RU2755179C1 - I-beam closed formed profile with bends and cavettos for shelves - Google Patents

Abstract

FIELD: building.

SUBSTANCE: described technical result is achieved by the fact that the I-beam closed formed profile with cavettos for shelves includes two elements, C-shaped in cross-section, wherein each element consists of a solid or perforated vertical wall and two cavettos, as well as two elements shaped as a channel, the walls whereof are in contact with adjacent cavettos and the edges of shelves thereof and the edges of the cavettos, made toothed, are connected with a form fit, forming the upper and lower shelves of the I-beam profile together with the cavettos. The cuts of the perforated adjacent walls of the C-shaped elements along the entire perimeter are made with toothed edges for form-fit connection. The radius of the cavettos is a quarter of the width of the shelf of the profile, the height of the cuts of the perforated wall equals 0.8703 of the height of the profile at a ratio of the width of the profile to the height thereof of 1/3.857, and the ratio of the width of the profile to the height thereof in the absence of perforation in the wall is 1/9.003.

EFFECT: technical result of the proposed solution is the sufficient local and general stability of I-beam closed formed profiles from the plane and in the plane of the supporting structure, an increase in the rigidity, a reduction in hardening of metal and concentration of stresses, an expansion in the scope of rational application, as well as a reduction in the additional costs and consumption of the structural material.

1 cl, 9 dwg

Description

The proposed technical solution relates to the field of construction and can be used as beam elements in the development of load-bearing structures of buildings and structures for various purposes. In particular, it can be elements of purlins, girders, beams.

Known steel composite beam of I-section, in which the upper and lower flanges, as well as the vertical wall is formed by a pair of bent thin-walled profiles. Flat sections of these profiles to form a vertical wall are interconnected by bends of stamped pins, mutually entering the formed holes from stamping. The longitudinal edges of the horizontal sections of the same paired profiles for the formation of tubular (cavity) shelves are bent until they touch the opposite face and are connected by welding [FS Zamaliev, EF Zamaliev, EF Zamaliev. Steel composite beam. - Patent No. 176505, 01/22/2018, bul. No. 3]. However, welded joints limit the minimum thickness of the welded elements and do not allow the use of galvanized steel, which provides a high resistance to corrosion of the structure. At the same time, the use of stamped pins and their holes is accompanied by a certain increase in additional costs.

Another known technical solution is a multi-span supporting structure (beam), including a tubular (hollow) profile of two curved walls and two flat shelves (upper and lower). Both walls are welded to the shelves and, being concave inward, are united by tie rods in the zone of their contact, which gives the hollow profile of the structure an I-beam [Veselov V.V., Fedorov A.M. Multi-span load-bearing beam. - Patent No. 176462, 19.01.2018, bul. No. 2]. As in the previous case, welding limits the minimum thickness of the elements to be welded and does not allow the use of galvanized steel, and tie rods and their holes cause a certain increase in additional costs.

The originality of the technical solution is distinguished by a rolling I-beam, made of four symmetrical elements. Two of these elements contain a vertically oriented wall that smoothly passes along the radius of the curve from above and below into a fillet that makes up a quarter of the section of a round pipe, then passes into a horizontal bend. The folds are connected to each other from above and from below by straps from a sheet to form closed trays. Connected directly to each other and the walls [KK Nezhdanov, VA Tumanov, AK Nezhdanov, AS Lashtankin. Beam. - Patent No. 2232125, 10.07.2004, bul. No. 3]. No less original are the riveted joints of the composite section of such a beam, which are fixed fastenings with hollow rivets-bushings with a core embedded in each [Nezhdanov K.K., Vasiliev A.V., Kalmykov V.A., Nezhdanov A.K. Method and device for fixed connection of metal structures. - Patent No. 2114328, 27.06.1998]. Such a beam, due to the folds and closed trays of the shelves, has increased rigidity. However, the complexity of the fasteners of its composite section and their significant number have a negative impact on the labor intensity and cost of manufacture.

Another technical solution (taken as an analogue) is known in the form of an I-beam bent-closed profile of two flat and two inwardly concave sheet blanks of an arcuate shape. The sheet blanks are attached to each other by means of serrated closures of the longitudinal edges and are mutually supported in their contact zone. In cross-section, the arcuate blanks have the form of circular half-rings, the diameter of which is equal to the width of the profile. The horizontal faces of flat blanks and semicircular faces of arcuate blanks, after closing their gear fasteners, form a pair of tubular shelves of triangular shape [Marutyan A.S. I-beam bent-closed profile. - Patent No. 2680560, 22.02.2019, bul. No. 6]. Such a profile, having a compact cross-sectional shape with equal dimensions in width and height, quite effectively resists longitudinal loads applied centrally and with eccentricities, which is typical for such rod elements as posts and columns. However, for the force resistance to lateral loads and actions inherent in beam structures, the form of an I-profile with an elongated distribution of structural material, including the maximum perforation of its wall, is more effective. With regard to I-beams, bent-closed perforation profiles of their walls can be given an additional functional purpose in the form of the formation of cuts of various shapes with serrated edge closures along the entire perimeter of each of these cuts. Such closures can provide the necessary connections for an elongated composite section and strengthen the edges of the cutouts of the perforated wall. The indicated study of I-beams bent-closed profiles with perforated walls, supplemented by the optimization of the design parameters, can contribute to the expansion of the area of their rational use.

The closest to the proposed one (adopted as a prototype) is a technical solution, which is an I-beam bent-closed profile with parallel flange edges and a perforated wall of two flat sheet blanks and two perforated sheet blanks with rectangular channel-shaped bends. The horizontal faces of the flat blanks and the same faces of the channel blanks, after closing their gear attachments, form a pair of flat I-profile flanges with parallel faces. The vertical faces of the channel blanks are mutually supported, provided with cutouts and form a perforated wall of the I-profile after closing their gear mountings located along the entire perimeter of each of these cutouts. The bending strength of such a profile is maximum if its height is 3 ... 4 times greater than the width of the profile, when the height of the cutouts is 0.7 ... 0.8 of the profile height, and also if its height is greater than the width of 5 , 9 ... 6 times, when the height of the notches is 0.1 ... 0.2 of the profile height [Marutyan A.S. I-beam bent-closed profile with a perforated wall. - Patent No. 2715778, 03.03.2020, bul. No. 7]. For all its optimality, the prototype has two main drawbacks: in terms of rigidity, its flat shelves are inferior to the tubular shelves of a triangular outline of the analog, and according to the work-hardening of the metal and the stress concentration, its channel-shaped sheet blanks with rectangular junctions are inferior to semicircular blanks of the same analog.

The technical result of the proposed solution is sufficient local (local) and general stability of I-beams bent-closed from the plane and in the plane of the supporting structure, increasing rigidity, reducing metal work hardening and stress concentration, expanding the area of rational use, as well as reducing additional costs and consumption of construction material.

The specified technical result is achieved in that the I-beam bent-closed profile with fillets of shelves includes two C-shaped elements in cross-section, each of which consists of a solid or perforated vertical wall and two fillets, as well as two elements having the shape of a channel, the walls of which are in contact with adjacent fillets, and the edges of its shelves and the edges of the fillets, made toothed, are connected with a form fit, forming, together with the fillets, the upper and lower flanges of the I-profile. The cuts of the perforated adjacent walls of the C-shaped elements along the entire perimeter are made with serrated edges for positive connection. The radius of the fillets is a quarter of the profile flange width, the height of the cutouts of the perforated wall is 0.8703 of the profile height when the ratio of the profile width to its height is 1 / 3.857, and the ratio of the profile width to its height in the absence of perforation in the wall is 1 / 9.003.

The proposed I-beam bent-closed profile has a fairly universal technical solution, with the implementation of which sheet blanks of the same and different thickness can be used for its manufacture, both with toothed closures and with welded, bolted or riveted joints. For the manufacture of bent-closed profiles without welded, bolted or riveted joints, the parameters of the serrated longitudinal edges of their sheet blanks should be selected so that one zigzag cut forms the edges of two blanks at once. At the same time, production costs will be minimal, which will ensure a decrease in additional costs. In addition, the bends of the gear fastenings of bent-closed profiles increase the thickness of crushing, which can contribute to a certain increase in the bearing capacity of the joints of thin-walled elements, working mainly in shear [Kuznetsov I.L., Fakhrutdinov A.F., Ramazanov P.P. The results of experimental studies of the shear performance of joints of thin-walled elements. - Bulletin MGSU, 2016, No. 12. - S. 34-43]. In addition, the bends of the gear fastenings ensure the preservation of local (local) stability and the shape of the section of thin-walled elements until the limiting state is reached, which makes it possible to calculate not reduced sections, but net sections [Bely G.I. To the definition of reduced sections of bar elements of light steel thin-walled structures. - Bulletin of civil engineers, 2017, No. 6. - S. 33-37]. It should be added that the bends of the gear fasteners, evenly distributed along the walls and shelves throughout the I-beam bent-closed profile, preserve its integrity and solidity to a greater extent than the zones of contact with friction of a folded-type connection in a rectangular profile of a beam with end-to-hook fastenings, which made it possible consider the cross-section of the beam to be monolithic [Yakovleva EL, Atavin IV, Kazakova Yu.D., Maksudov I.Kh. Strength characteristics of thin-walled elements. - Construction of unique buildings and structures, 2017, No. 12. - S. 125-139]. In some cases, in order to reduce additional costs, the integrity of the composite section of a bent-closed profile is quite achievable due to the use of similar contact zones with friction without perforating its wall.

The calculation of the optimal layout of the prototype, which is an I-beam bent-closed profile with parallel flange edges and a perforated wall, is made taking into account the size restrictions on the height of the cutouts in the perforated wall [Steel buildings in Europe. Multi-storey steel buildings. Part 2. Basic design solutions / Steel Construction Association. - M .: Axiom Graphics Union, 2017 .-- P. 56, fig. 5.7]:

for rectangular holes

h≤0.7V;

for round holes

h≤0.8V,

where h is the height of the cutouts; V - profile height.

Similar restrictions for an I-beam bent-closed profile with bends and fillets of the flanges lie in the features of its design and layout solution and are determined by the dimensions of the flat sections of the wall between the fillets of the flanges.

The proposed technical solution is illustrated by graphic materials, where on

fig. 1 shows a side view of an I-beam bent-closed profile with a solid wall without cutouts;

fig. 2 - cross-section of an I-beam bent-closed profile with a solid wall without cutouts;

fig. 3 - design diagram of a net cross-section of an I-beam bent-closed profile with a solid wall without cutouts;

fig. 4 shows a side view of an I-beam bent-closed profile with cutouts in the perforated wall;

fig. 5 - cross-section of an I-beam bent-closed profile within one of the notches of its perforated wall;

fig. 6 - design diagram of a net cross-section of an I-beam bent-closed profile within one of the notches of its perforated wall;

fig. 7 shows an exploded perspective view of a fragment of an I-beam bent-closed profile with a solid wall without cutouts;

fig. 8 is an exploded perspective view of a fragment of an I-beam bent-closed profile with a perforated wall;

fig. 9 shows graphs of changes in the main design parameters of an I-beam bent-closed profile depending on the growth of the relative height h / V of the notches of its perforated wall (h is the height of the notches, V is the height of the profile).

The I-beam bent-closed profile with fillets of shelves according to the proposed technical solution consists of two pairs of sheet blanks with a thickness. One pair of blanks 1 has a channel-shaped cross-section with orthogonal angular curvatures of flat faces with dimensions t × 0.25U + t × U + t × 0.25U, where U is the width of the bent-closed profile; V is the overall height of the same profile. Another pair of blanks 2 has a C-shaped cross-section and consists of a vertical face (wall) with dimensions t × (V-0.5U) and two fillets of shelves with a thickness of t and a radius of R = 0.25U, where V is the size of the same profile in height. Both pairs of blanks 1 and 2 are made along the entire length with serrated longitudinal edges, the teeth of which are staggered relative to each other and are mutually bent in grooves between themselves after closing the bent profile. Perforated paired blanks 2p are additionally made with the same serrated edges along the entire perimeter of each of the cutouts. The teeth of these edges in exactly the same way are staggered relative to each other and are mutually bent in the grooves between each other after the bent profile is closed. In this case, the height of the cutouts h of the perforated blanks 2p is limited by the size h _{max of} their flat sections, limited in height by the rounding of the inner edges, that is, h <h _max = V-2R = V-0.5U.

For a quantitative assessment of the resources of the bearing capacity of an I-beam bent-closed profile with fillets of shelves, it is advisable to calculate the area, as well as the moments of inertia of its section I _x and I _y relative to the main central axes. Here it is obvious that the cross-section of such a profile can be considered a composite figure, including a pair of horizontal rectangles with dimensions t × U, forming the horizontal edges of the shelves, two pairs of vertical rectangles with dimensions t × 0.25U, forming the folds of the shelves, four pairs of fillets with a radius of R = 0.25U forming inclined edges of the same shelves, as well as one pair of vertical rectangles with dimensions t × (V-0.5U) with or without notches of dimensions t × h (h = 0), forming a perforated wall. In this case, it is permissible to carry out the calculated calculations along the middle line of a thin-walled section without taking into account the angular roundings and without taking into account the numerical values containing the values of the thickness raised to the second and third powers (t ² , t ³ ) [Marutyan A.S. Optimization of structures made of tubular (bent-welded) profiles of square (rectangular) and rhombic sections. - Structural mechanics and calculation of structures, 2016, No. 1. - S. 30-38].

The accepted theoretical and computational prerequisites for the approved approximate calculation method as applied to an I-beam bent-closed profile with flange fillets make it possible to derive the basic formulas in the following form:

where n is the ratio of the dimensions of the width and height of the profile, n = V / U.

As the beginning of a quantitative assessment of the bearing capacity resources, it is advisable to consider the design case without cutouts in the wall of the I-profile (h = 0), which is of practical importance when the integrity of the composite section is sufficiently ensured without perforating the wall:

where A and t are, respectively, the cross-sectional area of the original workpiece to be zigzag cut into two pairs of workpieces, and its thickness; A = const, t = const.

To find the extreme value of the moment of resistance W _x, its formula must be differentiated by the variable n:

Equating to zero the derivative (dW _x / dn = 0), we can obtain the equation of the fourth degree

with roots

The third root n = 0.1110750 = 1 / 9.0029259≈1 / 9.003 is of practical importance for the continuation of the calculations, when the I-profile is a beam element with the largest value of the strength characteristic of the cross-section in absolute value, that is, W _x = W _{x, max} :

for h = 0

where further numerical calculations are more illustrative in comparison with the corresponding calculated parameters taken as reference (100 percent) values.

The continuation of the calculation of the I-beam bent-closed profile with tubular shelves and a perforated wall along the section with a cutout is as follows:

at h = 0.1V

where I _{x, 0} is the axial moment of inertia of the calculated net section of the profile without cutouts in the wall (h = 0); t _w - profile wall thickness, t _w = 2t.

As you can see, the size of the height of the cutouts in the perforated wall exceeded 1/10 of the maximum value, and the main characteristics of the calculated net section changed little. Therefore, for relatively small cuts that reduce waste of structural material, but ensure the integrity of the composite section, the design parameters are quite acceptable within the range n = U / V = 1 / 8.9 ... 1/9 at h / V = 0 ... 0.1.

By successively increasing the size of the height of the cutouts of the perforated wall, it can be brought closer to the maximum value:

at h = 0.8V

at h = 0.9V

Since the size of the height of the cutouts in the perforated wall exceeded the maximum value, and, accordingly, their ratio turned out to be greater than one, in practice this means that the perforation zone covered the entire wall and partially moved into the limits of the fillets of the interfaces between the wall and the shelves, thereby violating the accepted system of arrangement of the composite section I-profile.

It remains by the method of successive approximations to clarify the calculated parameters of the section where the size of the height of the cutouts in the perforated wall coincides with the maximum value, and, accordingly, their ratio is equal to unity:

at h = 0.8703125 V

Thus, the obtained results of calculating the composite section of an I-beam bent-closed profile with fillets of flanges allow us to conclude that its bending strength and wall perforation are optimal, that is, W _x = W _{x, man} and h = h _max at h / V = 0.8703 and n = U / V = 1 / 3.857. Without wall perforation (h / V = 0), the profile bending strength is optimal (W _x = W _{x, max} ) at n = U / V = 1 / 9.003.

From a comparison of the design parameters of the proposed (new) technical solution, which is a bent-closed I-profile with flange fillets, with its prototype, which is also an I-bent closed profile with a perforated wall, but with parallel flange edges, the approximate equivalence of the characteristics of both profiles is obvious (see table) ... The profile is more compact in width with folds and fillets of shelves. The round shape of these shelves, as well as their smooth mating with the wall and bends, provide a reduction in metal work hardening. It remains to add that the calculation of the optimal layout of I-beams and other bent-closed profiles, including C-shaped ones, makes it possible to increase their efficiency and expand the area of rational use by unifying sheet blanks that are the same or different both in terms of thickness and strength properties of structural material.

Claims (1)

I-beam bent-closed profile with fillets of shelves, characterized by the fact that it includes two C-shaped elements in cross-section, each of which consists of a solid or perforated vertical wall and two fillets, as well as two elements in the form of a channel, the walls of which are in contact with adjacent fillets , and the edges of its flanges and the edges of the fillets, made toothed, are connected with a form fit, forming together with the fillets the upper and lower flanges of the I-profile, while the cutouts of the perforated adjacent walls of the C-shaped elements along the entire perimeter are made with jagged edges to connect with the form fit , and the radius of the fillets is a quarter of the width of the profile flange, the height of the cutouts of the perforated wall is 0.8703 of the profile height with the ratio of the width of the profile to its height 1 / 3.857, and the ratio of the width of the profile to its height in the absence of perforation in the wall is 1 / 9.003.

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