@article{khan_kowalsky_nau_2016, title={Equivalent Viscous Damping Model for Short-Period Reinforced Concrete Bridges}, volume={21}, ISSN={1084-0702 1943-5592}, url={http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000803}, DOI={10.1061/(asce)be.1943-5592.0000803}, abstractNote={Abstract This paper investigates the effect of spectral shape (intensity and width of the constant acceleration region) and postyield stiffness ratio on equivalent viscous damping for short-period RC bridge columns ( effective period<1s). The modified Takeda degrading stiffness hysteretic model, with parameters appropriate to bridge columns (often termed thin Takeda in the literature), is used for analysis. Insight regarding the importance of these parameters is provided, and a new equivalent viscous damping model is proposed that includes the effect of spectral shape and postyield stiffness ratio, as well as effective period and ductility. The proposed damping model is compared with two existing models. The results indicate that significant improvement is achieved in predicting the peak displacement using the proposed damping model when compared with existing models.}, number={2}, journal={Journal of Bridge Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Khan, Easa and Kowalsky, Mervyn J. and Nau, James M.}, year={2016}, month={Feb}, pages={04015047} }
 @article{khan_sullivan_kowalsky_2014, title={Direct Displacement-Based Seismic Design of Reinforced Concrete Arch Bridges}, volume={19}, ISSN={["1943-5592"]}, DOI={10.1061/(asce)be.1943-5592.0000493}, abstractNote={AbstractThis paper extends the direct displacement–based design (DDBD) procedure, which was developed for buildings and conventional bridges, to the special case of RC deck arch bridges. New design expressions are formulated for the yield drift and deformation capacity of bridge piers seated on arches. The proposed methodology is applied to three case study deck arch bridges in both the longitudinal and transverse directions, and the designs are validated by nonlinear time-history analyses. The results indicate that the proposed methodology is capable of capturing the deck displacement and pier chord rotation within a reasonable degree of accuracy, although the response of the arch bridge is complex and can be affected by higher modes. The research reveals that the arch displacement may be underestimated by the DDBD procedure, but because the arch displacements are very small in comparison with the deck displacement, the DDBD procedure is still successful in controlling peak chord rotation demands on the ...}, number={1}, journal={JOURNAL OF BRIDGE ENGINEERING}, author={Khan, Easa and Sullivan, Timothy J. and Kowalsky, Mervyn J.}, year={2014}, month={Jan}, pages={44–58} }