A new steel jacketing method for RC columns

Abstract

This paper introduces a new steel jacketing method for reinforced concrete (RC) columns with lap splice and evaluates its performance by a series of axial tests of concrete cylinders. At first, 45 concrete cylinders were fabricated with varying design compressive strengths of 21, 27 and 35 MPa and then part of them was jacketed with two split-steel jackets under lateral confining pressure. The parameters in the first test were the steel jacket's thickness and the existence of adhesive between steel and concrete surface. In the second test, whole steel jackets were used to wrap cylinders with lateral pressure. Also, a double-layered jacket consisting of two steel plates was introduced; a cylinder was jacketed by two steel plates one after another. The effect of the new method was verified through comparing the results of the compressive tests for plain and jacketed cylinders. The steel jacket built following the new method showed good results of increasing the compressive strength and ductility of the jacketed cylinders with respect to the plain cylinders. The thicker steel jackets showed that the increased compressive strength, and the ductility at failure depended on the welding quality of the steel jackets. The adhesive between steel and concrete surface reduced the confining effect of the steel jackets. The whole jacket showed more ductile behaviour than the two split jackets. The double-layered jackets were estimated to possess an equal performance to that of a single steel jacket having the same thickness of the double-layered jacket. Finally, the experimental results were compared with the constitutive model of steel-jacketed concrete; which showed a good agreement between the experimental results and the models.

Bond and splitting behaviour of reinforced concrete confined by steel jackets without grouting

“…The 100 mm lengths from the top and the bottom of the specimen were wrapped with oil papers. The jacketing process was described well in a previous study (Choi et al, 2009). Figure 2 shows the process briefly.…”

“…The clamp had two hoops with a thickness of 5 mm and an arc length of 100 mm; the contacting are was therefore 1000 mm 2 : The pressure of the three steel bands was too small to compare that of the two clamps relatively. The compressive force by a clamp owing to manual screwing was measured as 15 kN in a previous study (Choi et al, 2008). Thus, the pressure just under the hoops was 15 MPa; however, the area of the two hoops occupied only 3 .…”

“…Shape memory alloy wire jackets were also introduced; however, no application exists for field practices (Chai et al, 1991, Pantelides et al, 2004, 2007. The strong and weak points of the above two jacketing methods have been discussed in several studies (Choi et al, 2010(Choi et al, , 2009). The critical inconvenience of the steel jacketing method is the grouting between steel and concrete, which provides composite behaviour.…”

“…The critical inconvenience of the steel jacketing method is the grouting between steel and concrete, which provides composite behaviour. A new steel jacketing method was introduced to overcome this drawback, and its performance was demonstrated by experimental tests of concrete cylinders (Choi et al, 2009). The difference between the new method and the conventional one is that in the new method a non-grouting process is used to attach a steel jacket onto a concrete surface.…”

Equivalent stress block for normal-strength concrete incorporating strain gradient effect

“…18%). The cross-sections of the test specimens were those commonly adopted by other researchers (Choi et al, 2009;Han et al, 2010;Sim et al, 2009). Table 3 summarises the section properties of all the specimens.…”