Study On Bearing Capacity Characteristic And Damage Evolution Of Concrete Confined With Double Stirrups

Reinforced concrete with steel skeleton to sustain tension, with concrete as the bonding material under pressure, are suitable for constructing beams, slabs, columns, ladders, platforms, and other structural position. Both residential buildings and commercial buildings in modern urban development are using the types of tall or super-tall forms with responsibility for the high volume rate, the resulting problem is that the underlying structure component is over load. In order to withstand the upper load and meet the requirements of specification about the axial compression ratio, the diameter of the columns has to become larger and larger, which influence the efficiency of buildings and unsightly. For this reason, this essay investigated the high strength concrete columns with high-strength Stirrup reinforcement in smaller diameter, which can meet the capacity requirements and reduces the diameter of the columns, and improve the efficiency of the building. Vertical bearing capacity experiments were conducted with circular double-layer stirrup confined concrete columns as study objects, data acquisition was carried out using acoustic emission(AE) equipment and the AE parameters and graphs acquired during the experiments were analyzed to obtain the damage evolution of steel reinforced concrete columns under compression. The correlation between fractal dimension of AE graphs and p-s curve was studied using the fractal theory, and the results show that the AE parameter graphs have fractal characteristics and the box dimension of each AE parameter graph constantly increases with the increase in stress, with a positive correlation exhibited between the fractal dimension and stress level. The loss variable expressed with fractal dimension was defined to establish actual equivalent stresses and the equivalent stress curves and experimental curves were compared; the results show that the fractal dimension of acoustic emission parameter graph can characterize the damage laws of the concrete member. Data acquisition was also carried out using digital image correlation(DIC) equipment. By analyzing the measurement data, the results showed that the strains performed dissimilarly along with different loading stage which exactly reflects the feature of confined high-strength concrete. Based on the DIC user software, the full-field strains is carried out and strains spectrum maps under various stress levels were obtained. Through the distribution of cloud contour, it can be seen that the strain contour line changes with different location and different time interval. After the peak stress, it appears the phenomenon of “strain relaxation”. At the same time, it also indicates that big differences are in the process of calculating the audience strain when choose the computational area. The appearances of “strain relaxation” in the computational area play a greater influence in the strain calculation and it can lead to distortional results. What’s more, it is indicated that the digital image correlation technique is suitable in the measurement of structural bearing capacity for its superiority of full-field and non-contact.