A method for identifying shear deformation of a concrete deep flexural member under strain and crack field

Abstract

The application discloses a kind of strain and crack field's concrete deep flexural member shear deformation identification method, it is related to deformation identification technical field, for solving the problem of shear force transmission participation opportunity not timely, by the crack identification of the deep flexural member of the measured concrete, extract crack direction information and select target crack, in crack evaluation period, the number of connected cracks is counted and the trend of crack direction stability is analyzed, and then directional aggregation characteristics are formed, shear span ratio data are introduced to generate shear configuration class, and the compression strut path zone inside the deep flexural member is demarcated according to the shear configuration class, the stirrups are classified and strain monitored, the shear stress growth characteristics are analyzed, and the shear constraint coefficient is calculated, to determine whether the compression strut path stirrups enter the actual shear force transmission state, to effectively identify the shear deformation stage of the deep flexural member and the shear force transmission participation behavior of the stirrups.

Description

Technical Field

[0001] This invention relates to the field of deformation identification technology, and more specifically, to a method for identifying shear deformation in concrete members subjected to bending under strain and crack field conditions. Background Technology

[0002] Concrete members subjected to bending are prone to diagonal cracks due to their small shear span ratio and complex stress path. The shear stress mechanism gradually changes from the concrete itself to the coordinated force transfer between steel reinforcement and concrete. In lightweight aggregate concrete, the shear resistance at the crack interface decreases faster, and the shear performance of the member is highly dependent on whether the stirrups participate in the shear force transfer in a timely manner.

[0003] The existing technology has the following shortcomings:

[0004] Currently, existing engineering monitoring methods mainly rely on ultimate bearing capacity tests, overall deflection indices, or single-point rebar strain thresholds for judgment. These methods are insufficient to identify whether the stirrups have transitioned from a structurally constrained state to a state of actual shear force transmission in the early stages after the formation of diagonal cracks. Furthermore, they lack a phased identification mechanism that combines the evolution characteristics of crack direction in the shear span with the path of compression members within the component. This results in an unclear correspondence between the strain response of the stirrups and the propagation behavior of diagonal cracks, making it difficult to determine the shear deformation stage and the timing of shear force transmission in a timely and accurate manner. Therefore, this paper proposes a method for identifying shear deformation in concrete members subjected to deep bending based on strain and crack field.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for identifying shear deformation in concrete members subjected to deep bending based on strain and crack field. This method addresses the problems mentioned in the background art by employing a periodic evaluation mechanism for crack trajectory evolution and connectivity characteristics, a shear configuration classification method under shear span ratio constraints, and a strain coupling analysis strategy based on the strut path band for web reinforcement classification.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for identifying shear deformation of concrete members subjected to deep bending in terms of strain and crack field, comprising the following steps:

[0008] Step S1: Identify cracks in the deep bending member of the concrete to be tested, obtain the crack direction information of the deep bending member and filter the target cracks, set the crack evaluation cycle, count the number of connected cracks of the target cracks and detect the diagonal angle data within the crack evaluation cycle.

[0009] Step S2: Analyze the trend towards stability based on the diagonal dip angle data, assess the directional aggregation characteristics by combining the number of connected cracks, and determine whether to enter the reinforcement monitoring stage. When entering the reinforcement monitoring stage, retrieve the shear span ratio data of the concrete to be tested and generate shear configuration steps.

[0010] Step S3: Delineate the compression path zone region of the bending member based on the shear configuration hierarchy, classify and mark the web reinforcement in the compression path zone region as compression path web reinforcement or control shear web reinforcement, perform strain detection on the classified and marked web reinforcement and obtain web reinforcement strain data;

[0011] Step S4: Analyze the shear force growth characteristics using the strain data of the web reinforcement, collect the crack width of the target crack and calculate the shear constraint coefficient, combine the shear force growth characteristics to generate the shear force transmission state of the web reinforcement of the compression bar path and determine whether a shear force transmission participation signal is generated.

[0012] In a preferred embodiment, in step S1, cracks are identified in the deep bending member of the concrete under test by a crack imaging sensor, and an image of the surface crack distribution of the deep bending member is obtained.

[0013] After image binarization processing of the surface crack distribution image, crack orientation information is extracted, including the skeleton lines of each crack in the bending member.

[0014] The main direction of the cracks in the crack skeleton line is obtained by linearly fitting each crack skeleton line using the least squares linear fitting algorithm.

[0015] Using the longitudinal axis of the member subjected to severe bending as the directional baseline, the angle between the main direction of the crack and the directional baseline is taken as the crack direction angle.

[0016] Access the crack database to obtain the target crack orientation angle range. If the crack orientation angle is within the target crack orientation angle range, then filter the crack skeleton line as the target crack.

[0017] Conversely, crack skeleton lines are not considered target cracks.

[0018] In a preferred embodiment, in step S1, a crack evaluation period is preset, and the minimum spatial distance between the crack skeleton line corresponding to the target crack and other crack skeleton lines is calculated. When the minimum spatial distance is less than a preset spatial connectivity threshold, it is recorded as a connected crack of the target crack.

[0019] The number of connected cracks within the evaluation period is counted as the number of connected cracks for the target crack.

[0020] Within the preset crack assessment period, the crack orientation angle of the target crack is continuously collected to obtain the crack dip angle sequence.

[0021] The diagonal dip angle data is obtained by subtracting the strike angles of adjacent cracks in the crack dip angle sequence.

[0022] In a preferred embodiment, in step S2, if the tilt angle data is less than a preset tilt angle threshold, the tilt angle data is marked; otherwise, the tilt angle data is not marked.

[0023] The dipping angle data of each marker are sorted in chronological order, and adjacent dipping angle data of markers are combined into a strike-stable segment;

[0024] The number of marked dipping angle data for each strike-stable segment is used as the strike-stable segment length, and the maximum value of the strike-stable segment length is used as the maximum stable segment length.

[0025] The trend toward stability is calculated based on the length of the maximum stable segment.

[0026] After standardizing the trend toward stability and the number of connected cracks respectively, we obtain the stability coefficient and the connected crack coefficient.

[0027] The directional clustering characteristics are calculated based on the stability coefficient and the connectivity crack coefficient.

[0028] In a preferred embodiment, in step S2, if the directional aggregation feature is greater than a preset directional aggregation threshold, it is determined that the abdominal muscle monitoring stage has been entered.

[0029] Conversely, if the condition is not met, it is determined that the abdominal muscle monitoring phase will not begin.

[0030] The shear span ratio data of the concrete to be tested is retrieved from the component information database. The shear span ratio data refers to the ratio of the shear span length to the effective height of a member subjected to severe bending.

[0031] A first scissor span ratio grading threshold and a second scissor span ratio grading threshold are preset, and the first scissor span ratio grading threshold is greater than the second scissor span ratio grading threshold;

[0032] The shear span ratio data is compared with the preset first shear span ratio classification threshold and the second shear span ratio classification threshold to generate shear configuration levels;

[0033] Shear configuration classes include bending-shear dominant configuration class, compression bar web synergistic shear configuration class, and compression bar dominant shear configuration class.

[0034] In a preferred embodiment, in step S3, for the bending-shear dominant configuration class, based on the component geometric parameters and force boundary conditions, the compression bar path zone area is preset to be the compression bar path zone area covering the web reinforcement of the shear zone;

[0035] For the compression bar web reinforcement cooperative shear configuration level and the compression bar dominant shear configuration level, the line connecting the compression bar start point and the compression bar end point is taken as the compression bar center axis, and a preset path band width is set along the normal direction of the compression bar center axis to form the compression bar path band area;

[0036] Obtain the spatial arrangement parameters of the web reinforcement in a member subjected to severe bending, including the position coordinates of the web reinforcement in the longitudinal, vertical, and cross-sectional directions of the member;

[0037] The spatial inclusion relationship between the spatial location of the web reinforcement and the compression bar path zone is determined. If the longitudinal projection of a web reinforcement overlaps with the defined path zone area, the web reinforcement is marked as a compression bar path web reinforcement.

[0038] Otherwise, mark the abdominal fascia as the control sheared abdominal fascia.

[0039] In a preferred embodiment, in step S3, strain sensors are arranged on each marked web reinforcement. The strain sensors are fixedly installed along the axial direction of the web reinforcement to collect data on the axial strain change of the web reinforcement in real time during shear loading.

[0040] During the monitoring process, the strain signals of each fascia are continuously acquired at a preset strain sampling frequency to form a strain time series of the fascia:

[0041] The strain time series corresponding to the compression bar path web reinforcement is summarized into a compression bar path web reinforcement strain dataset, and the strain time series corresponding to the control shear web reinforcement is summarized into a control shear web reinforcement strain dataset.

[0042] In a preferred embodiment, in step S4, the strain growth rate of the web reinforcement is calculated using the strain difference between adjacent sampling times in the strut path web reinforcement strain dataset and the control shear web reinforcement strain dataset, thereby obtaining the strut path web reinforcement strain growth rate sequence and the control shear web reinforcement strain growth rate sequence.

[0043] The strain growth rate sequence of the compression bar path web reinforcement was statistically summarized, and its average strain growth rate was calculated as the shear force growth characteristic of the compression bar path web reinforcement. At the same time, the strain growth rate sequence of the control shear web reinforcement was subjected to the same statistical processing to obtain the shear force growth characteristic of the control shear web reinforcement.

[0044] The crack width data of the target crack is collected. During the rib monitoring stage, the crack width value of the target crack is continuously acquired at different time nodes through the crack width measurement sensor to form a crack width time series.

[0045] In a preferred embodiment, in step S4, starting from the entry into the reinforcement monitoring stage and ending at the current time, an analysis window is established. Within the analysis window, the average strain increase of the reinforcement along the compression bar path and the crack width increment of the crack width time series are calculated.

[0046] The ratio of the average strain increase to the crack width increase is used as the shear constraint coefficient.

[0047] Specifically, when the shear force growth characteristics of the compression bar path web reinforcement are higher than those of the control shear web reinforcement, and the shear constraint coefficient is greater than the preset shear constraint threshold, the compression bar path web reinforcement is determined to be in a shear force transmission participation state, and a shear force transmission participation signal is generated.

[0048] Conversely, if the web reinforcement along the compression bar path is determined to be in a state of not participating in shear force transmission, no shear force transmission participation signal will be generated.

[0049] The technical effects and advantages of this invention are as follows:

[0050] This invention identifies cracks in deeply bent concrete members, extracts crack direction information, and filters target cracks. Within the crack assessment period, it counts the number of connected cracks and analyzes the stability trend of crack direction, thereby forming directional clustering characteristics. Shear span ratio data is introduced to generate shear configuration levels, and based on this, the compression bar path zone region inside the deeply bent member is delineated. The reinforcement bars are then classified and strain monitored in a targeted manner. Shear stress growth characteristics are analyzed, and shear constraint coefficients are calculated. It is determined whether the compression bar path reinforcement bars have entered the actual shear force transmission state, thus achieving effective identification of the shear deformation stage of deeply bent members and the shear force transmission behavior of the reinforcement bars. Attached Figure Description

[0051] Figure 1 This is a flowchart illustrating the implementation of a method for identifying shear deformation in concrete members subjected to bending under strain and crack field, according to the present invention.

[0052] Figure 2 This is a schematic diagram illustrating the steps of a method for identifying shear deformation in a concrete member subjected to bending under strain and crack field according to the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] This invention identifies cracks in deeply bent concrete members, extracts crack direction information, and filters target cracks. Within the crack assessment period, it counts the number of connected cracks and analyzes the stability trend of crack direction, thereby forming directional clustering characteristics. It introduces shear span ratio data to generate shear configuration levels and delineates the compression bar path zone area inside the deeply bent member. It performs targeted classification and strain monitoring of the stirrups, analyzes the shear force growth characteristics, calculates the shear constraint coefficient, and determines whether the stirrups in the compression bar path have entered the actual shear force transmission state.

[0055] Example 1, such as Figures 1 to 2 As shown, a method for identifying shear deformation in concrete members subjected to high-intensity bending (CIB) based on strain and crack field includes the following steps:

[0056] Step S1: Identify cracks in the deep bending member of the concrete to be tested, obtain the crack direction information of the deep bending member and filter the target cracks, set the crack evaluation cycle, count the number of connected cracks of the target cracks and detect the diagonal angle data within the crack evaluation cycle.

[0057] Step S2: Analyze the trend towards stability based on the diagonal dip angle data, assess the directional aggregation characteristics by combining the number of connected cracks, and determine whether to enter the reinforcement monitoring stage. When entering the reinforcement monitoring stage, retrieve the shear span ratio data of the concrete to be tested and generate shear configuration steps.

[0058] Step S3: Delineate the compression path zone region of the bending member based on the shear configuration hierarchy, classify and mark the web reinforcement in the compression path zone region as compression path web reinforcement or control shear web reinforcement, perform strain detection on the classified and marked web reinforcement and obtain web reinforcement strain data;

[0059] Step S4: Analyze the shear force growth characteristics using the strain data of the web reinforcement, collect the crack width of the target crack and calculate the shear constraint coefficient, combine the shear force growth characteristics to generate the shear force transmission state of the web reinforcement of the compression bar path and determine whether a shear force transmission participation signal is generated.

[0060] The specific implementation is as follows:

[0061] In step S1, the surface cracks of the concrete member under deep bending are geometrically identified and their orientation features are extracted, which provides a reliable basis for accurately identifying shear-dominant cracks in the early stage of stress on the member under deep bending and for establishing subsequent shear force transmission analysis.

[0062] Cracks are identified in the deep bending concrete member under test by using a crack imaging sensor. The surface crack distribution image of the deep bending member is obtained. After image binarization processing of the surface crack distribution image, the crack direction information is extracted, including the skeleton lines of each crack in the deep bending member.

[0063] Among them, the bending member refers to the bending member whose span to section height ratio is less than the preset span-to-height ratio threshold. The preset span-to-height ratio threshold can be retrieved from design databases such as concrete structure design codes or engineering design standards.

[0064] Crack skeleton lines refer to the geometric extension path of cracks on the surface of deeply bent members, which are composed of a continuous sequence of pixels.

[0065] The least squares linear fitting algorithm is used to linearly fit each crack skeleton line to obtain the main crack direction of the crack skeleton line. The main crack direction is the direction vector that minimizes the sum of the squares of the vertical distances from each pixel point in the crack skeleton line to the fitted line, reflecting the overall extension direction of the crack.

[0066] Using the longitudinal axis of the member subjected to severe bending as the directional baseline, the angle between the main direction of the crack and the directional baseline is taken as the crack direction angle.

[0067] Access the crack database to obtain the target crack orientation angle range. The target crack orientation angle range refers to the range of crack orientation angle values ​​that are preset according to the development direction of the diagonal crack in the bending member under shear stress, and is used to screen the shear-dominant crack.

[0068] If the crack orientation angle is within the target crack orientation angle range, then the crack skeleton line is selected as the target crack.

[0069] Conversely, crack skeleton lines are not considered target cracks.

[0070] It needs to be explained that a crack imaging sensor is an image acquisition device used to collect images of cracks on the surface of concrete components; image binarization processing refers to the process of converting cracked areas and non-cracked areas in a crack distribution image into a binary image by segmenting them using a grayscale threshold; the least squares linear fitting algorithm is a linear fitting method that determines the main direction of the crack based on minimizing the sum of the squares of the vertical distances from each pixel to the fitted line; and the crack database is a database used to store the crack orientation angle ranges under different types of heavily bent components and historical monitoring conditions.

[0071] The crack assessment cycle is preset, and connectivity statistics are performed on the target crack. The crack skeleton line corresponding to the target crack and other crack skeleton lines are used as the connectivity determination objects. The minimum spatial distance between the crack skeleton line corresponding to the target crack and other crack skeleton lines is calculated by Euclidean distance algorithm. When the minimum spatial distance is less than the preset spatial connectivity threshold, it is recorded as a connected crack of the target crack.

[0072] The minimum spatial distance between crack skeleton lines refers to the minimum Euclidean distance between any pair of pixels in two crack skeleton lines.

[0073] The number of interconnected cracks during the evaluation period is counted as the number of interconnected cracks of the target crack. The more interconnected cracks there are, the more the target crack has spread along similar directions and formed a continuous crack band in the deeply bending member.

[0074] Within the preset crack assessment period, the crack strike angle of the target crack is continuously collected to obtain the crack dip angle sequence. The difference between adjacent crack strike angles in the crack dip angle sequence is used to obtain the diagonal dip angle data, which reflects the fluctuation range of the target crack's strike during the crack assessment period.

[0075] It should be noted that the preset crack assessment cycle can be set according to the monitoring sampling frequency or the structural operating conditions; the Euclidean distance algorithm is a distance calculation method based on pixel coordinates to calculate the spatial straight-line distance; the preset spatial connectivity threshold can be set according to the image resolution and the size parameters of the bending member.

[0076] In step S2, within a preset crack assessment period, each diagonal dip angle data is compared with a preset diagonal dip angle threshold.

[0077] If the tilt angle data is less than the preset tilt angle threshold, the tilt angle data is marked; otherwise, the tilt angle data is not marked.

[0078] The dip angle data of each marker are sorted in chronological order. Adjacent dip angle data of markers are combined into a strike-stable segment. The number of dip angle data of markers in the strike-stable segment is counted as the strike-stable segment length. The maximum value of the strike-stable segment length is taken as the maximum stable segment length.

[0079] The ratio of the maximum stable segment length to the total number of diagonal angle data within the crack assessment period is taken as the trend toward stability.

[0080] After standardizing the trend toward stability and the number of connected cracks respectively, we obtain the stability coefficient and the connected crack coefficient.

[0081] Targeted clustering characteristics are calculated based on the stability coefficient and the connectivity crack coefficient: ,in, As a preset adjustment factor, To achieve a stable coefficient, The coefficient for connectivity cracks. It is a directional aggregation characteristic;

[0082] The directional aggregation characteristics are compared with a preset directional aggregation threshold to determine whether to enter the abdominal muscle monitoring stage.

[0083] If the directional aggregation characteristic is greater than the preset directional aggregation threshold, then the abdominal muscle monitoring stage is entered.

[0084] Conversely, if the condition is not met, it is determined that the abdominal muscle monitoring phase will not begin.

[0085] When the directional aggregation characteristic is greater than the preset directional aggregation threshold, it indicates that the expansion direction of the target crack is more stable and the number of cracks that connect with it in space is greater. The crack field changes from a discrete distribution to a directional aggregation distribution, and the process enters the reinforcement monitoring stage to further analyze the reinforcement strain response and shear force transmission state.

[0086] The shear span ratio data of the concrete to be tested is retrieved from the component information database. The shear span ratio data refers to the ratio of the shear span length to the effective height of the bending member. Based on the shear span ratio data, the shear stress mode of the bending member is classified and a shear configuration class is generated.

[0087] The larger the shear span ratio, the longer the shear span length relative to the effective height, the less dominant the shear failure is on the overall response, the more dispersed the crack orientation, and the less likely the force transmission path of the compression bar is to concentrate into a band.

[0088] A first scissor span ratio grading threshold and a second scissor span ratio grading threshold are preset, and the first scissor span ratio grading threshold is greater than the second scissor span ratio grading threshold;

[0089] The shear span ratio data is compared with a preset first and second shear span ratio grading thresholds to generate shear configuration classes.

[0090] If the shear span ratio data is greater than or equal to the first shear span ratio classification threshold, then a bending-shear dominant configuration class is generated;

[0091] If the shear span ratio data is less than the first shear span ratio classification threshold and greater than or equal to the second shear span ratio classification threshold, then a cohesive strut web reinforcement cooperative shear configuration class is generated.

[0092] If the shear span ratio data is less than the second shear span ratio grading threshold, then a compression bar-dominated shear configuration tier is generated;

[0093] The bending-shear dominant configuration class refers to a shear stress configuration in which a stable compression member force transmission path has not been formed inside a deeply bending member; the compression member-reinforcement cooperative shear configuration class refers to a shear stress configuration in which a compression member force transmission tendency is formed inside a deeply bending member and the reinforcement participates in shear force transmission, but the compression member path has not completely dominated the overall stress; the compression member-dominant shear configuration class refers to a shear stress configuration in which the load inside a deeply bending member is mainly transmitted through the compression member-tension member path, and the shear effect dominates the overall response.

[0094] It should be noted that the preset tilt angle threshold can be set based on the statistical results of the variation amplitude of adjacent orientation angles in historical stable crack samples; the standardization processing methods include, but are not limited to, standard linear transformation based on interval scaling, Z-Score standardization method based on statistics, or normalization method based on nonlinear mapping function. The application methods of standardization processing will not be elaborated here; the preset adjustment factor can be set based on the reliability of crack orientation identification and the statistical stability of connected cracks; the component information database is used to store information such as the shear span ratio data of the concrete to be tested; the preset first shear span ratio grading threshold and second shear span ratio grading threshold are used to grade the shear force transmission mechanism of the deep bending member, and their values ​​can be retrieved or set through the design code of the concrete structure to be tested, engineering design standards, or component type parameter table.

[0095] In step S3, the spatial constraints of the shear force transmission path formed inside the bending member are defined based on the shear configuration hierarchy, thereby clarifying the key area and control area for strain monitoring of the web reinforcement within the member scale, and improving the pertinence and reliability of web reinforcement shear force identification.

[0096] Specifically, the potential distribution pattern of the force transmission path of the compression bar is determined based on the shear configuration hierarchy.

[0097] For the bending-shear dominant configuration class, since a stable compression force transmission path has not yet been formed inside the bending member, based on the member's geometric parameters and force boundary conditions, the compression path zone is pre-defined as the compression path zone covering the web reinforcement in the shear zone. For the compression-web reinforcement co-shear configuration class and the compression-dominant shear configuration class, it is assumed that the member already has the conditions to form a directional compression force transmission path, and it is necessary to further define the directional compression path zone.

[0098] Based on this, taking the shear zone of the bending member as the analysis object, and combining the loading point position, support position and effective height parameters of the member recorded in the member geometric information database, the starting point and ending point of the compression member are determined. The starting point of the compression member is located in the compression zone near the loading point, and the ending point of the compression member is located in the compression zone near the support.

[0099] The line connecting the start and end points of the compression member is taken as the center axis of the compression member, and a preset path band width is set along the normal direction of the center axis of the compression member to form the compression member path band area.

[0100] It should be noted that the component geometry information database is a data set used to centrally store and manage the geometry and stress boundary related parameters of the concrete bending member to be tested. It includes the overall size parameters of the member, cross-sectional geometry parameters, effective height parameters, spatial position of the loading point in the member coordinate system, support position and support type, etc. The parameters are derived from the member design drawings and structural design models. The path band width is set according to the spacing of the stirrups or the width of the member cross-section, for example, twice the spacing of the stirrups or 0.3 times the width of the member cross-section, to cover the range of stirrups that may be involved in the actual force transmission of the compression member.

[0101] After spatially delineating the compression member path zone, the web reinforcements located within the compression member path zone are classified and marked. Specifically, the spatial arrangement parameters of the web reinforcements in members subjected to severe bending are obtained, including the position coordinates of the web reinforcements in the longitudinal, vertical, and cross-sectional directions of the member.

[0102] The spatial inclusion relationship between the spatial location of the web reinforcement and the compression bar path zone is determined. If the longitudinal projection of a web reinforcement overlaps with the defined path zone area, the web reinforcement is marked as a compression bar path web reinforcement.

[0103] Otherwise, mark the abdominal fascia as the control sheared abdominal fascia.

[0104] After classifying and marking the web reinforcement, strain testing is performed on each web reinforcement. In practice, strain sensors are installed on each marked web reinforcement, and the strain sensors are fixedly installed along the web reinforcement axis to collect real-time data on the axial strain changes of the web reinforcement during shear loading.

[0105] During the monitoring process, the strain signals of each abdominal ligament are continuously collected at a preset strain sampling frequency to form a strain time series of the abdominal ligament.

[0106] The strain time series corresponding to the compression bar path web reinforcement are summarized into a compression bar path web reinforcement strain dataset, and the strain time series corresponding to the control shear web reinforcement are summarized into a control shear web reinforcement strain dataset.

[0107] The strain dataset for the reinforcing bars contains the strain sampling time, instantaneous strain value, and time index information corresponding to the crack assessment cycle. It is used to analyze the shear stress growth characteristics of the reinforcing bars in subsequent steps and to couple and determine the crack width evolution characteristics of the target crack.

[0108] Through the above implementation, spatial screening and functional differentiation of the monitoring objects of the web reinforcement based on the shear configuration hierarchy were realized, transforming the web reinforcement strain detection from indiscriminate acquisition to directional monitoring oriented towards the force transmission path of the compression member, providing a clear and quantifiable input data foundation for subsequent shear force transmission state identification.

[0109] In step S4, based on the strain dataset of the compression bar path reinforcement and the strain dataset of the control shear reinforcement, the stress behavior of the reinforcement participating in shear force transmission in the deep bending member during the formation and stable propagation stage of the diagonal crack is coupled and analyzed to determine whether the compression bar path reinforcement has changed from a structural stress state to a stress member that actually undertakes shear force transmission.

[0110] Specifically, the strain growth rate of the web reinforcement is calculated by the strain difference between adjacent sampling times in the web reinforcement strain dataset of the compression bar path and the control shear web reinforcement strain dataset, thus obtaining the strain growth rate sequence of the web reinforcement of the compression bar path and the strain growth rate sequence of the control shear web reinforcement.

[0111] The strain growth rate sequence of the compression bar path web reinforcement was statistically summarized, and its average strain growth rate was calculated as the shear force growth characteristic of the compression bar path web reinforcement. At the same time, the strain growth rate sequence of the control shear web reinforcement was subjected to the same statistical processing to obtain the shear force growth characteristic of the control shear web reinforcement.

[0112] By comparing the shear stress growth characteristics of the compression strut web reinforcement with those of the control shear web reinforcement, we can identify whether the strain growth of the compression strut web reinforcement is higher than that of the control web reinforcement, thereby characterizing the concentrated growth characteristics of shear stress in the web reinforcement within the compression strut path.

[0113] Based on this, crack width data of the target crack is collected synchronously. During the rib monitoring phase, crack width values ​​of the target crack are continuously acquired at different time points using crack width measurement sensors, forming a crack width time series.

[0114] It should be noted that the crack width measurement sensor is a measuring device used to continuously and quantitatively monitor the degree of crack opening on the concrete surface during the stress process of a component. It is placed on the concrete surface on both sides of the target crack, and obtains the relative displacement change on both sides of the crack by measuring the base distance across the crack, and converts the relative displacement change into the crack width value output.

[0115] Starting from the entry into the reinforcement monitoring stage and ending at the current time, an analysis window is established. Within this window, the average strain increase of the reinforcement along the compression bar path and the crack width increment of the crack width time series are calculated to characterize the extent of the expansion of the target diagonal crack during the reinforcement stress response stage.

[0116] Furthermore, based on the correspondence between the average strain increase and the crack width increment, the shear constraint coefficient is calculated, specifically expressed as:

[0117] ;

[0118] in, This is the shear constraint coefficient. This represents the average strain increase of the web reinforcement along the compression member within the analysis window. This represents the increment in crack width.

[0119] When the average strain increase is greater and the crack width increase is smaller, the shear constraint coefficient is larger, indicating that the strain increase of the web reinforcement has a significant constraint effect on the propagation of the diagonal crack.

[0120] After obtaining the shear constraint coefficient, the shear constraint coefficient is compared with the preset shear constraint threshold, and the shear force transmission state determination result of the web reinforcement of the compression bar path is generated by combining the shear force growth characteristics.

[0121] Specifically, when the shear force growth characteristics of the compression bar path web reinforcement are higher than those of the control shear web reinforcement, and the shear constraint coefficient is greater than the preset shear constraint threshold, it is determined that the compression bar path web reinforcement has participated in shear force transmission, and a determination result of the compression bar path web reinforcement being in the state of shear force transmission is generated.

[0122] Conversely, if the shear force growth characteristics of the compression bar path reinforcement are not higher than those of the control shear bar reinforcement, or if the shear constraint coefficient is lower than the preset shear constraint threshold, the compression bar path reinforcement is determined to be in a state of not participating in shear force transmission.

[0123] It should be noted that the preset shear constraint threshold is a criterion used to distinguish whether the strain growth of the web reinforcement has an effective inhibitory effect on the propagation of the target diagonal crack. The specific setting is based on the material mechanical parameters and the theoretical growth model of the initial crack width.

[0124] After completing the shear force transmission state determination, if the determination result is that the web reinforcement of the compression bar path is in the shear force transmission participation state, then a shear force transmission participation signal is generated.

[0125] Conversely, no shear force transmission signal is generated, the current monitoring state is maintained, and the strain data and crack width data of the stirrups are continuously updated to achieve dynamic tracking and identification of the stress state transformation process of the stirrups.

[0126] It should be noted that the shear force transmission participation signal is a trigger signal for structural safety assessment, deformation mode early warning, or subsequent loading control. It is used to indicate that the bending member has entered the stage of force transmission dominated by the web reinforcement or in coordination with the web reinforcement and compression member after the formation of the diagonal crack.

[0127] Finally, it should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0128] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0129] In this document, the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0130] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0131] The above description of the disclosed embodiments will enable those skilled in the art to make or use various modifications to these embodiments. It will be readily apparent to those skilled in the art that the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for identifying the shear deformation of a concrete deep flexural member in a strain and crack field, characterized by: The method comprises the following steps: Step S1: crack identification is performed on the deep flexural member of the concrete to be tested, the crack direction information of the deep flexural member is obtained, the target crack is screened, the crack evaluation period is set, the number of connected cracks of the target crack is counted in the crack evaluation period, and the oblique inclination data is detected; The longitudinal axis of the deep flexural member is taken as a direction baseline, and the included angle of the crack main direction relative to the direction baseline is taken as the crack direction angle; The target crack direction angle interval is obtained by accessing the crack database, and if the crack direction angle is within the target crack direction angle interval, the crack skeleton line is screened as the target crack; On the contrary, the crack skeleton line is not the target crack; Step S2: the trend of the crack direction is analyzed according to the oblique inclination data, the directional aggregation feature is evaluated in combination with the number of connected cracks, and it is judged whether to enter the web reinforcement monitoring stage; when entering the web reinforcement monitoring stage, the shear span ratio data of the concrete to be tested are called and the shear configuration grade is generated; Step S3: the compression strut path zone of the deep flexural member is divided based on the shear configuration grade, the web reinforcement in the compression strut path zone is classified and marked as compression strut path web reinforcement or contrast shear web reinforcement, the strain of the classified and marked web reinforcement is detected, and the web reinforcement strain data are obtained; Step S4: the shear stress growth feature is analyzed by using the web reinforcement strain data, the crack width of the target crack is collected, the shear constraint coefficient is calculated, the shear force transfer state of the compression strut path web reinforcement is generated in combination with the shear stress growth feature, and it is judged whether to generate the shear force transfer participation signal.

2. The method according to claim 1, wherein in step S1, the crack imaging sensor is used to identify the cracks of the deep flexural member of the concrete to be tested, and the surface crack distribution image of the deep flexural member is obtained. After the image binarization processing of the surface crack distribution image, the crack direction information including the crack skeleton lines of the deep flexural member is extracted. The least square linear fitting algorithm is used to linearly fit each crack skeleton line to obtain the crack main direction of the crack skeleton line.

3. The method according to claim 1, wherein in step S1, the crack evaluation period is preset, the minimum spatial distance between the crack skeleton line corresponding to the target crack and other crack skeleton lines is calculated, and when the minimum spatial distance is less than the preset spatial connection threshold, the crack skeleton line is recorded as the connected crack of the target crack. In the evaluation period, the number of connected cracks is counted as the number of connected cracks of the target crack. In the preset crack evaluation period, the crack direction angles of the target crack are continuously collected to obtain the crack inclination sequence. The oblique inclination data is obtained by subtracting the adjacent crack direction angles in the crack inclination sequence.

4. The method according to claim 3, wherein in step S2, if the oblique inclination data is less than the preset oblique inclination threshold, the oblique inclination data is marked; otherwise, the oblique inclination data is not marked. The marked oblique inclination data is sorted in time sequence, and the adjacent marked oblique inclination data is combined as a crack direction stable section. ​ ​ ​ The number of marker inclined angle data of the strike stable section is counted as the length of the strike stable section, and the maximum value of the length of the strike stable section is taken as the maximum stable section length; The strike stability trend is calculated based on the maximum stable section length; The strike stability coefficient and the connected crack coefficient are obtained by respectively standardizing the strike stability trend and the connected crack number; The directional aggregation feature is calculated based on the strike stability coefficient and the connected crack coefficient.

5. The method according to claim 1, wherein: In step S2, if the directional aggregation feature is greater than a preset directional aggregation threshold, it is determined to enter the web monitoring stage; Otherwise, it is determined not to enter the web monitoring stage; The shear-span ratio data of the concrete to be measured are called from the component information library, and the shear-span ratio data refer to the ratio of the shear-span length to the effective height of the deep flexural component; The first shear-span ratio classification threshold and the second shear-span ratio classification threshold are preset, and the first shear-span ratio classification threshold is greater than the second shear-span ratio classification threshold; The shear-span ratio data are compared with the preset first shear-span ratio classification threshold and the second shear-span ratio classification threshold respectively to generate a shear configuration grade; The shear configuration grade includes a flexural-shear dominant configuration grade, a compression strut web synergistic shear configuration grade, and a compression strut dominant shear configuration grade.

6. The method according to claim 1, wherein: In step S3, for the flexural-shear dominant configuration grade, a compression strut path band region covering the web of the shear region is preset according to the component geometric parameters and the stress boundary conditions; For the compression strut web synergistic shear configuration grade and the compression strut dominant shear configuration grade, a compression strut central axis is taken as the line connecting the compression strut starting point and the compression strut ending point, and a preset path band width is set in the normal direction of the compression strut central axis to form a compression strut path band region; The spatial arrangement parameters of the deep flexural component web are obtained, including the position coordinates of the web in the longitudinal direction, the vertical direction and the cross-sectional direction of the component; The spatial position of the web is compared with the compression strut path band region to determine the spatial inclusion relationship, if the longitudinal projection of a certain web overlaps with the defined path band region, the web is marked as a compression strut path web; Otherwise, the web is marked as a contrast shear web.

7. The method according to claim 6, wherein: In step S3, a strain sensor is arranged on each marked web, which is fixedly installed along the axial direction of the web to collect the axial strain change data of the web during the shear loading process in real time; In the monitoring process, the strain signals of each web are continuously collected at a preset strain sampling frequency to form a web strain time series: The strain time series corresponding to the compression strut path web are summarized as a compression strut path web strain data set, and the strain time series corresponding to the contrast shear web are summarized as a contrast shear web strain data set.

8. The method according to claim 1, wherein: In step S4, the web strain growth rate is calculated by the strain difference between the strain data set of the presser bar path web and the strain data set of the adjacent sampling time of the control shear web, to obtain the presser bar path web strain growth rate sequence and the control shear web strain growth rate sequence; The presser bar path web strain growth rate sequence is statistically summarized, and the average strain growth rate is calculated as the shear stress growth characteristic of the presser bar path web; the control shear web strain growth rate sequence is synchronously statistically processed in the same way to obtain the shear stress growth characteristic of the control shear web; The crack width data of the target crack is collected, and the crack width values of the target crack at different time nodes are continuously obtained by the crack width measuring sensor in the web monitoring stage to form a crack width time sequence.

9. The concrete deep flexural member shear deformation identification method of strain and crack field according to claim 8, characterized in that: In step S4, the average strain growth amount of the presser bar path web and the crack width increment of the crack width time sequence are calculated in an analysis window with the entry into the web monitoring stage as the starting point and the current time as the ending point; The ratio of the average strain growth amount to the crack width increment is taken as the shear constraint coefficient; Specifically, when the shear stress growth characteristic of the presser bar path web is higher than that of the control shear web, and the shear constraint coefficient is greater than the preset shear constraint threshold, it is determined that the presser bar path web is in the shear force transmission participating state, and a shear force transmission participating signal is generated; On the contrary, it is determined that the presser bar path web is in the non-participating shear force transmission state, and no shear force transmission participating signal is generated.

Images