JP4859550B2 - Method for judging the soundness of concrete structural members - Google Patents

Description

  The present invention relates to a soundness determination method for a concrete structural member. More specifically, the present invention relates to a method for determining the soundness of concrete structural members such as columns, beams, walls, floors and the like constituting a concrete structural member such as a reinforced concrete building.

  Various methods have been proposed so far for determining the soundness of concrete structural members such as columns, beams, walls, and floors constituting reinforced concrete buildings or steel reinforced concrete buildings. As a method for determining the soundness of a concrete structural member, a method by visual inspection of cracks is generally used, and the length, width, occurrence pattern, and the like of the cracks on the surface of the concrete structural member are used as judgment information.

  Therefore, a method has been proposed in which a crack state generated on the surface of a reinforced concrete structure is automatically detected by image measurement to diagnose the degree of damage to the structure (Patent Document 1). There is also a method of diagnosing the degree of damage by preliminarily embedding a linear sensor or strain sensor capable of storing strain in the concrete structure member, and evaluating the strain experienced by the concrete structure member by detecting the strain of the sensor. It has been proposed (Patent Documents 2 and 3). Further, a method has been proposed in which an optical fiber is embedded in a concrete structure member in advance as a sensor and the soundness of the concrete structure member is diagnosed by monitoring the output from the optical fiber (Patent Document 4). Also, by measuring the microtremors of the building and extracting only the vibration components of the entire building included in the measurement record, the vibration characteristics such as the natural frequency and natural mode of the building are identified, and the vibration characteristics are A method of diagnosing structural integrity by monitoring a vibration characteristic for a long period using a phenomenon that changes before and after has been proposed (Patent Document 5).

  Furthermore, as a method of judging the soundness of a reinforced concrete building or structural member, there is also a method of seeing through the inside of concrete using electromagnetic waves or X-rays for the purpose of confirming an appropriate amount of reinforcing bars (rebar ratio). It is used a lot.

JP 2003-35528 A JP 2005-337818 A JP 2005-337819 A JP 2005-257570 A JP 2003-322585 A

  However, the method by visual inspection of cracks and the diagnostic method of Patent Document 1 have a problem that cannot be implemented unless the surface of the concrete structural member is exposed. That is, in the case of a concrete building or a structural member, a method of covering with a decorative material is often adopted, and the surface of the concrete structural member must be exposed by peeling off the decorative material, which consumes cost and time.

  In addition, the strains that can be evaluated by any of the techniques of Patent Documents 2 to 4 are limited to the position where the sensor is embedded. In other words, it is necessary to match the position where the sensor is damaged and the position where the sensor is embedded, and it is necessary to predict the embedded position of the sensor in advance, and the sensor does not function if the damaged position deviates from the previous prediction. is there. In addition, since the method is established by embedding a sensor in the concrete structural member in advance, the concrete structural member that can be evaluated is limited to a new one in which the sensor is embedded, and cannot be applied to an existing concrete structural member. . When it is applied to an existing concrete structural member, there is a problem that it cannot be carried out without damage, such as partial destruction for embedding the sensor.

  In addition, since the diagnostic method described in Patent Document 5 evaluates the structural soundness of a building based on changes in vibration characteristics before and after damage, data on the natural frequency at the time of new building is required as vibration characteristics before damage. There is a problem that cannot be applied to existing buildings that do not have data at the time of new construction (when healthy). In addition, it is impossible to know the concrete damage of the concrete structural member and the structural performance of the reinforcing bars. Moreover, even if the data on the natural frequency of the concrete structural member at the time of new construction can be obtained, there is no guarantee that it is a sound concrete structural member.

  Furthermore, even in the method of non-destructive investigation of reinforcing bars using electromagnetic waves and X-rays, there is a problem that structural mechanical performance such as reinforcing bars cannot be evaluated even though the existence and arrangement of reinforcing bars can be known. is there.

  Then, an object of this invention is to provide the soundness determination method which can determine the soundness of a concrete structure member correctly, even if the concrete structure member is covered with the decorative material. It is another object of the present invention to provide a method for determining the soundness of a concrete structural member that can detect damage that is difficult to predict in advance. Furthermore, there is a method for determining the soundness of a concrete structural member that can determine the soundness of a concrete structural member regardless of whether the concrete structural member is newly installed or existing. It is also intended to provide. Furthermore, the present invention diagnoses the structural deterioration of concrete that is evaluated to be sound at the present stage, the structural deterioration of concrete, the deterioration of the adhesion performance of reinforcing bars, or the cross-sectional defect due to corrosion. Another object of the present invention is to provide a concrete soundness evaluation method that enables early prediction of damage to concrete or deterioration of structural performance of reinforcing bars.

  In order to achieve such an object, there are various relations between the natural frequency change and the soundness of the concrete structural member when the present inventors give a temperature change that causes a nonuniform temperature distribution to the concrete structural member. As a result of conducting experiments and research, when the concrete part was healthy, the natural frequency increased or remained constant when heated, and when it was damaged, the natural frequency decreased when heated. .

  When the concrete structural member is subjected to a temperature change that causes a non-uniform temperature distribution in the cross section of the member, the concrete structural member generates a temperature stress in which a compressive stress and a tensile stress are generated simultaneously. This temperature stress changes the Young's modulus of concrete, which is the main material of the concrete structural member. On the other hand, the Young's modulus of reinforcing steel, which is another main material for concrete structural members, hardly changes as long as the temperature changes to such an extent that the concrete is not damaged. Since the Young's modulus is one of constants that determine the natural frequency of the concrete structural member, if the Young's modulus changes, the natural frequency of the concrete structural member also changes.

  The temperature stress distribution is for all concrete structural members including rebar and concrete, and is the sum of rebar and concrete. That is, the temperature stress generated in all member cross sections is distributed between the reinforcing bars and the concrete portion. On the other hand, the greater the amount of reinforcing bars, the smaller the stress borne by the concrete. On the other hand, the smaller the amount of reinforcing bars, the greater the stress borne by the concrete. As an extreme example, in unreinforced concrete that does not contain any reinforcing bars, the generated temperature stress is borne entirely by the concrete.

  Therefore, it is considered that a mechanism is established in which the greater the temperature stress acts on the concrete part, the greater the elastic modulus (Young's modulus) of the concrete, the more rigid the concrete structural member, and the higher the natural frequency. According to this mechanism, the natural frequency of the member increases as the temperature stress of the concrete portion increases. That is, when there are few reinforcing bars and the stress acting on the concrete increases, the increase in the natural frequency of the member increases. On the other hand, if there are many reinforcing bars and the stress acting on the concrete is small, the increase in the natural frequency of the member is small. Even if reinforcing bars are present, if the engaging force between the reinforcing bars and the concrete is reduced, the distribution of stress acting on the concrete is increased, so that the natural frequency of the concrete structural member as a whole increases.

That is, according to the knowledge obtained from the experiments by the present inventors, the fluctuation ratio of the natural frequency after the reinforcement ratio of the concrete structural member and the structural damage of the concrete and the temperature change of the concrete structural member are given. Are the following features (a) to (c).
(a) When the concrete part is healthy, the natural frequency after heating increases.
(b) As long as the concrete part is healthy, the increase rate of the natural frequency after heating increases as the reinforcing bar ratio decreases.
(c) When the concrete part is not healthy, the natural frequency after heating decreases.

  Therefore, if the change in the natural frequency of the concrete structural member is measured when a temperature change is applied to the concrete structural member so as to have a non-uniform temperature distribution in the cross section of the member, the “natural frequency increases slightly” or “ It is possible to estimate the damage state of concrete from qualitative phenomena such as “transition constant”, “much (too much) going up”, “falling down”, and the rate of increase of natural frequency when temperature change is given To obtain an evaluation index of the structural performance of the reinforcing bar, and to estimate the reinforcing bar ratio quantitatively from the increasing rate of the natural frequency by obtaining the relative relationship between the increasing rate of the natural frequency and the reinforcing bar ratio in advance. Can do. It can also be used to estimate the presence of reinforcing bars, and hence the amount of reinforcing bars, as well as the adhesion between reinforcing bars and concrete (increase in gaps between concrete and reinforcing bars and deterioration of familiarity).

  In addition, the structural performance of concrete and reinforcing bars in concrete structural members can be quantitatively grasped as the rate of increase of the natural frequency, so the natural frequency when the soundness judgment is performed periodically and temperature changes are given. By analyzing the change in the rate of increase over time, it is possible to predict the deterioration of the structural performance of concrete and reinforcing bars in the future before fatal damage to the structure is reached.

  That is, the soundness determination method for a concrete structural member according to the present invention is based on the above-described knowledge, and gives the concrete structural member a temperature change that causes a non-uniform temperature distribution in the cross section of the member. Changes in the natural frequency of a concrete structural member after being applied to the concrete are detected. When the natural frequency changes tend to increase or remain constant, there is no structural damage to the concrete, and when there is a tendency to decrease. The concrete is judged to have structural damage.

  Further, the invention according to claim 2 is the method for determining the soundness of a concrete structural member according to claim 1, wherein the concrete structural member is intermittently hit and the natural vibration is generated from the vibration of the concrete structural member caused by the hit. In addition to calculating the number, the pattern of change with time of the natural frequency is obtained, and the change direction of the natural frequency is determined from the pattern of change with time.

  Further, the invention according to claim 3 is the soundness determination method for a concrete structural member according to claim 1, wherein the change in the natural frequency of the concrete structural member is compared with the natural frequency before giving the temperature change. The change of the natural frequency after giving a temperature change is calculated | required.

  According to a fourth aspect of the present invention, there is provided a method for determining the soundness of a concrete structural member, wherein the concrete structural member is subjected to a non-uniform temperature change in a cross section, and the natural frequency of the concrete structural member after the temperature change is determined. By measuring the change, the increase rate of the natural frequency is obtained, and by comparing the increase rate with the increase rate of the natural frequency at the time of the temperature change of a sound concrete structural member, the structural performance of the reinforcing bar is used as an evaluation index. The soundness of the member is determined.

  According to a fifth aspect of the present invention, in the method for determining the soundness of a concrete structural member according to the fourth aspect, the rate of increase of the natural frequency when a non-uniform temperature change is applied to the concrete structural member with a known reinforcement ratio. Is obtained in advance, and the reinforcement ratio is estimated from the increase rate of the natural frequency of the concrete structural member after the temperature difference is given using this correlation.

  The invention according to claim 6 is the method for judging the soundness of a concrete structural member according to claim 4 or 5, wherein the concrete structural member is intermittently applied to the concrete structural member in a state where a non-uniform temperature change is given in the cross section. The natural frequency is calculated from the vibration generated by the impact, the pattern of the natural frequency change with time is obtained, and the increase rate of the natural frequency is determined from the pattern.

  The invention according to claim 7 is the method for determining the soundness of a concrete structural member according to claim 4 or 5, wherein the increase rate of the natural frequency of the concrete structural member is compared with the natural frequency before giving a temperature change. It is what you want.

  The method for determining the soundness of a concrete structural member according to an eighth aspect of the present invention provides the concrete structural member after the temperature change is given to the concrete structural member such that the concrete cross section has a non-uniform temperature distribution in the cross section of the member. Periodic detection of changes in natural frequencies of the natural frequency and accumulation of data on the rate of increase or amount of change in natural frequencies, and when the time-series transition of the rate of increase or change is decreasing, It diagnoses that either damage or minor degradation that may lead to concrete damage in the future is progressing.

  The method for determining the soundness of a concrete structural member according to the invention according to claim 9 is the concrete structural member after the temperature change is given to the concrete structural member so as to have a non-uniform temperature distribution in the cross section of the member. Periodic detection of changes in natural frequency of the steel and accumulation of data on the rate of increase or amount of change in the natural frequency, and adhesion of reinforcing bars when the time-series transition of the rate of increase or amount of change tends to increase It diagnoses that the deterioration of the structural performance of the reinforcing bars is progressing due to the progress of cross-sectional defects due to performance degradation or corrosion.

  Here, in the soundness determination method for a concrete structural member according to the present invention, the non-uniform temperature change given to the concrete structural member may be realized by a natural phenomenon such as air temperature or sunlight, or may be artificial. It may be realized by forcibly heating by a heat source. In addition, the method for judging the soundness of a concrete structural member according to any one of claims 5 to 9, that is, when a structural evaluation of a reinforcing bar is performed, an uneven temperature change applied to the concrete structural member is forced by an artificial heat source. It may be realized by giving a relative temperature difference by being cooled. In addition, when a concrete structure member is given a non-uniform temperature change by forcibly heating or cooling with an artificial heat source, all surfaces of the concrete structure member may be heated or cooled. Heating or cooling a part of the surface, more preferably one surface, in some cases controlled by forcibly heating one surface with an artificial heat source and simultaneously cooling the other surface A non-uniform temperature change may be realized by providing the temperature distribution. Furthermore, it is preferable that the artificial heat source is a heater directly attached to a concrete structure member or a cooling / heating device.

  According to the soundness determination method for a concrete structural member of the present invention, a change in the natural frequency of a concrete structural member after a temperature change that causes a nonuniform temperature distribution in the cross section of the concrete structural member is detected. Therefore, even if the concrete structural member is covered with a decorative material, the natural frequency can be obtained by hitting the concrete structural member from above the decorative material, and the decorative material is peeled off. Therefore, the soundness of the concrete structural member can be determined. That is, the soundness of the concrete structural member can be determined not only at locations that can be visually confirmed, but also at locations that cannot be visually confirmed. Furthermore, the presence or absence of internal defects that do not appear on the surface of the concrete structural member can also be detected.

  Further, according to the soundness determination method for a concrete structural member of the present invention, the presence or absence of damage is determined based on a change in the natural frequency of the concrete structural member when a temperature change that results in a non-uniform temperature distribution is given. Therefore, it is possible to detect the damage to the concrete structural member without predicting a portion that is likely to be damaged by the concrete structural member and embedding a sensor or the like for detecting the strain in that portion. That is, whether or not damage has occurred can be detected even if it is unknown where damage occurs in a concrete structural member (for example, a column) to be evaluated. In addition, since it is not necessary to embed a sensor in the concrete structural member in advance, the concrete structural member is not damaged or can be diagnosed for an existing concrete structural member.

  Furthermore, according to the soundness determination method for a concrete structural member of the present invention, based on a change in the natural frequency of the concrete structural member when a temperature change that causes a non-uniform temperature distribution is given, Since structural mechanical validity such as adhesion of reinforcing bars, evaluation of the appropriate amount of reinforcing bars, and the presence or absence of reinforcing bars can be determined, data for natural frequency at the time of newly installing a sample for comparison or concrete structural member (when healthy) can be obtained. Without it, the soundness of the concrete structural member can be determined. In other words, even with existing concrete structural members, there is no guarantee of data such as the presence or absence of damage to the concrete or structural mechanical validity such as adhesion of reinforcing bars, evaluation of the appropriate amount of reinforcing bars, or presence or absence of reinforcing bars. Even if it is a new concrete structure member, it can judge about those soundness.

  Further, according to the soundness judgment method for a concrete structural member according to the present invention, the natural vibration is measured by measuring the change in the natural frequency of the concrete structural member when the concrete structural member is subjected to a non-uniform temperature change in the cross section. By determining the rate of increase in number and comparing this rate of increase in natural frequency with the rate of increase in natural frequency of sound concrete structural members, the soundness of concrete structural members is judged using the structural performance of reinforcing bars as an evaluation index. be able to. Although this judgment method is a test in a small strain range, the actual structural mechanical performance can be directly evaluated, and the structural mechanical validity such as adhesion of the reinforcing bars can be evaluated. The present invention can also be applied to the estimation of the amount and the diagnosis of the adhesion between the reinforcing bar and the concrete (increase in the gap between the concrete and the reinforcing bar or deterioration of the familiarity).

  Further, according to the present invention, a correlation between the rate of increase of the natural frequency and the reinforcing bar ratio when a non-uniform temperature change is given to a concrete structural member with a known reinforcing bar ratio is obtained in advance, and this correlation is used. Since the reinforcement ratio is estimated from the rate of increase in natural frequency, the structural performance of the reinforcement, including the amount of reinforcement (rebar ratio) and adhesion, can be directly evaluated from a mechanical standpoint. In combination with this, it is possible to estimate the presence of reinforcing bars, and hence the amount of reinforcing bars, or to diagnose the adhesion between reinforcing bars and concrete.

  Furthermore, according to the present invention, a simple mechanism for applying temperature to the concrete structural member and a mechanism for applying free vibration are sufficient.

  Furthermore, the present invention periodically performs soundness evaluation, accumulates data on the rate of increase of the natural frequency when temperature changes are applied, and also determines the structural performance of concrete damage or rebar from the trend of time series transition. The progress of deterioration of steel is diagnosed, so that the progress of deterioration of concrete structural members that are evaluated to be healthy at the present stage and future deterioration of concrete damage or deterioration of structural performance of reinforcing bars will be fatal damage. It can be predicted early before it arrives. Therefore, for example, if the minimum level of the reinforcing bar ratio is obtained in advance, it is highly likely that the reinforcing bar ratio will exceed the minimum level at the next periodic inspection when the soundness judgment is carried out regularly, and some measures will be taken Judgment that it should be possible.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  FIGS. 1-6 shows an example of embodiment of the soundness determination method of the concrete structure member of this invention. The method for determining the soundness of a concrete structural member according to the present embodiment gives a temperature change to the concrete structural member such that a non-uniform temperature distribution in the cross section of the member (simply referred to simply as a non-uniform temperature change in this specification). The change in the natural frequency of the concrete structural member after the change in temperature is detected, and the soundness of the concrete structural member is determined from the change in the natural frequency. Examples of the concrete structural member 1 in the present embodiment include, for example, columns, beams, walls, floors, and the like that constitute a reinforced concrete building, but are not particularly limited thereto, such as a precast concrete plate or concrete. It includes buildings, steel reinforced concrete buildings and parts of steel concrete buildings.

  The method of giving the temperature change to the concrete structural member is not limited as long as the temperature distribution in the cross section of the concrete structural member is at least uniform, and the surface to be heated or cooled is limited, It is not particularly limited to the type of heat source, heating method or cooling method. For example, the uneven temperature change given to the concrete structural member may be realized by natural phenomena such as air temperature or sunlight, or may be realized by forcibly heating by an artificial heat source. Anyway. Also, when evaluating the structural performance of reinforcing bars, the uneven temperature change given to the concrete structural members is realized by giving a relative temperature difference due to forced cooling by an artificial heat source. It may be.

  In addition, when a concrete structure member is given a non-uniform temperature change by forcibly heating or cooling with an artificial heat source, all surfaces of the concrete structure member may be heated or cooled. Heating or cooling a part of the surface, more preferably one surface, in some cases controlled by forcibly heating one surface with an artificial heat source and simultaneously cooling the other surface A non-uniform temperature change may be realized by providing the temperature distribution. Furthermore, it is preferable that the artificial heat source is a heater directly attached to a concrete structure member or a cooling / heating device. Further, in the present embodiment, an example in which the rubber heater 5 is attached to the surface of the concrete structural member 1 and the concrete structural member 1 is heated from the surface side is described. However, instead of the rubber heater 5, for example, a panel heater Or you may make it heat the heating apparatus which uses radiant heats, such as a halogen heater and a stove, or the heat from a boiler or a chimney close to the surface of the concrete structure member 1. It is preferable to heat only one surface of a concrete structural member with an artificial heat source such as a heater or a natural heat source because the temperature difference is the largest and non-uniform.

  In the present invention, it is particularly important to make the temperature non-uniform in order to generate temperature stress, and it is only necessary to generate temperature stress. Furthermore, the greater the stress, the better. For example, even when the heaters are heated on two surfaces, the temperature applied to the adjacent two surfaces is more uneven than the two adjacent surfaces because the heater has a non-uniform temperature distribution in the cross section. It is preferable in generating. Furthermore, when the heater is attached to only one surface, the temperature difference, that is, the non-uniformity of the temperature distribution in the member cross section increases, which is much more effective. It is also effective to attach a heater to two adjacent surfaces among the four surfaces. In this case, the temperature gradient becomes tight on the diagonal line in the cross section, and the temperature difference becomes large, which is effective. Furthermore, even when a heater is attached to all four surfaces of the pillar and heated simultaneously, it is effective because a temperature difference is generated between the periphery and the center at the beginning of heating. However, in this case, the temperature difference between the surroundings and the center decreases with the passage of time, and it is necessary to perform an operation for detecting a change in the natural frequency at an early stage. If the temperature distribution in the cross section becomes uniform after a sufficient amount of time has elapsed, temperature stress is no longer generated, and effective data cannot be acquired.

  Here, it is said that the concrete without a reinforcing bar has a possibility of cracking when the surface temperature difference exceeds 20 ° C. Therefore, the maximum temperature difference caused by the temperature change given to the concrete structural member, for example, table The temperature difference between the back surfaces is desirably at least 20 ° C. or less. On the other hand, when the temperature difference is about 5 ° C., it seems that the change in natural frequency is small and inappropriate. Therefore, the surface temperature difference caused by a temperature change that causes a non-uniform temperature distribution in the cross section of the concrete structural member 1 is about 10 ° C. to 15 ° C., preferably about 10 ° C.

  Furthermore, as the heating time, the non-uniform temperature change given in the cross section of the concrete structural member 1, in other words, the surface temperature difference reaches the above-mentioned appropriate range and the natural frequency before and after heating is sufficiently compared. This is the time during which non-uniform temperature change is maintained to the extent that a waveform pattern of the natural frequency that can be changed over time is obtained (within the time during which temperature stress occurs). It seems to be.

  In addition, in order to measure the natural frequency of a concrete structural member to which a nonuniform temperature change is applied, free vibration is generated by applying a striking force and the free vibration is detected by a vibration sensor or the like. . In addition, when detecting the change over time of the natural frequency of the concrete structural member as a waveform by a method such as intermittently hitting after the start of heating, the fluctuation curve of the natural frequency after heating the concrete is shown. It is diagnosed by reading. That is, since the soundness can be evaluated only by the tendency of the natural frequency after the start of heating to change with time, the natural frequency before heating the concrete is unnecessary. However, in order to accurately read the fluctuation curve of the natural frequency, it is useful to obtain the natural frequency before heating the concrete structural member. If there is data on the natural frequency before heating, it is not always necessary to repeat the impact and obtain the fluctuation curve of the natural frequency, but before giving the natural frequency and temperature change after a certain period of time from the start of heating. By comparing with the natural frequency, it can be judged whether the change of the natural frequency after the temperature change is increasing or decreasing, in other words, whether the concrete is damaged or not. . Therefore, it is desirable to obtain the measurement of the natural frequency before heating.

  By the way, even before the concrete structural member is heated, non-uniform temperature acts on the concrete structural member due to fluctuations in sunshine, air temperature, and room temperature. It is conceivable that the natural frequency fluctuates due to temperature fluctuation. However, the temperature variation is a negligible temperature change as compared with the artificially given temperature difference between the front and back surfaces or the intentionally given temperature difference. Therefore, the natural frequency before heating, particularly just before heating, may be a single test value or a statistical value of multiple test values. Adoption of the amount is preferred. As the statistic, the average value, median (median), or mode can be used, but the median is not affected by fluctuations in the natural frequency due to sudden causes. In many cases, stable values can be obtained. The median refers to the value of the measured value corresponding to the middle number, with numbers assigned to the measured values from the largest.

  FIG. 1 shows an example of a concrete structure member soundness judgment apparatus (hereinafter referred to as a “healthiness judgment apparatus”) for carrying out the concrete structure member soundness judgment method of the present invention. This soundness determination device 4 is referred to as one surface of the concrete structural member 1 (hereinafter, this surface is referred to as “front surface”, the opposite surface is referred to as “back surface”, and the other surface is referred to as “side surface”. ) To heat the concrete structural member from the front side, a free vibration generator 9 for striking the concrete structural member 1 to generate free vibration in the concrete structural member 1, and the freedom of the concrete structural member 1 A vibration sensor 10 that detects vibration and a vibration analyzer 11 that calculates a natural frequency from a vibration waveform obtained by the vibration sensor 10 and records the calculation result in time series are provided. The free vibration generator 9 includes a pair of support columns 6 standing on the floor 3 of the experimental table, a hammer 8 suspended upside down via a rotating shaft 7 therebetween, and the hammer 8 is operated by a timer. It has a drive device (not shown) that is rotated so as to be lifted around the rotation shaft 7 at regular time intervals, and the hammer 8 lifted by the drive device is rotated by free fall to provide concrete from above the rubber heater 5. The central portion of the surface of the structural member 1 is hit in the horizontal direction. Of course, the concrete structural member may be hit manually with a hammer or the like. The vibration sensor 10 is installed at the central height of one side surface of the concrete structural member 1 and detects free vibration of the concrete structural member 1.

  The hammer 8 of the free vibration generator 9 is actuated by a driving force of a motor (not shown) at a predetermined time interval (for example, every 2 minutes), and strikes the concrete structural member 1 with a constant force. The hammer 8 hits the concrete structural member 1 with a light force that does not damage the concrete structural member 1, for example, at the center of the concrete structural member 1 (in the case of a columnar object, the central height position). When the concrete structural member 1 is hit with the hammer 8, the shape of the vibration of the concrete structural member 1 becomes such that the vibration amplitude becomes the largest at the central portion of the concrete structural member 1 as shown in FIG. The vibration sensor 10 detects free vibration generated in the concrete structural member 1 every time the hammer 8 is hit, and outputs a signal indicating the detection result to the vibration analyzer 11. By striking at a constant time interval (2 minute intervals), a pattern (profile) of the natural frequency with time is obtained. The vibration analyzer 11 includes a control unit 11a configured by a CPU, for example, which operates based on a predetermined control program, and a memory 11b for storing data. The controller 11a records the detection result input from the vibration sensor 10, that is, the free vibration waveform in the memory 11b as time series data of acceleration as shown in FIG. The control unit 11a reads the repetition period from the free vibration waveform shown in FIG. 4, calculates the reciprocal of the period, records the calculation result as a natural frequency in the memory 11b along the time series, and stores it in the vibration analysis apparatus 11. The aspect of the change over time of the natural frequency is displayed on the connected display device 12.

  When determining the soundness of the concrete structural member 1 using the soundness determination device 4 configured as described above, first, the free vibration generator 9 and the vibration analyzer 11 are operated, and a predetermined time is determined. The concrete structural member 1 is struck with a hammer 8 at every interval, the natural frequency of the concrete structural member 1 is obtained from the free vibration obtained by the struck, and this is recorded in the memory 11b along the time series and the display device 12 shows the mode of change over time. Then, the surface of the concrete structural member 1 is heated by the rubber heater 5, and the natural frequency is continuously recorded in the memory 11b along the time series, and the mode of change with time is displayed on the display device 12.

  When the temperature of the surface portion of the concrete structural member 1 rises, the portion tends to expand due to thermal expansion. On the other hand, since the heat from the rubber heater 5 is difficult to be transmitted to the back surface of the concrete structural member 1, or even if heat is transmitted, the temperature rise is larger than the surface of the concrete structural member 1 as shown in FIG. Since it is small, the back surface portion of the concrete structural member 1 does not thermally expand or hardly thermally expands. Due to the difference in thermal expansion between the front surface portion and the back surface portion of the concrete structural member 1, compressive stress and tensile stress are generated in the concrete structural member 1 as shown in FIG. The generation of these stresses changes the Young's modulus of the concrete portion of the concrete structural member 1. Since the Young's modulus is one of constants that determine the natural frequency of the concrete structural member 1, the natural frequency of the concrete structural member 1 also changes when the Young's modulus changes.

  Therefore, the concrete structural member 1 is intermittently hit with the non-uniform temperature change, the natural frequency is calculated from the vibration generated by the hit, and the change of the natural frequency with time is calculated. By monitoring, it is possible to judge the soundness of the concrete part of the concrete structural member 1 from the change pattern of the natural frequency over time, and to grasp the amount of reinforcing bars from the rate of increase or increase of the natural frequency. Become. Moreover, since both crack diagnosis and reinforcing bar ratio diagnosis are determined based on the behavior of the natural frequency change when a temperature change is applied, the change rate is more preferable than the increase rate or increase amount of the natural frequency. If the pattern of change with time is obtained, the soundness of the concrete structural member as an evaluation index for both the damage of the concrete and the structural performance of the reinforcing bar can be evaluated by one test or data as follows.

(Evaluation of concrete damage)
Regarding concrete damage, as shown in FIG. 7 which schematically illustrates the change in natural frequency when a temperature change resulting in a non-uniform temperature distribution is given, the natural frequency may increase even slightly after heating. Is judged to be healthy. For example, when the route A in FIG. 7 is passed, the natural frequency increases immediately after heating, so that it is diagnosed as “sound”. On the other hand, when the path B (dotted line) is passed, that is, when the natural frequency decreases, the concrete is diagnosed as “damaged”. Therefore, when the pattern of the natural frequency change with time when applying a nonuniform temperature change tends to decrease, or the natural frequency after giving the temperature change, the natural frequency before giving the temperature change When it becomes smaller than this, it can be determined that there is structural damage to the concrete.

  That is, if the temperature is raised so that the temperature distribution in the member cross section of the concrete structural member becomes non-uniform, a temperature stress is generated, so that a healthy concrete portion becomes hard and the natural frequency increases. The increase in natural frequency due to this temperature stress is much larger than the slight decrease due to “material softening due to heating”, so if the temperature of a sound reinforced concrete member is raised unevenly, The slight decrease due to “material softening due to temperature” is offset, and the natural frequency increases. On the other hand, when the temperature of a reinforced concrete member with cracks is raised unevenly, the natural frequency decreases due to the cracks opening. This change in the natural frequency is manifested as an increase in the natural frequency or a constant transition or decrease.

That is, there are the following three fluctuation factors of the natural frequency.
(H1) Increase in natural frequency due to uneven heating and temperature stress
(H2) Slight reduction of natural frequency due to “softening of materials by heating”
(H3) Reduction of natural frequency due to opening of cracks in concrete due to heating Among these, (H2) is negligibly small compared to (H1) and (H3), and (H3) is (H1) Is larger than the amount of change. Therefore, by adding the effect of (H1) with a non-uniform temperature rise factor, when there is a tendency for the natural frequency change to increase or to remain constant, there will be no concrete damage and it will decrease. When there is a tendency, the relationship that the concrete is damaged is established, and the soundness of the concrete can be evaluated and judged.

  From the above-mentioned meaning, even if the concrete structural member is evenly heated, cracks in the concrete can be detected by fluctuations in the natural frequency due to (H2) and (H3), but the effect of (H1) can be detected. If the temperature change due to non-uniform heating, such as heating only one side taking into consideration, the direction of the natural frequency change after heating is reversed depending on the presence or absence of cracks, Since the presence or absence can be clearly identified, it is preferable for detecting cracks more reliably.

  In the diagnosis of cracks in the concrete of the present invention, it is important to grow the cracks as large as possible. Therefore, even if a nonuniform temperature change is given, it is preferably by heating. Giving a change is not preferable for detecting a change in the natural frequency. However, in order to improve diagnostic accuracy, it may be desirable to not only increase the temperature of one surface but also to arbitrarily control the temperature distribution in the member cross section by cooling the temperature of the other surface to prevent the temperature increase. is there.

  Incidentally, the concrete damage targeted by the present invention is mainly cracking and peeling. With these two, most other forms of damage can be covered. Therefore, according to the method for determining a concrete structural member of the present invention, all of the structural damage of the concrete can be covered. In addition, a crack means a state in which a crack enters but sticks to a member as a concrete lump, and a peeling means a state in which a large crack has entered and separated from the member as a concrete lump.

(Evaluation of structural performance of reinforcing bars)
The diagnosis of the structural performance of the reinforcing bars is based on the assumption that the concrete damage diagnosis described above is sound. And when the concrete part is healthy without cracks, the reinforced concrete member is not suitable for the non-uniform temperature change, for example, the natural frequency change when one side of the concrete structural member is heated for a certain period of time by the heater. The structural performance of the reinforcing bars is inferior to that of a sound concrete structural member that is sufficient in volume and the engaging strength of the reinforcing bars and concrete. The rate of increase and the amount of increase tend to increase.

  That is, the temperature stress generated by applying a nonuniform temperature change to the concrete structural member is that of all the reinforced concrete members including the reinforcing bars and the concrete, and is expressed as the sum of the reinforcing bars and the concrete. That is, the temperature stress generated in all member cross sections is distributed between the reinforcing bars and the concrete portion. Thus, the smaller the amount of reinforcing bars, the greater the stress borne by the concrete. As an extreme example, in unreinforced concrete without any reinforcing bars, the generated temperature stress is borne entirely by the concrete. Therefore, it is presumed that the greater the temperature stress acts on the concrete part, the greater the elastic modulus of the concrete, and the more rigid the reinforced concrete member and the higher the natural frequency. According to this mechanism, the natural frequency of the member increases as the temperature stress of the concrete portion increases. That is, when there are few reinforcing bars and the stress acting on the concrete increases, the increase in the natural frequency of the member increases. On the other hand, if there are many reinforcing bars and the stress acting on the concrete is small, the increase in the natural frequency of the member is small. Therefore, based on the change pattern of natural frequency or the increase / increase rate of the natural frequency when a non-uniform temperature change is applied to a concrete structural member (called a sound concrete structural member) manufactured without damage at an appropriate rebar ratio. Then, in the pattern in which the natural frequency change is larger than that, the ratio of reinforcing bars is small (the amount of reinforcing bars is small) or the adhesion of concrete to the reinforcing bars is weak, and the structural performance of the reinforcing bars deteriorates overall. It can be judged that it is in a state. It should be noted that the reinforcing bar ratio represents the amount of reinforcing bars and the adhesion performance represents the quality of reinforcement with respect to the concrete. When the quantity and quality are sufficient, the reinforcing bars have the required structural performance.

  Here, the time course of the natural frequency when a non-uniform temperature change is applied to a healthy reinforced concrete member having no cracks in the concrete portion can be schematically represented as shown in FIG. That is, the change in the natural frequency of the concrete structural member when the non-uniform temperature change is applied, when the heating is started, the natural frequency rapidly increases and reaches the maximum value f1. If the heating time is long, the natural frequency may decrease during the heating. When the heating is stopped, the natural frequency decreases, falls below the first frequency f0, reaches the minimum value f2, and then returns to the original f0. The natural frequency before heating is f0.

The increase rate of the natural frequency at this time is given by, for example, the following two calculation formulas. An increase rate Δf of the natural frequency under a constant temperature heating condition (for example, a surface temperature difference of 10 ° C.) is defined by
Δf = (f1-f0) / f0 × 100 (unit%) (1)
Δf = (f1-f2) / f0 × 100 (unit%) (2)

  Therefore, the fluctuation pattern of the natural frequency when the reinforced concrete column is heated under various conditions of the reinforcing bar ratio is obtained by experiments, and the rate of increase of the natural frequency according to the formula (1) or (2) If the correlation of the ratio is obtained in advance, the reinforcing bar ratio of the target concrete structural member 1 can be evaluated only by detecting the increase rate of the natural frequency. Note that the amount of increase (or amount of decrease, that is, the absolute amount) of the natural frequency varies depending on the cross-sectional dimensions of the concrete structural member and the physical properties of the concrete material (due to the scale effect). However, this scale effect can be eliminated by using the increase rate normalized by the initial natural frequency. This eliminates the need to consider the cross-sectional dimensions of the concrete structural member and the physical properties of the concrete material. Therefore, in this embodiment, the increase rate of the natural frequency is used as the evaluation index. However, in some cases, the change in the natural frequency may be grasped using the change amount of the natural frequency or the change pattern itself. good.

  The relationship between the increase rate of the natural frequency and the reinforcing bar ratio is, for example, a reference curve as shown in FIG. Naturally, the reference curve is different between Expression (1) and Expression (2). Practically, a heating test is performed on the rebar concrete member to calculate the increase rate Δf of the natural frequency defined by the equation (1) or (2), which is applied to the reference curve in FIG. The procedure is to find the ratio from the figure.

  Here, when the evaluation value of the reinforcing bar ratio of the concrete structural member is low (that is, when the increase rate of the natural frequency is large or the change amount shows a large pattern), the cause is the lack of the reinforcing bar ratio or the adhesion performance. It cannot be judged whether it is due to lack of However, even if the cause cannot be specified, it is clear that the structural performance of the reinforcing bar is structurally low enough to affect the soundness of the concrete structural member. It is a sufficient evaluation index for sex determination. That is, even if a reinforcing bar is contained, it is equivalent to a non-barbed state if no adhesive force is generated with the concrete, and if the adhesive force is low, it is equivalent to a small reinforcing bar ratio. Moreover, since the presence, number, and thickness of reinforcing bars can be evaluated by using known inspection techniques such as X-ray inspection and electromagnetic wave inspection, the reinforcing bars can be evaluated by referring to the inspection results of X-ray inspection and electromagnetic wave inspection. It is possible to specify whether or not the cause of the low structural performance is the adhesion of concrete to the reinforcing bars. For example, the presence of reinforcing bars in concrete structural members can be clarified by X-ray photography or electromagnetic waves, so that the presence of reinforcing bars is obvious by other inspection methods, but the ratio of the reinforcing bars is obtained. If not, it can be determined that the adhesion performance has deteriorated. Since the increase rate of the natural frequency and the reinforcing bar ratio have an inverse correlation, when the increase rate of the natural frequency increases, the evaluation value of the reinforcing bar ratio becomes low.

  Reinforcing bar ratio is only one of evaluation indexes or evaluation items, and it is a unique effect of the present invention that the performance of reinforcing bars of reinforced concrete members related to new construction can be diagnosed from the viewpoint of structural mechanics. In other words, in the current X-ray inspection and electromagnetic wave inspection, even if the number and thickness of the reinforcing bars can be evaluated, it cannot be determined whether the reinforcing bars are effective in the structural dynamics of the core. Therefore, even if the number and thickness of reinforcing bars are appropriate, if there is a problem with the adhesion of concrete to the reinforcing bars, the desired structural performance of the reinforcing bars cannot be obtained, and this cannot be evaluated at all. It was.

  In the method for determining the soundness of a concrete structure using the reinforcing bar ratio as an evaluation index, the non-uniform temperature change applied to the concrete structural member can be obtained not only by heating but also by cooling.

(Aging evaluation)
Furthermore, although the present invention is characterized by the fact that it is not necessary to secure data at the time of soundness, by storing the data at the time of soundness, there is no danger at this stage in the concrete structure at the time of soundness. Predict the timing of the current deterioration progress and the future deterioration of concrete, the deterioration of the adhesion performance of reinforcing bars, or the loss of cross-section due to corrosion before the fatal damage occurs. Can do.

  In other words, the structural performance of concrete and rebars in concrete structural members can be quantitatively grasped as the rate of increase of the natural frequency, so the natural frequency when the soundness judgment is performed periodically and temperature changes are given. By analyzing the change in the rate of increase over time, it is possible to predict the deterioration of the structural performance of concrete and reinforcing bars in the future before fatal damage occurs.

  For example, when the test of the present invention is performed as a periodic check several times from immediately after a new construction, when data showing an increase rate of the natural frequency over time as shown in FIG. It can be diagnosed that the deterioration of performance (reinforcing bar and concrete is in close contact) or cross-sectional defect due to corrosion (rusting and rebar thinning) is progressing. Reinforcing bar adhesion performance deteriorates when the reinforcing bar rusts. When the reinforcing bars rust and become worn out and the adhesion performance deteriorates, the estimated value of the reinforcing bar ratio obtained from the present invention becomes smaller. That is, the estimated value of the reinforcing bar ratio fluctuates and becomes small before and after rusting. Here, since the increase rate of the natural frequency and the reinforcing bar ratio are inversely related, the evaluation value of the reinforcing bar ratio decreases as the increase rate of the natural frequency increases over time (the apparent reinforcing bar ratio decreases). ) Here, if the upper limit value of the increase rate of the natural frequency is calculated backward from the minimum reinforcing bar ratio allowed in terms of structure, the time when the reinforcing bar ratio becomes insufficient can be predicted at an early stage. For example, in FIG. 10, at 30 years later, it can be expected that there will be a shortage of reinforcing bar ratio during the next 10 years.

  In addition, as shown in FIG. 11, the natural frequency does not fall below 0% (the frequency increases after heating), but when data that has decreased over time is obtained, the concrete frequency is Although there is no damage, slight structural deterioration has progressed, and it can be judged that there is a risk of damage to concrete. For example, in Fig. 11, at 30 years later, it is highly likely that the natural frequency increase rate will turn negative within the next 10 years, that is, there is a high possibility of cracking in concrete. Predictable.

  Although not shown in the figure, if periodic inspection results show that the increase rate of natural frequency during heating is constant over time, structural and structural damage or deterioration of concrete and rebar Can be diagnosed as not present and not progressing.

  As described above, the concrete structural member is subjected to a temperature change that causes a non-uniform temperature distribution in the cross section of the member, and the change in the natural frequency of the concrete structural member after the temperature change is periodically detected. The data on the rate of increase of the natural frequency is accumulated and the concrete or rebar at this stage depends on whether the time-series transition of the rate of increase is decreasing, increasing, or constant. Predicting the future progress of cross-sectional defects due to structural deterioration of concrete members or deterioration of rebar adhesion performance or corrosion due to corrosion evaluation of structural members that are evaluated as having no damage in their structural performance can do.

  Therefore, the present inventors investigated the pattern of change over time of the natural frequency for each of an unreinforced concrete column, a healthy reinforced concrete column, and a reinforced concrete column in which the concrete portion is damaged. As a result, when the concrete structural member 1 is an unreinforced concrete column, the natural frequency at the time of heating increases rapidly, and when the concrete structural member 1 is a healthy reinforced concrete column, the natural vibration at the time of heating. When the number rose slightly and gently, and the concrete structural member 1 is a reinforced concrete column in which the concrete portion is damaged, the phenomenon that the natural frequency during heating is suddenly and greatly reduced was found and confirmed.

  As the test concrete structural member 20, there are three types of concrete columns (hereinafter referred to as test columns): unreinforced concrete without reinforcing bars, reinforced concrete, and damaged concrete that contains reinforcing bars but is intentionally damaged. Prepared). By the way, the damage test column was loaded and damaged from the side of the rebar test column with a hand-held hydraulic jack until the maximum strength was reached. Moreover, the size of the test column 20 is a columnar object of 10 × 10 × 56 cm (see FIGS. 12 and 13). Then, an experiment was performed on the three types of test columns having the same size to monitor the change with time of the natural frequency using the soundness determination device 4 shown in FIG. The reinforced concrete columns used in this experiment are those in which rebars with a diameter of 1 cm are inserted at four corners with a cover thickness (distance from the outer surface of the column to the surface of the nearest rebar) of 10 mm, and the rebar ratio is 3.2. %.

  The above three test columns are all set up on the floor 3 (see FIG. 12 and FIG. 13) in the same state under the same conditions, and the soundness determination device 4 is the same for each column. Set to

  The test column 20 was fixed at the lower end to the floor 3 and the upper end as a free end. The free vibration generator 9 hits the upper part of the test column 20 with the hammer 8, and the vibration sensor 10 was installed at the top of each column. The vibration sensor 10 was connected to the vibration analyzer 11. In addition, a display device 12 is connected to the vibration analyzer 11 so that a change with time of the natural frequency can be monitored through a screen of the display device 12. Further, the rubber heater 5 was attached to one side surface of the test column 20 (hereinafter, this surface is referred to as “front surface” and the opposite surface is referred to as “back surface” in the present embodiment). Further, a thermometer 21 is installed on the installation surface of the rubber heater 5 of the test column 20, and a thermometer 22 is installed on the back surface of the test column. In addition, a thermometer 23 is installed inside the test column 20 near the installation surface of the rubber heater 5. A thermometer 24 was embedded inside the column 20 near the back surface.

  The experiment was conducted at a constant room temperature of 25 ° C., and heating was performed once for 2 hours with the rubber heater 5 and repeated four times in a 6-hour cycle. Here, the amount of heat of the rubber heater 5 is the difference between the internal and external temperature (the difference between the test column surface temperature and the back surface temperature) 2 hours after the start of heating, that is, the temperature measured by the thermometer 21 and the temperature measured by the thermometer 22. The difference was adjusted to 10 ° C. Specifically, after 2 hours from the start of heating, the surface temperature heated by the heater was adjusted to 45 ° C., and the back surface temperature not heated was adjusted to 35 ° C.

  The experimental results are shown in FIG. FIG. 14A is a graph showing a change in temperature with time measured by the thermometers 21 to 24. In FIG. 14 (a), the uppermost graph shows the change over time of the temperature measured by the thermometer 21, and the graph located one below is the time of the temperature measured by the thermometer 23. The graph located at the bottom of the graph shows the change over time of the temperature measured by the thermometer 24, and the graph located at the bottom shows the temperature measured by the thermometer 22. It shows a change with time. FIG. 14B is a graph showing a change with time of the natural frequency of the unreinforced concrete column 20. FIG.14 (c) is a graph which shows the time-dependent change of the natural frequency of a sound reinforced concrete column. FIG.14 (d) is a graph which shows the time-dependent change of the natural frequency of the reinforced concrete column where the concrete part is damaged. Here, the vertical axis in FIG. 14 (a) is the concrete structural member temperature (° C.) indicated by the thermometer, the vertical axis in FIGS. 14 (b) to 14 (d) is the natural frequency of the concrete structural member, and FIG. The horizontal axis of FIGS. 14 (d) to 14 (d) indicates the material age, which is indicated by the number of days since each test column was placed.

  From the respective graphs shown in FIGS. 14B and 14C, in the case of the unreinforced concrete column 20, the natural frequency at the time of heating increases rapidly, and in the case of a healthy reinforced concrete column, the heating. It can be seen that the natural frequency at the time increases slightly and slowly. In other words, it can be seen that the change over time in the natural frequency during the heating of a sound reinforced concrete column is smaller than that in the case of the unreinforced concrete column 20. From this, it can be predicted that the rate of increase of the natural frequency during heating increases as the reinforcing bar ratio decreases (the amount of reinforcing bars decreases). Also, when the concrete column contains reinforcing bars but the reinforcing bars are not attached to the concrete, the natural frequency change pattern with time of the natural frequency of the unreinforced concrete column 20 is almost the same. It is possible that

  On the other hand, it can be seen from the graph shown in FIG. 14 (d) that the natural frequency of the reinforced concrete column in which the concrete portion is damaged decreases rapidly and greatly when heated. Accordingly, it is possible to distinguish between a healthy reinforced concrete column and a reinforced concrete column in which the concrete portion is damaged depending on whether the natural frequency is increasing or decreasing.

  Incidentally, in this experiment, heating by the rubber heater 5 was repeated four times in a 6-hour cycle, but the same frequency change pattern with time could be obtained each time heating was performed. Therefore, it was confirmed that the natural frequency pattern with time was reproducible.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the concrete structural member 1 has been described by taking an example of monitoring the pattern of change over time in the natural frequency of a square column. However, the concrete structural member 1 is not necessarily limited to a column, and concrete. It may be a beam, floor or wall made of a structure. For example, when judging the soundness of the floor, the floor surface is heated with a rubber heater 5 or a halogen heater, and the floor is intermittently hit with a temperature difference between the front surface and the back surface. Thus, the natural frequency of the vibration generated by the impact may be obtained and the change with time of the natural frequency may be monitored.

  In addition, the present invention has been mainly described with an example in which temperature stress is generated by giving a temperature change that causes a non-uniform temperature distribution in the cross section of the concrete structural member. In order to evaluate the soundness of concrete structural members by detecting changes in the natural frequency of concrete structural members and estimating the damage to concrete or deterioration of structural performance of reinforcing bars It is also possible. If the temperature is raised so that the temperature rises uniformly in all sections of the concrete, that is, temperature stress does not occur, damage to the concrete structural member occurs due to a phenomenon called “material softening due to heating” Even if not, the natural frequency is slightly reduced. Therefore, when the temperature of the concrete structural member is raised uniformly, the natural frequency decreases slightly when the concrete is healthy without cracks, and (b) the natural frequency decreases greatly when there is a crack. It becomes. Therefore, the difference between (a) and (b) can be distinguished by pattern comparison by collecting and generalizing a large number of data.

  In addition, regarding the means for giving a temperature change or the means for measuring the natural frequency in the diagnostic method for concrete structural members, according to the above-described method of vibration by impact or heating using an artificial heat source, the magnitude as intended The natural frequency and temperature difference can be easily given, and it is preferable because it can be diagnosed much more easily.However, the excitation method and the temperature difference application method are not limited to this, and it is also possible to use temperature and sunshine, Furthermore, it is possible to combine these natural heat sources and artificial heat sources. For example, one surface may be cooled, or the temperature change may be given by a combination of radiation heating by sunlight or the like and radiation cooling in the shade. Furthermore, the temperature difference between the inside and outside of the building may be artificially created by forcibly heating or cooling the inside of the building by air conditioning. Further, it is effective to prepare a heater in a concrete structural member such as a concrete column in advance and turn it on / off because a temperature difference is generated between the periphery and the center. However, in this case, the temperature difference in the cross section does not increase.

It is the block diagram which looked at the soundness determination apparatus and concrete structure member which enforce the soundness determination method of the concrete structure member concerning this invention from the front side. It is the block diagram which looked at the soundness determination apparatus and concrete structure member which enforce the soundness determination method of the concrete structure member concerning this invention from the right side surface side. It is an image figure which shows the shape of the vibration of a concrete structural member. It is a graph which shows the free vibration waveform of a concrete structural member. It is a figure which shows the temperature distribution of a rubber heater and a concrete structure member after the heating of a concrete structure member. It is a figure which shows the stress distribution after the heating of a concrete structural member. It is a schematic diagram of the fluctuation | variation of the natural frequency at the time of the presence or absence of damage in the damage diagnosis of concrete. It is a schematic diagram which shows the example of the time passage of the natural frequency when diagnosing a reinforcing bar ratio. It is a schematic diagram which shows the relationship between a reinforcing bar ratio and a natural frequency. It is a graph which shows the example of the time-dependent change of the natural frequency which shows aged deterioration of a reinforcing bar ratio. It is a graph which shows the example of the time-dependent change of the natural frequency which shows aged deterioration of concrete damage. It is the block diagram which looked at the test pillar and the soundness determination apparatus set with respect to this pillar from the front side. It is the block diagram which looked at the test pillar and the soundness determination apparatus set with respect to this pillar from the right side surface side. It is a graph which shows a time-dependent change of the data obtained in the experiment of Example 1, (a) is a graph which shows a time-dependent change of the temperature of a test column, (b) shows a time-dependent change of the natural frequency of an unreinforced concrete column. A graph, (c) is a graph which shows a time-dependent change of the natural frequency of a healthy reinforced concrete column, (d) is a graph which shows a time-dependent change of the natural frequency of the reinforced concrete column where the concrete part is damaged.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Concrete structural member 4 Soundness determination apparatus 5 Rubber heater 9 Free vibration generator 10 Vibration sensor 11 Vibration analyzer 20 Test column (concrete column)

Claims (17)

The concrete structural member is subjected to a temperature change that causes a non-uniform temperature distribution in the cross section of the member, the change in the natural frequency of the concrete structural member after the temperature change is detected, and the change in the natural frequency A method for judging the soundness of a concrete structural member, in which when there is a tendency to increase or remain constant, there is no structural damage to the concrete, and when there is a tendency to decrease, the concrete is judged to have structural damage. The concrete structural member is intermittently hit, and the natural frequency is calculated from the vibration of the concrete structural member generated by the hit, and the pattern of change with time of the natural frequency is obtained. The method for determining the soundness of a concrete structural member according to claim 1, wherein the direction of change of the natural frequency is determined. The concrete structure according to claim 1, wherein a change in the natural frequency after the temperature change is obtained by comparing the change in the natural frequency of the concrete structural member with the natural frequency before the temperature change. A method for determining the soundness of a member. Giving a non-uniform temperature change in the cross-section to the concrete structural member, measuring the change in natural frequency of the concrete structural member after giving the temperature change, obtaining an increase rate of the natural frequency, the increase rate The soundness of a concrete structural member is judged by using the structural performance of the reinforcing bar as an evaluation index by comparing with the rate of increase of the natural frequency at the time of temperature change of the sound concrete structural member. Method. A correlation between the increase rate of the natural frequency and the reinforcing bar ratio when the non-uniform temperature change is applied to the concrete structural member having a known reinforcing bar ratio is obtained in advance, and the temperature difference is calculated using this correlation. 5. The method for judging the soundness of a concrete structural member according to claim 4, wherein the reinforcing bar ratio is estimated from a rate of increase in the natural frequency of the concrete structural member after being applied. The concrete structural member is intermittently hit with the non-uniform temperature change in the cross section, and the natural frequency is calculated from the vibration generated by the hit, and the natural frequency is elapsed over time. The method for determining the soundness of a concrete structural member according to claim 4 or 5, wherein a change pattern is obtained and an increase rate of the natural frequency is determined from the pattern. 6. The method for determining the soundness of a concrete structural member according to claim 4 or 5, wherein an increase rate of the natural frequency of the concrete structural member is obtained by comparison with a natural frequency before temperature change. The concrete structural member is subjected to a temperature change that results in a non-uniform temperature distribution in the cross section of the member, and the change in the natural frequency of the concrete structural member after the temperature change is periodically detected and the When data on the rate of increase or change in natural frequency is accumulated, and the time-series transition of the rate of increase or change is decreasing, it may cause minor damage that may lead to concrete damage or concrete damage in the future. Method for determining the soundness of a concrete structural member that diagnoses that any of the deteriorations is progressing. The concrete structural member is subjected to a temperature change that results in a non-uniform temperature distribution in the cross section of the member, and the change in the natural frequency of the concrete structural member after the temperature change is periodically detected and the Accumulation rate or change data of natural frequency is accumulated, and when the increase rate or change time-series trend is increasing, cross-sectional defect due to rebar deterioration or corrosion progresses and structural performance of rebar A method for determining the soundness of a concrete structural member that diagnoses that the deterioration of the steel is progressing. The method for determining the soundness of a concrete structure member according to any one of claims 1 to 9, wherein the uneven temperature change given to the concrete structure member is realized by a natural phenomenon such as air temperature or sunlight. . The method for determining the soundness of a concrete structural member according to claim 1 or 9, wherein the uneven temperature change given to the concrete structural member is realized by forcibly heating by an artificial heat source. The soundness determination method for a concrete structure member according to any one of claims 5 to 9, wherein the uneven temperature change given to the concrete structure member is forcibly cooled by an artificial heat source. The concrete according to any one of claims 1 to 9, wherein the uneven temperature change given to the concrete structural member is realized by forcibly heating one surface with an artificial heat source. A method for determining the soundness of structural members. The concrete structural member according to any one of claims 5 to 9, wherein the uneven temperature change given to the concrete structural member is realized by forcibly cooling one surface by an artificial heat source. Soundness judgment method. The uneven temperature change given to the concrete structural member is realized by forcibly heating one surface with an artificial heat source and simultaneously cooling the other surface. The soundness judgment method of the concrete structure member as described in any one. 16. The method for determining the soundness of a concrete structure member according to claim 11, wherein the artificial heat source is a heater directly attached to the concrete structure member. The method for determining the soundness of a concrete structural member according to any one of claims 12, 14 and 15, wherein the artificial heat source is an indoor air conditioner.

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