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Past research has shown that reinforced concrete members exposed to the combined effect of extreme low temperatures and cyclic reversals undergo a gradual increase in strength and stiffness coupled with a reduction in displacement capacity. This paper presents a methodology to quantify the effects of low temperatures on the seismic behavior of reinforced concrete bridge columns and provides appropriate design recommendations.
Keywords: columns; ductility; seismic; strength; temperature.
(ProQuest: ... denotes formulae omitted.)
INTRODUCTION
Results obtained from low temperature experimental tests1-3 have shown that reinforced concrete (RC) columns exposed to the combined effect of subfreezing temperatures and cyclic loads undergo a gradual increase in shear and flexural strength coupled (in the case of flexural-dominated columns), with a reduction in displacement capacity. In this paper, the experimental results from past research1,2 are used to calibrate a fiber-based lumped-plasticity model capable of simulating the response of RC columns to cyclic load reversals while subjected to subfreezing temperatures. The model is used to analyze typical RC bridge bent configurations. To determine the impact of subfreezing temperatures on the seismic response of RC bridge bents, the bent models were subjected to inelastic lateral pushovers and a series of incremental inelastic time-history analyses using a set of spectrum-compatible records. Based on the results obtained from the experimental tests, the nonlinear simulations and a moment-curvature parametric analysis, a simple methodology was developed to account for the low temperature flexural overstrength and reduction in ductility capacity.
RESEARCH SIGNIFICANCE
Seismic design of RC bridges is generally based on the principles of capacity design, where a strength hierarchy is established in the bridge to ensure that damage is controllable and occurs only where the designer intends.4 Special importance is then placed on the ductility of the structural members selected to develop plastic hinges (usually the bent columns), which should be specially detailed to sustain large inelastic deformations. All other members should be designed to remain elastic (the cap beam in the case of bridge bents) while resisting the overstrength moments from adjacent members. subfreezing temperatures affect both the displacement capacity of the column and the overstrength moment transmitted to the cap beam. To the authors' knowledge, however, the low temperature effect is not included in any design code. The final goal of this research...