Demir, Ugur; Goksu, Caglar; Unal, Goktug; Green, Mark; Ilki, Alper

This paper presents the results of an experimental study that was conducted to investigate the postfire seismic behavior of reinforced concrete columns. Five full-scale, flexure-critical code-complying (e.g., ACI 318-14) cast-in-place reinforced concrete columns were tested to failure under a constant axial load and reversed cyclic lateral displacements after being exposed to an ISO-834 standard fire for 30, 60, and 90 min. Other than the effects of the duration of the fire exposure, the effects of the thickness of the concrete cover (25 and 40 mm) on the structural performance was also investigated for the short fire exposure duration (30 min). The responses of the columns were analyzed in terms of lateral load-displacement relationships, ductility, stiffness, energy dissipation capacities, and residual displacements. The test results indicated that the fire exposure reduced the lateral load capacity of the columns, whereas the deformability capabilities were found to be satisfactory in terms of a structural response. It was also observed that the thickness of the concrete cover had only a slight influence on the postfire seismic behavior of the columns. Furthermore, a numerical study was conducted to predict the load-displacement response of the fire exposed columns. The comparison of the experimentally and numerically obtained load-displacement relationships indicated that the principles of structural mechanics usually applied to conventional columns are also valid for the columns exposed to fire. (c) 2020 American Society of Civil Engineers.

Yalciner, Hakan; Sensoy, Serhan; Eren, Ozgur

Deterioration due to corrosion becomes a more serious problem when future earthquakes with unpredicted intensity and time are considered. Therefore, the prediction of performance levels of corroded reinforced concrete structures is important to prevent serious premature damage. In this study, a corroded, 50-year-old high school building was analyzed by considering corrosion effects and is presented here as a case study. The relevant data obtained from the structure were used to predict its performance level for different time periods by combining two major effects of corrosion. Deformation due to bond-slip relationships and loss in cross-sectional areas of reinforcement bars were examined as a function of corrosion rate for five corrosion levels. Plastic hinges were defined as a consequence of corrosion effects, and they were used to perform nonlinear push-over analyses. Incremental dynamic analysis was then performed for 20 individual earthquake ground motion records to predict the structure's time-dependent performance levels as a function of corrosion rate. Results showed that corrosion had a serious effect on the performance levels of the school building considered in this study by decreasing bond strength. (C) 2015 American Society of Civil Engineers.