Four real buildings with three to six stories, strong irregularities in plan and little engineered earthquake resistance are subjected to inelastic response-history analyses under 56 bidirectional EC8-spectra-compatible motions. The average chord rotation demand at each member end over the 56 response-history analyses is compared to the chord rotation from elastic static analysis with inverted triangular lateral forces or modal response spectrum analysis. The storey-average inelastic-to-elastic-chord-rotation-ratio was found fairly constant in all stories, except when static elastic analysis is applied to buildings with large higher mode effects. Except for such buildings, static elastic analysis gives more uniform ratios of inelastic chord rotations to elastic ones within and among stories than modal response spectrum analysis, but generally lower than 1.0. With increasing EPA the building-average inelastic-to-elastic-chord-rotation-ratio decreases but scatter in the results increases. Static elastic analysis tends to overestimate the inelastic torsional effects at the flexible or central part of the torsionally flexible buildings and underestimate them at their stiff side. Modal response spectrum analysis tends to overestimate the inelastic torsional effects at the stiff or central part of the torsionally stiff buildings and underestimate them at the flexible side. Overall, for multistorey RC buildings that typically have fundamental periods in the velocity-sensitive part of the spectrum, elastic modal response spectrum analysis with 5% damping gives on average unbiased and fairly accurate estimates of member inelastic chord rotations. If higher modes are not significant, elastic static analysis in general overestimates inelastic chord rotations of such buildings, even when torsional effects are present. Copyright © 2007 John Wiley & Sons, Ltd.
[1]
Stavros A. Anagnostopoulos,et al.
Inelastic torsion of multistorey buildings under earthquake excitations
,
2005
.
[2]
E. Miranda,et al.
Inelastic Displacement Ratios for Design of Structures on Soft Soils Sites
,
2004
.
[3]
Negro Paolo,et al.
Full-Scale PsD Testing of the Torsionally Unbalanced SPEAR Structure in the 'As-Built' and Retrofitted Configurations
,
2006
.
[4]
A. Chopra,et al.
Inelastic Deformation Ratios for Design and Evaluation of Structures: Single-Degree-of- Freedom Bilinear Systems
,
2004
.
[5]
E. Miranda.
INELASTIC DISPLACEMENT RATIOS FOR STRUCTURES ON FIRM SITES
,
2000
.
[6]
H. Krawinkler,et al.
Estimation of seismic drift demands for frame structures
,
2000
.
[7]
Michael N. Fardis,et al.
Estimation of inelastic deformation demands in multistorey RC frame buildings
,
1999
.
[8]
E. Miranda.
Estimation of Inelastic Deformation Demands of SDOF Systems
,
2001
.
[9]
Iztok Peruš,et al.
TORSIONAL EFFECTS IN THE PUSHOVER-BASED SEISMIC ANALYSIS OF BUILDINGS
,
2005
.
[10]
Molina Ruiz Francisco Javier,et al.
Full-Scale Bidirectional PsD Testing of the Torsionally Unbalanced SPEAR Structure: Method, Algorithm and Experimental Setup
,
2005
.
[11]
E. Miranda,et al.
Inelastic displacement ratios for evaluation of structures built on soft soil sites
,
2006
.
[12]
Iztok Peruš,et al.
On the inelastic torsional response of single‐storey structures under bi‐axial excitation
,
2005
.
[13]
Helmut Krawinkler,et al.
Evaluation of Drift Demands for the Seismic Performance Assessment of Frames
,
2005
.
[14]
Peter Fajfar,et al.
On the inelastic seismic response of asymmetric buildings under bi-axial excitation
,
2005
.