RU207351U1 - STRUCTURE WITH U-PROFILE GRILLE - Google Patents

Abstract

The proposed technical solution relates to construction, namely to building load-bearing lattice structures, and can be used in the manufacture of trusses, girders, columns, arches, frames and other frame systems. The technical result of the proposed solution is to increase stability, reduce the consumption of structural material, reduce weight (weight) of the lattice structure. The specified technical result is achieved by the fact that in a structure including chords of bent-closed profiles connected by lattice rods, the flattened ends of which are provided with slots and coaxial holes for bolts, the lattice rod elements have a U-shaped cross-section with the ratio of the dimensions of the width and a height of 1 / 1.39 along the midline of the same section.

Description

The proposed technical solution relates to construction, namely to structural lattice structures, and can be used in the manufacture of trusses, girders, columns, arches, frames and other frame systems.

A well-known technical solution is a truss, which includes belts from bent Tavras, the double walls of which are bolted with the rod elements of the lattice from single corners [Kuznetsov I.L., Salakhutdinov M.A., Fakhrutdinov A.E. Farm. - Patent No. 2647137, 03/14/2018, bul. No. 8]. Each of the corners is connected to the belt element by only one shelf, which significantly limits its carrying capacity.

Another technical solution (taken as an analogue) is known in the form of a building element for the manufacture of lattice structures, including a thin-walled rod of a polygonal closed section, the rib of which along the entire length has a double thickness and a number of coaxial bolt holes. This row also provides connections with the rod elements of the lattice from single corners [Kuznetsov I.L., Salakhutdinov M.A., Sayanov S.F. Building element for the manufacture of lattice structures. - Patent No. 2633851, 18.10.2017, bul. No. 29]. Since each of the corners of the lattice is connected to the belt element by only one shelf, the disadvantage of the analogue coincides with the disadvantage of the above truss.

The closest technical solution (prototype) to the proposed structure with a lattice made of a U-shaped profile is a lattice structure, including belts of closed profiles with sheet gussets for the entire length, connected by lattice rods from single corners attached to the gussets with bolts and differing in the opening angle of the shelves

γ = 2arccos ((4a ² -t ² ) / (5a ² -2t ² )) ^1/2 ,

where a is the length of the angle flange, t is the thickness of the angle flange. At the same time, in the butts at the ends of the corners, slots are made for the width of the waist gussets, the shelves of the corners in the attachment points are flattened to contact with the gussets, in the flattened shelves and gussets there are coaxial holes for bolts [Kuznetsov I.L., Fakhrutdinov A.E., Salakhutdinov M .A. Lattice construction. - Patent No. 2715785, 03.03.2020, bul. No. 7].

In the technical solution of the prototype, the rod elements of the lattice are optimized according to the criterion of equal stability, which provides stability that is the same in the plane of greatest rigidity and in the plane of least rigidity. With this optimization, due to the acute opening angle of the shelves, the profiles of the lattice bar elements are transformed from corner profiles with orthogonal conjugation of these shelves into V-shaped ones. With the transition from a straight to an acute angle, the structural material in both flanges of the profile is located at a smaller distance from the center of gravity of the cross section, which reduces the stability of the rod element. Therefore, a certain elaboration of the profile with a large distance of the structural material from the center of gravity of the section can increase its stability.

The technical result of the proposed solution is to increase stability, reduce the consumption of structural material, and reduce the mass (weight) of the lattice structure.

The specified technical result is achieved by the fact that in a structure including belts of bent-closed profiles connected by lattice rods, the flattened ends of which are provided with slots and coaxial holes for bolts, the lattice rod elements have a U-shaped section with a ratio of the width and height dimensions of 1 / 1.39 along the midline of the same section.

In the proposed design, the upper and lower chords are made of bent-closed profiles having a tubular (closed) part of a single (single) thickness and a rib part of a double thickness. The rib part closes the sheet reamer (workpiece) into a profile using bolted, riveted, welded, locking (folded or serrated) and other connections. To directly adjoin the rib part of the bent-closed profile of the upper or lower belt with the formation of a connecting unit, the U-shaped profile of each of the rod elements of the lattice is cut and flattened at the ends. Due to the length of the longitudinal slots and the width of the flattened ends, it is quite possible to unify the structural and layout design of nodal joints on bolts without eccentricities, taking into account the fastening of one, two or more rod elements of the U-shaped lattice with one bolt. Proceeding from this, in order for the lattice bar elements in the plane and out of the plane of the structure to have the same flexibility, it is advisable to have such a profile of their cross-section, in which the radii of gyration along the main central axes have equal values. This condition is fully met by a thin-walled U-shaped section with a ratio of dimensions of width and height of 1 / 1.39 along its centerline, where the larger dimension is located in the plane of the structure, and the smaller one is out of the plane.

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

fig. 1 shows a fragment of a structure with equally high chords and a grid made of a U-shaped profile;

fig. 2 - cross-section of a structure with equally high belts;

fig. 3 - a fragment of a supporting structure with belts of different heights and a lattice made of a U-shaped profile;

fig. 4 - cross-section of the supporting structure with belts of different heights;

fig. 5 is a perspective view of a fragment of a rod element from a U-shaped profile;

fig. 6 - design diagram of the cross-section of the U-shaped profile.

The proposed technical solution of the structure includes the upper (compressed or compressed-bendable) chord 1, the lower (stretched) chord 2, as well as a lattice connecting them from the rod elements of the U-shaped profile 3 using bolted fasteners 4. The section of the U-shaped profile is matched with the ratio dimensions of width and height 1 / 1.39 along the centerline of its design section, where the larger dimension is located in the plane of the structure, and the smaller one is out of the plane. In a design with different-height belts made of bent-closed profiles, for example, in non-runner pavements, the profile of the upper belt 1 has a higher rib portion than the profile of the lower belt 2 [Marutyan A.S. Bent profiles and calculation of their optimal parameters. - Structural mechanics of engineering structures and structures. 2019, no.1. - S. 33-43]. In this case, with the displacement of the longitudinal axis of the upper belt profile from its pipe part, it becomes possible to fix one, two or more rod elements of the lattice of the U-shaped profile 3 with one bolt 4.

To derive the reduced ratio and quantify the resources of the bearing capacity of the lattice bar elements from the U-shaped profile, it is advisable to take a composite figure as the design section of this profile. Such a figure includes a pair of vertical rectangles with dimensions t × (V-0.5U), united by a circular semicircle of thickness t and a radius along its middle (median) line R = 0.5U, where V is the overall height of the profile along the midline of the profile section, U - dimension of the profile width along the center line of the profile section.

The calculated values of the geometric (static) characteristics of the cross-section of the U-shaped profile can be determined by the formulas:

square

A = tU (2 / n + 0.57);

center of gravity ordinate

y ₀ = U (1 / n ² +0.034955) / (2 / n + 0.57);

moment of inertia about the abscissa axis

I _x = tU ³ (0.6666666 / n ⁵ + 0.95 / n ⁴ + 0.07678 / n ³ -0.018247 / n ² + 0.0098689 / n + 0.001058) / (2 / n + 0.57) ² ;

moment of inertia about the ordinate

I _y = tU ³ (0.5 / n-0.05375),

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

Since the design cross-section of U-shaped profiles differs from the same cross-section of semi-flat shaped pipes (bent-welded profiles) by the absence of a shelf (horizontal face), the correctness of the above formulas was confirmed using an approximate calculation method, tested when optimizing rod and beam elements from such pipes [Marutyan A .WITH. Calculation of the optimal parameters of semi-flat pipes for truss and girder structures. - Structural mechanics and calculation of structures. 2019, no. 2. - S. 68-74].

So that the radii of gyration along the main central axes do not differ from each other (i _x = i _y ), the corresponding moments of inertia must have zero difference, that is, I _x -I _y = 0.

If we substitute the values of the moments of inertia, then for the ratio of the overall dimensions of the profile (n = U / V), we can obtain the equation of the fifth degree

0.6666666 / n ⁵ + 0.95 / n ⁴ -1.92322 / n ³ -0.9432427 / n ² -0.0300311 / n + 0.0185213 = 0 with roots

n ₁ = -3.9025612; n ₂ = -3.5087055; n ₃ = 0.7191272; n ₄ = 8.7321874.

Of these roots, the third is of practical interest, the value of which can be rounded to the ratio given above:

n = 0.7191272 = 1 / 1.3905754≈1 / 1.39.

Then, for a U-shaped profile optimized according to the criterion of equi-stability, we can write:

n = 0.5 = 1 / 1.39;

A = 3.3511491tU;

U = 0.2984051A / t; V = 0.4149545A / t; y ₀ = 0.5874559U = 0.1752998A / t;

I _x = 0.6414454tU ³ = 0.0170442A ³ / t ² ; I _y = 0.6415372tU ³ = 0.0170466A ³ / t ² ;

i _x = 0.4375048U = 0.1305536A / t; i _y = 0.4375361U = 0.1305630A / t;

I _x / I _y = 0.9998569 ~ 1.0; i _x / i _y = 0.9999284≈1.0.

7×100×100 мм, оптимизированный по техническому решению из прототипа:To compare the proposed (new) technical solution with the known as the base object, you can take a rolling corner with a cross-section

7 × 100 × 100 mm, optimized according to the technical solution from the prototype:

A = 13.024 cm ² ;

I _x = 75.262 cm ⁴ ; I _y = 75.480 cm ⁴ ;

i _x = 2.404 cm; i _y = 2.407 cm; V = 8.32 cm,

where V is the overall height of the optimized corner with the opening angle of its shelves γ = 53.1 ° [Salakhutdinov MA, Kuznetsov IL, Fakhrutdinov A.E. Lattice construction. - Academic bulletin UralNIIproekt RAASN. 2019, no. 2. - S. 86-90].

The proposed technical solution is represented by a U-shaped profile with a height dimension V = 8.32 cm and the following characteristics of its design section:

t = 0.4149545A / V = 0.4149545 × 13.024 / 8.32 = 0.6496 cm → 6.0 mm;

A = tV / 0.4149545A / V = 0.60 × 8.32 / 0.4149545 = 12.042 cm ² (92.46%);

U = 0.2984051 × 12.042 / 0.60 = 5.989≈6.0 cm;

I _x = 0.0170442 × 12.042 ³ / 0.60 ² = 82.674 cm ⁴ (109.8%);

I _y = 0.0170466 × 12.042 ³ / 0.60 ² = 82.686 cm ⁴ (109.5%);

i _x = (82.674 / 12.042) ^1/2 = 2.620 cm (109.0%);

i _y = (82.686 / 12.042) ^1/2 = 2.623 cm (109.0%),

where the corresponding characteristics of the design section from the base object are taken as the reference (100 percent) indicators.

From the obtained results of the comparative calculation, it follows that the transition from the prototype to the proposed technical solution is accompanied by a decrease in the area of the design section and, as a consequence, the consumption of structural material by 7.54%, as well as an increase in the geometric (static) characteristics of the same section by 9.0 ... 9.8% and a corresponding increase in the stability of the rod elements of the lattice.

Claims (1)

A structure with a U-shaped lattice, including belts of bent-closed profiles connected by lattice rods, the flattened ends of which are equipped with slots and coaxial bolt holes, characterized in that the lattice rod elements have a U-shaped section with a ratio of width and height dimensions of 1 / 1.39 along the midline of the same section.

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