Experimental Study On Seismic Performance Of Corroded RC Frame Beam Under Artificial Climate

In this paper, artificial atmosphere accelerated corrosion method is chosen toachieve accelerated corrosion of RC frame beams, which extended gradually in the fieldof durability of concrete structures. The seismic performance degradation of RC framebeams under different corrosion degree is investigated. The restoring force model ofcorroded RC beams is established, and numerical modeling analysis for the RC framecorroded beams on the seismic is conducted. The achievement is applied to theoreticalguidance for the seismic performance research of RC frame multi-age structuresconsidered the environmental effects.(1)The effects of steel corrosion and stirrup ratio on the seismic performance of RCframe beams are investigated based on the quasi static loading test of corroded RCframe beam. Artificial atmosphere accelerated corrosion method is chosen for steelcorrosion.The speed of accelerated corrosion is controlled by crack width. After thequasi-static test, the concrete of RC frame corroded beams are knocked off to quantifysteel corrosion rate. Test data is processed to obtain the hysteretic curve, skeleton curve,stiffness degradation, strength degradation and energy dissipation capacity degradationof the RC frame beams.(2) The effects of steel corrosion on the seismic performance of RC frame beamsare investigated. Mechanical Performance: With the increasing in the degree of steelcorrosion, bearing capacity, stiffness, ductility, plastic rotation, deformation restoringcapacity and hysteretic energy of corroded RC frame beams decreases gradually; Stirrupratio has the similar influence on the seismic performance of RC frame beams anduncorroded beams. Damage mode: With steel corrosion intensified, the bending shearfailure dominated by the flexural failure of RC frame beam came into a more obvious brittle destruction. The former is due to the buckling of longitudinal reinforcementgradually and core concrete crushed;The latter is caused by inclined cracks widely orinclined cracks within the scope of the cross section, the shear capacity of RC framebeam shear capacity weakened severely, the shear deformation of plastic hinge zoneincreased significantly.(3) Based on threefold skeleton curves with negative stiffness segment, hystereticmodel of corroded RC frame beams is established.According to regression analysis forthe experimental data, the formula of skeleton curve characteristic point of corroded RCframe beams is obtained. Based on hysteretic energy cyclic degradation index, restoringforce model established in this paper took into account pinching effect, strengthdegradation, unloading stiffness degradation, hardening stiffness degradation andreloaded stiffness accelerated degradation. The comparison between hysteretic curvecalculated and experimental hysteretic curve demonstrates that: the restoring forcemodel can describe the hysteretic characteristics of the corroded RC frame beam fairly.(4)Based OpenSees, Apply constitutive model of the corroded stirrups confinedconcrete to source program of the opensees and seismic performance of the corrodedRC frame beams of under cyclic loading were analyzed. The comparison betweennumerical simulation results and seismic performance experimental demonstrates that:the finite element numerical modeling methods considering corrosion effects of RCframe beam is well applicable.