Seismic-Fire-Combined Loadings Applied to Carbon Fiber-Reinforced Polymer-Confined Reinforced Concrete Columns

This paper presents analytical investigations into the behavior of a reinforced concrete column with and without carbon fiberreinforced polymer (CFRP) confinement when subjected to earthquake and fire loadings. A data set of 100 ground motions covering short and long durations is collected and integrated with 0 to 3 hours of fire exposure. Two strengthening categories are implemented: 1) one to six CFRP layers; and 2) six layers of CFRP with a 40 mm (1.6 in.) thick insulation. A computational platform incorporating autonomous discrete entities is used for the simulation of heat transfer, while static pushover and nonlinear dynamic analyses predict the seismic response of the unconfined and confined columns. Thermal gradients are generated across the column section to identify the physical and mechanical properties of constituents at elevated temperatures, which are linked with the static and dynamic models. The CFRP-confined column with insulation outperforms its unconfined counterpart from a behavioral standpoint, specifically for axial capacities, flexural failure, energy dissipation, and deformability. The implications of the seismic-fire-combined loadings are remarkable in terms of degrading the load-resisting ability of the columns compared with those of the uncoupled actions. The duration of the ground motions dominates the development of a relationship between the spectral acceleration and drift ratio of the columns. Design recommendations are rendered to address the limitations of current practice.