CC BY
12
Akhmadiyorov Ulugbek Solijonovich, Senior lecturer,
Tashkent Institute of Architecture and Civil Engineering Tashkent, Republic of Uzbekistan Е-mail: usa190380@mail.ru
RESEARCH OF TRAILING COVERINGS OF WIDE-SPAN UNIQUE BUILDINGS BY THE MODELLING METHOD
Abstract: The article provides tested models of the guy farms made of thermally processed guys, destroying efforts and deformations also were more in comparison with models of the farms made of thermally raw samples. Keywords: models, guys testing, loading, calculation, deformation.
Introduction
Nowadays design and construction of unique responsible buildings and constructions based on results of pilot studies of models of designs. Test methods, scale of models and their number depend on research problems. It should be note that features ofbehavior of a new studied unique design in the conditions of a various combination of static loading represents a little studied task.
Experimental researches were carried out on models in scale from M 1:4 to M 1:100 to nature with the subsequent test of elements of bearing designs of trailing systems and their fragments for various combinations of static loadings. Sizes of loadings accepted from experimental operating conditions of natural designs with development of recommendations about their widespread introduction. Test of natural buildings and constructions specifies settlement parameters and the corresponding elements of constructive decisions.
Models of trailing coverings carried out with observance of requirements of physical similarity of the theory of modeling. Characteristics of the materials used for modeling, fragments and elements of designs of the studied types of trailing coverings, defined from predesigned on various schemes of a loading.
Loads of studied model and natural design (or its fragment) we define taking into account strength characteristics of materials [1-3]:
" , (1)
_-. FM _
a
ata„
where qM, qMi, FM - respectively, uniform distributed on the area, distributed on length (strip) and concentrated loads of model; qH, qH1, FH - respectively, on natural designs; am = LH / Lm - coefficient of scale of geometrical similarity; aR = RH / RM - coefficient of scale of durability's of materials or scale of power similarity; aE = EH / EM - coefficient of scale of modules of elasticity or deformation similarity.
At application of expression (1) load of guys (threads) of models of trailing systems is considered consisting of the sum [1]
q(x) = q = g + p + &p (2)
where, g - constant loading, p - temporary loading, Sp -loading of preliminary tension at the settlement loading, equal 10-15% from g + p. Thus, function q(x) can be both continuous, and faltering.
At calculation of the main deformations the coefficient of similarity considering a ratio of modules of elasticity of a material of model entered aE, then deformations of movement of natural designs we determine by formulas
-;wH =awM ; uH =AL (3)
£H =
a
fH aRaj
ßna c
Flexural and axial efforts in designs of trailing systems determined by formulas:
MH = MMa2ma ; NH = NMamaR ; HH = amaR, (4) where, MM NM u Нм - the bending moment, longitudinal force and a spacer in model;
NH u НН - same, in a natural design.
Efforts in external and internal rings of an one-zone or two-zone round covSering from action having unstitched guy systems is determined by a formula
Nr. = RqK, Nm = rqm, (5)
Hn Hn
where, q =-, q = u u (6)
R,r - radius of an external and internal ring
Here n and n% - number of guys in external and internal rings. Thus in round coverings the external ring can be one-zone, and internal two-zone, or on the contrary. Thus the one-zone ring tests the sign-variable intense deformed condition.
Average tension in rings
N NKU
=X
^cpn
(7)
where, A and A - the area of cross section of external and
K ^
internal rings.
Shortening and lengthening of outer and internal diameters of rings we define from expression
-M = -
v E y
2nR, Ml =
a
cpM
2nr
(8)
KU
RESEARCH OF TRAILING COVERINGS OF WIDE-SPAN UNIQUE BUILDINGS BY THE MODELLING METHOD
The coefficient of a pliability of external and central rings is represent able in a look:
C = (R-R)E, Cu = (r' ± r)E (9)
where, R ' and r' - the radius of an external and internal ring after deformations from a loading ofall guys oftrailing coverings
R, = -M + 2nR , ^ (1Q)
2n 2n
Compression of an external basic ring by a tension of people will have essential impact on deflections of spatial system. Diameter reduction Ai on from action of full temporary loading p = yg determined by a formula
Ygl4
±M„ + 2nr
Ml = ■
(11)
48EKAK (f + Af)
where, ErAK - longitudinal rigidity of a ring.
Expression (3.11) taking into account the settlement resistance of a ring of Rk can be present in a look
Ml =
1 +
1 —
^Mt f
1 + y
E„
(12)
At a big arrow ofsagging the relation f /1 = [1 /20-1/8] of pro-weight to an initial arrow can be determined by a formula
ii\2
(13)
Af f
5 + (1 + X)Rs
36E
where Rs - the settlement resistance of guys; E - the module of elasticity of guys, X - the parameter considering compression of a ring. If to consider only a pliability of an external ring, lowering a pliability of the central ring, then it is X possible to present as a ratio of settlement resistance k = ERr / ER = EAs / CI.
Rigidity of support of a thread taking into account a pliability of external and central rings determined by a formula
AH- ^2 , (14)
С =
Ml
24( f + Mf )
1+
EAnd
EJ ,
Ml
where d - diameter of the central ring; An and Ar - the areas of cross section of the central and external rings.
Radial people in the covering center usually fasten to rigid (in two-zone rings the bottom belt can be flexible) to a ring. At a loading of one-half of a round, covering payload shift of the center of a ring will happen towards the loaded half of a covering. This shift determined by expressions [1]:
pi
AX = 0,0425-f (15)
H + H 2 1
Thus the knot of stabilizing guys will be displaced to the opposite side. The tension of guys is made for ensuring stabilization of a covering from a condition of their loading taking into account shift of the central point.
Horizontal movement of bearing and stabilizing guys Axx and Ax2 in the middle of flight at a loading of a half of flight is determined by expressions
Pf^-------PJf^ (16)
Axj = Ye
-;Ax 2 =Ye
Hi + H2 Hi + H2
respectively for the systems untied and connected in the center.
If under the influence of loading, the basic ring was, displace and flight D decreased by size AD, the additional deflection caused by it is Af determine by expression
Af = K— AD (17)
1 + ai fi
where K = 0,06944 - repulse coefficient for evenly distributed loading. Efforts in belts of guys decrease on
AH1 = E^ 1 Drf
1 -
1 -a 1 + a1
A
AD AH2 =
EnAn
Z1
where u, = —, u2 = —, a = D D
Dv,
2
u
1 -
1 -a 1 + aj
AD, (18)
u2
E2 a2
f2; a. =a^, Z E1A1 f 1 f
- thread length, D = I - flight.
Kind of work of trailing coverings depends on character and the size of loadings, which cause in guys both axial and flexural tension. Thus the size of destroying efforts in the guys testing flexural tension can be much lower in comparison with the guys testing axial tension and on which it is necessary to pay special attention at design.
Results of the conducted researches used when modeling the two-zone previously strained trailing coverings by flight of 120 m and its fragments intended for application in wide-span unique public buildings of different function. These data are provided in (tab. 1 and 2).
Table 1. - Characteristics of the studied models two-zone Preliminary and intense round trailing coverings
a. Designs of guys Coefficients similarity
1 2
1. Geometrical similarity of am = DJD„ = 100
2. Power similarity of aD= BJBM = 3
3. Elastic similarity of a= EJE, = 3-26
b. External ring
4. Geometrical similarity of ami, = Ah/AM = 188 a„, = JJL = 437
1 2 3
5. Power similarity \ = VR^23
6. Elastic similarity aE = Eh/EM = 1.05
в. century. Internal ring 1. bottom belt
7. Geometrical similarity of = AH/AM = 144 % =UJM = 882
8. Power similarity of «r = RH/RM=097
9. Elastic similarity UE = EH/EM = 1.05
2. top belt
10. Geometrical similarity of <0™ =Vam = 108
11. Power similarity of \ = Rh/RM = °.97
12. Elastic similarity ^E = EH/EM = 1.05
Table 2. - Mechanical and deformativny characteristics of samples fragments of designs of models of trailing designs
and
№ Studied designs, samples Look Tests Size, mm ff ,MPa
1. Samples of guys Stretching 295 1.76/560 0.978
2. Samples of guys t.o Stretching 295 1.63/520 6.39
3. Samples of guys Bend 295 0.833/265 0.88
4. Samples of guys t.o Bend 295 0.96/305 3.29
5. External basic ring Stretching 25f 8.8/440 18
6. Central basic ring Stretching 20f 7.09/483 17
7. Model fragment (farms two-zone) the Distributed loading of R = 600 mm r = 300 mm 1.37/218 0.42 2.5
8. Model fragment (farms two-zone, guys t.o) the Distributed loading of R = 600 mm r = 300 mm 2.32/369 0.84 4.9
9. Model fragment (farms two-zone) the Concentrated loadings of the central ring of R = 600 mm r = 300 mm 1.08/172 0.42 2.5
10. Fragment of model of a (farm two-zone, guys t.o) the Concentrated loadings of the central ring of R =600 mm r = 300 mm 1.37/218 0.84 5.2
Note: m.o.- The thermal processed
Conclusions. Results of the carried-out tests of samples of guys showed that at stretching the explosive effort of thermally processed (annealed) steel is lower, and deformation characteristics it is more, than at thermally raw samples of guys. At a bend for thermally processed samples of guys de-
stroying efforts and deformations were more in comparison with thermally raw samples. For the tested models of the guy farms made of thermally processed guys, destroying efforts and deformations also were more in comparison with models of the farms made of thermally raw samples.
References:
1. Recommendations about design of trailing coverings.- M: TsNIISK,- 1974.- 176 p.
2. Moskalev N. S. Designs of trailing coverings.- M: Stroyizdat,- 1980.- 331 p.
3. Razzakov S. R., Friedman G. S., Akhmadiyarov U. S. Razzakov N. S. Experimental researches previously intense two-zone trailing coverings // On Saturday. scientific works. Assessment of risks and safety in construction.- M:. MGSU,- 2012.-P. 162-165.
