RU199895U1 - TWO-TURN BENDED LOCKED PROFILE WITH TUBULAR SHELVES AND PERFORATED WALL - Google Patents

Abstract

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, these can be elements of girders, girders, beams. The technical result of the proposed solution is sufficient local (local) and general stability of I-beams bent out of the plane and in the plane of the supporting structure, increasing rigidity, reducing metal work hardening, expanding the area of rational use, and also a decrease in additional costs and consumption of structural material. The specified technical result is achieved by the fact that in the I-beam bent-closed profile the tubular shelves and the perforated wall are connected to each other by means of toothed closures of the longitudinal edges and mutual support in the contact zones of its two flat sheet blanks and two of its perforated sheet U-shaped blanks, in which the bends are made in the form of fillets with a radius equal to half the width of the shelves, and the vertical sections are provided with cutouts with serrated edges along the entire perimeter of each of these cutouts. Wall perforation and bending strength are maximum when the height of the notches reaches 0.6844 of the profile height and the ratio of the overall dimensions of the profile in width and height is 1 / 3.168.

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, these can be elements of purlins, crossbars, beams.

Known steel composite beam of I-section, in which the upper and lower flanges, as well as the vertical wall forms a pair of bent thin-walled profiles. The flat sections of these profiles to form a vertical wall are interconnected by bends of stamped pins, mutually entering the formed holes from the 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, 22.01.2018, bul. Number 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 well-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 inwardly, 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 structural beam. - Patent No. 176462, 19.01.2018, bul. No. 2]. As in the previous case, welding limits the minimum thickness of the welded elements and does not allow the use of galvanized steel, and tie rods and their holes cause a certain increase in additional costs.

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 profile width. 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 influences inherent in beam structures, the shape 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 additional functionality in the form of the formation of cuts of various shapes with toothed closures of the edges 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 design parameters, can contribute to expanding 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 flat blanks and the same faces of channel blanks, after closing their gear fastenings, form a pair of flat flanges of an I-profile 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 overall 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, its channel-shaped sheet blanks with rectangular bends are even more inferior to the semicircular blanks of the same analog.

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

The specified technical result is achieved by the fact that in the I-beam bent-closed profile, the tubular shelves and the perforated wall are mated to each other by means of toothed closures of the longitudinal edges and mutual support in the contact zones of two of its flat sheet blanks and two of its perforated sheet blanks of a channel shape, in which the bends are made in in the form of fillets with a radius equal to half the width of the flanges, and the vertical sections are provided with cutouts with serrated edges along the entire perimeter of each of these cutouts. Wall perforation and bending strength are maximal when the height of the notches reaches 0.6844 of the profile height and the ratio of the overall dimensions of the profile in width and height is 1 / 3.168.

The proposed I-beam bent-closed profile has a sufficiently versatile 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 the edges of two blanks are formed with one zigzag cut. 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 the bent-closed profiles increase the crushing thickness, 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 work of joints of thin-walled elements in shear. - Vestnik 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, distributed evenly 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 allowed 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].

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, SV,

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

Such restrictions for an I-beam bent-closed profile with tubular flanges and a perforated wall lie in the peculiarities of its structural 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:

fig. 1 shows a side view of an I-beam bent-closed profile with tubular shelves and rectangular cutouts of the perforated wall;

fig. 2 is a side view of an I-beam bent-closed profile with tubular shelves and round cutouts of the perforated wall;

fig. 3 is a side view of an I-beam bent-closed profile with tubular shelves and hexagonal cutouts of the perforated wall;

fig. 4 is a side view of an I-beam bent-closed profile with tubular shelves and rhombic notches of the perforated wall;

fig. 5 is a side view of an I-beam bent-closed profile with tubular shelves and oval cutouts of the perforated wall;

fig. 6 is a top (or bottom) view of an I-beam bent-closed profile with tubular shelves and a perforated wall;

fig. 7 shows a cross-section of an I-beam bent-closed profile with tubular shelves within one of the cutouts of its perforated wall;

fig. 8 - design diagram of the cross-section of an I-beam bent-closed profile with tubular shelves within one of the cutouts of its perforated wall;

fig. 9 is an exploded perspective view of a fragment of an I-beam bent-closed profile with tubular shelves and rectangular cutouts of its perforated wall;

fig. 10 shows graphs of changes in the main design parameters of an I-beam bent-closed profile with tubular shelves, depending on the growth of the relative height h / V of the notches of its perforated wall.

или без вырезов (h=0), образующих перфорированную стенку, где t - толщина листовой заготовки, U - размер ширины профиля, V - размер высоты профиля, h - высота выреза перфорированной стенки. Расчетные выкладки при этом допустимо выполнять по средней линии тонкостенного сечения без учета угловых закруглений и без учета численных величин, содержащих значения толщины, возведенной во вторую и третью степень (t², t³) [Марутян А.С. Оптимизация конструкций из трубчатых (гнутосварных) профилей квадратных (прямоугольных) и ромбических сечений. - Строительная механика и расчет сооружений, 2016, №1. - С. 30-38]. Угловые закругления в предлагаемом двутавровом гнутозамкнутом профиле отсутствуют, и этим он отличается от модификации двутаврового гнутосварного профиля с двойной стенкой и одним сварным швом [Марутян А.С. Двутавровый гнутосварной профиль. - Патент №2686762, 30.04.2019, бюл. №13]. Кроме того, если сварной профиль выполнен из единой листовой заготовки, то составное сечение гнутозамкнутого профиля включает две пары листовых заготовок. Однако принятые расчетно-теоретические предпосылки и одинаковые очертания профилей позволяют повторно применить уже апробированные выкладки:For a quantitative assessment of the resources of the bearing capacity of an I-beam bent-closed profile with tubular shelves and a perforated wall, 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 tubular shelves, two pairs of fillets with a radius of R = 0.5U, forming the inclined edges of the same shelves, and one pair of vertical rectangles dimensions t × (VU) with cutouts dimensions

or without cuts (h = 0) forming a perforated wall, where t is the thickness of the sheet blank, U is the size of the profile width, V is the size of the profile height, h is the height of the cut of the 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 from tubular (bent-welded) profiles of square (rectangular) and rhombic sections. - Structural mechanics and calculation of structures, 2016, No. 1. - S. 30-38]. Corner roundings in the proposed I-beam bent-closed profile are absent, and this differs from the modification of the I-beam bend-welded profile with a double wall and one welded seam [Marutyan A.S. I-beam bent-welded profile. - Patent No. 2686762, 30.04.2019, bul. No. 13]. In addition, if the welded profile is made of a single sheet blank, then the composite section of the bent-closed profile includes two pairs of sheet blanks. However, the accepted theoretical and theoretical prerequisites and the same outlines of the profiles make it possible to reapply the already approved calculations:

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

On the other hand, the calculation formulas can be obtained if it is conventionally assumed that one I-beam bent-closed profile with tubular shelves and a perforated wall is composed of two of the same channel profiles, each of which has a vertical facet with a section t × V removed [1. A. S. Marutyan Channel bent closed profile with a perforated wall. - Patent No. 197291, 20.04.2020, bul. # 11; 2. Marutyan A.S. Comparative calculation of the optimal parameters of bent and bent-closed channels. - Construction mechanics of engineering structures and structures, 2019, vol. 15, No. 6. - S. 415-432]:

- площадь и осевой момент инерции расчетного сечения нетто швеллерного профиля;

- размер ширины расчетного сечения нетто швеллерного профиля,

- отношение размеров ширины и высоты расчетного сечения нетто швеллерного профиля,

- размер высоты расчетного сечения нетто швеллерного профиля,

Where

- area and axial moment of inertia of the calculated net section of the channel profile;

- the size of the width of the calculated net section of the channel profile,

- the ratio of the dimensions of the width and height of the calculated net section of the channel profile,

- the size of the height of the calculated net section of the channel profile,

(где А - площадь сечения исходной заготовки, подлежащей зигзагообразному резу на две пары заготовок).As you can see, the calculation formulas practically coincided, which can be conventionally taken as their control check and applied to solve the optimization problem. This problem is the calculation of the optimal layout of a composite section of an I-beam bent-closed profile with tubular shelves and a perforated wall, when its bending strength and wall perforation are maximum:

(where A is the cross-sectional area of the original workpiece to be zigzag cut into two pairs of workpieces).

To start solving the problem, it is advisable to consider the calculated case without cutouts in the wall of the I-profile (h = 0), which is also of practical importance for its welded modification:

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

можно получить уравнение четвертой степениEquating to zero the derivative

you can get the equation of the fourth degree

with roots

когда двутавровый профиль является балочным элементом с наибольшим по абсолютной величине значением прочностной характеристики поперечного сечения, то естьThe third root is of practical importance for the continuation of calculations.

when the I-profile is a beam element with the largest absolute value of the strength characteristic of the cross section, that is

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 optimization calculation of an 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 cutouts 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 / 5.22 ... 1 / 5.2 at h / V = 0 ... 0, l ...

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 = 0.6V

at h = 0.7V

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 more than one, then in practice this means that the perforation zone covered the entire wall and partially moved into the limits of the tubular shelves, thereby violating the accepted system of arrangement of the composite section of the 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 = 0,684375V

при h/V=0, 6844 и n=U/V=1/3,168.Thus, the obtained results of calculating the optimal layout of a composite section of an I-beam bent-closed profile with tubular shelves and a perforated wall allow us to conclude that its bending strength and wall perforation are maximum, that is,

with h / V = 0, 6844 and n = U / V = 1 / 3.168.

It is of practical importance to further refine the design characteristics of the proposed profiles with the addition of toothed fasteners instead of welded, bolted or riveted joints. For this, in the considered profiles, it is necessary to select the dimensions of the gear attachment elements (teeth), which must be at least 1/10 of the overall cross-sectional size [SP 260.1325800.2016. Thin-walled steel structures from cold-formed galvanized profiles and corrugated sheets. Design rules. - M, 2016. - P. 16, formula (7.2)]. In this case, this dimension is 0.1 U, where U is the width of the flange (belt) of the bent-closed profile.

In the calculated calculations, the parameter of the gear fastenings (the size of the teeth) will be reflected in a 12-fold manner, as in the prototype, since the I-bend bent profile has a composite section of 4 sheet blanks (strips or molded strips) with longitudinal toothed edges, of which 2 are additionally perforated blanks equipped with the same scalloped edges along the entire perimeter of each of the cutouts:

at n = 1 / 5.219

at n = 1 / 5.208

at n = 1 / 3.168

двутавровых гнутозамкнутых профилей с трубчатыми полками и перфорированными стенками не превышают аналогичных отношений прототипа (двутавровых гнутозамкнутых профилей с параллельными гранями полок и перфорированными стенками) и находятся примерно в тех же пределах, что и редукционный коэффициент стержневых элементов легких стальных тонкостенных конструкций (ЛСТК):Found ratio values

I-beams bent-closed profiles with tubular flanges and perforated walls do not exceed similar prototype ratios (I-beams bent-closed profiles with parallel flange edges and perforated walls) and are approximately within the same limits as the reduction coefficient of rod elements of light steel thin-walled structures (LSTK):

where A _red is the calculated area of the reduced (effective) section, A is the calculated area of the full section.

So, in relation to continuous bent profiles of C-shaped and channel section ρ = 0.694 ... 0.950 [Recommendations for the design, manufacture and installation of enclosing and supporting structures from steel bent sections of increased rigidity. - M .: TsNIIPSK im. N.P. Melnikova, 1999. - S. 10-11, tab. 2].

From a comparison of the design parameters of the proposed (new) technical solution, which is an I-beam bent-closed profile with tubular shelves and a perforated wall, with its prototype, which is also an I-beam curved profile with a perforated wall, but parallel edges of the shelves, the approximate equivalence of the characteristics of both profiles in the load-bearing plane of the supporting structure (see table). From the plane of the structure, a profile with tubular shelves with increased bending and torsional rigidity is more preferable. Moreover, the round outlines of these shelves, as well as their smooth mating with the wall, provide a decrease in metal work hardening. It remains to add that the calculation of the optimal layout of I-beams and other bent sections, including U-sections, 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 in strength properties of structural material.

Claims (1)

I-beam bent-closed profile with tubular shelves and a perforated wall, mated to each other by means of toothed closures of the longitudinal edges and mutual support in the contact zones of two of its flat sheet blanks and two of its perforated sheet blanks of a channel shape, in which the bends are made in the form of fillets with a radius equal to half the width of the flanges, and the vertical sections are provided with cuts with serrated closures of the edges along the entire perimeter of each of these cuts, characterized in that its wall perforation and bending strength are maximum when the height of the cuts reaches 0.6844 of the profile height, and the ratio of the profile dimensions in width and height is 1 / 3.168.

Images