Effect of sulfate attack, drying-wetting cycles and freezing-thawing cycles on reinforced concrete columns under eccentric loads

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Mechanical responses of reinforced concrete (RC) columns exposed to sulfate attack, dry-wet cycles and freeze-thaw cycles under eccentric loads were assessed. Two groups of RC columns with eccentric distances of 50 mm (small) and 100 mm (large) were selected. The experimental results showed that the ultimate bearing capacity of eccentric RC columns increased first and then decreased with the increase of sulfate dry-wet cycles. Compared with the specimen without sulfate dry-wet cycle, the ultimate bearing capacity of RC column with large eccentricity with 30 dry-wet cycles decreases by 36.5 %. Added to freeze-thaw cycles, the ultimate bearing capacity of RC columns with large eccentricity reduced gradually and the deterioration degree increased by 10 % due to the advanced drying and wetting cycles of sulfate. Under the same conditions, the ultimate bearing capacity of RC columns with small eccentricity had slightly variation. With the increase of sulfate dry-wet cycles, although the ultimate bearing capacity and the ductility factor for RC columns with large eccentricity increased firstly and then decreased, its energy absorption still reduced gradually. The ultimate lateral deflection and energy absorption of RC columns with small eccentricity decreased gradually with the increase of sulfate dry-wet cycles, but increased first and then decreased after superimposed freeze-thaw cycles. Freezing-thawing cycle may cause stress redistribution of small eccentric RC columns, leading to greater bending characteristics. The negative effects of sulfate attack, dry-wet cycles and freeze-thaw cycles on large eccentric RC columns were much greater than small ones. The prediction models of ultimate bearing capacity, ductility factor and energy absorption of RC column with large eccentricity were further established to evaluate its mechanical behaviors subjected to multiple sulfate environmental conditions.