JP2013002904A - Method of preventing cracks in concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preventing a crack in concrete, which can take a countermeasure against tha crack in the concrete with high accuracy and using a generally applicable method, by taking into consideration an energy state in a hardening process of the concrete.SOLUTION: In a method of preventing a crack in concrete, a countermeasure against the crack is configured by using an analysis result based on that total energy consisting of heat generating energy discharged from the concrete to an external field, dynamic energy exerting constraint force by means of a chemical action, and internal energy functioning in the concrete itself, is constant in a concrete hardened body in a constraint state. Accordingly, the method of preventing the crack in the concrete can predict a shape of the crack in the concrete with high accuracy and can effectively take the appropriate countermeasure against the crack.

Description

  The present invention relates to a method for suppressing cracks in concrete in which a countermeasure for cracks in concrete is taken with high accuracy by taking into consideration the energy state in the hardening process of concrete.

  Concrete is a hardened body formed as a hydrate formed by the reaction between cement and water, but the heat of hydration generated when the cement and water react increases the temperature inside the concrete and increases the external environment. In addition to causing the hardened concrete to expand and contract while following changes in temperature, self-shrinkage occurs due to the movement of moisture inside the concrete and drying shrinkage occurs due to the diffusion of moisture into the atmosphere. I am letting.

  The expansion and contraction behavior exhibited in such hardened concrete functions as a stress on the hardened concrete because the distribution inside the concrete is not uniform and the behavior is constrained from the outside. Thus, it additionally acts as a compressive stress and a tensile stress on the hardened concrete. However, the hardened concrete has a characteristic that the resistance to tension is small although it is strong in the compression form, so if the tensile stress exceeds the tensile strength of the hardened concrete, it will eventually crack in the hardened concrete. Will be generated.

  Cracks that occur in hardened concrete deteriorate the usability and durability of concrete, watertightness, etc. In order to design and construct a concrete structure, it is necessary to suppress cracks in the hardened concrete. Since it was an important issue, if cracks in the hardened concrete are predicted by suppressing the cracks in the hardened concrete and then performing a simulation before construction of the concrete structure, harmful cracks are predicted Therefore, it was necessary to devise measures for suppressing such cracks.

Conventionally, in order to suppress cracking due to expansion / contraction behavior in concrete structures, the empirical method or numerical analysis of the generated strain, generated stress, position of generated crack and width of generated crack in a hardened concrete is generally used. In finite element analysis (FEM analysis), which is a typical technique, it has been implemented by a method of calculating deformation and stress solution by directly inputting free expansion strain as initial strain based on temperature, humidity or amount of inflated material mixed in. It was. (Non-Patent Document 1)
However, in the concrete example in which the expansion material is mixed, in the experimental example by the method of directly inputting the free expansion strain measured in advance as an initial strain of the FEM analysis in the concrete, the test piece is a prismatic concrete specimen. Reinforcing steel bars that restrain two steel plates arranged on both sides are arranged at the center of the cross section, and concrete test specimens are made from steel without reinforcing bars in 4 cases with rebar diameters of 6 mm, 13 mm, and 19 mm. The effect of chemical prestress when the space was filled with expanded concrete was quantitatively evaluated. However, in the time-dependent change of the expansion amount measured after placing the expansive concrete, the actual measurement value 21 without the reinforcing bar and the actual measurement value of the reinforcing bar diameter 6 mm with respect to the calculated value curve 20 with the reinforcing bar diameter 6 mm shown in FIG. As shown by the actual measurement values of 22 and 13 mm and the actual measurement value 24 of 19 mm, the calculated value curve and the actual measurement value are greatly deviated in any case, and the free work strain is used as the initial strain. The "Constant Law" clarifies that it is impossible to reproduce a safe target shape in the planned concrete.

Such a phenomenon is the same as the calculated value and the experiment in the expansive concrete in both the calculated value curve 25 using the initial strain and the actually measured value 26 even when comparing the accuracy of FIG. In terms of the values, the degree of coincidence is confirmed to be in a dissociated state, and the above-mentioned method of expansion hardening analysis in which the free expansion strain is directly input as the initial strain must be skeptical. It was.

  Therefore, the idea of calculating the deformation and stress solution with the free expansion strain constant even if the constraint is different by giving the data that has been measured in advance through experiments and the like as the input data directly in the structural analysis. Since the calculated value and the actual measurement value greatly deviate, it can be applied only when the amount of the expanded material mixed is specified, and it is a method that cannot be used when a large amount of expanded material is mixed. Since the predicted results are accompanied by large fluctuations, it has been difficult to select an appropriate measure, and this has raised a serious problem that it is deceived in actual application. In addition, analysis based on the so-called `` constant work rate rule '' has been made for the expansion effect without relying on the initial strain method, but the analysis method in that case is poor in generality and it is impossible to formulate a finite element. It was.

Yukikazu Tsuji: Estimation method of chemical prestress and expansion analysis, concrete engineering, Vol. 6, pp99-105, 1981.6

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for suppressing cracks in concrete, which takes into account the energy state in the hardening process of concrete and can be taken with a method that can generally be applied to cracks with high accuracy.

  The method for suppressing cracking of concrete according to the present invention is a method for predicting crack width, but it is a method for predicting crack width in various construction methods, that is, a crack suppressing method. The cracking countermeasure is composed of the analysis results based on the constant value of the total energy consisting of the heat energy released from the concrete to the outside, the mechanical energy that exerts a binding force due to chemical action, and the internal energy that functions on the concrete itself. By doing so, it is possible to effectively take accurate crack countermeasures with a method that can generally apply the crack shape of concrete with high accuracy.

  The second method for suppressing cracks in concrete according to the present invention is the above-described method for suppressing cracks in concrete, in which the hardened concrete is divided into meshes, and the relational data is used for temperature analysis, moisture transfer analysis and stress analysis in the concrete. After the input, the calculation is made based on the fact that the total mechanical energy made by the expansion material is a constant value, and based on the result, the countermeasures for cracks mainly based on concrete stress are made more precise and accurate.

  The third method for suppressing cracks in concrete according to the present invention is the above-described method for suppressing cracks in concrete, in which the hardened concrete is divided into meshes, and then the relationship data is used for temperature analysis, moisture transfer analysis, and crack shape analysis in the concrete. Is calculated based on the fact that the total energy is a constant value after input, and based on the result, the crack countermeasures based on the crack shape of concrete are more precisely and accurately configured.

The fourth concrete crack suppression method according to the present invention is the above-described concrete crack suppression method, in which the hardened concrete is divided into meshes, and then temperature analysis, moisture transfer analysis, stress analysis, and crack shape analysis are performed on the concrete. After inputting the related data, the calculation is based on the fact that the total mechanical energy made by the expansion material is a constant value, and based on the result, the entire crack countermeasure is more precisely and accurately configured. .

  The method for suppressing cracking of concrete according to the present invention is an analysis based on the fact that the internal temperature, generated strain, generated stress, and generated crack shape of the hardened concrete are constant values of the total mechanical energy of the expansion material in the hardened concrete. By precisely analyzing the results, it is possible to construct a countermeasure that can accurately control the crack shape due to the expansion / contraction behavior of the concrete structure and suppress it with high accuracy.

Experimental model of concrete cracking suppression method of the present invention Chart showing calculated values and actual measured values according to the crack control method for concrete of the present invention Volume change diagram in crack control method of concrete of the present invention Analytical model diagram of experiment in crack control method of concrete of the present invention Analysis progress chart in concrete crack control method of the present invention Analysis condition table in analysis process Outside temperature diagram in the analysis process Temperature analysis in the analysis process Moisture transfer analysis in the analysis process Maximum principal strain analysis in analysis process Maximum principal stress analysis in the analysis process Crack width analysis in the analysis process Analysis of crack equivalent strain distribution in analysis process Crack shape in the analysis process The figure which shows the calculated value and the actual measurement value with the conventional “working constant law” Partial enlargement of the calculated value and the actual measurement value based on the conventional "constant workload rule"

  The method for suppressing cracking of concrete according to the present invention is based on heat generation energy released from the concrete to the outside, mechanical energy that exerts restraint force due to chemical action, and internal energy that functions on the concrete itself, in the concrete hardened body in a restrained state. By configuring the countermeasures against cracks based on the analysis results based on the total energy consisting of a constant value, it is possible to effectively take precise crack countermeasures with a general method with high accuracy in the cracking form of concrete. ing.

[Example 1]
The method for suppressing cracking of concrete according to the present invention is based on heat generation energy released from the concrete to the outside, mechanical energy that exerts restraint force due to chemical action, and internal energy that functions on the concrete itself, in the concrete hardened body in a restrained state. Since the analysis result based on the total energy consisting of a constant value constitutes a countermeasure against cracking, FIG. 1 showing an experimental example when the concrete cracking suppression method according to the present invention is implemented and the concrete cracking in the same experimental example This will be described below with reference to FIG.

  A concrete structure is a hardened body that is configured as a hydrate formed by the reaction of cement and water while appropriately placing any restraining steel material, and only the internal region of the structure is generated without causing initial strain. This is a subelastic body that exhibits a certain amount of work in other regions such as constraining steel while causing volume expansion, and also receives a constraining force from it while dissipating heat to the outside.

When these energy relationships are arranged by applying the first law of thermodynamics and the third law of Newton, the amount of heat released from the inside to the outside world is expressed as ΔH, and the mechanical external action is caused by chemical action. When the mechanical energy acting on the environment is changed to ΔM and the internal energy stored inside itself to ΔQ, and the direction of energy transfer from the hardened concrete to the outside is changed as a positive sign, Therefore, the following equation holds.

次に、コンクリート硬化体において力学的な拘束度が異なるが、他の条件は全く同じである２つのケースを考えると、２つそれぞれのケース１、２については式（１）より次式が成立する。

Next, considering the two cases where the degree of mechanical constraint is different in the hardened concrete body, but the other conditions are exactly the same, the following equation is established from Equation (1) for each of the two cases 1 and 2. To do.

ここで、式（２）から式（３）を差し引くと、次式となる。

Here, when the equation (3) is subtracted from the equation (2), the following equation is obtained.

又、ケース１およびケース２の過程において、膨張あるいは収縮作用などの化学的な内部エネルギー変化ならびに発熱から放熱する過程が、現実的にはほぼ同じであると仮定できる場合には、

In the process of Case 1 and Case 2, when it can be assumed that the chemical internal energy change such as expansion or contraction and the process of heat release from heat generation are practically the same,

が成立する。

Is established.

  Since these relationships are considered to be typical examples of the expansion action of the expansion material or the alkali-aggregate reaction of the aggregate in the concrete hardening process, from the equation (4),

が成立する。

Is established.

  Equation (7) shows that the mechanical energy that the hardened concrete body acts on the mechanical external environment by chemical action is constant regardless of the degree of restraint. It proves that the "total energy constant law" holds.

On the other hand, when the above-mentioned mechanical energy ΔM is further examined, when ΔM is developed as energy from Newton's third law, which is the law of action and reaction, in general, the stress tensor and the total strain tensor excluding the free expansion strain are The amount of work Δξ _A in the expanded concrete hardened body itself and the amount of work Δξ _B in the material constraining the expanded concrete hardened body, expressed in the form of the volume integral with respect to the product, is the work in the hardened concrete body. Since the chemical energy Δξ _che expressed in the form of volume integral with respect to the product of the stress tensor and the strain tensor as a free expansion or contraction due to chemical action as the sum of the quantities, in the end, as the sum of the work in the hardened concrete mechanical energy ΔM expressed, the following equation is equal to the chemical energy .DELTA..xi _che It can be expressed as.

式（７）で表わされた「総エネルギー一定則」と式（８）によって、いかなる拘束条件下においても、化学エネルギーΔξ_cheは一定になることが明らかである。この考え方は、
化学的に膨張あるいは収縮する物質で構成される構造体の膨張量あるいは収縮量を決定する上での根幹となる考えである。

From the “total energy constant law” expressed by the equation (7) and the equation (8), it is clear that the chemical energy Δξ _che is constant under any constraint condition. This idea is
This is a basic idea for determining the amount of expansion or contraction of a structure composed of a chemically expanding or contracting substance.

  From the above view, it is possible to apply the concept of “constant total energy” to hardened concrete to suppress cracking of concrete, and thereby cracking due to expansion of aggregates that react with alkali silica. And cracks caused by static crushing agent can be quantitatively predicted, and the crack suppression effect of the expansion material that introduces compressive force chemically into the hardened concrete body can be quantitatively predicted. The present invention can constitute a measure that can reliably prevent cracks in concrete over a wide range.

  Next, the calculated value proved as the experimental result of FIG. 1 showing an experimental model for verifying the validity of the concrete crack control method of the present invention carried out based on the idea of “constant total energy”. FIG. 2 shows the relationship between the measured values and the measured values.

  The shape of the test specimen used in the experiment and the experimental model used for verification are arranged on both sides at the center of the cross section of the concrete 2 to be tested in order to form a prismatic concrete test specimen 1 as shown in FIG. The reinforcing bars 4 for restraining the two steel sheets 3 and 3 are arranged, and the reinforcing bars 4 and the steel sheet 3 are integrated by welding. The concrete test specimen 1 is prepared in four cases in which the diameter of the reinforcing bars is 6 mm, 13 mm, and 19 mm including those without a reinforcing bar, and the ratio of the reinforcing bars in the concrete test specimen 1 is 0.00%, 0.22, Constructed at 0.88 and 1.99, the storage state of the concrete specimen 1 is maintained in a plastic bag wetted with a wet cloth at a temperature of 40 ° C. and a humidity of 100%.

  The verification result of the crack control method for concrete according to the present invention is proved by comparing the calculated value and the actually measured value shown in FIG.

  In this verification result, the elapsed time (days) is taken on the horizontal axis, and the amount of expansion (%) of the concrete specimen is recorded on the vertical axis. Show.

  In the case of a test specimen that does not employ reinforcing bars and has no binding force, the amount of expansion changes the largest in the calculated value and expands greatly from the initial 50 days to 100 days, but after that it gently increases. It is a background. On the other hand, even if it is in the actual measurement value, even if the inclination becomes gentle, the same tendency is shown. In addition, in the case where the rebar diameter is 6 mm, the calculated value and the actual measurement value are inclined earlier than in the case of the non-rebar, but in the case of the rebar diameter 13 mm, the expansion amount is small and converges at 100 days. Such a tendency becomes more remarkable at a reinforcing bar diameter of 19 mm, but the degree of coincidence between the calculated value and the actually measured value is increasing.

  As described above, the verification results of the crack control method for concrete according to the present invention are completely different from the deviation state between the calculated value and the actual measurement value performed by the initial strain substitution method that has been practiced many times as shown in the figure. In any case, the calculated value and the measured value are in good agreement with each other, and the concept of the “constant total energy law” that gives chemical energy as input data for structural analysis is appropriate. It has been confirmed that the concrete crack control method of the invention is appropriate.

  The contents of this verification are that the prediction accuracy regarding the deterioration and reinforcement effect in the concrete structure containing the expansion material is remarkably improved. According to the method for suppressing cracking of concrete according to the present invention, the effect of the chemical prestress by the expansion concrete or the alkali bone It is proved that the prediction of deformation and deterioration of concrete members due to the material reaction can be clearly and reasonably more accurately performed than the previous method.

  Another method for suppressing cracks in concrete according to the present invention is the above-described method for suppressing cracks in concrete, in which the hardened concrete is divided into meshes, and then temperature analysis, moisture movement analysis, stress analysis, and crack shape analysis in the concrete are performed. Based on the result calculated based on the total energy being constant after inputting related data for single or simultaneous implementation, the effect of crack countermeasures is quantitatively evaluated while taking into account actual bar arrangement. Appropriate measures are made more precise and precise.

[Example 2]
Another method for suppressing cracks in concrete according to the present invention is the above-described method for suppressing cracks in concrete, in which the hardened concrete is divided into meshes, and then temperature analysis, moisture movement analysis, stress analysis, and crack shape analysis in the concrete are performed. After inputting the relevant data to implement alone or simultaneously, calculate based on the constant value of the total mechanical energy of the expansion material, and based on the result, concrete countermeasures to prevent cracks in the concrete are constructed Since the appropriate software has been created, the contents will be described with reference to FIGS.

As described above, concrete is a hardened body configured as a hydrate formed by the reaction between cement and water, and the heat of hydration generated when the cement and water react with each other depends on the temperature inside the concrete. The concrete hardened body exhibits expansion and contraction behavior while following the temperature change of the outside world by raising the temperature, and in the interior of the concrete, the self-shrinkage due to the movement of moisture and the moisture dissipating into the atmosphere. Since the drying shrinkage due to the above is generated, these relationships are expressed as a change in volume of concrete and a process leading to cracking as shown in FIG.

  That is, in the hydration reaction between cement and water, the temperature is increased by the heat generation, and the temperature is increased while following the temperature change of the outside world. In addition, self-shrinking strain is generated by self-drying, and expansion strain is aroused by the action of the expanding material mixed in the cement, resulting in creep. In addition, moisture movement performed in concrete causes drying shrinkage strain in the hardened concrete after passing through the dry state, and each of these strains generally generates creep in the hardened concrete. When the tensile stress due to each of the above creeps exceeds its own tensile strength, a cracking phenomenon occurs in the hardened concrete.

  In the concrete crack control method according to the present invention, the stress / deformation state generated by each initial strain generated in the concrete at the time of hardening from construction to service in the concrete structure as described above is comprehensively analyzed, Measures that can be reliably suppressed while skillfully controlling cracks that may occur by quantitatively elucidating the analysis results are made possible.

  In order to explain an analysis method in another method for suppressing cracking of concrete according to the present invention, a basic analysis process will be described below based on FIG. 5 by adopting a simple analysis model 5 shown in FIG.

  This analysis model 5 is an analysis that adopts the entire real phase structure as an analysis model for a real phase structure 27 of a hardened concrete in which wall concrete is placed on the foundation concrete as shown in the figure. Considering the enormous amount of input data required for the analysis and the increase in the operating time of the computer required for the analysis, it is not an appropriate choice, and the actual structure 27 to be analyzed is structurally taken into consideration. If a symmetrical 1/4 model can be analyzed in terms of performance, one of the rectangular foundation concrete 6 corresponding to half the length and width of the real phase structure 27 from the overall model can be analyzed. In the present embodiment, there is no inferiority even in a form in which a small-sized wall concrete 7 corresponding to half the length and width of the real phase structure 27 is arranged on the side. It is the analysis model 5 in such a shape. In this example, the case where no reinforcing bars are arranged inside the concrete is adopted. However, if the concrete specimen to be judged uses reinforcing bars, the conditions for adopting reinforcing bars are also entered in this analysis model 5 in advance. By doing so, the analysis is performed. Further, when the actual phase structure 27 has a different shape, it is possible to select an analysis model that is subdivided into a form in which the overall value can be estimated from the analysis result.

  An overall image of the analysis process in this embodiment is started from the creation zone 8 of the analysis model 5 described above. Next, analysis condition input data 9 relating to the generated analysis model 5 is performed on the temperature analysis zone 10, the moisture movement analysis zone 12, the stress analysis zone 14, and the crack width analysis zone 15. Further, the temperature 11 that is the analysis output of the temperature analysis zone 10 is supplied to the moisture movement analysis zone 12, the stress analysis zone 14, and the crack width analysis zone 15, and similarly the relative output that is the analysis output of the moisture movement analysis zone 12. Humidity 13 is supplied to the stress analysis zone 14 and the crack width analysis zone 15. Further, the analysis output group 16 of the stress analysis zone 14 and the analysis output group 17 from the crack width analysis zone 15 are combined with the analysis output 11 of the temperature analysis zone 10 and the analysis output 13 of the moisture movement analysis zone 12 in the accumulation zone 18. Have been collected. Then, from the analysis output group 17 from the crack width analysis zone 15, the crack width 19 is made the output of this analysis process by utilizing the analysis result of crack equivalent strain.

  The output of the various analysis results described above can be used individually or collectively, and these are used to terminate the analysis process.

  As shown in the table of FIG. 6, the analysis condition input data 9 supplies necessary values for each physical property value below the thermal conductivity of the basic concrete 6 and the wall concrete 7 with respect to the analytical model 5. Regarding the outside air temperature of the environment in which it is placed, the circumstances are provided as one of the conditions as shown in FIG. 7 for each analysis time.

  In each analysis zone, necessary analysis calculations are performed based on the input conditions of the supplied analysis. In the temperature analysis zone 10, thermal characteristic values such as thermal conductivity, specific heat and calorific value in concrete, Unsteady heat conduction analysis is performed by inputting the density, unit cement amount, implantation temperature, exothermic characteristic value, etc. As a result, the temperature history (a) and temperature density diagram as shown in FIG. (B) is output. This output is set so that the calculated value analyzed as shown in the figure and the actually measured value actually measured on the actual phase structure 27 can be compared for each elapsed time. The output form allows visual comparison as appropriate.

  The actual measurement value shown by the solid line in the temperature history is the same as the calculated value displayed by the thin line when the temperature rises in the first half of the elapsed time, and shows a slightly different temperature when turning from high temperature to falling, In the latter half of the elapsed time of 4 hours after continuing the temperature drop, the calculated value and the actually measured value show almost the same temperature gradient. On the other hand, the temperature transition in the analysis model 5 is as follows: the temperature at the upper end position of the wall concrete 7 is 30 ° C. and 35 ° C. from the 20 ° C. of the basic concrete 6 toward the wall concrete 7 in the shaded state of the temperature. The temperature rises to the same value as in Fig. 5, and it can be confirmed by visual analysis output until it reaches the maximum temperature of 65 ° C in the middle position of the wall concrete.

  The temperature 11 of the analysis output in the temperature analysis zone 10 is added together with the analysis condition input data 9 as an input condition for analysis in the following moisture movement analysis zone 12, stress analysis zone 14 and crack width analysis zone 15. Therefore, it is used at any time in each analysis.

  The analysis in the moisture movement analysis zone 12 analyzes the moisture movement based on the input conditions regarding the moisture permeability, moisture capacity and moisture density of the concrete from the input data 9 of the analysis conditions and the output temperature 11 from the temperature analysis zone 10. The output value is the relative humidity in each part of the base concrete bottom slab, outside the bottom slab and outside the side wall of the wall concrete, in the side wall, outside the top slab, and inside the top slab for the elapsed time (days) shown in FIG. (%) Is displayed.

  The relative humidity shows a value of around 95% after the relative humidity in the bottom slab of the foundation concrete, the side wall of the wall concrete, and the top slab has dropped gently, but rapidly outside the top of the wall concrete. After the decrease, the value transitions to about 63% and is fixed at a value approximate to the value in the top plate.

  The analysis output value indicating the humidity distribution in the analysis model 5 of the concrete is useful for calculating the drying shrinkage amount. Therefore, the analysis conditions are input to the stress analysis zone 14 and the crack width analysis zone 15 as analysis conditions. The calculation of dry shrinkage strain corresponding to the estimation formula of JCI-TC911 and the CEB formula in each analysis zone, and the self-shrinkage strain conforming to the Japan Society of Civil Engineers concrete standard manual and JCI crack control guidelines. It will be used meaningfully in each analysis zone, such as enabling calculation.

Analysis in the stress analysis zone 14 includes thermal expansion coefficient, compressive strength, tensile strength, Young's modulus, Poisson's ratio from the input data 9 of the analysis conditions, temperature strain based on hydration reaction and water movement in concrete, self-contraction Input the creep generated from the strain, expansion strain and drying shrinkage strain, calculate the drying shrinkage strain corresponding to the JCI-TC911 estimation formula and CEB formula, the Japan Society of Civil Engineers concrete standard manual and JCI crack control guidelines Unsteady temperature stress analysis that enables calculation of shrinkage strain is performed.

  The expansion strain introduced by the expansion material employed at this time is analyzed in accordance with the idea of the “constant total energy”, which is a feature of the concrete crack suppression method in the present invention, and as a result, an analysis model The maximum principal strain and maximum principal stress are output together with the displacement, strain, stress and crack index in FIG.

  The maximum principal strain shown in FIG. 10, which is the analysis result, is examined. When the expansion strain introduction specification is in accordance with the idea of the initial strain method in accordance with the JCI crack control guidelines, the “constant total energy law” In the case of the mixing amount of 20 kg in line with the idea of “there is no problem in quality control as both pass with substantially the same strain value. However, when the introduction of expansion material is not considered and the initial strain method based on the JCI crack control guideline, the case where the mixing amount is 40 kg shows a great difference. Even if it is at the time of construction, it can be questionable from the viewpoint of quality control.

  Similarly, in the result of the maximum principal stress shown in FIG. 11, the maximum principal stress is calculated to be larger when the introduction of the expansion material is not taken into consideration, and conversely, the mixing amount of the expansion material is 40 kg. In this case, the maximum principal stress is negatively displayed until 18 days have elapsed, and the maximum principal stress is calculated to be larger from the 21st.

  In any case, the above-mentioned tendency is similar, and the situation in which large stress is generated is regarded as a serious problem in the construction of concrete structures. Even if the idea of the “constant energy law” is clear, the construction management of concrete structures in accordance with the conventional idea of the initial strain method is difficult to apply except for a specific range of 20 kg of expanded material mixed in. It can be said that there is.

  Analysis in the crack width analysis zone 15 is similar to the analysis in the stress analysis zone, and inputs thermal expansion coefficient, compressive strength, tensile strength, Young's modulus, Poisson's ratio, and corresponds to JCI-TC911 estimation formula and CEB formula. Unlike the results in the stress analysis zone, the displacement, crack equivalent strain, stress and stress in the analysis model 5 are carried out by the calculation of the drying shrinkage strain, the Japan Society of Civil Engineers concrete standard manual, and the distributed crack model in accordance with the JCI crack control guidelines. The crack width 19 separated from the crack equivalent strain is independently calculated by the output of the crack index and the integration in the range where the crack equivalent strain is generated separately from these outputs.

  What is shown as an analysis result is crack equivalent strain related to cracks in concrete appealing visually, one of which is a crack equivalent strain density diagram shown in FIG. 12 and a crack equivalent strain distribution diagram disclosed in FIG. .

In FIG. 12, the crack equivalent strain density is output as a crack equivalent strain presenting the degree of crack tension assumed by the strength of the color density by appealing to the visual recognition of the cracking degree of the concrete by identifying the color, Display of crack equivalent strain-Change from 5.00E-05 to 0.00E + 00 to 1.00E-04 to 2.50E-04, 4.50E-04 to visually indicate the existence and degree of crack equivalent strain Is presenting. According to this, it is calculated as an analysis result that two large crack equivalent strains exist at the position of the analysis model 5 corresponding to the central portion of the real phase structure 27. The similar analysis result is also clear in FIG. 13 which is a crack equivalent strain distribution table, and the degree of intense crack equivalent strain generated in the analysis model 5 and the distribution state in which it exists are clarified. By combining with the distance from the specific end of the model 5, it is possible to sensuously recognize the form of cracks in the concrete including the position where the cracks appear.

  As the output from the crack width analysis zone 15, the nonlinear constitutive law is introduced into the concrete and the reinforcing bar in consideration of the effect of the reinforcing bar in the form of the reinforcing bar ratio in the form separated from the output of the crack equivalent strain as described above. 14 is calculated as an analysis result in the table shown in FIG. 14. In this table, the initial crack width 0.18 as the sum of integral values calculated from the degree of longitudinal crack equivalent strain and strain length coordinates (mm) together with the distance from the specific end shown in FIG. It is possible to analyze (mm) and further specify a large crack width of 0.29 (mm) generated at the central portion of the real phase structure.

  The output in this analysis process is the analysis output (temperature) 11 of the temperature analysis zone 10 in the analysis result zone 18, the analysis output (relative humidity) 13 of the moisture movement analysis zone 12, and the “displacement, strain, stress from the stress analysis zone 14. Analysis output group 16 of "and crack index" and analysis output group 17 of "displacement, crack equivalent strain, stress and crack index" from crack width analysis zone 15 are presented as the results of the analysis in the form of summing up individually or simultaneously. In addition to this, as described above, an analysis output can also be presented for the crack width 19.

  As embodied in the above analysis zone, the increase in strain due to creep in FIG. 3 described above requires a large amount of storage capacity because information in all steps is essential in the conventional Step by Step method (superposition method). It is different from the situation where the calculation time is required, and the cost is reduced and the analysis time is reduced by reducing the input data by shortening the operating time of the computer by reducing the input data by adopting the appropriate analysis model logically away from the real phase structure It is possible to calculate only with the information in the immediately preceding step by introducing the rate type theory by the Dirichlet series added to this, and so it is calculated extremely appropriately and quickly. Quantifies the total phenomena that occur due to the use of expansion material in the building and the inherent expansion of the aggregate It is possible to elucidate the crack shape generated in the hardened concrete with high accuracy and to demonstrate the excellent effect that it is possible to quantitatively evaluate the effectiveness of measures to accurately control the crack shape. .

  The present invention provides a concrete structure that can safely and reliably achieve the construction of concrete structures that can be taken in a highly accurate and generally applicable manner by taking into account the energy state in the hardening process of the concrete. The present invention relates to a crack suppression method.

  DESCRIPTION OF SYMBOLS 1 ... Concrete test body, 2 ... Concrete, 3 ... Steel plate, 4 ... Rebar, 5 ... Analysis model, 6 ... Foundation concrete, 7 ... Wall concrete, 8 ... Analysis model creation zone, 9 ... Analysis condition input data, 10 ... temperature analysis zone, 11 ... analysis output of temperature analysis zone (temperature), 12 ... moisture transfer analysis zone, 13 ... analysis output of humidity transfer analysis zone (relative humidity), 14 ... stress analysis zone, 15 ... crack width analysis zone 16 ... Analysis output group of stress analysis zone, 17 ... Analysis output group of crack width analysis zone, 18 ... Aggregation zone of analysis output, 19 ... Analysis output of crack width (crack width), 20 ... Calculated value of rebar diameter 6mm Curve: 21 ... Measured value of unrestricted reinforcing bar, 22 ... Measured value of reinforcing bar diameter 6 mm, 23 ... Measured value of reinforcing bar diameter 13 mm, 24 ... Measured value of reinforcing bar diameter 19 mm, 25 ... "Work load one Calculated curve by law ", 26 ... measured value in the case of" workload constant law ", 27 ... reality structure

Claims (4)

It is based on the fact that the total energy consisting of heat generation energy released from the concrete to the outside, mechanical energy that exerts restraining force due to chemical action, and internal energy that functions on the concrete itself is set to a constant value in the hardened concrete body in a restrained state. A crack control method for concrete that constitutes a countermeasure against cracks in the analysis results. After the hardened concrete is divided into meshes, the calculation is based on the total energy being constant after inputting the relational data for the temperature analysis, moisture transfer analysis and stress analysis in the concrete. The method for suppressing cracks in concrete according to claim 1, wherein: After the hardened concrete is divided into meshes, it is calculated based on the total energy being constant after inputting the relational data for temperature analysis, moisture transfer analysis and crack shape analysis in the concrete, and cracks based on the result The method for suppressing cracks in concrete according to claim 1, comprising a countermeasure. After the hardened concrete is divided into meshes, the total energy is set to a constant value after inputting the relational data for temperature analysis, moisture transfer analysis, stress analysis and crack shape analysis in the concrete. The crack control method for concrete according to claim 1, wherein a crack countermeasure is configured based on the crack.

Images