Experimental Study On Dynamic Mechanical Properties Of Concrete Under Confining Pressure

Concrete as of today’s most widely used building material. In different stress state, the concrete strength and de formation will change. In daily life, the state of concrete under confining pressure is common, such as being lining structure in tunnel engineering, underground bunkers structures, the concrete on the inside of CFST columns, etc. In special circumstances concrete structures might be subjected to dynamic loads in addition to withstanding static loads. When the concrete is loading on dynamic load, its mechanical performance is different from under static load. Therefore, the study of dynamic mechanical properties of concrete under confining pressure is of great significance. This paper includes the following aspects of the research work:(1) Using pressure testing machine for different initial strength of concrete specimens to carry out the static uniaxial compression test. Using SHPB test device for test the dynamic mechanical properties of concrete specimens under two different strain rate(10/s~40/s) under. Through the study found that, low initial strength of concrete is more sensitive on the enhanced effect of strain rate than the higher, and get a formula considered the concrete initial strength and the strain rate effected on DIF.(2) Based on the redesign confining pressure device, make the confining pressure load on the specimen accurately, combining the SHPB experiment with SHPB test to carry out the compression test of concrete specimens under different confining pressure(5MPa and 10MPa) and different impact speeds. Through the study found that, with the increase of initial strength of concrete, the enhanced effect of confining pressure for peak stress of concrete gets weak。(3) using LS-DYNA software to carry out numerical simulation of the SHPB test of concrete under confining pressure. Proving the geometry model, material model and the model parameters is reasonable. Analyzed the effect of stress wave, when the bar is under confining pressure, The results show that, with the length of bar under confining pressure increased, the calculated value of strain is bigger, the stress is smaller. and with the increase of confining pressure, the transmission wave decreases worse. in the experiment, we should make the confining pressure accurately load on the concrete, it can ensure the accuracy of the test data. analyzing the failure pattern of the concrete under 10 MPa confining pressure which the static strength is 54.82 MPa, and the failure pattern shows the characteristics of inclined shear failure, has the damage characteristics of ductile material.