Structural Performance of Partially Encased Orthogonal Composite Columns with Bond Strength Strategies

Experimental investigation of CFRP-confined partially encased composite columns under axial compression

Global stability capacity of partially encased composite columns with cruciform-shaped section under axial compression

A nonlinear fibre beam-column model for partially encased composite columns incorporating local buckling effect

Post-earthquake fire performance of partially encased composite steel and concrete columns

This paper presents a detailed parametric study, conducted using finite element tools to cover a range of several geometric and material parameters, on the behaviour of thin-walled partially encased composite (PEC) columns. The PEC columns studied herein are composed of thin-walled built-up H-shaped steel sections with concrete infill cast between the flanges. Transverse links are provided between the opposing flanges to improve resistance to local buckling. The parametric study is confined to eccentrically-loaded columns subjected to major axis bending only. The parameters that were varied include the overall column slenderness ratio (L/d), load eccentricity ratio (e/d), link spacing-to-depth ratio (s/d), flange plate slenderness ratio (b/t) and concrete compressive strength (fcu). The overall column slenderness ratio was chosen to be the primary variable with values of 5, 10 and 15. Other parameters were varied within each case of L/d ratio. The effects of the selected parameters on the behaviour of PEC columns were studied with respect to the failure mode, peak axial load, axial load versus average axial strain response, axial load versus lateral displacement response, moment versus lateral displacement behaviour and the axial load.moment interaction diagram. The results of the parametric study are presented in the paper and the influences of each of the parameters investigated are discussed.

A steel plate shear wall often uses partially encased composite (PEC) columns instead of edge frame columns. Such a steel plate shear wall not only bears the gravity load of the structure and resists the bending moment caused by lateral force by taking advantage of the high bearing capacity and bending stiffness of PEC columns, but also effectively anchors with the frame column to counteract the tension field generated by the steel plate. Therefore, the performance of the steel plate shear wall after buckling can be fully exerted and the seismic performance of the structure can be improved. In order to investigate the seismic performance of the structure, a 1/3-scale specimen test of steel plate shear wall with PEC columns is designed and fabricated, and a finite element model is established with the same size of test. It is found that the test and simulation results are in good agreement, which confirms the reliability of the simulation. Subsequently, 20 models with different parameters of steel plate shear wall with PEC columns are analyzed using ABAQUS. Finally, the failure mode, hysteretic behavior, skeleton curve, and bearing capacity of steel plate shear wall with PEC columns are obtained. The results show that PEC columns have a good anchoring effect on the diagonal tension field and can fully exert the plasticity of the infill steel plate, so that steel plate shear wall with PEC columns has superior seismic performance. Experiments also reveal that the crack type of damages appear in a steel plate shear wall with PEC columns, and, as a future work, the authors will explore the use of structural health monitoring methods, such as piezoceramic transducer-based method, to monitor such cracks.

Simplified relations for confinement factors of partially and highly confined areas of concrete in partially encased composite columns

The test results of nine stub-column tests performed on partially encased composite (PEC) columns made with welded H-section steel are described and presented. The H-section steel is stiffened with transverse link and concrete is poured between the flanges of the steel section. The axial comprehensive study has been conducted on all specimens to investigate the ultimate axial capacity of PEC columns. The failure of all columns is due to local buckling of the flanges along with concrete crushing. Closer link spacing improves the ductility of the columns; however, the measurements show that in general yielding do not occur before the peak load in the links. The additional longitudinal bars have no a remarkable effect to the strength of the composite columns. Finally, an equation is proposed to predict the ultimate axial capacity of the partially encased composite column.

Protected steel columns vs partially encased columns: Fire resistance and economic considerations

A Concrete encased steel (CES) composite column is an alternative to pure steel reinforced column. The application of such columns can be found in basement construction and metro railway stations. In this study, structural behavior of both partially encased composite (PEC) column and fully encased composite column (FEC) were investigated.A total of 12 specimens of partially encased steel composite column and fully encased com-posite column were analyzed. Analysis of columns was done in Ansys workbench. Steel profile used in the columns isH-section and cruciform section. The effects of some key parameters such assteel contribution ratio, end condition, and thickness of steel profiles on the performance of proposed column sections were investigated in termsof load-de-formation relationship and strain behavior.Partially encased composite columns are found to be most efficient compared to fully encased composite columns.Flange thickness has a greater influence on load carrying capacity of the composite columns.

Behaviour of steel plate shear walls with different types of partially-encased H-section columns

Parametrical analysis of partially encased composite columns with fiber reinforced concrete subjected to uniaxial and biaxial non-constant bending moments

In this study, experimental tests of the behaviour of steel and partially encased composite (PEC) columns subjected to compressive loading is performed. Evaluation of this type of composite column under axial loading and numerical analysis of its behaviour under combined torsional and axial loading are the main objectives of this study. At first, a parametric study of PEC columns under axial loading was performed in order to find the relationship between flange slenderness ratio of steel column section and concrete confinement. Width-to-thickness ratio of the flange, diameter and spacing of the transverse links were considered as variables in this study. It was observed that dimension of transverse links had almost no effect on the capacity of the specimens, however smaller transverse links spacing increased both capacity and deformability of the specimens. The comparison of the code equations given in CSA S16-14 and EN 1994-1-1 revealed that the equation in CSA S16-14 underestimates the capacity. Furthermore, different types of retrofit of cross-shaped steel column including concrete encasement, use of stiffener plates and transverse links were investigated in this research. Results revealed that concrete confinement and use of transverse links had respectively the most and the least effect on increasing torsional capacity of the specimens.

Local and post-local buckling behavior of welded steel shapes in partially encased composite columns

Hollow and concrete-filled steel tubes (CFSTs) are extensively employed as columns in various structural systems, yet they are susceptible to local buckling under axial compression loading. Local buckling tends to manifest near the column ends where moments are the highest. To address this issue and enhance the strength and ductility of CFSTs, carbon fiber-reinforced polymers (CFRPs) emerge as a simple and effective solution, having been successfully utilized in prior studies. This investigation focuses on assessing the axial load behavior of CFRP-strengthened CFST slender columns using the finite element (FE) method. The study begins with a verification phase, followed by comprehensive parametric studies exploring the impact of CFRP layers, numbers, confinement lengths, and positions. The FE results demonstrate that a single CFRP sheet, with a thickness of 1.2 mm, enhances the composite column’s axial load resistance by 8.5%. Doubling the CFRP sheets to a total thickness of 2.4 mm increases the resistance to 23.5%, while three sheets totaling 3.6 mm and four sheets totaling 4.8 mm result in axial load resistances of 35.1% and 44.5%, respectively. Furthermore, the study reveals that varying the lengths of CFRP sheets improves axial load resistance by 8.5%, 4.6%, 0.1%, and 0.5% for length percentages of 100%, 75%, 50%, and 25%, respectively. These findings underscore the efficacy of CFRP in strengthening CFST columns and provide valuable insights into optimizing the design parameters for an enhanced structural performance.