317 publications from this institution
Instead of conventional ductility, deformability is proposed for various load-deformation curves of members made of new materials, such as fiber reinforced polymer (FRP). After analyzing the existent performance indices, the design-aimed state and the ultimate failure state are defined as the characteristic behavior states for members. Moreover, a set of performance indices, including deformability factor D, strength factor S , deformation energy factor Y and overall performance factor F, are presented to describe the behavior and the safety storage of flexural members comprehensively. Comparing with the traditional members, the relation among the performance indices is analyzed by the numerical results of five types of members and the ranges of the indices are acquired. It is drawn that the safety storage for strength and deformation can be exchanged without overall safety margin loss. F factor is suggested to serve as the scale for determining the design-aimed state, by which the reasonable uniform safety storage for various flexural members can be acquired. It is proven by evaluating eight specimens in references. The proposal of the performance indices including deformability provides a reference for the design of members made of new materials.
Concrete-filled steel tubular (CFST) columns have been extensively studied and widely used in practice. Existing research has shown that non-circular CFST columns is much less ductile than their circular counterparts, particularly when thin/high strength steel (HSS) tubes and high-strength concrete are used. To address this problem, a new form of CFST columns has recently been proposed by the first author. The new column consists of a steel tube filled with concrete that is confined with HSS spiral reinforcement typically with a yield stress exceeding 1000 MPa. These columns, referred to as confined concrete-filled steel tubular (CCFST) columns, also maintain the ease for connection to CFST or steel beams. This paper presents the results of a series of concentric axial compression tests on such columns of square cross-section to demonstrate their advantages. The experimental program included 13 CCFST columns, four CFST columns without internal spiral confinement, two hollow steel tube (HST) columns, and 11 circular HSS spiral-confined concrete columns. Three different compressive strengths and three HSS spiral pitches were examined in the experimental program. The CFST columns, HST columns, and HSS spiral-confined concrete columns were all tested under axial compression to gain a good understanding of the confinement mechanism in a CCFST column. The test results show that the new columns possess much greater ductility than those without internal spiral confinement, although the use of HSS spirals increases the steel volume by only a small percentage. It is also shown that the axial load-axial strain curve of a CCFST column can be conservatively predicted by summing the axial load-axial strain curves of the hollow steel tube without local buckling, the HSS spiral-confined concrete core, and the sandwiched concrete between the two.
