Abstract— Stability coefficient is defined as the ratio of the moment induced by the P-Delta effects to the moment due to the lateral forces. For columns with small lateral displacement, it is perfectly acceptable to neglect the P-Delta effects, but for columns which experience high levels of nonlinearity it is crucial to accurately capture the P-Delta effects. An important issue regarding the P-Delta effect is the threshold of safely ignoring it, without compromising on well-being of the structure or being too conservative. Whenever P-Delta effects can be ignored Caltrans SDC provides predefined displacement ductility levels for designing different structural components. Stability coefficient has been the basis for many scholar works regarding design for P-Delta effects. Conservative limits on elastic and plastic stability coefficient have been introduced in order to prevent P-Delta effects from becoming dominant in the structural response. Three different safe thresholds for ignoring the P-Delta effects which are based on stability coefficient have been subjected to study in this research. The displacement ductility corresponding to ignoring the P-Delta effects obtained from these methods are being compared with the Caltrans SDC design target ductility. Using nonlinear time-history analysis ductility levels corresponding to ignoring the P-Delta effects have been evaluated. This research intends to evaluate Caltrans SDC design target ductility for single column bingle column bingle column bingle column bingle column bingle column bingle column bingle column bingle column bingle column bingle column bingle column bents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on ents supported on fixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundationfixed foundation and compare it with displacement ductility levels corresponding to ignoring the P-Delta effects obtained from methods which are based on stability coefficient.
 

Index Terms—stability coefficient, P-Delta effects, nonlinear time history analysis, RC bridge column design, caltrans SDC, ignoring the P-Delta effects

Cite: Parsa Heydarpour, Pedro F. Silva, and Rigoberto Burgueño, "An Investigation on Ignoring P-Delta Effects Based on Stability Index," International Journal of Structural and Civil Engineering Research, Vol. 7, No. 2, pp. 151-156, May 2018. doi: 10.18178/ijscer.7.2.151-156