CN107063892A - A kind of method that utilization Hopkinson pressure bar calculates concrete dynamic shear strength - Google Patents

Abstract

The invention discloses a method for calculating the dynamic shear strength of concrete by using a Hopkinson compression bar. A cylindrical concrete specimen is installed on the Hopkinson compression bar, and the axial ends of the cylindrical concrete specimen are dynamically pressurized. , so as to load the specimen with shear force, ε _i (t), ε _r (t), ε _t (t) measured by the device, Hopkinson compression bar elastic modulus E, Hopkinson compression bar transverse The cross-sectional area A ₀ , the radius R of the cylinder specimen, and the shear length H of the cylinder specimen are calculated to obtain the dynamic shear strength τ of the material; the advantage of the present invention is that by using the method used in the present invention, the Hopkinson pressure can be used The dynamic shear strength of concrete is measured by the rod, which expands the application range of the Hopkinson compression rod. At the same time, the dynamic shear performance of concrete can be studied more deeply, and the dynamic shear strength of concrete under short-term high-strength loads is difficult. Problems with measurement calculations.

Description

A Method for Calculating Dynamic Shear Strength of Concrete Using Hopkinson Compression Bar

technical field

The invention relates to a method for testing the dynamic shear strength of concrete by using a cylindrical concrete specimen, belonging to the technical field of material performance testing

Background technique

The dynamic shear performance of concrete is an important performance of concrete. At present, the shear performance test of concrete is limited to static shear, and it is difficult to measure the shear strength of concrete under short-term high-intensity loads, while dynamic tests are limited to dynamic compression. And dynamic splitting test, a test method is needed to test and calculate the dynamic shear strength of concrete.

Contents of the invention

The technical problem mainly solved by the invention is to propose a method for measuring and calculating the dynamic shear strength of concrete by using a cylindrical concrete test piece and a Hopkinson compression bar.

The invention utilizes the feature that the Hopkinson compression bar can apply impact load to the test piece, and provides a feasible solution for the measurement and calculation of the concrete dynamic shear strength.

The technical solution of the present invention is as follows: a method for calculating the dynamic shear strength of concrete using a Hopkinson compression bar, wherein the cylindrical concrete specimen is installed on the Hopkinson compression bar, and the axial direction of the cylindrical concrete specimen is Both ends are dynamically pressurized, so that the specimen is loaded with shear force, and the measured ε _i (t), ε _r (t), ε _t (t), Hopkinson compression bar elastic modulus E, The cross-sectional area A ₀ of the Hopkinson compression bar, the radius R of the cylindrical specimen, and the shear length H of the cylindrical specimen can be calculated according to the following formula to obtain the dynamic shear strength τ of the material;

In the formula, ε _i (t) is the incident strain pulse, ε _r (t) is the reflected strain pulse, ε _t (t) is the transmitted strain pulse, E is the elastic modulus of the Hopkinson bar, and A ₀ is the Hopkinson The cross-sectional area of the compression bar, R is the radius of the cylinder specimen, H is the shear length of the cylinder specimen,

The unit of dynamic shear strength τ is MPa, the unit of A ₀ is mm ² , and the unit of R and H is mm.

The concrete specimens used are cylindrical specimens, and the shear force is applied to them by Hopkinson compression bars.

Advantages of the present invention: Utilizing the method used in the present invention, the dynamic shear strength of concrete can be measured using the Hopkinson compression bar, which expands the application range of the Hopkinson compression bar, and can further deepen the dynamic shear resistance of concrete at the same time The study solved the problem that the shear strength of concrete under short-term high-strength loads is difficult to measure and calculate.

At present, the shear strength of concrete is mostly measured in the static shear test. The main form of the specimen is a cube. The double-sided shear method is used for testing, and it is impossible to perform dynamic shear loading and short-term high-strength shear on the specimen. It is difficult to study the shear performance and failure mechanism of concrete under sudden high-strength shear loads.

The Hopkinson compression bar can perform dynamic loading and short-term high-strength load loading on the specimen, but it is mainly used in compression and splitting tests. The present invention expands the scope of application of the Hopkinson compression bar to shear tests. The form is similar to that of the Hopkinson compression bar standard specimen, and will not cause additional effects. At present, the Hopkinson compression bar is widely used, and the test principle is mature, which can ensure the accuracy of the test.

Description of drawings

Figure 1 is a schematic diagram of a perspective view of a cylindrical specimen.

detailed description

The present invention will be further described below in conjunction with the drawings and specific implementation process, and the measurement and calculation in the invention will be described.

Example 1:

Embodiment 1. When carrying out dynamic shear resistance test on SHPB (Split Hopkinson Pressure Bar, Hopkinson pressure bar, be called for short SHPB) device, choose diameter and be 100mm, the concrete cylinder specimen that height is 50mm, it is placed in SHPB The incident rod and the transmission rod of the device are in close contact, and then an impact load is applied to the other end of the incident rod, and the incident strain pulse, reflected strain pulse, and transmitted strain pulse during the impact load test are recorded, and calculated according to the following formula: The dynamic shear strength of concrete can be obtained as:

In the formula: τ is the shear strength (MPa), E is the elastic modulus (MPa) of the Hopkinson bar, and is the calibration value of the Hopkinson bar, and _A0 is the circular cross-sectional area of the Hopkinson bar (mm ² ) can be calculated by measurement, ε _i (t) is the incident strain pulse, ε _r (t) is the reflected strain pulse, ε _t (t) is the transmitted strain pulse, and the three can pass the Hopkinson compression bar test The measured R is the radius (mm) of the specimen, and H is the shear length (mm) of the specimen.

Claims (1)

1. A method utilizing the Hopkinson compression bar to calculate the dynamic shear strength of concrete, characterized in that, Install the cylindrical concrete specimen on the Hopkinson compression bar, and dynamically pressurize the axial ends of the cylindrical concrete specimen, so as to load the specimen with shear force. The ε _i (t ), ε _r (t), ε _t (t), elastic modulus E of the Hopkinson compression bar, cross-sectional area of the Hopkinson compression bar A ₀ , radius R of the cylinder specimen, and shear length H of the cylinder specimen , according to the following formula to calculate the dynamic shear strength τ of the material; In the formula, ε _i (t) is the incident strain pulse, ε _r (t) is the reflected strain pulse, ε _t (t) is the transmitted strain pulse, E is the elastic modulus of the Hopkinson bar, and A ₀ is the Hopkinson The cross-sectional area of the compression bar, R is the radius of the cylinder specimen, H is the shear length of the cylinder specimen, The unit of dynamic shear strength τ is MPa, the unit of A ₀ is mm ² , and the unit of R and H is mm.