Earthquake induced torsion in buildings: critical review and state of the art

Abstract

The problem of earthquake induced torsion in buildings is quite old and although it has received a lot of attention in the past several decades, it is still open. This is evident not only from the variability of the pertinent provisions in various modern codes but also from conflicting results debated in the literature. Most of the conducted research on this problem has been based on very simplified, highly idealized models of eccentric one-story systems, with single or double eccentricity and with load bearing elements of the shear beam type, sized only for earthquake action. Initially, elastic models were used but were gradually replaced by inelastic models, since building response under design level earthquakes is expected to be inelastic. Code provisions till today have been based mostly on results of such models or on results from elastic multistory idealizations. In the past decade, however, more accurate multi story inelastic building response has been studied using the well-known and far more accurate plastic hinge model for flexural members. On the basis of such research some interesting conclusions have been drawn, revising older views about the inelastic response of buildings based on one-story simplified model results. The present paper traces these developments and presents new findings that can explain long lasting controversies in this area and at the same time may raise questions about the adequacy of code provisions based on results from questionable models. To organize this review better it was necessary to group the various publications into a number of subtopics and within each subtopic to separate them into smaller groups according to the basic assumptions and/or limitations used. Capacity assessment of irregular buildings and new technologies to control torsional motion have also been included.

Pushover Analysis for Plan Irregular Building Structures

“…Some research is still under development in this field (for state-of-the-art reports, refer to Anagnostopoulos et al 2013 and to previous reviews by Rutenberg 1992Rutenberg , 2002Rutenberg and De Stefano 1997;De Stefano and Pintucchi 2008), even if the assumptions made for formulating such models involve many simplifications.…”

“…In the former case, methods considering uni-directional eccentricity, strength and ground motion were developed, subsequently improved considering these parameters in both principal directions. Concerning the multistorey models, some simplified shear-type models have been developed as well as detailed plastic hinge type models (see reviews by Rutenberg 1992Rutenberg , 2002Rutenberg and De Stefano 1997;De Stefano and Pintucchi 2008;Anagnostopoulos et al 2013).…”

Torsional Response Induced by Lateral Displacement and Inertial Force

“…Although torsional response induced by seismic ground motion has been investigated for more than 60 years, several factors still remain unclarified (Anagnostopoulos et al, 2015). As causes of the torsional response of buildings, researchers have studied eccentric distribution of stiffness (Georgoussis, 2009;Stathi et al, 2015), damping (Goel, 2000;Lin and Tsai, 2007), and the mass of a structure (Chandler and Hutchinson, 1986), in addition to spatially non-uniform or torsional ground motion input (De la Llera and Chopra, 1994;Heredia-Zavoni and Barranco, 1996;Basu and Giri, 2015;Falamarz-Sheikhabadi and Ghafory-Ashtiany, 2015;Gičev et al, 2015).…”

“…As causes of the torsional response of buildings, researchers have studied eccentric distribution of stiffness (Georgoussis, 2009;Stathi et al, 2015), damping (Goel, 2000;Lin and Tsai, 2007), and the mass of a structure (Chandler and Hutchinson, 1986), in addition to spatially non-uniform or torsional ground motion input (De la Llera and Chopra, 1994;Heredia-Zavoni and Barranco, 1996;Basu and Giri, 2015;Falamarz-Sheikhabadi and Ghafory-Ashtiany, 2015;Gičev et al, 2015). A comprehensive review article has also been written by Anagnostopoulos et al (2015). Therefore, their target buildings in general have an irregular, asymmetric structural property for the former perspective, which includes accidental eccentricity due to non-structural component or structural damage, and a long or large base mat that can incur phase difference of input ground motion for the latter.…”

Practical Modal Pushover Design of one-way asymmetric-plan reinforced concrete wall buildings for unidirectional ground motion

“…Nonlinear, torsional and 'higher mode' effects significantly affect the seismic response of irregular ductile buildings. The state of the art of designing and analyzing irregular structures has been reviewed by Rutenberg (2002) and Anagnostopoulos et al (2015). Additional material on the seismic behavior and design of irregular and complex civil structures can be found in Lavan and De Stefano (2013).…”