Xinpei Liu

Behavior of High-Strength Friction-Grip Bolted Shear Connectors in Sustainable Composite Beams

Composite beams comprised of concrete slabs and steel beams joined by mechanical shear connectors are commonly used in modern building design. The use of innovative deconstructable high-strength friction-grip bolt (HSFGB) shear connectors and reduced-emissions precast geopolymer concrete slabs in composite beam design can greatly enhance the sustainability of building infrastructure. Hitherto, research contributions that address the behavior of composite beams with HSFGB shear connectors and precast geopolymer concrete slabs are very limited. To provide a contribution to this area of research, an effective finite element model of push-out testing is developed to investigate the ultimate strength and the load-slip characteristics of shear connection using HSFGB connectors and geopolymer concrete slabs in this proposed sustainable composite beam application. The accuracy of the proposed finite element model is validated by comparing its predictions with experimental results on push-out test specimens also reported in the paper. The effects of the change in the bolt pretension, its clearance between the hole in the steel flange, its diameter and tensile strength,and the compressive strength of the geopolymer concrete are elucidated through parametric studies. Practical design recommendations in algebraic form are proposed and verified for predicting the ultimate strengths and the load-slip relationships for composite beams with HSFGB shear connectors.

Axial Compressive Behavior of Through-Beam Connections between Concrete-Filled Steel Tubular Columns and Reinforced Concrete Beams

AbstractThis paper investigates the axial compressive behavior of a through-beam connection between concrete-filled steel tubular (CFST) columns and reinforced concrete (RC) beams. In this connection system, the steel tube is completely curtailed at the corresponding beam location, with the longitudinal steel reinforcing bars for the beam remaining continuous through the connection region. A strengthening ring beam is used to enlarge the connection zone in order to compensate for the possible decrease of the axial load-carrying capacity as a result of the discontinuity of the steel tube that encases the column. Two series of axial compressive tests on 32 beam-column specimens are reported. The first series of tests, including 5 full-scale connection specimens with CFST columns, show that with proper design, the axial load-carrying capacity of the connection can be higher than that of the CFST column. The feasibility of this type of connection is verified. The second series of tests, including 27 specimens...

Time-Dependent Response of Spatially Curved Steel-Concrete Composite Members. I: Computational Modeling

This paper develops a numerical formulation for the nonlinear time-dependent analysis of steel-concrete composite members that are curved arbitrarily in space, which includes the effects of concrete shrinkage, creep, and geometric nonlinearity. This formulation is applicable to the analysis of composite arches and composite beams curved in plan, representing the limiting cases of members that are vertically and horizontally curved. The flexibility of the shear connection at the interface surface between the steel girder and the concrete deck is taken into consideration in the formulation. For an accurate serviceability limit state analysis of composite curved members, it is essential to include the shrinkage and creep response of the concrete component in the analysis. To also include the effects of geometric nonlinearity, a step-by-step incremental iterative solution procedure is adopted. Comparisons of the numerical solutions with those based on much less efficient and tractable viscoelastic ABAQUS shell element models, and with available experimental results, verify the accuracy of the computational formulation that is developed. Examples are chosen to illustrate the effects of partial interaction and initial curvature on the time-dependent behavior of spatially curved composite beams.