RU199331U1 - CROSSLATING OF ROD STRUCTURES WITH Y-SHAPED OR Ψ-SHAPED SEMI-STRUCTURES - Google Patents

Abstract

The proposed technical solution relates to the field of construction and can be used in rod structures of coatings and ceilings, towers and masts, bridges and flyovers, stadiums and sports facilities, power transmission towers, loading cranes, as well as other supporting and communication systems. the solution is to shorten the panels of compressed or compressed-bent (upper) chords, unify these chords with stretched (lower) chords, as well as reduce labor costs and consumption of structural material. or compressed-bending) and lower (stretched) chords, as well as braces, half-struts and support struts, half-struts have a Y-shaped or Ψ-shaped shape. The upper elements of the half-props are connected with one end to the upper chord, and with the other end they are supported on the lower elements of the same half-props. The upper nodal connections of the upper elements divide the panels of the upper chord into their component parts, and the lower nodal connections of the lower elements are aligned with the intersection nodes of the braces.

Description

The proposed technical solution relates to the field of construction and can be used in rod structures of coatings and floors, towers and masts, bridges and flyovers, stadiums and sports facilities, power transmission towers, loading cranes, as well as other supporting and communication systems.

Known bar structures (trusses) with double-sided loads and a cross-shaped lattice of flexible elements, in which compressed braces due to increased flexibility are turned off and the lattice functions as a diagonal with I-shaped (rectilinear) uprights and stretched braces. The rod structures of the cross links of the bearing systems work according to the same scheme. In trusses with T-belts, a cross lattice of single corners attached directly to the belt elements is rational [1. Metal constructions. In 3 vols. V. 1. Elements of structures / Ed. V.V. Goreva. - M .: Higher school, 2004. - S. 420-421, fig. 7.6, f, g; 2. Metal structures / Ed. Yu.I. Kudishina. - M .: Publishing Center "Academy", 2007. - P. 264, 269, fig. 9.6, f, g]. The difference between the cross lattice and the cross lattice is the absence of posts connecting the upper and lower chords (with the exception of the support posts of the lattice). The disadvantage of this technical solution is the extended rod elements of compressed and compressed-bending belts, which leads to additional consumption of structural material to ensure their stability.

Also known are rod structures (trusses) with parallel belts, the triangular lattice of which is equipped with additional posts of an I-shaped (rectilinear) outline and the same semi-posts in outline. Each of these half-struts is attached at one end to the brace, and the other end to the lower chord, which helps to reduce the consumption of structural material by reducing the estimated length of the diagonal bars of the lattice [Bekker G.N. Truss with parallel belts. - Copyright certificate No. 781293, 11/23/1980, bull. No. 43]. The disadvantage of this technical solution is that additional half-racks (unlike additional racks) do not work on the local (local) load and perform the functions of connecting elements only in the plane of the lattice, without affecting the calculated length of the diagonal bars from the plane of the lattice.

Another well-known technical solution is an arched-cable-stayed combined covering, which includes an arched upper belt, a sagging broken tie and elements that combine them in the form of Y-shaped struts. All nodal mates of the rod elements are made without the use of hinges, and the distances between them have certain relationships with each other and the span of the structure [Eremeev PG, Kiselev DB, Pavlinov VV. Arched cable-stayed combined coating. - Patent No. 2396396, 08/10/2010, bul. No. 22]. To ensure the geometric invariability of the combined coating, its rod elements, as well as their nodal joints, must have the required bending stiffness, which increases the consumption of structural material.

Among the known technical solutions also includes a triangular lattice with additional posts and half-slopes [Marutyan A.S. Triangular lattice of bar structures with additional posts and half-slopes. - Patent No. 2573889, 01/27/2016, bul. Number 3]. Additional struts and half-slopes have a Ψ-shaped outline and in rod structures (trusses) with a triangular lattice divide the compressed or compressed-bending panels of the upper chords into four, as a rule, equal parts. In this case, the length of the half-slopes of the additional сто-shaped outlines reaches half the length of the braces of the triangular lattice, which increases the material consumption of the structure. In addition, стойки-shaped posts need some processing, when the panels of the upper chords are quite enough to be divided not into four, but into three parts.

A common disadvantage of triangular lattices, both without pillars and with pillars of I-shaped, Y-shaped or Ψ-shaped outlines, is their limited efficiency and rationality when working structures for large transverse forces, as well as in bearing and tie systems with significant heights ( distances between belts).

As an analogue, you can take a technical solution of a cross lattice, consisting of two systems of braces, the intersections of which, in addition to the nodes of the upper and lower chords, form an intermediate row of nodes in a truss of a low height, which can be called a lattice beam or the same run [Design of metal structures: Spec. course / V.V. Biryulev, I.I. Koshin, I.I. Krylov, A.V. Silvestrov. - L .: Stroyizdat, 1990. - S. 85-88, fig. 3.1, d]. The intersection nodes divide each of the braces of the two systems, usually in half, which halves the calculated length of the compressed braces. However, this does not reduce the length of the rod elements of the compressed and compressed-bendable chords.

For the prototype (the closest technical solution) to the proposed cross lattice with Y-shaped or Ψ-shaped half-struts, you can take the same lattice with half-struts or half-suspensions, consisting of two systems of braces, the intersections of which, in addition to the nodes of the upper and lower chords, form an intermediate row of nodes , which are support for half-posts or half-hangers. These half-struts (half-suspensions) have an I-shaped (rectilinear) outline and, with their upper (lower) nodes, divide the compressed or compressed-bending (stretched) chord panels into two, as a rule, equal parts. [Paton E.O., Gorbunov B.N. Steel bridges. T. 1. Beam system trusses: material and rivets. - Kharkov-Kiev: ONTI NKTP NTIU, 1935. - p. 364, fig. 781, 782]. The disadvantage of the accepted prototype is inherently similar to that of an analogue. I-shaped half-struts divide the panels of the upper chords into two, as a rule, equal parts. If it is necessary to further shorten the belt panels by dividing them into three or four parts using truss elements, a certain increase in material consumption and additional labor costs for tie and bearing systems is inevitable.

The technical result of the proposed solution is the shortening of the panels of compressed or compressed-bent (upper) chords, the unification of these chords with the stretched (lower) chords, as well as a reduction in labor costs and consumption of construction material.

The specified technical result is achieved by the fact that in the cross lattice of rod structures, including the upper (compressed or compressed-bent) and lower (stretched) chords, as well as braces, half-posts and support posts, the half-posts are Y-shaped or Ψ-shaped. The upper elements of the half-props are connected with one end to the upper chord, and with the other end they are supported on the lower elements of the same half-props. The upper nodal connections of the upper elements of the half-struts divide the panels of the upper chord into their component parts, and the lower nodal connections of the lower elements of the same half-struts are aligned with the intersection nodes of the braces.

The proposed technical solution is quite versatile. In it, Y-shaped or Ψ-shaped half-racks have a double function. Working on a local (local) load, they do not participate in the transfer of lateral force to the support. At the same time, as tie elements, they reduce the calculated length of a compressed or compressed-bendable belt. In this case, unification of the upper (compressed or compressed-bendable) and lower (stretched) belts is quite achievable, which, as a rule, is accompanied by a certain reduction in labor costs and consumption of structural material.

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

fig. 1 shows a diagram of a cross lattice of a bar structure (truss) with Y-shaped floor pillars;

fig. 2 is a diagram of a cross lattice of a bar structure (truss) with Ψ-shaped half-struts;

fig. 3 is a diagram of a cross lattice of a bar structure (truss) with a combination of I-shaped, Y-shaped and Ψ-shaped half-struts;

fig. 4 shows a diagram of a cross lattice of a serial (typical) truss with a span of 30 m;

fig. 5 - design diagram of the cross lattice of a serial (typical) truss with a span of 30 m with Y-shaped and I-shaped semi-racks;

fig. 6 - design diagram of the cross lattice of a serial (typical) truss with a span of 30 m with Ψ-shaped and I-shaped half-racks.

In one embodiment, the proposed cross lattice of rod structures includes an upper (compressed or compressed-bendable) chord 1, a lower (stretched) chord 2, braces 3, support posts of the lattice 4 and half-struts of the Y-shape 5. One end of the upper elements of the Y-shaped half-struts 5 are connected to the panels of the upper chord 1, and the other end is supported on the lower elements of the same Y-shaped half-struts 5. The upper nodal connections of the upper elements of the Y-shaped half-struts 5 divide the panels of the upper chord 1 into three parts. The lower nodal connections of the lower elements of the Y-shaped half-struts 5 are aligned with the intersections of the braces 3.

In another embodiment, the proposed cross lattice of rod structures includes an upper (compressed or compressed-bendable) chord 1, a lower (stretched) chord 2, braces 3, support posts of the lattice 4 and half-posts of Ψ-shaped shape 6. One end of the upper elements of Ψ-shaped half-struts 6 are connected to the panels of the upper chord 1, and the other end is supported on the lower elements of the same V-shaped half-struts 6. The upper nodal connections of the upper elements of the V-shaped half-struts 6 divide the panels of the upper chord 1 into four parts. The lower nodal connections of the lower elements of the Ψ-shaped half-struts 6 are aligned with the intersections of the braces 3.

In another embodiment, the proposed cross lattice of rod structures includes an upper (compressed or compressed-bendable) chord 1, a lower (stretched) chord 2, braces 3, support posts of the lattice 4, as well as a combination of Y-shaped half struts 5, Ψ-shaped shape 6 and I-shape 7.

For an example of the implementation of the proposed (new) technical solution, it is advisable to use a basic object in the form of a serial (typical) FS30-6.35 truss with a cross grid, a span of 30 m, a mass of 6130 kg and a design load of 63.5 kN / m (6.50 tf / m) [Steel structures of coverings of one-story industrial buildings using trusses with belts made of wide-shelf T-bars with a cross lattice from single corners: Typical project. Series 1.460.3-18. Issue 1. Drawings of KM. - M .: TsNIIproektstalkonstruktsiya them. N.P. Melnik, 1983. - L. 40].

Strength of the stretched (lower) belt will be ensured provided:

σ / R _y = N / (AR _y ) ≤0.95,

where σ is the calculated value of normal tensile stress; R _y is the design resistance of the structural material according to the yield point; N is the calculated tensile force;

γ _n = 0.95 - the coefficient of reliability for the intended purpose [Steel structures of the coatings of one-story industrial buildings using trusses with belts of wide-shelf T-bars with a cross lattice of single corners: Typical design. Series 1.460.3-18. Issue 1. Drawings of KM. - M .: TsNIIproektstalkonstruktsiya them. N.P. Melnik, 1983. - L. 15].

The limiting slenderness of the rods of the lower (stretched) chords, the strength of which is ensured, should not exceed 400 out of the plane and in the plane of the truss, and 350 when taking into account seismic effects.

The stability of the compressed (upper) chord will be ensured provided:

σ / R _y = N / (ϕAR _y ) ≤0.95,

where σ is the calculated value of the normal compressive stress; N is the calculated compression force;

ϕ - coefficient of longitudinal bending,

ϕ = 1-0.066 (λ _pr ) ^3/2 for 0 <λ _pr ≤2.5,

ϕ = 1.46-0.34λ _pr +0.02 (λ _pr ) ² at 2.5 <λ _pr ≤4.5;

λ _pr - conditional slenderness of a compressed member [Steel Structural Design Manual. - M .: TSITP, 1989. - S. 17];

λ _pr = λ (R _y / E) ^1/2 ;

λ - design flexibility of the compressed element;

- расчетная длина сжатого элемента; i - радиус инерции расчетного сечения;

- calculated length of the compressed element; i is the radius of gyration of the design section;

E is the modulus of elasticity of the structural material (for steel E = 2,100,000 kgf / cm ² ).

For the lower (stretched) belt of the base object, a cross-section is taken from a wide-flange 20ShT3 (A = 78.14 cm ² ; t = 18 mm; i _x = 5.15 cm; i _y = 7.20 cm; m = 61.30 kg / m [Metal structures. In 3 volumes. V. 1. General part (Designer's Guide) / Under the editorship of V.V. Kuznetsov (TsNIIproektstalkonstruktsiya named after NP Melnikov) - M .: Publishing house ASV, 1998. - S. 109-111]):

σ / R _y = N / (AR _y ) = 234000 / (78.14 × 3500) = 0.856 <0.95,

where N = 234.0 tf is the design force in the N5 panel of the lower chord of the FS30-6.35 truss;

R _y is the design resistance of the structural material, for steel grade 14G2-6-1 (with a thickness of t = 11 ... 20 mm) R _y = 3500 kgf / cm ² [Steel structures of coatings of one-story industrial buildings using trusses with belts of wide-shelf T-bars with with a cross lattice from single corners: Typical project. Series 1.460.3-18. Issue 1. Drawings of KM. - M .: TsNIIproektstalkonstruktsiya them. N.P. Melnik, 1983. - L. 19].

Lower Belt Flexibility:

where λ _x - flexibility of the belt in the plane of the truss; λ _y - flexibility of the belt from the plane of the truss.

For the upper (compressed) belt of the base object, a wide-flange Tavr 250ShT3 was adopted (A = 99.04 cm ² ; t = 20.5 mm; i _x = 6.95 cm; i _y = 6.83 cm; m = 77.70 kg / m):

σ / R _y = 224000 / (0.852 × 99.04 × 3200) = 0.830 <0.95,

where R _y is the design resistance of the structural material, for steel grade 14G2-6-2 (with a thickness of t = 11 ... 20 mm) R _y = 3200 kgf / cm ²

N = -224.0 tf - design force in panel B5 of the upper chord of the FS30-6.35 truss;

λ _x = 300 / 6.95 = 43.17; λ _y = 300 / 6.83 = 43.92; λ _pr = 43.92 (3200/2100000) ^1/2 = 1.714; ϕ = 1-0.066 (1.714) ^3/2 = 0.852.

The next stage of the implementation of the proposed technical solution is the replacement of the upper (compressed) belt of the basic object from the wide-flange brand 25ShT3 with the same belt from the 20ShT3 profile adopted for the lower belt, due to the inclusion of I-shaped half-struts in the cross lattice dividing the B5 panels of the compressed belt into two parts (300/2 = 150 cm):

σ / R _y = 224000 / (0.914 × 78.14 × 3500) = 0.896 <0.95,

where λ _x = 150 / 5.15 = 29.13; λ _y = 150 / 7.20 = 20.83; λ _pr = 29.13 (3500/2100000) ^1/2 = 1.189; ϕ = 1-0.066 (1.189) ^3/2 = 0.914.

It's obvious that

0.856 <σ / R _y = 0.896 <0.95,

that is, the bearing capacity resources of the same profile under compression in the upper chord have decreased compared to tension in the lower chord.

If you include in the cross lattice Y-shaped half-racks dividing the B5 panels of the compressed belt into three parts (300/3 = 100 cm), then you can repeat the calculation of the 20ShT3 wide-shelf brand, taking into account its reinforcement:

σ / R _y = 224000 / (0.953 × 78.14 × 3500) = 0.859 <0.95,

where λ _x = 100 / 5.15 = 19.42; λ _y = 100 / 7.20 = 13.89; λ _pr = 19.42 (3500/2100000) ^1/2 = 0.793; ϕ = 1-0.066 (0.793) ^3/2 = 0.953.

As you can see, in this case, the conditional overvoltage was

100 (0.859-0.856) / (0.859 ... 0.856) = 0.349 ... 0.350%, which does not exceed the permissible threshold of 3%.

Of practical interest is the strengthening of the B5 panel of the compressed belt when it is divided into four parts (300/4 = 75 cm) due to the inclusion of Ψ-shaped half-struts in the cross lattice:

σ / R _y = 224000 / (0.970 × 78.14 × 3500) = 0.844 <0.856,

where λ _x = 75 / 5.15 = 14.56; λ _y = 75 / 7.20 = 10.42; λ _pr = 14.56 (3500/2100000) ^1/2 = 0.594; ϕ = 1-0.066 (0.594) ^3/2 = 0.970.

The use of Ψ-shaped half-struts to strengthen the upper belt increased the resources of its bearing capacity in comparison with the lower belt by

100 (0.856-0.844) / (0.856 ... 0.844) = 1.40 ... 1.42%.

Next, you need to check the 3-meter panel of the upper belt of the base object B4 (N = -205.0 tf):

σ / R _y = 205000 / (0.758 × 78.14 × 3500) = 0.989> 0.95,

where λ _x = 300 / 5.15 = 58.25; λ _y = 300 / 7.20 = 41.67; λ _pr = 58.25 (3500/2100000) ^1/2 = 2.378; ϕ = 1-0.066 (2.378) ^3/2 = 0.758.

B4 panels of the compressed chord must be reinforced with I-shaped half racks (300/2 = 150 cm) and checked by calculation again:

σ / R _y = 205000 / (0.914 × 78.14 × 3500) = 0.820 <0.856.

Further, in the same way, it is necessary to check the 3-meter panel of the upper belt of the base object B3 (N = -175.0 tf):

σ / R _y = 175000 / (0.758 × 78.14 × 3500) = 0.844 <0.856.

The above calculation shows that the inclusion of I-shaped half-struts in panels B4 and the same inclusion of Y-shaped or Ψ-shaped half-struts in B5 panels leads to the unification of the upper chord with the lower one and a reduction in the consumption of structural material for the upper (compressed) chord in 77, 70 / 61.30 = 1.27 times.

To assess the effect of the reduced unification of belts on the mass of the base object (FS30-6.35 trusses), it is necessary to select the sections of I-shaped, Y-shaped and Ψ-shaped half-struts.

If the design load on the FS30-6.35 truss is 6.5 tf / m, then the design force in the I-shaped half-rack will be

N = -6.5 × 1.5 = -9.75 tf,

then it is advisable to choose a compressed brace with a cross-section from an equal angle ⎣ 110 × 8 mm with a design force N = -18.1 tf, length in the axes from the assortment of bars of the cross lattice of the considered truss

(3150 ² +3000 ² ) ^1/2 = 4350 mm

and linear (running) weight of 13.5 kg / m (Equal angles according to GOST 8509-72) [Metal structures. General course / Under total. ed. E.I. Belenya. - M .: Stroyizdat, 1986. - S. 545].

The masses of the bar elements of the FSZO-6.35 truss and its modifications are:

top belt (wide-shelf brands 25SHT3)

m = 78.2 × 30 = 2346 kg;

lower belt (wide-shelf brand 20SHT3)

m = 61.7 × 30 = 1851 kg;

I-shaped floor stand (equal angle ⎣ 110 × 8 mm)

m = 13.5 × 3.150 / 2 = 13.5 × 1.575 = 21.3 kg;

Y-shaped floor stand (equal angle ⎣ 110 × 8 mm)

m = 13.5 (2 × 1.575 / 3 + 2 × 4.350 / 6) = 33.8 kg;

Ψ-shaped half-rack (equal angle ⎣ 110 × 8 mm)

m = 13.5 (1.575 + 2 × 4.350 / 4) = 50.6 kg.

The mass of the bar structure (truss) with a cross grid and floor racks:

I-shaped and Y-shaped

m = 6130-2346 + 1851 + 2 (21.3 + 33.8) = 5745 kg;

I-shaped and Ψ-shaped

m = 6130-2346 + 1851 + 2 (21.3 + 50.6) = 5779 kg,

where 6130 kg is the weight of the FS30-6.35 farm.

The use of the proposed (new) technical solution provided a reduction in the mass of the rod structure (truss) with a cross grid and floor racks:

Y-shaped

100 (6130-5745) / (6130 ... 5745) = 6.3 ... 6.7%;

Ψ-shaped

100 (6130-5779) / (6130 ... 5779) = 5.7 ... 6.1%.

Thus, the metal consumption of the upper belt has decreased by 1.27 times, and the total mass of the bar structure has decreased by 5.7 ... 6.7%. At the same time, the unification of both belts takes place, which is the characteristic task that has become decisive in the design of standardized trusses from rectangular shaped pipes (bent-welded profiles) with a span of 36 m [Baranovsky M.Yu., Tarasov V.A. Standardized truss structures with 10% slope spans 24, 30, 36 meters. - Construction of unique buildings and structures, 2014. No. 7 (22). - S. 92-106]. In addition, the connecting nodes of the upper chord with I-shaped, Y-shaped or Ψ-shaped half-struts make it possible to support a certain number of additional purlins on them and to release its compressed panels from the truss plane. As the total number of runs increases, their lightening occurs, which can be of decisive importance for load-bearing structures designed for special loads and impacts [Marutyan A.S. Optimization of truss structures with uprights and half-slopes in triangular grids. - Structural mechanics and calculation of structures, 2016, No. 4. - S. 60-68].

Thus, summing up some of the results, we can come to the main conclusion that the proposed cross lattice of rod structures with half-struts of the Y-shaped or-shaped form is quite promising for use as part of the bearing and communication systems of various buildings and weapons. In particular, the area of their rational application can cover collapsible bridges [SA Bokarev, DV Protsenko. Experimental and theoretical studies of the span structure of the TAIPAN collapsible bridge. - Proceedings of universities. Construction, 2017, No. 8. - S. 24-33] and large-span coverings of football stadiums [Lebed EV, Mitev Zh.M. Investigation of the bearing capacity resource of a large-span stadium covering made of metal orthogonal trusses. - Bulletin of RUDN University, Engineering Research Series, 2016, No. 3. - S. 95-105].

Claims (1)

Cross lattice of rod structures with upper (compressed or compressed-bent) and lower (stretched) chords, braces, support posts of the lattice and half-posts, characterized in that the half-posts are Y-shaped or Ψ-shaped, where the upper nodal connections of such half-posts divide panels of the upper chord into component parts, and the lower nodal connections of the same half-struts are aligned with the nodes of intersections of the braces.

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