Experimental Studies On The Effect Of Ductility Properties Of Reinforcing Steel On Seismic Behavior Of Columns

The uniform elongation is the characteristic strain of reinforcement steel at maximum force in simple tension test, it is an important indicator to reflect the ductility of reinforcing steel, and directly affects the seismic behavior of structure. The ratio of actual tensile strength to yield stress means strain-hardening ratio, when large plastic deformation or the plastic hinge appear at one part of a component, it is the key factor to ensure there are both enough bearing capacity and good inelastic rotation capacity.The regulations about uniform elongation and strain-hardening ration of some mainly countries and regions (like in China, New Zealand, and in EU) are different. Higher elongation and strain-hardening ratio means safer for the structure just considering about the way of earthquake resistance. But good ductility of reinforcing steel always means high cost and paying more rare mineral resources. If the elongation and strain-hardening ratio of steel bars is too large, the advantage of the ductility is not able to give full play to the resistance under the aim of"no damage under frequent earthquake, repairable damages under basic earthquake and no collapse under rare earthquake", which may lead to the waste in construction. To research how the elongation and strain-hardening ratio of reinforcing steel effects the structure seismic behaviors, and get the values not only meet seismic but also the economical and practical demands is very important.In this case,the article do low cyclic loadings to the four reinforced concrete columns. Comparisons were set between the bars with good and ordinary ductility, also considering about the buckling to longitudinal reinforcement, strain history and axial compression ratio. The results indicated that the steel bars with value of uniform elongation over 7%, and strain-hardening ratio more than 1.25 was capable of satisfying the demands of Chinese seismic code. Besides, through research the strain data of reinforcing steel in experiment and software simulation, found that the low cycle fatigue affects reinforcing steel significantly. This will lead the steel to damage prematurely.