Cyclic loading tests of semi-precast circular steel tubular columns incorporating precast segments containing demolished concrete lumps

摘要

This paper is concerned with the cyclic response of circular steel tubular column incorporating precast segments (PSs), a structural component proposed to facilitate the use of demolished concrete lumps (DCLs). Such a semi-precast column has been demonstrated to be easy-to-assemble, and sustain static axial load well; yet its seismic behavior is still a big concern, particularly when the precast construction technique is involved. An experimental program was therefore conducted to see how those columns would fare under simulated seismic action. Sixteen model columns were fabricated and tested cyclically, considering the following variables: compressive strength of post-pouring concrete (PPC), axial load ratio, lateral loading direction, cross-sectional size of PS, and vertical location of spacing between adjacent PSs within potential plastic hinge zones. Experimental outcomes indicated that the proposed columns showed comparable cyclic responses to their cast-in-situ counterparts; generally, integrity between PSs and their outer shell (i.e. PPC) was retained, leading to an overall monolithic flexural-dominated behavior. The effects of the PPC's strength and the axial load ratio on the columns' cyclic performances were significant, whilst the other variables appeared to be less influential, thereby allowing a high construction tolerance. A simplified model is suggested to determine the equivalent plastic hinge length of the columns. Moreover, ultimate strength prediction using current standards, as well as fiber-beam based numerical modeling, are made to evaluate their predictive capability for the current case. Overall, this study helps establish initial confidence in applying the semi-precast columns in seismic areas.