g-g Chen

Experimental Evaluation of Crossties in Large Reinforced Concrete Columns under Pure Compression

The effectiveness of crossties in six sets of large-scale reinforced concrete short columns under monotonic axial compression is evaluated experimentally. The primary variables were type of crosstie engagement, type of crosstie, and crosstie placement offset. It was observed that minor placement offset up to 20 mm between hooks of crossties and longitudinal steel bars does not bring unfavorable consequences in confinement. The crosstie hook engagement of both hoop and longitudinal steel bar is better than that engagement of the longitudinal steel bar alone, but it is difficult in installation. Crossties composed of two straight end-180-deg hook steel bars give the best performance among the types of crosstie and it is convenient to facilitate the fabrication of reinforcing cages. However, the effectiveness under cyclic loading needs further study.

Panel Zone Shear Behavior of Through-Flange Connections for Steel Beams to Circular Concrete-Filled Steel Tubular Columns

AbstractThis research investigated the panel zone shear behavior of a proposed through-flange connection for steel beams to circular concrete-filled steel tubular (CFT) columns. Four exterior beam-column specimens were designed and tested using cyclic loading applied to the beam end. Three design variables were examined: concrete infill in the column tube, stiffeners to the column tube in the panel zone, and the width of the through-flange plates. Test results showed significant panel zone shear yielding for all specimens. Failure of the specimens was caused by fracture of the column tube near the through-flange plates and crushing of concrete at the stiffener side in the panel zone if concrete infill was present. The use of concrete infill, stiffeners, and 25% wider through-flange plates increased the peak applied load by 156, 7, and 14%, respectively. A model that considers crushing of concrete at the stiffener side as failure mode was proposed to calculate the panel zone shear strength contribution fro...

Ductility enhancement of RC beams confined by steel cover plates

Abstract By confining the cover concrete of the beam on the compression side with steel cover plate, the ultimate compressive strain of cover concrete can be increased, the buckling of compression steel bars can be retarded, and the ductility of the beam can be elevated. Eleven large‐scale beams were tested to evaluate the effectiveness of the proposed scheme. Test results showed that the confining system used in this study was able to provide sufficient confinement to the beam cover concrete and was able to raise the ductility value of an existing beam up to 349% that of the original beam. Compared to concrete jacketing technique, the ductility enhancement scheme proposed in this study requires less demolition and less labor.

Size effect on axial behavior of concrete-filled box columns

The use of concrete-filled box columns could provide an economical alternative to building and bridge construction. Past experimental results showed that current building codes provided an adequate accuracy in determining axial capacity of such composite members. However, the sizes of the previously studied test specimens were mostly smaller than those for practical applications. As the column size increases, the size effect may become significant. Therefore, the applicability of extrapolating those test results to larger concrete-filled box columns needs to be justified. This study was devoted to investigating the potential size effect on axial behavior of concrete-filled box columns. Six short square concrete-filled box columns, with cross-sectional dimensions ranging from 300 to 750 mm, were tested under axial loading. Comparisons between experimental and analytical results were presented. It was observed that the size effect was prominent for the concrete-filled box columns studied herein. The results of this study showed that current design codes overestimated the axial capacity of the test columns with a dimension of 750 mm. In addition, finite element simulations of the axially loaded specimens were conducted to investigate the stress–strain behaviors of the concrete enclosed in different sizes of steel box columns. Results from the finite element analysis suggested that the larger steel box columns were less effective in enhancing the compressive strength of the enclosed concrete than smaller steel box columns.

FLEXURAL ANALYSIS AND DESIGN METHODS FOR SRC BEAM SECTIONS WITH COMPLETE COMPOSITE ACTION

Abstract Section analysis, that complies with complete composite and strain compatibility conditions of 810 SRC beam sections, was carried out to investigate the flexural behavior of SRC beam sections. As well, a correlation between the curvature ductility ratio and the depth of the neutral axis was established with fairly good agreement. A section analysis procedure, that fulfills all composite conditions with plastic stress distribution, is introduced for the calculation of moment capacity and the curvature ductility ratio of SRC beam sections. In addition, a design method, based on complete composite and plastic stress distribution, is proposed for the design of SRC beam sections to meet both the moment and curvature ductility requirements. The analysis and design methods proposed here are able to provide tools for more economical and rational SRC beam design, and are superior to the strength superposition design method.