CN115308063A

CN115308063A - Concrete strength sampling detection method for existing building

Info

Publication number: CN115308063A
Application number: CN202211014285.5A
Authority: CN
Inventors: 刘祥锦
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-08-23
Filing date: 2022-08-23
Publication date: 2022-11-08

Abstract

The invention discloses a concrete strength sampling detection method for an existing building, relates to a building detection technology, and provides a scheme aiming at the contradiction between the damage degree caused by detection and the evaluation accuracy in the prior art. Detecting and classifying the components of the existing building in batches; randomly sampling the components in a test batch in proportion; detecting the concrete quality or strength of all the sampling components by using a non-destructive detection method, and counting and sequencing detection results; calibrating quantiles of the counted and sequenced detection results; and accurately detecting the members corresponding to the scores to estimate the final result of the detection of the batch of concrete. The method has the advantages that the damage frequency to the building is reduced on the basis of ensuring the detection precision by utilizing the positive correlation between the non-damage detection method and the concrete strength. The number of loose cores is reduced, so that the construction cost is effectively reduced, and the property and life safety is guaranteed.

Description

Concrete strength sampling detection method for existing building

Technical Field

The invention relates to a concrete detection technology, in particular to a concrete strength sampling detection method for an existing building.

Background

The structural safety of the existing buildings needs to be fully evaluated when the existing buildings have changed functional purposes, are modified or reach the service life. With the longer construction annual cost, the corresponding construction data are generally stored less, and the existing construction data of more than ten years are insufficient or even unavailable. The construction is changed into the construction without exploration, design and completion data. The evaluation of such buildings requires the detection of meeting national standards, where concrete strength is the most important task in relation to the safety evaluation of the building and the property and life safety.

The existing concrete strength detection comprises the following steps:

the core-pulling method with the best accuracy for evaluating the concrete strength is difficult to directly apply to actual work due to high cost, large sample capacity (national standard requirement is not lower than 15 samples) and damage to buildings. How to reduce the damage to the building and ensure the evaluation accuracy is a problem sought to be solved in the industry all the time.

Disclosure of Invention

The invention aims to provide a concrete strength sampling detection method for an existing building, so as to solve the problems in the prior art.

The invention discloses a concrete strength sampling detection method of an existing building, which comprises the following steps:

s1, detecting and dividing members of an existing building in batches, and randomly sampling according to the proportion of the number of the detecting and dividing members in batches;

s2, detecting the concrete quality or strength of all the sampling components by using a non-destructive detection method, and sequencing detection results;

s3, calibrating quantiles of the detection results after statistics and sequencing;

s4, accurately detecting components corresponding to the quantiles;

and S5, estimating a final result of the concrete detection of the detection batch of the components.

In step S1, the inspection lot is classified by layer and component type.

In step S2, the non-invasive detection method is an ultrasonic method or a rebound method.

In step S2, the sorting is a decreasing sorting, which is an increasing or decreasing sorting.

In step S3, the quantile is one or more; the quantile is the quantile of the detected number or the quantile of the detected value.

When the quantile is one, the quantile is any value of the inspection result, and is usually an average value or a minimum value; when the quantile is plural, it may be any value between 0.01% and 99.99%, and positions corresponding to 75%, 50%, and 25% and the minimum value position are generally used.

Taking one or more than one measuring area for each component, and setting a plurality of detecting points in each measuring area; and obtaining the average value of a plurality of detection points of each detection area of each component as the detection result.

In step S4, performing accurate detection as core-pulling detection;

in step S5, it is estimated that the final result of the concrete inspection of the inspection lot is performed by the probabilistic method.

The probability method is weighted statistics and is estimated according to the national standard method.

The sampling detection method for the concrete strength of the existing building has the advantages that the damage frequency to the building is reduced on the basis of ensuring the detection precision by utilizing the positive correlation between the non-damage detection method and the concrete strength. And the number of loose cores is reduced, so that the construction cost is effectively reduced, and the property and life safety is ensured.

Drawings

Fig. 1 is a schematic flow chart of a concrete strength sampling detection method of an existing building according to the invention.

Detailed Description

The concrete strength sampling detection method of the existing building is shown in the specific flow chart of fig. 1 and is explained by the following embodiment.

Example one

A5-layer old building is built before 2010 and is a private homestead building, and the existing data does not contain design drawings and construction completion data. At present, as the business application, each layer of columns has 13, the beams have 32, the method has been used for more than 12 years, namely more than 3000 days, the rebound method or the ultrasonic rebound method cannot be used, only the core-pulling method can be adopted, and even other methods such as the post-pulling-out method and the post-anchoring method after the ultrasonic rebound method are adopted, the core-pulling method detection is required to be carried out for correction. The following steps are carried out in batches according to layers by taking the column of the first layer as an example:

randomly sampling according to the proportion according to the quantity of various components in a detection batch; 13 columns in each layer are used for meeting the statistical sample size, and the sampling proportion is 100 percent, namely the total number is subjected to spot check. Each column is provided with 2 measuring areas, each measuring area is provided with 3 detecting points, and the general investigation is carried out by adopting an ultrasonic method. And carrying out general survey on the quality or the strength of the sampling component, and finding out the quality or the strength of the sampling batch sample. For the same batch of concrete, the quality or strength is in positive correlation with the speed of the ultrasonic wave passing through the concrete member, and the higher the speed is, the better the quality or the higher the strength of the concrete member is. Columns with the same detection items, the same quality requirements and the basically same production process are listed in the same batch.

And (3) adopting and detecting 13 sampled columns by using a concrete ultrasonic detector, wherein 2 detection areas are uniformly distributed on each column from bottom to top. The number of members can be adjusted as desired between 1-10 points, in this case 3 points per area. The ultrasonic concrete detecting instrument is calibrated mainly by measuring its initial reading t ₀ And detecting the sampled 13 column samples one by one, and recording the position numbers of the columns and the corresponding detection data values thereof. Particularly, an ultrasonic detection method for an uncompacted area in concrete is adopted, and the detected numerical value is ultrasonic wave speed-the speed of ultrasonic waves passing through a concrete member, V _d ＝L/(t _i -t ₀ )，V _d As the point of wave velocity (km/s), t _i To detect point sound, t ₀ Is the initial reading of the detection instrument (time delay of the instrument itself) (in mus) and L is the distance of the ultrasound measurement at the detection point (in mm). Obtaining the wave velocity V of 3 detection points in each measurement area of each column by measuring 2 measurement areas of 13 columns _d Average value of 13 × 2=26 detection area wave velocities V _d . The specific method for detecting the sound velocity is carried out according to the national relevant technical regulations.

Sequencing according to the data size of the sampling members, wherein the mass or the strength is positively correlated with the speed of the ultrasonic wave passing through the concrete member, and the speed is higher to indicate that the mass of the concrete member is better or the strength is higher; therefore, the relative quality or strength of the sampling inspection component is sorted, and the following list is sorted from high to low:

and determining one or more quantiles needing to be detected next from the quality or strength high-low ranking or the low-high ranking. In this embodiment, two cases of one quantile and four quantiles are respectively explained as follows:

in the first case, the safety of the house is designed (determined) if only the lowest value of the concrete of the layer of columns is obtained. And taking the quantile as the minimum value, namely keeping the value rate of statistics to be more than 99% and keeping the quantile to be 0.01). And further accurately detecting the concrete strength of the detection parts of part or all of the components corresponding to the detected quantiles. Core-pulling detection is carried out on the lowest three detection areas in the table, and the detection data are respectively 17.8MPa,17.0MPa and 17.3MPa; the average value is 17.4MPa; the result is that the safety of the house is calculated by 17.4 MPa.

In the second case, if the safety of the house is designed (determined) as long as the estimated value (required by the national standard regulation method) of the statistical probability guarantee rate of 95% of the layer of column concrete is obtained, the quantile is divided into 4 points (namely the statistical guarantee rate is greater than 75%, 50%, 25% and the minimum value).

Statistical sound velocity average: v _dm =3.34 (km/S), standard deviation of sound speed S =0.077 (km/S), and the median V of the maximum value and the average value is taken as the 75% value _0.75 =3.41 (km/S); the 25% value is the median V of the maximum and mean values _0.25 ＝3.28(km/S)。

Concrete strength is further accurately detected at detection parts of part of components respectively corresponding to 75%, 50%, 25% and the minimum value of the detected quantiles, specifically core-pulling detection is carried out in detection areas with sound velocities of 3.41 (km/S), 3.34 (km/S), 3.28 (km/S) and 3.21 (km/S), and detected data are shown in the table.

And carrying out statistics on the concrete accurate strength of the detected members in the detection batch, and estimating the concrete strength rate fixed value of all the members in the detection batch according to the related fixation. The statistics are weighted statistics. The weight is the number of the sound velocity at the core-pulling detection position and the maximum sound velocity or the first-stage sound velocity measurement (below the sound velocity at the last core-pulling position).

And (3) weighting statistical results:

average intensity value: f. of _cm ＝(7x24.2+7x22.0+6x19+6x17.3)/26＝20.8MPa；

Standard deviation: s =2.71MPa;

according to the strength estimation value of the core-pulling concrete of relevant specifications,

upper limit of law (assumed) value: f. of _cm1 ＝20.8-1.255x2.71＝17.4MPa；

Lower limit of law (estimate): f. of _cm2 ＝20.8-2.220x2.71＝14.8MPa；

Because f is _cm1 -f _cm2 =17.4MPa8-14.8MPa, =2.6MPa < 5MPa; therefore, the safety of the house is directly calculated by adopting 17.4 MPa.

Wherein, when the specification stipulates 26 sample capacities for 1.255 and 2.220, the quantile is 0.05, namely, the upper limit coefficient and the lower limit coefficient which guarantee the probability of 95%.

The conclusion is consistent through the two kinds of accurate detection after sequencing, but the first type only needs 2-3 loose cores and the second type only needs 5-6 loose cores, if the traditional random loose core detection method needs 15 loose cores at least, the work load of the random or sampling ultrasonic rebound method is much larger, and the rebound working time is 2 times of that of ultrasonic waves, 6 loose cores with the diameter of 100mm or 10 loose cores with the diameter of 70 mm. Therefore, the method is proved to be capable of reducing the workload under the condition of reducing the damage of the building and also be accurate.

Example two

A4-layer standard factory building is built as a clothing factory before 1999, and the existing materials lack the original design drawings and construction completion data. The application needs to be changed into an electronic factory, one layer of the electronic factory has an area of 3000 square meters, 66 columns and beams on each layer have 80 columns and beams, the electronic factory is used for more than 22 years and more than 7000 days at present, a rebound method or an ultrasonic rebound method cannot be used simply, only a core-pulling method is adopted, and even other methods such as an ultrasonic rebound method post-pulling-out method and a post-anchoring method need to be used for detection and correction by the core-pulling method. The following steps are carried out in batches according to layers by taking the column of the first layer as an example:

randomly sampling according to the proportion according to the quantity of various components in a detection batch; specifically, the minimum detection capacity of the regulation (detection standard B) is 13 randomly extracted from 66 columns in each layer for strength detection, the detection capacity of the high standard (detection standard C) is 20 randomly extracted from the columns in each layer, and the technical specification JGJ/T384-2016 for detecting the concrete strength by a core-extracting method requires no less than 15 samples. Therefore, 20 samples were used in this example.

And carrying out general survey on the quality or the strength of the sampling component, and finding out the quality or the strength of the sampling batch sample. And detecting 20 sampled columns by adopting a concrete ultrasonic detector, wherein 3 measuring points are uniformly distributed on each column from bottom to top. The number between 3 and 10 measuring points can be adjusted by the skilled person according to the technical needs of the actual field. And (4) calibrating the concrete ultrasonic detector, detecting the sampled 20 column samples one by one, and recording the detection data values of the position numbers of the columns. Specifically, an ultrasonic detection method is adopted for the uncompacted area in the concrete, and the detected numerical value is the ultrasonic wave speed. Obtaining the wave velocity V of 3 detection points of each column sample by respectively measuring 3 detection points of 20 columns _d All of the detected spot wave velocities V are 20x3=60 _d . The specific method for detecting the sound velocity is carried out according to the national regulation.

And sorting according to the quality or strength data of the sampling components, namely sorting from high to low or from low to high according to the relative quality or the height of the relative values. Because concrete quality or strength is directly related to the speed of the ultrasonic waves through the concrete member, the greater the speed, the better the quality or strength, or the higher the strength. The mass or intensity data of the sampling member thus directly corresponds to the wave speed V of the sampling member _d . There are at least two kinds of methods counted in this embodiment: first, wave velocity V is measured at 60 detection points _d For statistical purposes, the mean or median, maximum, minimum and standard deviation were calculated. Second 3 detection point wave velocity V of each sample member of 20 column samples _d Calculate the average value V _dm For statistical purposes, the mean or median, maximum, minimum and standard deviation were calculated. The following table shows the wave velocity V at 3 detection points of 20 column members _d The minimum is statistic:

calculated average value V _dm =4.37, standard deviation S =0.06, median V _m =4.38 and 4.37.

Finding out quantiles needing to be accurately detected in the next step from the quality or intensity ranking; and finding out component detection points corresponding to four quantiles respectively, namely an average value or a median value, a minimum value, a median between the median and the minimum value, and a median between the median and the maximum value according to the data, selecting 1 or 2 detected point positions according to each special representative value, and taking 4 or 8 detected point positions as point positions for the next detection. It should be noted that, in total, 60 detected point locations may have 1 or several detected point values for each representative value. For example, only 1 or no completely equal point locations that are adjacent to the particular value of the range may represent the point location of the representative value. The maximum value is not selected in the process, so that the discreteness of final statistics can be reduced, and the safety and the reliability of the statistics can be better ensured.

And (3) performing core-pulling detection on the selected 4 quantiles corresponding point positions by adopting a core-pulling method on part or all components corresponding to the quantiles which are accurately detected to obtain 4 or 8 concrete strength values. The core-pulling detection is the most accurate method for detecting the strength of the existing building concrete.

And counting the concrete accurate strength of the detected members in the current detection batch, and estimating the concrete strength rate fixed value of all the members in the detection batch according to related fixation. And (3) performing weighted statistics on 4 concrete strength values obtained by core pulling detection, and if 8 concrete strength values adopt an average value with each quantile point as strength to perform weighted statistics, performing corresponding weighted statistics on the number of detection components (or the number of measuring points) with the highest sound velocity value and the second accurate detection quantile in a high-to-low sequence, or the number between the second accurate detection quantile and the number of detection components (or the number of measuring points) with more quantile sound velocity values. And obtaining the concrete rate fixed value of the layer of column according to the relevant regulations of national regulations, thereby determining the concrete strength value.

And (4) weighting statistical results:

average value of intensity: f. of _cm ＝(41.5x5+37.8x5+36.2x5+35.8x5)/20＝38.1(MPa)；

Standard deviation: s =2.34 (MPa);

according to the estimated value of the strength of the core-pulling concrete of relevant specifications,

concrete strength estimation upper limit value: f. of _cu,c1 ＝f _cm --S*k1＝38.1-2.34x1.1746＝35.4(MPa)；

The lower limit value of the concrete strength estimation is as follows: f. of _cu,c2 ＝f _cm --S*k2＝38.4-2.34x2.2078＝32.9(MPa)；

Because f is _cu,c1 -f _cu,c2 ＝35.4MPa-32.9MPa＝2.5MPa<5MPa meets the presumptive requirement. 35.4MPa can be used as a representative value for this column; the value-preserving rate of the strength of 35.4MPa is not less than 95 percent according to the statistics of national standard presumption probability; rather than the sampled minimum of 35.8MPa.

Where k1=1.1746 and k2=2.208 are assigned to the specification for 20 sample capacities, the upper limit coefficient and the lower limit coefficient of the quantile 0.05 are assigned. In this example, only 20 columns were extracted, and 60 columns were always extracted, and the concrete strength of 35.8MPa directly obtained by using the member (column) having the minimum sound velocity value in the full sampling method of the first example could not be used.

The embodiment accords with the national related minimum capacity detection, can find whether the column has defects in the first-stage detection of the column, and can well ensure that the second-stage detection is more purposeful and safer.

If the core-pulling method is adopted according to the existing detection method at present, 15 samples are required to be extracted for detection, and the statistics of the intensity of the 15 samples cannot necessarily meet the requirement of statistical discreteness. Because the discreteness of the concrete core-pulling strength is large, if the core-pulling range cannot be enlarged, sampling needs to be carried out on site for the second time, at least 10-15 samples are added, the workload is increased, the damage to the original building is large, and the cost is high. Although the method of the invention has 15 components (columns), the quality detection of 60 points is 4 times of that of direct core pulling, and the relativity of ultrasonic detection is very high, and the nondestructive detection is realized. Therefore, the technical effect of accurate measurement is ensured on the basis of reducing the damage.

It will be apparent to those skilled in the art that various other changes and modifications may be made in the above-described embodiments and concepts and all such changes and modifications are intended to be within the scope of the appended claims.

Claims

1. A concrete strength sampling detection method of an existing building is characterized by comprising the following steps:

s2, detecting the concrete quality or strength of all sampling components by using a non-destructive detection method, and sequencing detection results;

s4, accurately detecting components corresponding to the quantiles;

and S5, estimating a final result of the concrete detection of the detection batch of components.

2. The method for sampling and testing the concrete strength of the existing building according to claim 1, wherein in step S1, the test lots are classified according to the types of the floors and the types of the members.

3. The method for sampling and testing the concrete strength of the existing building according to claim 1, wherein in the step S2, the non-damage type testing method is an ultrasonic method or a rebound method.

4. The method for sampling and detecting the concrete strength of the existing building according to claim 1, wherein in the step S2, the sequence is a progressive sequence, and the sequence is an increasing sequence or a decreasing sequence.

5. The method for sampling and detecting the concrete strength of the existing building according to claim 1, wherein in the step S3, the quantile is one or more; the quantile is the quantile of the detected number or the quantile of the detected value.

6. The sampling test method for the concrete strength of the existing building according to claim 5, wherein when the quantile is one, the quantile is an arbitrary value of the inspection result, generally an average value or a minimum value; when the quantile is plural, it may be any value between 0.01% and 99.99%, and positions corresponding to 75%, 50%, 25%, and the minimum value position are generally used.

7. The sampling test method for the concrete strength of the existing building according to claim 1, characterized in that one or more test areas are taken for each member, and a plurality of test points are set for each test area; and obtaining the average value of a plurality of detection points of each detection area of each component as the detection result.

8. The sampling detection method for the concrete strength of the existing building according to claim 1, characterized in that in step S4, the accurate detection is core-pulling detection.

9. The method as claimed in claim 1, wherein the step S5 of estimating the final result of the concrete testing of the members is performed by a probabilistic method.

10. The method for sampling and detecting the concrete strength of the existing building according to claim 9, wherein the probability method is weighted statistics and is estimated according to a national standard method.