COMPOSITE BEAMS FOR BRIDGE-DECKS AND FLOOR CONSTRUCTIONS

Abstract: An improved composite beam consisting of a concrete slab and a steel beam whose top flange is cast into the concrete slab characterized by having the top flange profiled on both sides and thus transfers the shearing forces between the top flange (12) or (22) and the concrete slab (13) or (23) respectively. The composite beam is characterized by the fact that the top flange (12) on the welded beam (11) is manufactured between rollers with grooves in the finish rolling so that the flange plate (12) gets ridges (14) on both sides across the flange (12). The rolled steel beam (21) has one-side profiled steel plates (24) with the ridges (26) firmly attached to the top flange (22).

Description: COMPOSITE BEAMS FOR BRIDGE-DECKS AND FLOOR CONSTRUCTIONS This invention relates to a beam construction composed of a steelbeam roller or a welded steel beam and a concrete slab resting on the steel beam and bonded to the same with suffi¬ cient rigidity as to restrain the shear stresses developed from the load. The concrete slab together with the steel area above the neu¬ tral axis of the composite beam forms the zone of compression of the composite beam. More especially the invention relates to beams in which the concrete slab constitutes the floor when the composite members are spaced in accordance with load and span. Floor constructions having steelbeams as load bearing members and a concrete slab transmitting the load to said beams are usu¬ ally design in such a manner that the stresses in the steel beams shall balance the bending moments without any contri¬ buting effect from the concrete slab between the beams. No contri¬ buting effect can be secured because nothing is done to secure a sufficiently rigid connection between the steel beams and the concrete slab as is the case with the improved beam. Of course so-called 'Studs' have been welded to the top-flanges of steel beams in some bridge-constructions but the cost and the demand of control!-inspections have placed obstacles in the way. By sufficiently bonding the concrete slab to the steel beam so that the slab will be forced to deform in the same proportion as the top flange of the beam,as will be described below, a consid¬ erable saving of steel can be obtained. In this way the zone of compression will be composed of the steel area above the neutral axis of the composite beam, in addition to the area of the concrete slab between the steel beams, as compared to the steel alone, as with present constructions. Furthermore an additional saving of steel in the bottom flange is obtained, owing to the fact that the level arm between the tension member and the neutral axis of the improved composite beam is in percentage considerably greater than with a regular steel beam. The saving of steel in the bottom flange is in proportion to these levelarms for useful load. O PI There is another aspect on the composite beam, the shrinking in the concrete slab. The shrinking produces a bending moment in the composite beam with tensile stresses in the concrete slab and in the bottom flange of the steel beam. In the top flange the shrinking produces compressive stresses but all these shrink- ing stresses diminish when the composite beam is loaded with use¬ ful load. The main object of the improved composite beam is tb secure the connection between the concrete slab and the top flange of the steel beam with sufficient rigidity so as to develop the same de- formation in the concrete slab as in the steel in compression. The invention has two embodiments: 1. A welded steel beam, see drawing 1. The finish rolling of the steel plate to the top flange is manufac¬ tured between rollers with groves parallel to the axis of the roll- ers at the same distance round the mantel area. The flange plates gets ridges on both sides across the flange. These ridges secure the connection between the concrete slab and the steel beam with sufficient rigidity. The ridges also give the normal gap between the web and flange at the welding of the beam. Figure 1 is a cross section in line A - A on the Figure 2 of the single-symmetrical welded beam with the ridges across the flange on both sides. Figure 2 is a vertical section view on the line B - B of Figure 1 of the welded steel beam and the concrete slab. Figure 3 shows a vertical section view in detail C on Figure 2 of the profiling of the top flange. 2. A Rolled steel beam, see drawing 2. With a rolled steel beam one has slight possibility at the rolling mill to make the profiling across the top flange. On the other hand one has the possibility to weld or tight screw one-sided profiled steel plates onto the two sides of the flange which are to be cast in the concrete slab. Naturally the ridges shall extend across the flange. Steel-construction screws must be used. The screwheads and nuts also function as the 'Studs' mention- ed earlier. JO PI _, " wϊϊ-o " On the drawing 2 the screws are shown in the second alternative. The distance between the screws varies in relation to the shearing forces between the concrete slab and the steel beam. Figure 4 is a cross section in the line D - D on Figure 5 of a rol- led steel beam with the two one-sided profiled steel plates tightly screwed onto the top flange, and the concrete slab. Figure 5 is a vertical cross section view on the line E - E on Fi¬ gure 4 of the steel beam and the concrete slab. Figure 6 shows a vertical section view in detail F on Figure 5 of the top flange and the one-sided profiled steel plates tightly attached with screws. On drawing 1. 11 indicates a welded steel beam, 13 indicates a con¬ crete slab into which the doubble-sided profiles flange 12 is cast. The ridges 14 have the effect transfering the shearing forces bet- ween the top flange 12 and the concrete slab 13. The drawing also shows a supporting steel plate 15 and the web stiffening steel plates 16. On drawing 2, 21 indicates a rolled steel beam, 23 indicates a con¬ crete slab into which the flange 22 firmly attached one-side profiled plates 24 are cast. The attachment can be done with steel- construction screws 25 or by welding. The ridges 26 on the plates 24 have the effect of transfering the shearing forces between the top flange 22 and the concrete slab 23. The drawing also shows the supporting steel plate 27 and the web stiffening steel plates 28. OMP * . W1H

Claims: CLAIMS 1. An improved composite beam consisting of a concrete slab and a steel beam whose top flange is cast into the concrete slab characterized by having the top flange profiled on both sides and thus transfers the shearing forces between the top flange (12) or (22) and the concrete slab (13) or (23) respectively. 2. The improved composite beam according claim 1 is characterized by the fact that the top flange (12) on the welded steel beam (11) is manufactured between rollers with grooves in the fi- nish rolling so that the flange plate (12) gets ridges (14) on both sides across the flange (12). 3. The improved composite beam according to claim 1 is"character¬ ized by the fact that the flange (22) on the rolled beam (21) has on both sides firmly attached one-side profiled steel plates (24) with the ridges (26) across the flange (22). OMPl

Inventors: ELLNER KARL ERIK, ELLNER, KARL, ERIK
Applicants: ELLNER KARL ERIK, ELLNER, KARL, ERIK
Application year: 1984
Main classification: E04B5
IPC codes: E01D2, E04B5, E04C3