Reinforced concrete beam shear crack motion measuring device

Abstract

The utility model discloses a reinforced concrete beam shear crack motion measuring device, which comprises a camera, a data acquisition system and a loading device, two steel columns are vertically arranged above a steel base, an upper cross beam and a lower cross beam are connected between the two steel columns, a jack is arranged below the upper cross beam, and the data acquisition system is connected with the loading device. The acting force is downwards and vertically applied to the distribution beam through the loading head; the distribution beam transmits load to the test beam through the two distribution supports, the test beam is placed on the two supporting supports of the lower cross beam steel base, and the camera is placed at the front end of the test beam and connected with the data acquisition system. A distribution support in the loading device adopts a roll shaft and can rotate bidirectionally, and a loading head adopts a hemispherical hinge and can rotate freely. The device is novel in measurement mode and convenient to use, the motion state of the shear crack of the reinforced concrete beam can be accurately obtained, and an analysis basis is provided for quantification and evaluation of contribution of various anti-shear components to the anti-shear bearing capacity.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of crack testing of reinforced concrete beam, and particularly relates to a reinforced concrete beam shearing crack motion measuring device. BACKGROUND

[0002] The shear performance of reinforced concrete members has been a classic research problem in the field of civil engineering. The shear bearing capacity is composed of multiple parts, including the shear effect of stirrups, the shear effect of concrete, the pinning effect of longitudinal reinforcement, and the aggregate interlocking effect, etc. Under the action of bending-shear load, the initial shear crack is generated along the direction of the maximum principal tensile stress of concrete. With the increase of load and the development of deformation, the stress-strain state of the shear crack position is redistributed, and the principal tensile stress direction changes, resulting in the relative slip of the concrete on both sides of the crack. For concrete members, the motion state (opening and slip) of the shear crack will significantly affect the aggregate interlocking effect of concrete, and further affect the overall shear bearing capacity of the member. Traditional crack measurement methods include visual observation, crack width gauge, strain gauge, displacement meter, etc. However, these methods have low measurement accuracy and can only provide single-point measurement data, and cannot obtain the crack motion in a large range. Therefore, a new device is proposed to measure the opening and slip of the shear crack of the reinforced concrete beam, so as to clarify the variation law and spatial distribution characteristics of the shear crack with load, which is the basis for quantifying and accurately evaluating the contribution of various shear components. SUMMARY

[0003] To solve the above problems, the utility model discloses a reinforced concrete beam shearing crack motion measuring device, which is novel in structure, convenient to use, and can accurately obtain the motion state (opening and slip) of the reinforced concrete beam shearing crack, providing an analysis basis for quantifying and evaluating the contribution of various shear components to the shear bearing capacity.

[0004] To achieve the above purpose, the technical scheme of the utility model is as follows:

[0005] A reinforced concrete beam shearing crack motion measuring device, comprising a camera, a data acquisition system and a loading device, the loading device comprising a steel base, a steel column, a steel seat, an upper cross beam, a lower cross beam, a distribution beam, a jack, a loading head, a distribution support and a supporting support; two steel columns are vertically arranged above the steel base, and an upper cross beam and a lower cross beam are connected between the two steel columns; the jack is arranged below the upper cross beam, and the force is applied vertically to the distribution beam through the loading head downward; the distribution beam transmits the load to the test beam through two distribution supports; the test beam is placed on the two supporting supports of the lower cross beam steel seat, the camera is placed at the front end of the test beam, and the camera is connected to the data acquisition system.

[0006] As an improvement of the utility model, the distribution support adopts three-layer base plate double roller shaft structure, can rotate bidirectionally, the first layer base plate and the second layer base plate are provided with horizontal roller shaft, the second layer base plate and the third layer base plate are provided with longitudinal roller shaft, and the side of three-layer base plate is equipped with spring being connected with each other.

[0007] As an improvement of the utility model, the loading head adopts hemispherical hinge structure, can rotate freely.

[0008] As an improvement of the utility model, the total length of test beam is 1.1L, the distance between distribution beam left distribution point (one of distribution supports) and beam left end face is 0.4L, the distance between distribution beam right distribution point (another distribution support) and beam right end face is 0.2L, the distance between two distribution supports is 0.5L, the distance between beam lower surface left supporting point (one of supporting supports) and beam left end face is 0.2L, the distance between beam lower surface right supporting point (another supporting support) and beam right end face is 0.4L, and the distance between two supporting supports is 0.5L.

[0009] As an improvement of the utility model, the load applied by loading head in loading device is P, and the load borne by left distribution support and right distribution support under distribution beam is 0.7P and 0.3P respectively.

[0010] The utility model has the advantages that:

[0011] The device for measuring the motion state (opening and sliding) of the shear crack of the reinforced concrete beam provided by the utility model adopts an asymmetric four-point bending loading scheme to obtain a pure shear surface, forms a shear crack, adopts a DIC method to measure and obtain the full-field displacement of the beam surface, four mark points are selected on both sides of the shear crack, the opening and sliding of the shear crack can be calculated, and the variation law and spatial distribution characteristics thereof with load can be determined, thereby providing an analysis basis for quantifying and accurately evaluating the contribution of each shear component. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is the whole structure schematic diagram of the utility model;

[0013] Figure 2 It is the distribution support detail view of the utility model;

[0014] Figure 3 It is the loading head detail view of the utility model;

[0015] Figure 4 It is the test beam loading scheme schematic diagram of the utility model;

[0016] Figure 5 It is the test beam shear force distribution schematic diagram of the utility model;

[0017] Figure 6 The test beam bending moment distribution schematic diagram of the utility model is shown in the figure.

[0018] Figure 7 The shear crack opening and slip calculation method schematic diagram of the utility model is shown in the figure.

[0019] List of figure marks:

[0020] 1, test beam; 2, camera; 3, data acquisition system; 4, steel base; 5, steel column; 6, steel seat; 7, upper cross beam; 8, lower cross beam; 9, distribution beam; 10, jack; 11, loading head; 12, distribution support; 13, supporting support, 14, base plate, 15, transverse roller shaft, 16, longitudinal roller shaft, 17, spring. Specific implementation

[0021] The utility model is further illustrated below in combination with the drawings and specific implementation, and it should be understood that the following specific implementation is only used for illustrating the utility model and is not used for limiting the scope of the utility model.

[0022] As Figure 1 shown, the embodiment provides a reinforced concrete beam shear crack movement measuring device, test beam 1 adopts asymmetric four-point bending loading scheme to obtain pure shear surface (no bending moment), forms shear crack; the measuring method is non-contact full-field strain measurement technology (Digital Image Correlation, DIC), utilizes camera 2 and data acquisition system 3 to obtain the full-field displacement of beam surface, selects four mark points on the two sides of shear crack, and calculates the opening and slip of shear crack;The loading device includes: steel base 4, steel column 5, steel seat 6, upper cross beam 7, lower cross beam 8, distribution beam 9, jack 10, loading head 11, distribution support 12 and supporting support 13;Two steel columns 5 are vertically arranged above steel base 4, and upper cross beam 7 and lower cross beam 8 are connected between the two steel columns 5;The jack 10 is arranged below the middle of the upper cross beam 7, and the force is applied to the distribution beam 9 through the loading head 11 vertically;The distribution beam 9 transmits load to test beam 1 through distribution support 12;Test beam 1 is placed on the supporting support 13 of the lower cross beam steel seat 6.

[0023] As Figure 2 shown, the distribution support 12 in the loading device adopts a sandwich roller shaft structure and can rotate in two directions, the transverse roller shaft 15 is arranged between the first layer base plate and the second layer base plate, the longitudinal roller shaft 16 is arranged between the second layer base plate and the third layer base plate, and the side edges of the three layers of base plates are provided with springs 17 connected with each other;The loading head 11 adopts a hemispherical hinge and can rotate freely, as Figure 3 shown.

[0024] As Figure 4As shown, the total length of the test beam is 1.1L, the distance between the left support point of the distribution beam and the left end surface of the beam is 0.4L, the distance between the right support point of the distribution beam and the right end surface of the beam is 0.2L, the distance between the two distribution supports is 0.5L, the distance between the left support on the lower surface of the beam and the left end surface of the beam is 0.2L, the distance between the right support on the lower surface of the beam and the right end surface of the beam is 0.4L, and the distance between the two supports is 0.5L.

[0025] The two distribution supports 12 under the distribution beam in the loading device can move in the horizontal direction. The load applied by the loading head 11 in the loading device is P. Before loading, the positions of the distribution supports under the distribution beam should be adjusted so that the loads borne by the left and right distribution supports under the distribution beam are 0.7P and 0.3P respectively. The shear force distribution diagram and the bending moment distribution diagram of the beam are shown in Figure 5 and Figure 6 .

[0026] The method for measuring the opening and slip of the shear crack of the reinforced concrete beam comprises the following steps:

[0027] Step 1): Place the test beam 1 on the support supports 13 of the lower cross beam 8, and place the camera 2 for DIC measurement at the corresponding position to perform full-field displacement measurement on the beam surface monitoring area;

[0028] Step 2): Operate the loading device to carry out a shear test on the test beam 1, capture and process images through the camera 2 and the data acquisition system 3, and obtain the full-field displacement of the beam surface monitoring area;

[0029] Step 3): Calculate the opening and slip of the shear crack. Select two marker points A and B on both sides of the shear crack along the normal direction thereof after deformation, and the deformed marker point positions are A' and B' respectively. In order to eliminate the influence of the “rigid body rotation angle” caused by the deflection deformation of the shear span of the beam, two additional marker points C and D are selected on both sides of the shear crack, and the corresponding deformed marker point positions are C' and D' respectively. The vector is perpendicular to the vector , the vector is perpendicular to the vector , and the rotation angle of the marker line and is the rigid body rotation angle value. The rotation angle α is calculated according to the following formula:

[0030]

[0031] Further calculate the opening value w and the slip value Δ of the shear crack:

[0032]

[0033] The opening and the slip of the shear crack at each mark point in the monitoring area of the beam can be calculated by repeating the above steps.

[0034] The motion state (opening and slip) of the shear crack of the reinforced concrete beam can be accurately obtained by the method and the device, which provides an analysis basis for quantifying and evaluating the contribution of various shear components to the shear bearing capacity, the measurement method is novel and convenient to use, and is worth promoting.

[0035] It should be noted that the above content only illustrates the technical thought of the present application, and cannot limit the protection scope of the present application. For ordinary skilled persons in the art, some improvements and refinements can be made without departing from the principle of the present application, and these improvements and refinements fall within the protection scope of the claims of the present application.

Claims

1. A device for measuring the motion of shear cracks in reinforced concrete beams, characterized in that: The system includes a camera (2), a data acquisition system (3), and a loading device. The loading device includes a steel base (4), steel columns (5), a steel seat (6), an upper crossbeam (7), a lower crossbeam (8), a distribution beam (9), a jack (10), a loading head (11), a distribution support (12), and a support support (13). Two steel columns (5) are vertically arranged above the steel base (4), and the upper crossbeam (7) and the lower crossbeam (8) are connected between the two steel columns (5). The jack (10) is arranged below the upper crossbeam (7), and the force is applied vertically to the distribution beam (9) through the loading head (11). The distribution beam (9) transmits the load to the test beam (1) through the distribution support (12). The test beam (1) is placed on the support support (13) of the lower crossbeam (8) steel seat (6), and the camera (2) is placed at the front end of the test beam (1). The camera (2) is connected to the data acquisition system (3).

2. The device for measuring the motion of shear cracks in reinforced concrete beams according to claim 1, characterized in that: The distribution support (12) adopts a three-layer substrate double roller structure. A transverse roller (15) is provided between the first substrate and the second substrate, and a longitudinal roller (16) is provided between the second substrate and the third substrate. Springs (17) are connected to each other on the sides of the three substrates.

3. The device for measuring the motion of shear cracks in reinforced concrete beams according to claim 1, characterized in that: The loading head (11) adopts a hemispherical hinge structure.

4. The device for measuring the motion of shear cracks in reinforced concrete beams according to claim 1, characterized in that: The total length of the test beam (1) is 1.1L. The distance between the left distribution point of the distribution beam (9) and the left end face of the beam is 0.4L. The distance between the right distribution point of the distribution beam (9) and the right end face of the beam is 0.2L. The distance between the two distribution supports (12) is 0.5L. The distance between the left support point of the lower surface of the test beam (1) and the left end face of the beam is 0.2L. The distance between the right support point of the lower surface of the test beam (1) and the right end face of the beam is 0.4L. The distance between the two support supports (13) is 0.5L.

5. A motion measuring device for shear cracks in reinforced concrete beams according to claim 1 or 4, characterized in that: The load applied by the loading head (11) in the loading device is P, and the loads borne by the left and right distribution supports below the distribution beam (9) are 0.7P and 0.3P, respectively.

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