SUMMARYIn order to mitigate the e ect of torsion during earthquakes, most seismic codes of the world provide design guidelines for strength distribution based on the traditional perception that element sti ness and strength are independent parameters. Recent studies have pointed out that for an important class of widely used structural elements such as reinforced concrete exural walls, sti ness is a strengthdependent parameter. This implies that the lateral sti ness distribution in a wall-type system cannot be deÿned prior to the assignment of elements' strength. Consequently, sti ness eccentricity cannot be computed readily and the current codiÿed torsional provisions cannot be implemented in a straightforward manner. In this study, an alternate guideline for strength distribution among lateral force resisting elements is presented. To develop such a guideline, certain issues related to the dynamic behaviour of asymmetric wall-type systems during a damaging earthquake were examined. It is shown that both sti ness and strength eccentricity are important parameters a ecting the seismic response of asymmetric wall-type systems. In particular, results indicate that torsional e ects can be minimized by using a strength distribution that results in the location of the centre of strength CV and the centre of rigidity CR on the opposite sides of the centre of mass CM.

Recent studies have shown that for many lateral force‐resisting elements (LFRE) stiffness is dependent on strength, and as a result strength assignment to these elements would affect both the strength and stiffness distributions in a structure. Consequently, stiffness distribution cannot be considered known prior to strength assignment. This paper presents a yield displacement distribution‐based strength assignment strategy that does not require the knowledge of stiffness distribution prior to strength assignment. It is shown that structural systems with their center of rigidity (CR) and center of strength (CV) located on the opposite sides of the center of mass (CM) will have small torsional responses under seismic excitation. Copyright © 2003 John Wiley Sons, Ltd.

Recent studies have pointed out that the stiffness and strength of many lateral force-resisting elements (LFRE) are dependent parameters. This paper examines the implication of this finding in the distribution of design strength among LFRE. It is shown here that in order to minimize torsional response, one should use a strength/stiffness distribution combination that leads to the location of the center of strength, CV, and the center of stiffness, CR, on opposite sides of the center of mass, CM. A design-oriented strength-allocation procedure to arrive at such strength and stiffness distributions is presented. Its effectiveness in minimizing torsional response is demonstrated through comparison of seismic performance of structures having strength allocated on the basis of the proposed procedure with those following current UBC and EC8 torsional provisions.

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