P-Δ effect on inelastic displacement ratio spectra for inelastic structures

ZHAI Chang-hai¹, LI Ning¹, MA Yu-hong², XIE Li-li^1,3

1.School of Civil Engineering,Harbin Institute of Technology,Harbin 150090,China;2.Earthquake Engineering Research and Test Center,Guangzhou University,Guangzhou 510405,China;3.Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China



Abstract:

For the evaluation of structures with known ductility demands,the constant-ductility displacement ratio spectra(CDDRS) are particularly useful for providing inelastic displacement ratios to estimate maximum lateral inelastic displacement demands from maximum elastic displacement demands.The CDDRS are computed for single-degree-of-freedom systems(SDOF) by considering or ignoring P-Δ effect for different ductility levels when subjected to 344 earthquake ground motions recorded in four site classes.The modified expressions of CDDRS for P-Δ effect are proposed.It is concluded that the P-Δ effect on CDDRS is significant,and the effect increases with the increase of ductility level.In the long-period region,the CDDRS ignoring P-Δ effect almost conforms to the equal-displacement rule.But in the case of higher ductility level,the CDDRS considering P-Δ effect are much higher than 1.0,which do not conform to the equal-displacement rule.

Key words:  constant-ductility displacement ratio spectra  inelastic displacement estimation  P-Δ effect  ductility level  structural periods

DOI：10.11916/j.issn.1005-9113.2011.01.020

Clc Number:P315.9

Fund: