Shapai RCC arch dam temperature Creep Stress Simulation

1、 Shapai RCC arch dam temperature Creep Stress Simulation Abstract: According to Shapai Concrete creep test data, according to theory of creep of concrete curing, decomposition of Shapai RCC Function creep is obtained Shapai concrete viscoelastic phase-deformation, viscous phase deformation of the ma

2、thematical expression is proposed creep of concrete non-linear stress calculation method; Shapai RCC arch dam according to the material parameters and environmental parameters to simulate the construction process of concrete, has been Shapai RCC arch dam of the three-dimensional temperature field an

3、d three-dimensional stress field simulation results; compared the creep of concrete stress theory of linear and nonlinear theory of creep under the stress of arched crown cross-section of different elevation, different parts of the dam concrete stress process of change over time come to some interes

4、ting conclusions available for the dam temperature control design. Keywords: dam simulation analysis of thermal stress of concrete creep and creep can not be restored No transverse joints or contraction joints of the large spacing of RCC arch dam, whether it is during the construction period, or in

5、the run-time, temperature, the proportion of loads are very high, and has a quasi-periodic load characteristics. In calculating the concrete temperature creep stress should be considered unrecoverable creep of concrete on the dam stress effects. Unrecoverable due to concrete creep tests have a certa

6、in degree of difficulty, general works not do, therefore, from the concrete creep experimental data have been in isolated parts of which can not be restored, it has important engineering significance. Bazant curing creep theory formula 1 is composed of micro-mechanism from the concrete, the realitie

7、s of the physical properties of the constituent materials derived. With the concept of clear, few parameters, the good nature of the linear equations. 2 by right Shapai RCC project creep data fitting calculations show that: the formula fitting result is good, the only fitting parameter, the importan

8、ce of each parameter at the same level. Different age, different time of holding the Netherlands, the aging viscoelastic creep phase-Ca (t, ), non-aging viscoelastic creep phase-Cna (t, ), viscous flow and creep phase Cf (t, ) (not complex creep) creep in the concrete the total C (t, ) in the propor

9、tion of test data are basically consistent with the project can be used to establish non-linear creep of concrete theoretical model. This can not be re-considered creep at different stress levels of the non-linear nature of the theoretical formula, the study of dam concrete temperature creep stress

10、has a certain advantage. Because very few parting mass concrete in the temperature in the process of pre-stress is tensile stress of concrete post-temperature drop gradually until the go-ahead the process of digestion, showing a typical load then unload the creep stress problem and needs to the corr

11、esponding non-linear creep theory to calculate. 1 Shapai Roller Compacted Concrete Creep test data and their decomposition Curing theory of creep in accordance with Bazant formula 1, concrete creep degree function C (t, ) can be broken down as follows: C (t, ) = Ca (t, ) Cna (t, ) Cf (t, ) (1) Of wh

12、ich: Ca (t, ) = q2 (t, ) (2) Cna (t, ) = q3ln 1 (t-/0) (3) Cf (t, ) = q4ln (t / ) (4) Table 1 “Shapai project” Roller Compacted Concrete creep calculation with the experimental value Unit :10-6MPa-1 Loading age / d t- / d 3 7 28 90 180 Test Inspection Value 3 7 14 30 60 90 180 360 67 80 89 99 105 10

13、9 115 120 40 49 55 62 67 69 74 78 24 29 33 37 42 45 48 53 13 17 20 24 26 28 31 35 9 12 15 18 20 22 24 27 Meter Operator Value 3 7 14 30 60 90 180 360 66 (71) 81 (79) 86 (85) 90 (92) 97 (99) 105 (103) 118 (111) 123 (117) 43 (47) 53 (53) 56 (58) 58 (64) 64 (71) 67 (74) 76 (81) 85 (88) 23 (25) 30 (28)

14、31 (31) 33 (35) 36 (39) 38 (42) 44 (48) 50 (54) 16 (16) 20 (18) 21 (19) 23 (21) 26 (24) 28 (26) 33 (30) 38 (35) 13 (13) 16 (14) 18 (15) 19 (16) 22 (18) 24 (20) 29 (22) 34 (26) (5) load of concrete age, t- as the time of the concrete holding charge; 0, m, n for the empirical coefficient; q2, q3, q4 f

15、or specific projects to fit the experimental data when fitting coefficients. For the sand card works, the fitting results of 2: q2 = 133.23, q3 = 5.44, q4 = 7.98, coefficient of variation opt = 0.065. Shapai Roller Compacted Concrete Creep Testing value and according to equation (1) the calculated v

16、alues obtained are shown in Table 1. And the existing norms in order to compare the parentheses in Table 1 also gives the formula according to Zhu Bofang 3 obtained Shapai RCC creep calculation values. Can be seen from Table 1: Fitting results of both are quite good. In accordance with formula (2),

17、(3), (4) decomposition of equation (1) to be the aging of visco-elastic creep Xiang Ca (t, ), non-aging entries viscoelastic creep Cna (t, ) Q, Concrete non-complex creep, viscous flow of items that creep Cf (t, ) in Table 2. from Table 2 the following conclusions can be drawn: Table 2 Shapai Roller

18、 Compacted Concrete creep rate with a variety of age and load time variation of Concrete holding charge Time t- / d Loading age / d 3 7 28 90 18 Ca (t, ) C (t, ) 3 7 14 30 60 90 180 360 .853 .807 .765 .719 .679 .657 .623 .591 .843 .798 .751 .696 .647 .62 .5780 .539 .793 .764 .726 .670 .610 .575 .518

19、 .468 .708 .693 .671 .632 .582 .547 .485 .425 .638 .630 .616 .590 .552 .524 .467 .406 Cna (t, ) C (t, ) 3 7 14 30 60 90 180 360 .062 .060 .058 .056 .055 .054 .053 .052 .093 .089 .085 .080 .077 .075 .072 .069 .172 .167 .160 .149 .138 .131 .121 .112 .275 .270 .262 .248 .230 .218 .196 .175 .350 .346 .3

20、39 .326 .307 .292 .263 .232 Cf (t, ) C (t, ) 3 7 14 30 60 90 180 360 .084 .133 .177 .225 .266 .289 .324 .357 .065 .114 .164 .224 .276 .305 .351 .391 .034 .069 .114 .181 .252 .294 .361 .420 .018 .037 .067 .119 .188 .235 .320 .400 .011 .024 .045 .084 .141 .184 .271 .362 (5) (1) aging visco-elastic cre

21、ep Xiang Ca (t, ) the total creep in the concrete, always occupy a very high percentage. Study of its own characteristics in terms of time, short-age concrete items of the aging of visco-elastic creep of the proportion of large, and with the Dutch holding down the extension of the time; long age of

22、the concrete and the concrete nature of the short-age, like just to different degrees. (2) Non-aging visco-elastic creep Xiang Cna (t, ) with the growth of concrete age marked increase, its maximum ratio value of 0.350, with the Dutch holding time, the growth of viscous term concrete creep increased

23、, Cna (t, ) in the overall decline in the proportion of creep. (3) The creep of concrete is not complex, that entry viscous flow creep Cf (t, ) is rather complicated. In general, as long as the holders of the Netherlands not long ago, most of the creep of concrete can be restored; regardless of age

24、of concrete, which can not be held re-load creep with age increases monotonically. The most unrecoverable creep age began to appear in the 28d loading duration are really long situation. 90d start loading right within the concrete, as long as its holding charge for more than 180d, its no longer be t

25、he total creep creep ratio is 30% 40%. This is Zhu Bofang Academy of Sciences in 1982, before the results are expected 4 . Reposted elsewhere in the paper for free download Two non-linear creep theory of arch dam under temperature stress finite element implicit method 1 gives the non-linear creep th

26、eory, the finite element formulation and solution steps are carried out for the one-dimensional problem. Pairs of RCC arch dam temperature creep stress simulation, the need for three-dimensional finite element method. Therefore, it is necessary to establish the theory of creep of concrete curing thr

27、ee-dimensional finite element recursion to solve the column type. 2.1 Non-linear equations of the theory of creep in the creep theory of Bazant curing stress-strain equations, the total strain of concrete at any time vector of should be met: = /E0 c 0, c = v f (6) Where: c for concrete creep strain

28、vector; v Viscoelastic Phase of concrete creep strain vector; f viscous mobile phase of concrete creep strain vector; 0 for a variety of additional strain vector, including the autogenous volume deformation of concrete, concrete temperature of changes, such as concrete micro-cracks caused by expansi

29、on of the strain vector; of concrete macro-stress vector, /E0 the corresponding change of concrete elastic vector. Curing of concrete creep according to the theory of viscoelastic and viscous-phase phase-strain-rate micro-and macro-strain rate relationship between the conversion were: (7) (8) for th

30、e first time a Kalvin unit damping ( = 1, . N), F (1) for the concrete stress state function, 1 for the first principal stress (in compression is positive). for the stress-strain equations (6) by incremental Method. In the time t = ti 1-ti (i = 1,2 ., M) in (M-step of the total solution): = Dc (-c-0

31、) (9) Formula: Dc = ED, D for the conventional three-dimensional elasticity matrix. , for the time t the stress increment vector and strain increment vector. c, 0 respectively, and creep strain increment vector and the other strain increment vector. Type (9) for the finite element solving equations.

32、 RCC arch dam in the sand cards simulation calculations, 0 computing time for the two-step concrete temperature and autogenous volume deformation caused by strain increment. Creep stress equivalent modulus 1 E as follows: (10) (11) (12) Type (10), E for the first month Kalvin unit modulus of elastic

33、ity; formula (11) that ti 1 / 2 times the volume of concrete solid phase, is the experience factor, m the meaning with the former; formula (12) indicated that the function s and the stress level of concrete damage degree function for the next time-step increment of stress. fc for the concrete uniaxi

34、al compressive strength. F (1, i 1 / 2) represents a moment of ti 1 / 2 the maximum principal stress function of concrete. For programming convenience, the equation (9), the creep strain increment c decomposed into volume and shape of two parts, namely: c = cv cd (13) And (14) (15) (16) (17) From th

35、e equation (9), the exclusion of elastic strain, got the concrete section at this time, the creep strain increment c. The creep strain increment will be divided into macro-volume c again creep strain increment cv and macro-shape of creep strain increment cd. And so on, rv, rd representing the micro-

36、creep strain increment size and micro-shape of creep strain increment. vi, di the order on behalf of i times the volume of concrete stress and partial power. rvi, rdi time i turn on behalf of the first volume of components a Kelvin creep strain and creep strain bias. The recursive formula: (18) (19)

37、 In the concrete Poissons ratio unchanged, three-dimensional state of the elastic constants of Kelvin elements 5 Ev = E / 3 (1-2), G = E / 2 (1 ) (20) So far, the creep theory of curing the basic model and finite element method is briefly described. Below, this theory will be applied to the temperat

38、ure of RCC arch dam creep stress simulation analysis, and the nonlinear creep theory 6 proposed an algorithm to make a comparison. Reposted elsewhere in the paper for free download 3, two kinds of creep Comparison of theoretical calculations The force characteristics of arch dams is extremely comple

39、x. The focus of this paper, the temperature of concrete creep stress. To simplify the research content, design plan formulated by a unit of the water only as the temperature field boundary conditions. In the calculation of arch dam stress when the water regardless of load and weight load. Choice of

40、dam structure is most simple and transverse joints shall not set or set-induced seam along the rivers at the same time regardless of the overall rise in the dam sewing methods. In view of chapter limits the site of the study was limited to the arch crown arch section to the upper and lower surface s

41、tress, their elevation in the 1762m, 1798m, 1850m, representing the lower dam, middle and top, the location shown in Figure 1 2. Table 3 profiles the height of arch crown unit number on the downstream face 1762 Elevation 1798 Elevation 1850 Elevation Upstream face Downstream face Upstream face Downs

42、tream face Upstream face Downstream face 3024 3112 19880 19761 45542 45780 Figure 1 Shapai RCC arch dam upstream face grid launched Figure 2 Shapai RCC Arch Dam crown section of the grid According to the literature 5 to clarify the finite element - finite difference method-principles Calculation of

43、temperature field of dam. Concrete linear creep theory, according to literature 6 The implicit method calculation; concrete non-linear creep theory, according to the format described in the preceding calculations. Figure 3 Figure 8 that for the above-mentioned arch to the stress of each unit process

44、 of change over time. A total of 10 intercepted Time Output step. 20d, after finished construction of the dam before the time step 1d; construction of the dam finished 20d, the time step 20d, the total time-step is 400. Temperature output time and stress the same as the output, respectively, for the first 160d, 200d, 240d, 280d, 320d, 360d, 490d, 570d, 730d, 950d (to October 15, 1998 for the first 1d). At the top of the dam unit, due to concrete pouring late,