6a of the plates 6 connected to connection point L. In the applications presented, an I-beam 1 has been used as a main beam because of its advantageous structure. According to Fig. 1, plates 6 to be connected to connection point L have been installed on both sides of the frame structure 1, 2 , 3 which has been pre¬ fabricated, most suitably at an engineering workshop or the like, and installed to rest on vertical beams (not shown in Figure 1) . The figure illustrates also the most commonly used tie bars 5 which secure the connection of connector beam 1, 2, 3, 4 and the plates 6 connected to it. According to Fig. 1, the connector beam 1, 2, 3, 4 can be formed along with the surface casting 4a or concrete 4. Thus in the connection point L between the plates 6 to be connected, the bottom surface 2 of the frame structure 1, 2, 3 forms an essentially close part of the formwork surface, wherein concrete 4 which is to be cast on connection point L and which along with frame structure 1, 2, 3 forms connector beam 1, 2, 3, 4 is limited on its lower part by the said bottom surface 2, side surfaces 2a connected to bottom surface 2, and the end surfaces 1, 2, 3, 4 thus formed, the compression-strained part of the structure is the surface casting layer 4a and the upper part of the connector beam, and the exten- sion-strained part of the structure is the lower part of the connector beam, excluding said bottom surface 2 in a fire situation. According to conventional practice, it is usually advantageous, depending on the measurements of the frame structure, to support the frame structure longitudinally during concrete casting, most suitably by a separate supporting structure arranged in connection with its middle section, to minimize the detrimental internal tensions caused by the assembling stage. In the application according to Figs. 1 to 3, the said binding units are fixed to form a diagonal structure 3 for stiffening frame structure l, 2, 3 which diagonal structure is connected to the axial edge surfaces la 1 and lb 1 and the bottom surface 2 of both flange parts la and lb of the I-beam functioning as the main beam, essentially in vertical direction. In addition, bottom surface 2 and the adjacent side surfaces 2a have been manufactured from a solid plate material. In the application according to Figs. 4 and 5, frame structure 1, 2, 3 has been arranged to function as an edge beam in a way that side surface 2a connected with bottom surface 2 is fixed to extend above upper surface ly of main beam 1. Thus the above-mentioned diagonal structure 3 has been mounted on one side of I-beam 1 which functions as the main beam. In order to connect side surface 2a forming an edge to I-beam 1, single bars 3 functioning as binding units are arranged at certain intervals on one side of I-beam in the axial direction which connect the said side surface 2a to the upper flange la of I-beam 1. Further, bottom surface 2 and the adjacent side surface 2a are manufac¬ tured from a solid plate material. In the application shown in Figs. 6 and 7, bottom surface 2 is connected with I-beam 1 by single bars 3 arranged at certain intervals in the axial direction of the main beam connected with side surfaces 2a connected with bottom surface 2. A structure of this kind is applicable for use especially at plate loads which are small with respect to the size of I-beam 1 or in connection with concrete plates 6 to be casted on the site. In the alternative application according to Figs. 8 to 10, four brace bars 7 parallel to and of equal length as I-beam 1 are fixed to connect with the upper surface ly of lower flange lb of I-beam 1. In other respects, the structure corresponds entirely to the application shown in Figs. 1 to 3, and it is intended for use especially with plate loads relatively high with respect to the size of the I-beam used. It is clear that the invention is not limited to the above-mentioned applications but it can be modified within the basic idea even to a great extent. For instance the shape of the bottom surface and/or the adjacent side surface or surfaces can be, as distin¬ guished from the shapes presented, arched, angular, or the like. The main beam used in the frame structure can be a T- or L-shaped or tubular beam or the like, or it can be a bar or the like manufactured from a solid material, in which case the main beam structure may comprise one or more main beams of the aforesaid kind. Similarly, the height of the main beam structure used may vary, in which case it can be also essentially lower than the connection height of the plates to be connected. As distinguished from that presented, the binding units and/or the diagonal structures composed thereof can be installed also in a slanted manner wherein they are connected on one hand to the web part and lower flange and on the other hand to the side surface connected to the bottom surface of e.g. the I-beam presented. Furthermore, the main beam structure, such as the I-beam or the like in the application presented, can naturally be fixed in an asymmetric or slanted position e.g. towards the bottom surface or the plates to be connected or the like. The side parts that are connected to the bottom surface and extend outside the connection point may naturally also be fixed to the bottom surface by welded angle irons or other corresponding arrangements. The terminology both in the explanation above and in the patent claims refers to the position of the frame structure of the connector beam wherein it is in a casted connection point according to Figs. 2, 4, or 9.

Claims: Claims : 1. Frame construction of a connector beam (1, 2, 3) which is intended for use along with concrete as a binding and primary structure in plate connection points of plate sets or the like, comprising a main beam structure (1) , a bottom surface (2) which func¬ tions during concrete (4) casting as at least part of the formwork surface, and binding units (3) which secure the adhesion of concrete (4) and the main beam structure (1) , characterized in that the said bottom surface (2) is connected to the said main beam structure (1) by the said binding units (3) in a way that the bottom surface (2) is essentially separate from the main beam structure (1) , wherein the connector beam (1, 2, 3, 4) resulting from concrete (4) casting has a concrete layer (4) between the said main beam structure (1) and the said bottom surface (2) . 2. Frame structure according to claim 1, characterized in that the said bottom surface (2) is fixed to extend at least on one side of the said connector beam (1, 2. 3, 4) over the said connection point (L) , wherein a side surface (2a) or the like has been arranged on the corresponding side or the bottom surface (2) , which side surface contacts with the plate (6) to the connection point (L) . 3. Frame structure according to claim 1 or 2, charac- terxzed in that the said bottom surface (2) and/or a side surface or surfaces (2a) or the like are essen¬ tially arranged below the lower surface (6a) of at least one plate (6) connected to the connection point (L). 4. Frame structure according to one of the claims 1 to 3 above, characterized in that the said frame structure is fixed as an edge beam in a way that the said side surface (2a) connected to the bottom surface (2) or the like is fixed to extend above the upper surface (ly) of the main beam structure (l) . 5. Frame structure according to one of the claims 1 to 5 above, characterized in that the said bottom surface (2) and at least one side surface (2a) or the like connected thereof has been made of a solid plate material by working, moulding, or in a corresponding manner. 6. Frame structure according to one of the claims 1 to 5 above, characterized in that at least part of the said binding units are single bars (3) or the like, wherein the said bars (3) or the like, most suitably arranged at certain intervals in the axial direction of the main beam (1) , are arranged on one hand to the main beam structure (l) and on the other hand to the bottom surface (2) and/or a side surface (2a) connected thereof, or the like. 7. Frame structure according to one of the claims 1 to 5 above, characterized in that at least part of the said binding units are arranged as a diagonal brace structure (3) or the like, wherein most suitably at least on part of the main beam structure (1) , the said diagonal structure (3) or the like, arranged in the axial direction of the main beam structure (1) , is fixed on one hand to the main beam structure (1) and on the other hand to the bottom surface (2) and/or a side surface (2a) or the like connected to it. 8. Frame construction according to one of the claims 1 to 6 above, characterized in that the said main beam structure is an I-beam (1) or the like, wherein it comprises two essentially horizontal flange parts (la, lb) and an essentially vertical web part (lc) connecting them, wherein at least part of the said binding units (3) are connected to at least one of the said flange parts (la/lb) , most suitably either on the upper or the lower surface, essentially in a horizontal direction. 9. Frame construction according to one of the claims 1 to 7 above, characterized in that the said main beam stucture is an I-beam (1) or the like, wherein it comprises two essentially horizontal flange parts (la, lb) and an essentially vertical web part (lc) connecting them, wherein at least part of the said binding units (3) are connected most suitably to both of the said flange parts (la, lb) , most suitably to the axial edge surfaces (la 1 , lb') of the upper and lower flanges of the I-beam (1) or the like, essential¬ ly in a vertical direction, wherein the height of the said binding units (3) and/or the said diagonal structure formed by them or a part of such in a perpendicular cross-section towards the axial direction of the I-beam (1) or the like is most suitably essen¬ tially greater than the corresponding height of the said I-beam (1) or the like. 10. Frame construction according to the claims 8 or 9, characterized in that the said main beam structure comprises, in addition to the said I-beam (1) or the like, most suitably one or more brace bars (3) or the like which is essentially parallel to and/or of the same length as the said I-beam (1) , arranged in connection to the upper surface (lby) of the lower flange part (lb) of I-beam (1) .

Inventors: SALO SEPPO, SALO, SEPPO
Applicants: SALO SEPPO, SALO, SEPPO
Application year: 1991
Main classification: E04C3
IPC codes: E04C3, E04C5