CONSTRUCTION BEAM

Abstract: The invention relates to a construction beam used as a support structure in wooden constructions and comprising separate flange parts and one or more separate webs. In the beam according to the invention, the flange parts are attached to the web with double-sided spike plates, which are placed in the joint surface between the web and the flange part in such a way that their density is proportional to the stress in the part of the joint surface in question. Thus it is possible to reduce the costs on the joint.

Description: Construction beam The invention relates to a construction beam suitable for a support structure in wooden constructions. In construction, beams and pillars fabricated by sawing from timber are commonly used as support structures. At present, with the timber cross- sections used in conventional constructions it is, however, possible to obtain bearing distances of only ca. four metres. If one desires to use timber in bearing distances greater than this, it is necessary to make stronger beams by joining beams of timber with mechanical joint means, nails, screws or bolts. However, the construction of such beams at the site or by industrial production is laborious and slow, whereby the price of the beam is raised high by labour costs. Furthermore, a wooden beam of prior art is disclosed in patent publication FI 88685, which wooden beam is composed of two or more sawn and/or surfaced wooden beams joined together, and in which each single joint is implemented by means of one joining piece resembling a double-sided spike plate, manufactured of a plate of sheet metal or the like and placed between the two wooden beams. A drawback in this structure is the relatively high consumption of material required in the joint, for the joining piece has to equal the entire beam in length. Also, patent publication DE 2947513 discloses a rectangular or banded joining piece of metal, which resembles a double-sided spike plate and is intended for joining wooden parts together; as well as methods for pressing such a joining piece between wooden parts. The claims do not relate to structures produced as a result of pressing. The purpose of the invention is to reduce the disadvantages related to the beams of prior art which are constructed with mechanical joints. The construction beam according to the invention is characterized in what will be presented in the independent claim. Some advantageous embodiments of the invention will be presented in the dependent claims. The basic idea of the invention is the following: The construction beam is produced by joining ordinary constructional timber by means of double-sided spike plate pieces. The spike plates used to join the parts of the beam together are placed only in such locations on the joint surface in which they are necessary with respect to the stresses effective on the joint surface. The cross- sectional shape of the beam can be selected. One advantage of the invention is that the amount of material required in the joint is relatively small, because there are only as many spike plates as the stress requires. Furthermore, an advantage of the invention is that a relatively small amount of wooden material is consumed for the beam, because the cross-sectional shape of the beam can be selected optimally with respect to the stress. Moreover, an advantage of the invention is that the costs for assembling the beam are relatively low, because in the fabrication of the beam, it is possible to use ordinary timber and spike plates which are generally available, and the industrial production of the beam can be arranged automatic and fast. In the following, the invention will be described in more detail. In the specification, reference is made to the appended drawings, in which Fig. 1 shows a side view of an example of the construction beam according to the invention, Fig. 2 shows a longitudinal cross-section of the construction beam according to Fig. 1, Fig. 3 shows a cross-section of the construction beam according to Fig. 1, Fig. 4 shows the construction beam according to Fig. 1 viewed from the end of the beam, Fig. 5a shows a cross-section of a second construction beam according to the invention, and Fig. 5b shows a cross-section of a third construction beam according to the invention. Figs. 1 to 3 show a construction beam according to the invention. The beam in question is a so-called I beam, named after the shape of its cross-section. Fig. 1 shows a side view of the construction beam. The construction beam 6 is composed of an upper flange 1 forming the top part of the beam, a lower flange 2 forming the bottom part, and a web 3 located between them. The flange refers to a structural part with a horizontal cross-section, and the web refers to a structural part with a vertical cross-section. The terms 'upper', 'upward', Tower', 'downward', and 'horizontal' and 'vertical' are used in this specification according to the position of the beam shown in Figs. 1 and 3, irrespective of the position in which the beam is finally used. The upper and lower flanges of the beam are joined to the web of the beam by means of double-sided spike plates 4. The joint between the upper flange and the web is implemented in such a way that the spikes on the first side of said spike plates are arranged on the upwards facing side of the web, and the spikes on the second side are arranged on the downwards facing side of the upper flange. The lower flange of the beam is fixed to the lower surface of the web in a corresponding way. Fig. 2 shows the cross-section A-A of the beam of Fig. 1 along the line between the upper flange and the web. The figure shows the proportional sizes and locations of the spike plates in the beam used as an example. When producing the beam, it is necessary to know how it will be used. In this example, the beam will be placed in a horizontal position, supported at its ends, and it will be subjected to an even load from above. The result is that the shear force will be the greatest at the ends of the beam and will reduce towards the center of the beam. Therefore, there are fewer spike plates in the middle of the beam than in the ends of the beam. The smaller number of spike plates of course reduces the costs on the spike plates. Fig. 3 shows a cross-section, i.e. profile B-B, of the beam of Fig. 1 at the location of one spike plate. The I profile shown in the figure is advantageous with respect to the use of wooden material, for instance in the above-described case of loading. Fig. 4 also shows an I profile beam viewed from its end. The figure shows end bands 5 formed of one-sided spike plates. The end bands bind the ends of the upper and lower flanges to the end of the web, thereby securing the assembly of the beam during storage, transport and mounting. Fig. 5 shows examples of other beam constructions produced according to the invention. In Fig. 5a, there are two parts 3 of vertical profile between the flange parts 1 , 2 of horizontal profile, whereby a hollow structure is formed. Such an enclosed structure is advantageous in vertical beams, i.e. pillars, and in cases when the beam is subjected to torsional strain. Fig. 5b shows an I profile beam whose web consists of two parallel parts 3. Thus, of course, a greater strength is achieved at the expense of the quantity of wood and number of joint pieces used. The description above included some beam constructions according to the invention. The invention is not restricted solely therein. For example, it is possible to apply the fastening with spikes according to the invention together with adhesive bonding when fixing the parts of the beam, wherein it is possible to attempt to minimize the overhead costs of the spike plates and the adhesive. The fastening with spikes according to the invention can also be used when fabricating so-called pre-stilted beams, i.e. beams which are curved upwards in their rest position, wherein a higher bearing capacity is achieved without increasing the quantity of timber. The invention can be applied in various ways within the scope of the independent claim.

Claims: Claims 1. Wooden construction beam comprising at least one flange and at least one web, characterized in that the flange is fixed to the web with double- sided spike plates (4), which are placed in the joint surface between the web and the flange in such a way that the distance between two sequential spike plates is inversely proportional to the stress effective in the area between them in said joint surface in the situation where the beam is used. 2. Construction beam (6) according to claim 1, comprising two flanges and one web, characterized in that the flanges (1, 2) are fixed to the web (3) in such a way that the cross-section of the beam is a so-called I cross-section. 3. Construction beam according to claim 1, characterized in that the flanges are fixed to the web with double-sided spike plates as well as with adhesive. 4. Construction beam according to claim 1, characterized in that it has a so-called pre-stilted structure. 5. Construction beam according to claim 1, characterized in that it is equipped with end bands (5) consisting of one-sided spike plates.

Inventors: PELKONEN PENTTI, PELKONEN, PENTTI
Applicants: PELKONEN PENTTI, PELKONEN, PENTTI
Application year: 1998
Main classification: E04C3
IPC codes: E04C3