Научная статья на тему 'Dependencies to determine the measure of damage and calculation of residual life of reinforced concrete superstructure, exposed to salt corrosion'

Dependencies to determine the measure of damage and calculation of residual life of reinforced concrete superstructure, exposed to salt corrosion Текст научной статьи по специальности «Строительство. Архитектура»

CC BY
35
6
Поделиться
Ключевые слова
MEASURES THE DAMAGE / RESOURCE FORECASTING / EXHAUSTION BEARING CAPACITY OF THE STRUCTURE / CORROSION OF CONCRETE AND REINFORCEMENT / REMAINING SERVICE LIFE / LOAD-BEARING CAPACITY

Аннотация научной статьи по строительству и архитектуре, автор научной работы — Saatova Nodira Ziyayevna

In this paper we consider the current method of determining the measure of damage of concrete and reinforcement. The proposed dependence measures of damage, convenient for use in predicting the life of structures superstructures.The practical method of calculation determination of residual resource of the exploited superstructures developed. The main source of data for calculating the residual life are the parameters defined by the technical diagnosis.

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

Текст научной работы на тему «Dependencies to determine the measure of damage and calculation of residual life of reinforced concrete superstructure, exposed to salt corrosion»

When the device was placed into the closed storage their basic dimensions were accounted. So, taking into account the size of a typical warehouse of 54 to 24 meters 2 sets of devices were placed there. Developed storage scheme with new devices for loading of raw cotton in comparison with existing analogues has a positive effect on the following parameters:

1. Factor of storage loading is 0,90-0,96.

2. The high level of mechanization of the processes associated with the downloading and distribution of raw cotton for the entire volume of the closed stores.

3. Ability to automate processes and manage the download and delivery of raw cotton in the distribution area.

This scheme of loading into the storage and the device for its implementation is recommended for widespread use in the cotton industry to ensure the preservation of the natural properties of raw cotton.

References:

1. A useful model patent. FAP № 00520 «Storage for fibrous material" - 29.01.2010, M. T. Hodjiev, A. J. Jurayev, H. K. Rakhmonov, M. E. Ruzmetov.

2. A useful model patent. FAP № 00514 «Devices for supply and distribution of the fibrous material" - 21.12.2009, M. T. Hodjiyev, A. J. Jurayev, H. K. Rakhmonov, M. E. Ruzmetov.

DOI: http://dx.doi.org/10.20534/ESR-16-9.10-210-212

Saatova Nodira Ziyayevna, Tashkent institute of design, construction and maintenance of automotive roads E-mail: nsoatova@bk.ru

Dependencies to determine the measure of damage and calculation of residual life of reinforced concrete superstructure, exposed to salt corrosion

Abstract: In this paper we consider the current method of determining the measure of damage of concrete and reinforcement. The proposed dependence measures of damage, convenient for use in predicting the life of structures superstructures. The practical method of calculation determination of residual resource of the exploited superstructures developed. The main source of data for calculating the residual life are the parameters defined by the technical diagnosis.

Keywords: measures the damage, resource forecasting, exhaustion bearing capacity of the structure, corrosion of concrete and reinforcement, the remaining service life, load-bearing capacity.

Forecasting resource of intense machine elements and structures [1; 2], reinforced concrete and steel bridge spans [3; 4; 5; 6] are now used the main provisions of the theory of linear damage accumulation [7; 8].

In [10-12] considered a practical way of determining the degree of salt corrosion in the concrete, the use of which will be possible to establish the actual thickness of the concrete, exposed to salt corrosion; It developed a method of estimation of influence of salt corrosion of the concrete work and valves; calculation method for determining the measure of damage of concrete and reinforcement. The proposed permit depending on the results of the survey to determine reliably the load span structures, suitable for use in predicting the resource superstructure.

Thus damage caused by external impact during the considered time independent of the load history, and they can be summed with previous injuries. The value of the degree of damage is estimated as 0 < Y < 1, at the beginning of loading Y=0; at the moment of exhaustion bearing capacity of the structure Y=1.

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

The accumulation of damage over time is described by T t

Zt, =1 (1)

For structures operating under cyclic downloaded

t— = 1 (2) tf Nt

where n. - number of cycles at a uniform loading; N. - number of cycles to failure.

Y - measure damage to any point in time

t t V =T ^ ' t=0 T

In the case of non-linear voltage uploading a

T dt

= Í-

' 0 T (a)

(3)

(4)

On the basis of (3) in [5; 6] proposed to determine the dependence of the resource elements of metal bridges.

V. P. Chirkov [9] proposed a mathematical model for resource prediction of reinforced concrete bridge spans on the basis of these provisions.As a measure of concrete damaged by exposure to multiple repeated loads accepted the change of the transverse deformation coefficient Vand with this in mind, the dependences for determining resource superstructures.

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

In the work of R. Mamajanov is described the degradation process and development of cracking in the concrete of the compression zone spans used basic parameter fracture mechanics - stress intensity factor "K". The dependences for the description of the "K" in time, when repeatedly re-loading.

In the works of the above story loading is taken into account, the characteristics of loads and their statistical dispersion.

However, it should be noted that the use of measures to assess the damage for practical calculations are complex and require the presence of large statistical data.

Dependencies to determine the measure of damage and calculation of residual life of reinforced concrete superstructure.

Based on the analysis of the above studies, it can be concluded that the more promising as a measure of damage to receive actual performance concrete strength reinforcement corrosion degree [10; 11; 12]. Knowing the actual values of these parameters, it is possible to determine the value of the measure of damage and determine resource superstructures on the strength of concrete in the case of salt corrosion and corrosion of the reinforcement.

Considering the above measure of concrete damage, accept as

Rb - R p R„ - R

b cr

where Rb - design value of the concrete strength;

R - the value of the concrete strength at the time of technical

texp o

diagnostics;

R - the maximum allowable value, the strength reduction in

cr ' ©

the salt corrosion.

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

For (5) the condition

Y = 0 (6)

Y = 1 (7)

Thus, Y=0corresponds to the case when there is no salt corrosion and the strength is not reduced, and Y=1 - the time of the ultimate state.

Similarly, reduction of cross-sectional area of reinforcement can also be expressed in terms of the measure of damages

(12) (13)

= aS -bSA t,

S S S st '

a = -

A

A, - A

6 cr

1

(14)

Rb = R, „,

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

b texp '

Rep = R

texp cr

From (5) we have

Y. = a - bRe p;

b texp '

R

a = -

Rb - R

b cr

b = -

Rh - R

b cr

(8) (9)

(10)

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

Substituting Rbt = 0,9Rbe "°,01t ; in (8) we obtain

Y. = a - 0,9bRbe-

(11)

By (11) it is possible to determine the value of the measure concrete damage at any time t of technical diagnostics based on actual measurements of the strength of concrete.

bs =■

As - A

S cr

where AS - sectional area of the project of reinforcement;

A , - sectional area of the valve after the corrosion;

st '

A - the maximum allowable value, reducing the cross-section-

cr ' O

al area of reinforcement.

Given At = Aoe 0'015t expression (12) is written as

= as - 0,7bsA^'; (15)

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

Example of calculation of residual life of reinforced concrete spans, susceptible to salt corrosion

The dependences obtained in [10] to describe the damage in time measures allow us to determine the remaining service life of span structures as a result of technical diagnostics.

Initial data.

Reinforced concrete span structure with a length of 16.76 m of the overpass. Year of construction of the overpass — 1967. The project developed by the beam under the load L30 and wheel load WL80.

The scheme of the span of the bridge is shown in Figure 1. Main beam reinforced fittings periodic profile 014 mm Class A-II. Stove roadway reinforcement has 012 mm Class A-II in increments of 10 cm. The distance between the main beams 56 cm. Design concrete class — B25 (M300).

The examination found that due to salt corrosion original diameter rebar fell to 5.9 mm. Salts penetration depth, determined as described in [11; 12] is up to 12-17 mm. The actual strength of the concrete slab layer, susceptible to corrosion, R^ = 12,0 MPa.

Required to determine the residual life of the superstructure on the strength of the board.

Figure 1. The cross-section of the span

Calculation of bearing capacity of the slab at the time of h — the height of the compressed zone, impervious to salt

technical diagnostics corrosion.

Estimated circuit boards external console

1

where M — bending moment calculated in this section, the moment of diagnosis section carrying capacity is provided with a small margin. Exhaustion of the resource may occur at lower strength concrete to Rcrb = 8,0 MPa and a decrease in the actual area of reinforcement to A = 5,5sm2.

scr '

Determine the measure of damage accumulation in the concrete and reinforcement at the time of diagnosis by technical formulas

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

The height of the compressed zone of concrete in view of the actual state of the plate is determined by the expression:

Y =-

A 1 ii

R - R

bexp

Rh - R

b cr

35-12 35 - 8

= 0,85

x =-

RASxp 240 • 5,9

R,

bexp

12-100

= 2,36sm

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

ln

where Asexp - actual sectional area of the valve;

Rbexp - the actual design of concrete resistance.

^Tresb

cr lb

ln

1,92 - 0,85 1,18 .

a

Check bearing section capacity:

Rb bx

bexp

x

K - ~2

= 12-100 • 2,36

12 -

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

2,36

C = 0,9 Rbb = 0,9 T =■ 1

0,01 35 35 - 8,5 1

= 9,8 year

= 1,18

= 15,3KNm > M = 14,1Nm

Changes Y

cr

The probability of non-destruction

= 1,92

" 0,52

where [^F^ ] = 0,5 for the reliability level of 0.95 on the scale.

Table 1. - Scale

Y =

A - A,

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

'Sexp

A - A

0,35 0,999

= 0,93

0,4 0,996

0,45 0,989

0,5 0,971

0,55 0,934

0,6 0,864

0,65 0,722

ln

AT =-

11,3 - 5,9 11,3 - 5,5 1,923 - 0,93'

ln

1,42

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

0,015

= 25,2 year

C, = 0,7bsA == 0,7-

1

:11,3 = 1,42

11,3 - 5,5

Thus, the residual life of the superstructure slabs ATrts = 9,8 » 10 years on the basis of concrete corrosion bearing capacity.

Conclusions

The proposed calculation method and according to the definition of concrete measures damage in concrete structures suitable for use in predicting the resource superstructure.

A practical way to determine the estimated residual life of the exploited superstructures. It is shown that the main source of data for calculating the residual life are the parameters defined by the technical diagnosis. It was found that the residual life span structures exposed to salt corrosion, up to 3 times less than the residual life of the structures that are in normal operating conditions.

References:

BolotinV. V. Resource machines and structures. - M.: Mashinostroyeniye (Engineering), - 1990. - P. 446.

Iosilevskiy L. I., Sherbakov E. N., Mamajanov R. Prediction of resource elements subjected to the regime of loading//Paper. Academy of Science ofUzSSR. - 1989. - № 12. - P. 18-20.

Mamajanov R. Probabilistic Model of the resource elements of forecasting traffic facilities in the design stage//Paper. Academy of Science of UzSSR. - № 10. - 1988. - P. 18-19.

Mamajanov R. Probabilistic forecasting resource concrete bridge spans. - Tashkent: Fan. - 1993. - P. 156. Osipov V. O. The reserves of load capacity of metal bridges//Rail. - 1999. - № 8. - P. 42-45. Osipov V. O. The durability of metal superstructures of railway bridges. - M.: Transport. - 1982. - P. 287.

Не можете найти то, что вам нужно? Попробуйте наш сервис подбора литературы.

Mamajanov R. Prediction of the process of accumulation of damage in the elements subjected to regime of loading//Academy of science of Uz SSR. Series of tehn. sciences. - 1989. - № 2. - P. 22-25.

Tinkov I. B., Nizamutdinova R. Z. Causes of damage in reinforced concrete span structures operated in the conditions of Central Asia//The operational reliability of engineering structures under complex loading and the external environment. - Tashkent, - 1990. - P. 40. Chirkov V. P. Fundamentals of the theory of resource calculation of reinforced concrete structures//Concrete and reinforced concrete, - 1990 - № 10 - P. 35-36.

10. Saatova N. Z. The calculated method of determining the measure of damages of concrete and reinforcement. Scientific and technical journal//«Architecture and Construction of Uzbekistan». - № 6-2011 - P. 41.

11. Saatova N. Z. «Dependence to determine reduction of the strength of concrete and sectional area of armature in time»//«European Science Review», № 3-4 March-April-2016, «East West» Association for Advanced Studies and Higher Education GmbH.,.Austria, -Vienna. - 295-296 p.

12. Saatova N.Z. «Determination of salt corrosion of concrete in the concrete span highway bridges» // International scientific-technical conference «The strength of structures, seismodynamics buildings and structures.» - Tashkent - 2016. - 12-14sentyabr, - P. 169-171.

9.

c

c

2