Experimental Research on Reinforced Concrete Columns Strengthened with Steel Jacket and Concrete Infill

Abstract

Experimental research on axially compressed columns made from reinforced concrete (RC) and RC columns strengthened with a steel jacket and additional fill concrete is presented in this paper. A premade squared cross-section RC column was placed inside a steel tube, and then the space between the column and the tube was filled with additional concrete. A total of fourteen stub axially compressed columns, including nine strengthened specimens and five plain reinforced concrete specimens, were experimentally tested. The main parameter that was varied in the experiment was the compressive strength of the filler concrete. Three different concrete compression strength classes were used. Test results showed that all three cross-section parts (the core column, the fill, and the steel jacket) worked together in the force-carrying process through all load levels, even if only the basic RC column was loaded. The strengthened columns exhibited pronounced ductile behavior compared to the plain RC columns. The influence of the test parameters on the axial compressive strength was investigated. In addition, the specimen failure modes, strain development, and load vs. deformation relations were registered. The applicability of three different design codes to predict the axial bearing capacity of the strengthened columns was also investigated.

Behavior of Two-Chord Steel–Concrete Composite Columns under Axial Compression

“…Generally, the TCCFST column's load-bearing capacity increases with a higher compressive strength of the infill concrete. It was shown that, when the confinement factor increases, the influence of the concrete strength on the coefficient of the enhanced strength, ks, decreases [1].…”

“…Generally, the TCCFST column's load-bearing capacity increases with a higher compressive strength of the infill concrete. It was shown that, when the confinement factor increases, the influence of the concrete strength on the coefficient of the enhanced strength, ks, decreases [1]. After the concluded experiments, the steel tube was partially removed from one chord of the TCCFST column to investigate the mode of failure and to note the cracking and/or crushing of the concrete fill.…”

“…Moreover, the need to strengthen an RC structure may arise from enlarged loads, the extension of buildings, or even oversights in the design or construction process. A concrete-filled steel tube (CFST) was successfully used as a solution to improve the strength and ductility of an existing RC column as it was presented in [1]. RC structures strengthened with CFST have an improved load-bearing capacity for additional permanent, variable, accidental, and seismic loads.…”

Structural Behaviour of Axially Loaded Concrete-Filled Steel Tube Columns during the Top-Down Construction Method

“…Landović and Bešević [8] investigated the axial capacity of composite columns made of square RC columns strengthened with steel tubes and filled with concrete. The use of welded composite columns for retrofitting frames proved to be very successful since it increased the ultimate capacity, effective stiffness and energy dissipation [8].…”