Seismic Properties of HRB600 Steel Rebar
HRB600-grade hot-rolled ribbed steel bar (rebar) has an obvious yield stage and good ductility, making it suitable for seismic applications. The research aims to fit the maximum crack width calculation formula of GB 50010.
Cyclic tests were conducted on concrete columns configured with high-strength longitudinal and stirrup bars, analyzing the effect of the reinforcement strength, axial compression ratio, and the number of stirrups on their seismic performance. The results revealed that the low-cycle fatigue damage and premature fracture caused by inelastic buckling of longitudinal bars are significant factors.
Strength
High-strength HRB600 steel rebar is a powerful building material. It has a high tensile strength and can withstand large tensile forces, which helps to prevent building damage caused by insufficient strength. In addition, it is resistant to corrosion and can be used in a variety of applications.
In order to better understand the bond behavior between concrete and HRB600 steel rebar, cyclic loading tests have been performed on eight concrete beams reinforced with high-strength longitudinal bars. The experimental results show that the crack width in the pure bending section is independent of the concrete strength, and it is proportional to the reinforcement strain. A calculation formula for the maximum crack width suitable for RC columns is also developed.
The buckling behaviors of the longitudinal bars in the cover concrete were analyzed based on the lateral buckling displacements and ductility coefficient. The results showed that the buckling of HRB600 longitudinal bars was largely prevented by the covering concrete, which reduces the local plastic deformation concentration and low-cycle fatigue damage in the bars and increases their ductility reserves.
Ductility
HRB600 steel is an ideal material for reinforcing concrete slabs and columns in high-rise buildings. Its tensile strength is more than 600MPa, making it strong enough to withstand the massive bending forces that these structures are subjected to during construction. The ductility of the steel also ensures that it can absorb shock and other external forces without causing damage to the building.
During the research, eight concrete beams reinforced with different reinforcement ratios were constructed and tested. The cyclic loading tests revealed that the load-deflection response of these concrete columns Hot dipped galvanized SGCC steel plate was similar to those of normal-strength bar-reinforced concrete columns. Moreover, the failure process of the concrete columns was analyzed using a modified low cycle fatigue damage model.
The results of this study indicated that HRB600-grade hot-rolled ribbed high-strength longitudinal reinforcement has superior drift capacity capacities to conventional reinforcement bars for RC walls, and can significantly increase the seismic performance of the buildings. In addition, the ductility of the HRB600-grade steel meets the recommended value for the elastic modulus and ultimate strain of longitudinal reinforcement in GB 50010 codes.
Elongation after Fracture
HRB600 rebar has high elongation after fracture, which is an important property for construction. It can prevent premature fracture caused by low-cycle fatigue damage or inelastic buckling, and it also provides sufficient capacity for earthquake resistance. In addition, elongation after fracture of HRB600 rebar can be increased by using extruded sleeves, which can significantly improve the durability and reliability of splice connections.
Cyclic tests are conducted to investigate the seismic performance of RC columns configured with HRB600 bars. Results show that cyclic loading can lead to the formation of early cracks in longitudinal bars, which result in reduced shear capacity. Additionally, the influence of low-cycle fatigue damage and inelastic buckling on the seismic performance is also investigated.
The test results show that the DIFy ratios of rebars spliced with sleeves to those of unspliced rebars are larger at higher strain rates, as expected. The modified Cowper-Symonds formula fits the test data well, which demonstrates that it properly accounts for the effect of the strain rate on the DIFy of rebars spliced using sleeves. This confirms that the application of spliced HRB600 rebar is safe for structural applications.
Metallographic Structure
The metallographic structure of HRB600 rebar consists of two phases. The base steel is 55#, while the cladding is made of 316L stainless steel. This combination ensures that the rebar has high corrosion resistance and can DX52 galvanized steel be used in bridge construction, highways, and dams. It also provides high fatigue resistance and good tensile strength.
HRB600 has a higher yield strength than traditional reinforcing bar. As a result, it is more resistant to cyclic loads and can be used in high-rise buildings. This material also has high ductility, which allows it to absorb large tensile forces without fracturing. It is also easy to shape into various shapes and sizes, which makes it a suitable choice for construction.
In the study, a series of cyclic load tests were performed on concrete beams with HRB600 reinforcement. The buckling behaviors of longitudinal bars and the influence of premature fracture on the seismic performance were investigated. It was found that cover concrete had a significant constraint effect on the buckling of longitudinal bars. The premature fracture of the high-strength steel was mainly caused by low-cycle fatigue damage, worse plastic deformation capacity due to a higher fy, and local strain concentration from bar buckling.
Earthquake Resistance
High-strength Rebar is often used for building construction because it has a high tensile strength and can withstand large bending forces. It is also resistant to corrosion and can withstand heavy loads. Additionally, it is easy to weld, making it an ideal choice for construction projects.
Few experimental studies have been conducted on concrete columns built with HRB600-grade longitudinal and stirrup bars under cyclic loading conditions. Therefore, the influence of premature fracture caused by low-cycle fatigue damage, inelastic buckling, and repeated bending on the seismic performance of RC columns is not yet fully understood.
This study was designed to investigate the effects of a variety of parameters, including the reinforcement bar diameter, the volume-stirrup ratio, and the axial compression ratio, on the seismic performance of concrete columns. The results showed that the average crack spacing of concrete beams reinforced with HRB600-grade steel bars followed a linear relationship with the reinforcement strain, and this result was independent of the concrete strength grade. The elongation of the bars also increased as the axial load increased, and this result is consistent with the stress-strain behavior model proposed by the authors.