Mechanical properties of underpinning joints in structural moving: Experiments and numerical modeling

Abstract

Summary Underpinning is a key component in the structural moving process, especially for high-rise buildings with gravitational loads. In this paper, a most commonly used 4-sided wrapped underpinning joint with 2 underpinning beams and 2 coupling beams for the frame structures was investigated. Sixteen prototypes were tested considering different shear span-to-depth ratios, underpinning joint heights, reinforcement ratios, and so forth. The experimental results showed that the underpinning beams can fail in shear or flexure-shear. The interface between the column and the beam is also prone to failure during the loading. Further, the bearing capacity can be greatly improved with decreasing of the shear span-to-depth ratio, whereas more damage may occur within the interface domain. In the numerical simulations, a damage–plasticity constitutive model was adopted, and the cohesive elements were used to model the old-to-new concrete interface between the column and beams. It was found that the numerical results agreed quite well with the experimental results. Thus, the proposed approach can be a useful basis for further analysis and optimized design of underpinning joints.