INELASTIC BEHAVIOUR OF RC WALL-FRAME WITH A ROCKING WALL AND ITS ANALYSIS INCORPORATING 3-D EFFECT

摘要

In a reinforced concrete wall-frame structure, rocking of the wall and the three-dimensional (3-D) effect are two important factors influencing the inelastic response of the system. Rocking of the wall about a point close to the compression edge at the wall base induces large elongation along the wall tension chord, resulting in increased rotation demand on beams framing into the wall. The wall vertical elongation also triggers the 3-D effect, which acts back to play a stabilizing role on the rocking wall. A rational analysis of the above effects requires a realistic consideration of the wall-neutral axis migration towards the compression side, which, however, is often ignored. This paper aims to extend the relevant existing studies in the following three aspects: (1) the extent to which a rocking wall can affect the system behaviour; (2) the modelling of the wall-neutral axis migration and its significance; and (3) a quantitative assessment of the 3-D effect, particularly in terms of its role on controlling wall rocking. Results from a Code-compatible planar wall-frame specimen indicate that uncontrolled wall rocking could amount to causing beam-wall connection failure, leading to accelerated deterioration of the entire system. Pushover and dynamic time-history analyses show that by incorporating wall-neutral axis migration more satisfactory prediction of the inelastic response of the wall-frame is produced. A systematic improvement of the wall-frame inelastic behaviour can be achieved by involving the 3-D effect.