摘要 ：偏心率、结构扭转为主的第一自振周期与平动为主的第一自振周期之比和楼层最大水平位移（层间位移）与该楼层二端水平位移（层间位移）平均值之比（简称周期比和位移比）是平扭耦联问题中的三个关键参数。中美二国规范都把位移比大于1.2定义成平面不规则中的扭转不规则。但是，二国规范控制扭转效应的侧重点有所不同。美国规范不控制周期比，它对每层的动扭矩作了放大，以考虑扭转不规则对构件内力的影响，强调结构的地震反应和构件的内力；我国规范对周期比提出不大于0.85-0.90的限值要求，强调结构的自振特性。本文详细地叙述了结构工程师关心的刚心和质心的定义和计算机求解方法，综合结构的自振特性和地震反应，以周期比、第一振型中的扭平分量比和位移比为控制指标，第一次提出了结构动力规则性概念。明确指出结构的扭转不仅仅是几何规则性问题，本质上它更是一个动力规则性问题。结构可以是几何不规则的，但结构工程师要努力做到结构的动力特性是规则的。文中还列出了实现结构动力规则性的9条途径。同时笔者建议规范在今后的修订中增设动力规则性的有关条款。

关键词 ：抗震设计；平扭耦联；动力规则性

作者简介 ：扶长生（1944 — ），男，上海人，教授级高工，上海长福工程结构设计事务所董事长

Abstract : With regard to the design of torsionally coupled buildings, the three key parameters are eccentricity, ratio of the uncoupled torsional period to the uncoupled lateral period and ratio of the maximum story drift to the average of the story drifts. Both American and Chinese codes define that the torsional irregularity shall be considered to exist when the maximum story drift is more than 1.2 times the average of the story drifts at the two ends of a building structure. However, there exists a difference between the codes when dealing with design and analysis of a torsionally irregular building. In IBC a torsional amplification factor, Ax, is required to account for the effects of torsional irregularity in calculating internal forces of the elements. In GB50011-2001, however, the ratio of periods is required to be no more than 0.85-0.90 in modal analysis. This paper explains in details the definition of mass center and rigidity center, and how to evaluate them by computer, which concerns the structural engineers the most. It proposes a concept of dynamic regularity of a building structure in terms of the ratio of periods, the ratio of the maximum story drift to the average of the story drifts and the torsional content in the fundamental modal shape. The characteristics of torsional regularity of a structure are to be expressed not only in terms of geometrical, but also in essence of dynamic. A structure could be irregular in geometry. The structural engineers, however, shall design the building to be dynamically regular. Several ways are presented in the paper on how to design and propotion a structure dynamically regular. The author also suggests that new provisions regarding structural dynamic regularity would be included in the current design code.

Key words : seismic design; coupling of translational and torsional vibration; dynamic regularity