Compressive response of substandard steel-jacketed RC columns strengthened under sustained service loads: From the local to the global behavior

The aim of the study is to compare the compressive response of preloaded columns with respect to the tests without preload to obtain a more realistic prediction of load-carrying capacity of structural columns after retrofitting under serviceability loads. The influence of the preload level, the delayed contribution of the confining device during the loading process and the time dependent effects are highlighted for the tested specimens. Based on the experimental observations, an analysis-oriented model is proposed for the reproduction of the compressive response of steel jacketed columns taking into account the effects of the preload.