Experimental Study On Influence Of Concrete Strength On Mechanical Performance Of SSRC Columns

Compared with traditional carbon reinforcements,the use of stainless reinforcements can prolong the service life of the structure and reduce the maintenance costs in the later period,thereby reducing the life cycle cost.This paper takes the stainless reinforced concrete（SSRC）column as the research object.Through a combination of experimental research,numerical simulation and theoretical analysis,it revealed the failure mechanism of the SSRC column under compression,established the corresponding numerical analysis method and analyzed the existing theoretical calculation methods.The details are as follows:（1）8 SSRC columns were designed with concrete strength and loading eccentricity as varying parameters,and the pseudo-static loading test under eccentric offset was carried out.The test results show that under the eccentric load,the stainless reinforcements and concrete have a good working performance.The ultimate load was significantly affected by the concrete strength and the eccentricity.The concrete strength grade was increased from C30 to C50,and the ultimate bearing capacity of the specimens increased by 27.0%on average.When the eccentricity was small,the influence of concrete strength on the bearing capacity was more significant.The average crack width at peak load was between 0.04 and 0.25mm.The number and development of cracks were mainly affected by the eccentricity.When small eccentric compression failure occured,only tensile cracks appeared at the center of the column,and the development from the lateral cracks to the peak load developed quickly;when large eccentric failure occured,the concrete cracked earlier,and the number of transverse cracks is larger and the width of the cracks is larger.（2）With ABAQUS software,the finite element model of SSRC columns was established on the basis of the test data.The failure modes of the finite element model were consistent with the test.Some finite element models were established to analyze the influence of concrete strength,eccentricity,longitudinal reinforcement ratio,slenderness ratio and other parameters on its mechanical properties.When the slenderness ratioλ≥6,the bearing capacity and the slenderness ratio were approximately linear.Asλincreases,the SSRC axial compression model changed from compression failure to instability failure,and the bearing capacity gradually decreased.（3）Based on the test and FEA results,the calculation method of the sectional bearing capacity of the SSRC column in the current code GB50010-2010 was evaluated.It was found that there was a certain deviation between the standard calculated values and the results.The results was conservative when the eccentricity was small,and the result was unsafe when the eccentricity was large.Therefore,it is recommended to consider the influence of relative eccentricity e₀/h₀ on the second-order effect.The influence coefficient of e₀/h₀ on the section curvatureζwas proposed.The Nu-M curve of the optimization model was in good agreement with the experimental and finite element analysis results.（4）The load-average crack width curves of 8 SSRC columns were analyzed,and the applicability and differences of the two codes GB 50010-2010 and EN 1992-1in calculating the crack width of SSRC eccentric specimens were compared.It was found that the calculated values of the two codes were too small.Therefore,the expansion coefficientτ_s in the GB 50010-2010 calculation method was adjusted to 2.356,and the force characteristic coefficientα_{c r} was adjusted to 2.7.The short-term and long-term maximum crack width calculation results of the revised model were stable and safe.