Stretching curved wooden frame-type elements “Sinch” Текст научной статьи по специальности «Строительство и архитектура»

Stretching curved wooden frame-type elements "Sinch"

DOI: http://dx.doi.org/10.20534/ESR-17-1.2-223-225

Razzakov Sobirjon Juraevich, Associate professor, Ph.D, Head of Department Akhmedov Pakhritdin Sayfiddinovich, Senior teacher Chulponov Olimjon Gofurjonovich, Senior teacher Mavlonov Ravshanbek Abdujabborovich, Assistant teacher

Uzbekistan, Namangan engineering-pedagogical institute, department of Civil Engineering E-mail: [email protected]

Stretching curved wooden frame-type elements "Sinch"

Abstract: Substantiated the influence of longitudinal forces on the stress state stretched-bent wooden elements of the building frame and update their bearing capacity.

Keywords: wood element, a skeleton wooden "Sinch", normal stress, axial force, bending moment, bending stiffness, stability, strength, dynamic impact.

When dynamic effects in the elements of column and "Sinch" wooden frame occurs repeatedly opening and closing knots. At the same time applied to the compressed elements of stretching and tension member to compressive forces. Furthermore the tensile and compressive forces from the walls in the frame having transverse loads. That is, the frame members are in position eccentric compression and stretching.

When calculating the compressed-bent wooden rods to apply the theory of boundary stresses, proposed by prof. K. S. Zavriev. In line with this theory, the bearing capacity of the wooden rod is considered to be exhausted at the time when the edge compression stress becomes equal to the calculated resistance. This theory gives a simple explanation. Since the rigidity of the wood element is not infinite, it is under the influence of bending moment flex. This centrally applied force now will have an eccentricity equal to the deformation of the wooden rod from the moment, and thus creates an additional point of the longitudinal forces, which increases the deformation of the rod, which leads to an even greater increase in additional torque during compression. Such a build-up of additional torque and deflections will continue for some time [1].

Normal stress (oc) in compressed-bent elements is determined by the formula

a= N / A + M /W (1 - N / Nk) = N / A + M / WL (1)

c ras q ras^- kr' ras ras~ 1 V /

Coefficient , taking into account the additional torque from the longitudinal force in the rod deformation applied at values from 1 to 0 and it is determined by the formula

$ = 1 - , hereNkr =^RAbr

Nkr

And with the impact of vertically directed longitudinal forces, in addition to the bending moment acts centrally applied force, tensile compressed-bent wood element. Therefore, after the deflection element "Sinch" induced bending moment, the normal force will create additional torque of opposite sign and thus will reduce the total bending moment. At this time, stretched-bending elements are calculated without taking into account the additional longitudinal forces at the time of the wooden rod deformation by the formula (2) [2; 3; 4].

N MR a = — + < R

c A WR '

(2)

here Ant — sectional area of the net; Rr, R — calculated tensile strength and bending.

This formula can be applied to the wood of the 2nd and 3rd class, and the wood is 1st class, it does not match.

Based on the foregoing, it has been tasked to determine the normal stress with the additional point in the stretched-bent wooden elements. (see Figure 1) [2].

The applied tensile force forms a opposite moment to the bending moment on the lateral loads, ie, decreases the value of the total angular momentum and the formula takes the form of stress (3):

N M - N ■ f

a =±1L. +_q_r •/m" (3)

" A, W

nt nt

here Mq — moment, produced by shear forces q, — maximum deformation of the rod; Wnt — net cross sectional moment of resistance; Nr — tensile longitudinal force; Ant — net cross-sectional area; <Jrj — normal tensile stress-bending.

As a result of the bending load q transverse bending moment is formed, as a result of longitudinal stretching force N additional bending moment is formed with a negative sign.

We form the expression for the total bending moment at the point x of the rod (4):

Mx = Mq - Nr • y (4)

In two (3) and (4) the above equations, there are three unknowns Ur i, y, Mx, it is necessary to find another additional equation. Any curve can be theoretically expressed as a number, which in this case must be quickly convergent and satisfy the boundary values. That is a trigonometric series in the following form:

y = f ■ sinnx/l + f2 ■ sin2nx/l + f3 ■ sin3nx// +... Figure 2 shows the interpretation of this series. When balanced load enables the first term ofprecision equal to 95 to 97% [1]. Then, limited only by the first term of (5), we obtain:

y = f ■ sin(n x/l) (5)

However, the above equation has brought one more unknown f

Section 12. Technical sciences

Figurel. The deflection in the wood element [1]: Np — tensile longitudinal force; q — lateral load: f — deflection at the intermediate point; f — deflection of lateral load — q; f — deflection from the longitudinal force

Figure 2. Geometric interpretation of trigonometric series [1]: « f ■ sin(nnx/l)»:1, 2, 3 - номера строки; fl, f2, f3 -максимальные ординаты

In the structural mechanics we know that the second derivative of the equation y'' deformation curve is bending moment divided by the rigidity with the opposite sign, ie: d 2y _ Мх dx2 " EJ

Then after differentiation curve of the equation (5) we get

(6) (7)

d y rn . nx —— = -f — sin — dx2 l l Equating the value (6.6) and (6.7) we obtain Mx n . nx

—- = J,—sin— (8)

EJ Jl l2 l W

Now, the value of Mx (8) andy (5) substitute the expression

n2EI

(4) and after the conversion, bearing in mind that ——— = NKp,

. nx l

sin-— with x = —, where a symmetrical load is the maximum

ordinate is the deflection ymix = fi, is equal to unity, we find that l

M - N • y n2 712 n2EI

—3-— = /-sin-2-, M - N • y = f= f • Nk.

EI 1 l2 l q ' 1 l2 1 kr

Mq = Nr ■ f + fl • Nkr = fN + N) (9)

Deflection — f1 or trough line equation (y) can be determined from the following formula:

fi =

M

N. + N

kr r

(10)

Given that f = fmax, we get formula for a normal tensile stress bent rod:

N M W

N • М.

N_ ' A

M

__1

W

1 --

N

(Nb + N )

(11)

W N + Nr)

Thus, the resulting normal stress in the stretched formula bent-wood elements (11) shows that the tensile strength and bending strength has a magnitude of bending moment decreases, resulting in cross-section, ie.:

N

N M

a . =—1 + —1 A W

1 --

N + N )

(12)

As a result of simplifying the formula takes the following form:

N. ■ М_

a = -

N

AM W(N + N)

Introducing the notation

N М^ -l

N.

Nkr + N

= 1,

(13)

(14)

(15)

we get G =-

Ff W

nt nt

here Nr — longitudinal force;

Fnt — net cross-sectional area;

Wnt — net cross sectional moment of resistance;

M — bending moment;

Rr — calculated resistance of wood stretching along fibers.

For pine and spruce: a) elements of rectangular section (except as specified in sub-paragraphs "b", "c") 50 cm in height and: = 0,71 — for first-class, 0,54 — second-class; b) elements of rectangular cross section width of more than 11 to 13 cm at the height of the cross section of more than 11 cm: = 0,67 — for first-class, 0,5 — for second-class; c) rectangular elements of a width of more than 13 cm in cross-section height of more than 13 cm: | = 0,625 — for first-class, 0,47-for second-class [2].

n2EI

Having mean that Nr = RrAnt and Nkr = -

К

I=■

1

1

1

1+-

N

N.

R ■ A,

1 + :

R ■ A, ■ l2

(16) (17)

П ■ EI

1 +

П ■ EI

12

E/r — coefficient varying from 1 to 0, taking into account the additional torque from the longitudinal force due to the deflection element, defined by the formula

4 = - 1

1 +

Rr • A,, • 10

n2 ■ EI

here l0 — effective length of the element; n = 3,14;

EI — flexural rigidity element. Then for pine and spruce

(18)

for the

E = 104МПа, n= 3,14, Rp = 10 МПа, l = 4м

values of respectively

equal to = 0,67 . For poplars: E = 104Mna, n= 3,14, Rp = 8 Mna, l = 4 M respectively equal to = 0,72. Accounting for the additional factor will provide an opportunity to save of wood used in load-bearing timber constructions.

On the data longitudinal tensile forces, "Sinch" elements do not work nearly as well as the traditional wood-frame houses used nail connections, hinged connection — "Turm" without mechanical linkages.

Based on the above, in terms of improving the structural and seismic safety, it is possible to make the following recommendations and suggestions:

Modeling two-dimensional unsteady movement of flow, constrained by control structures

1. The elements of wood-sinchevyh houses erected in seismic zones, the use of traditional connecting "Turm" type units (drills) — is not enough, because in terms of tensile and shear loads Sinchi elements may be destroyed.

2. Therefore it is recommended to install in knots metal mechanical connections such as clamp, bolt, screw, etc., That will strengthen resistance to opening the cells and the appearance of residual deformations in the plastic timber frame elements.

3. Currently, according to QMQ_2.03.08-98, the calculation of

timber frame elements (paragraph 4.16), are in conditions ofbend-ing and stretching is done taking into account the factor P = ,

R

which gives approximate values for any type ofwood. Offered in the coefficient ^ =-1-- allows to obtain more accurate re-

1 +

R

A t ■ 11

nt_0_

EI

sults, taking into account the rigidity of stretched-bent wood framing members.

References:

1. Slitskoukhov Yu. V. Konstruktsii iz dereva i plastmass [Tekst]: uchebnik dlya VUZov/Yu. V. Slitskoukhov, V. D. Budanov, M. M. Gap-poyev [i dr.];/pod red. G. G. Karlsena i Yu. V. Slitskoukhova. - 5-ye izd., pereab. i. dop. - M.: Stroyizdat, - 1986. - 543 p.: il.

2. QMQ2.03.08-98. Derevyanniye konstruktsii. Tashkent: Goskomarkhitektstroy R Uz. - 1998, - 46 p.

3. Razzakov S. J. Experimental and theoretical approach to the determination of physical and mechanical characteristics of the material of the walls of the low-strength materials [Text]/S. J. Razzakov//European Science Review-Austria, - 2016. - No. 7-8. - P. 215-216.

4. Razzakov S. J. The study of seismic stability of a single-storey building with an internal partition with and without taking into account the frame [Text]/S. J. Razzakov, S. A. Holmirzaev, B. G. Juraev//European Science Review-Austria, - 2016. - No. 7-8. - P. 217-220.

DOI: http://dx.doi.org/10.20534/ESR-17-1.2-225-227

Rahimov Shavkat Khudergenovich, Doctor of technical sciences, professor,

Begimov Ismoil

Research Institute of Irrigation and Water Problems of Tashkent Institute of Irrigation and Melioration

Bakiev Masfarif Ruzmetovich, Doctor of technical sciences, professor, E-mail: [email protected] Shukurova Sevara Egamkulovna, assistant E-mail: [email protected] Kahharov Uktam Abdurakhimovich, Senior lecturer

of Tashkent Institute of Irrigation and Melioration E-mail: [email protected]

Modeling two-dimensional unsteady movement of flow, constrained by control structures

Abstract: The article describes the implementation of the model of two-dimensional unsteady movement of flow constrained by a combined dam on the basis of vector-matrix form of Saint-Venant equation in curvilinear coordinates.

Keywords: control structures, modeling, Saint-Venant equation, curvilinear coordinates, isoparametric transformations, boundary conditions, approximation, boundary and initial conditions, finite element method, algebraic equations, algorithm.

Introduction. Bank scouring annualy causes significant damage to the economy of Uzbekistan. Annually over 30 billion sums are allocated for bank protection and flood control works. Vast amount of funds are spent for reclamation work to eliminate emergency situations occurring as a result of existing dam breaks at Amudarya and Syrdarya rivers and their tributaries.

On the other hand the construction of large water reservoir hydrostructure systems at the main tributaries of the above rivers, Vahsh and Naryn, can result in lowering of water level for the existing non-dam water intake and respectively lower withdrawn discharge for large irrigation canals of the region.

Therefore protection and channel control works are being held at the heads of canals, dive culverts, aqueducts, at river port through

Termez and etc.

The main reasons for emergency situations and damages of protection and control structures (blank, through-flow and combined) are their imperfect structure and the methods of their calculation and design, associated with wrong prediction of channel reformation after their installation in river channel or floodplain.

In present, the justification of these protection structures is carried out mainly for steady-state conditions. Our proposed modeling method allows for justification of these structures on the basis of numerical experiments by the mathematical model [1] of two-dimensional unsteady movement of flow constrained by control structures.

Modeling. Inputting curvilinear coordinates x = x, y = y(Ç,n) and determining isoparametric transformation ele-