Abstract: Post-cast strips are widely used in the main building and annex, and the interaction analysis is more complicated. The interaction analysis method for the main building and annex with post-cast strips is introduced. Calculation should be done separately according to different working conditions during construction, and the calculation results should be added together. The limited compression layer model is used as the foundation model, and both resilience and recompression are considered. The structure stiffness is formed step by step. For the main building with annex on medium or low compressible soil, by analyzing simplified models with different locations of post-cast strips and different pouring time, the settlement and contact pressure show the feature as follow: the later post-cast strips are poured, the smaller the differential settlement between the main building and the annex is, but the settlement of the main building is larger; compared with post-cast strips at the first span outside the main building, both the maximum settlement of the main building and the differential settlement between the main building and the annex are decreased, and the average contact pressure under the main building is lower, when the post-cast strips are set at the second span outside the main building.

Key words: post-cast strips, the main building and annex, medium or low compressible soil, settlement, contact pressure