Inelastic response and design criteria of plan‐wise asymmetric systems

Abstract

SUMMARYThe study of the torsional response of buildings in the inelastic range of behaviour is of great interest since the ability of structures to resist strong earthquakes mainly relies on their ductility and capacity for energy dissipation. Furthermore, an examination of the performance of structures during past earthquakes demonstrates that plan-asymmetric buildings suffered greater damage due to torsional response. The paper deals with this subject by analysing a model which idealizes a one-storey building with resisting elements oriented along two perpendicular directions. In addition to the parameters of the elastic behaviour, the inelastic system response depends on full yield capacity and plan-wise strength distribution. The influence of the criterion adopted for the design of resisting elements on local ductility demand and damage has been evaluated by parametric analysis. In particular, a comparison has been carried out between systems with equal design levels for all elements and systems with design levels dependent on the element location. For a given elastic behaviour and total capacity, the strength distributions in plan have been defined which minimize ductility demand and structural damage. Finally, based on these findings, responses from models designed according to several seismic codes have been compared.

Effect of Overstrength on the Seismic Behaviour of Multi-Storey Regularly Asymmetric Buildings

“…Because of such an evidence, large research efforts have been devoted to examining effects of the lateral-torsional coupling on building seismic behaviour (Goel and Chopra, 1990;De Stefano et al, 1993, 1998De Stefano and Rutenberg, 1999) and to developing and proposing design procedures (Goel and Chopra, 1990;Chandler and Duan, 1992;Duan and Chandler, 1992;Tso and Zhu, 1992;Zhu and Tso, 1992; aimed at providing both plan-regular and plan-irregular systems with a similar level of seismic protection. To this purpose, most studies on seismic response of asymmetric structures have analysed response of single-storey models (Goel and Chopra, 1990;Tso and Zhu, 1992;Zhu and Tso, 1992;De Stefano et al, 1993, 1998De Stefano and Rutenberg, 1999; representing the most extreme idealisation of plan irregular buildings. Such models usually consist of a floor deck, rigid in its own plane and supported by massless, axially inextensible vertical resisting elements, characterised by a bi-linear elastic-hardening behaviour.…”

Inelastic response of bi-eccentric-plan asymmetric reinforced concrete buildings

“…Developing a specific design method defined for two types of eccentric systems without strength eccentricity and with a strength eccentricity equal to stiffness eccentricity, Tso and Ying (1990) highlighted that the flexible edge is more sensitive to the torsional effects and could experience additional ductility demands when the strength eccentricity exists. These conclusions have also been emphasised by other researchers (De Stefano et al, 1993;Chopra, 1990, 1991). However, Sadek and Tso (1989) observed that an increase in the strength eccentricity may lead to an increase in the torsional response of asymmetric structures.…”

Seismic Response of Plan‐Asymmetric Structures with Diaphragm Flexibility

“…Model 6 is a model with uniform strength distribution and stiffness eccentricity. Models 7 and 8 are known as "optimum configuration" models according to the study of De Stefano et al [32]. In model 7, the distance between the mass center and strength center is 0.25 of the distance between the mass center and the stiffness center, while in model 8, the strength center is between the mass and stiffness centers and in an equal distance from each of them.…”