Collapse Modes of Masonry Building with Bottom Frame-seismic Wall Subjected to Strong Ground Motions

摘要

Through damage of Wenchuan and Yushu strong earthquakes, in China, two typical collapse modes of masonry building with bottom frame-seismic wall were discovered recently. This paper presents the influence factors for the two collapse modes: the most critical collapse factor is the loss of lateral strength of structure. Owing to the P - δ effect, P - Δ effect and in-coordination of the foundation deformation associating with horizontal earthquake actions, the loss of lateral resistance causes the bottom frame seismic wall collapse; However, collapse of upper masonry stories is caused by combination of horizontal and vertical acceleration for the masonry integrality is not enough; The lateral stiffness ratio of upper masonry to bottom frame-seismic wall is the key for controlling failure modes of the whole structure. And then, through the simulation results of LS-DYNA of structural collapse modes with different lateral stiffness ratios, and which shows that the lateral stiffness ratio from 1.5 to 2.0 is the best value for preventing the structure from collapsing. Based on the two typical collapse modes and analysis results, the single degree of freedom simplified model of the upper masonry stories and anti-collapse measures are brought up at the same time.