Effects of Loading Protocol on the Strength and Deformation Capacity of Reinforced Concrete Column




Khedmatgozar Dolati, Seyed Sasan

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Continuum Finite Element models were proposed for simulating the seismic behavior of reinforced concrete columns exhibiting various types of degradation up to axial collapse. The effects of the lateral loading protocols on strength and deformation capacities of concrete columns were quantified. Additionally, relations are proposed to estimate reductions in drift capacities resulting from increased lateral cycling for both the initiation of lateral strength degradation and the initiation of axial degradation.i. Recommendations for selecting parameters in continuum finite element models are presented to simulate the seismic behavior of reinforced concrete columns with flexure (FC), flexure -shear (FSC) and shear (SC) degradation up to axial degradation. In total, 21 columns were calibrated to experimental data. The final proposed model parameters used across columns were able to capture the type of lateral strength degradation, and the sequence of lateral and axial strength degradation with relatively high accuracy. The FE models produced more accurate shear strength estimates than those obtained from ASCE/SEI 41-17 and ACI 318-19 for shear critical columns (SC).�ii. To investigate the effect of loading protocol on the strength and deformation capacity of concrete column, 18 calibrated columns based on experimental data, were subjected to four lateral load loading protocols: monotonic pushover, one, three, and six fully reversed cycles at increasing target drifts. It was found that increasing axial load reduced the effect of cycles on the drift ratio at lateral strength loss. On the other hand, increasing axial load increased the effect of cycles on the drift ratio at axial strength loss. In addition, axial degradation was found to initiate for columns with moderate to high axial load loading when columns lateral strength is close to zero, which is not the case for columns under low axial load and with a higher level of confinement, for which axial degradation initiates when lateral strength is still high.iii. To quantify the effect of loading history on the lateral and axial drift capacities of concrete columns, 18 calibrated columns, validated against experimental data using Finite Element Analysis (FEA), were subjected to various lateral drift histories; including monotonic pushover, and fully reversed cyclic loading protocols with different numbers of cycles. The simulations were conducted under three axial load levels: low (0-0.15), moderate (0.15-0.35), and high (0.36-0.6). The numbers represent the ratio of applied axial load to total gross axial capacity. In total, 116 simulations were conducted using the 18 column models. Relations are proposed that estimate changes in drift capacities due to lateral cycling. The relations are intended to transform a drift capacity obtained either experimentally or from a standard into an estimate of the drift capacity for a different loading protocol.?



Axial degradation, Collapse, Concrete, Finite Element Analysis, Lateral degradation, Structural Engineering



Civil and Environmental Engineering