Eccentric compressive behavior of PBL-stiffened double-skin composite walls in bridge pylons

Double-skin composite walls (DSCWs) stiffened with perfobond ribs (PBLs) have gained popularity for use in large-scale structures. This investigation aims to provide valuable insights into the performance of PBL-stiffened DSCWs when subjected to eccentric compressive loads. An experimental investigation was conducted on eight PBL-stiffened DSCWs. The failure modes, local buckling behavior, load-deflection behavior, moment-curvature relationship, and strain distribution were analyzed. The results indicate that an increase in the interval of longitudinal PBLs on the compressive zone of the DSCW specimens leads to a reduction in eccentric compressive resistance due to premature local buckling. However, the transverse PBL interval and removal of transverse rebars had negligible effects on the local buckling behavior of the faceplates and did not affect the resistance of the specimens. The ductility index of DSCWs slightly increased with an increase in concrete strength and was further enhanced by the presence of headed studs. The introduction of studs on the faceplates effectively delayed the onset of local buckling and improved the resistance of the DSCWs under eccentric loads. Throughout the loading process, the longitudinal strain remained almost linear, and the neutral axes remained unchanged, indicating that the plane section assumption works for PBL-stiffened DSCWs. To develop N-M interaction curves of PBL-stiffened DSCWs under eccentric loads, the effective area method was introduced to predict the postbuckling strength of unilaterally restrained PBL-stiffened plates. The proposed curves provided accurate and relatively conservative predictions of the experimental results due to the reasonable consideration of the local buckling effect.