Analytical Performance and Design of CECFST Column Assembled to PEC Beam Joint

Abstract

Concrete-encased concrete-filled steel tube (CECFST) columns and partially encased composite (PEC) beams are both steel-concrete composite members which have outstanding advantages and have been applicated in some engineering constructions. This paper makes an attempt to employ blind bolting technique to assemble CECFST columns to PEC beams. For the purpose of exploring the mechanical performance of this type of assembled joints, firstly, a nonlinear finite element (FE) model was established and validated, where complicated contact interaction was taken into consideration. Plenty of parametric analysis were adopted to find out the effect of ten parameters on strength and initial stiffness of the assembled joint. Numerical analysis showed that mechanic behavior is notably affected by axial load ratio, width and thickness of end-plate, bolt pretension force, bolt diameter, and steel ratio of CECFST column. Full-range analysis was then carried out to observe stress and strain developments and failure modes. Load transfer mechanism in CECFST column was also studied. Design methods to estimate the flexural capacity and initial stiffness of the connections were proposed in accordance with the component models. In comparison, it could be concluded that the calculation results fit well with the analytical results, which confirms that the design formulas could provide a favorable basis in practical design.