Behaviour of Internally Strengthening Hollow Stainless-Steel Hot-Rolled Circular Columns Filled With Crumb Rubber and Recycled Aggregate Concrete

Stainless-steel sections are increasingly being utilised in favour of their higher durability. Simultaneously, the use of recycled materials in concrete is aligned with the global concern to encourage sustainable and environmentally friendly construction. The paper examined the behaviour of stainless-steel columns filled with concrete with crumb rubber (CR) and recycled aggregate (RA). It analysed the effect of different percentages of CR (0, 15, and 30) and RA (0, 15, and 50) on the compressive strength of the concrete and the performance of the columns using stainless-steel hollow sections. 20 specimens were manufactured, 18 of which were cast with concrete containing RA and CR at different percentages. A hollow stainless steel circular section with a 100 mm diameter, 600 mm height, and 1.5 mm thickness was tested. To increase the section strength and reduce the weight, two types of stiffeners were added to the specimens: V-shaped and round-shaped. The addition of stiffeners improved the column performance. However, the inclusion of RA and CR led to a reduction in compressive strength and overall column capacity. The most common failure mode observed was local buckling, with V-shaped stiffeners performing better than round-shaped stiffeners in resisting axial loads due to the smaller area deduction from the concrete. Experimental results are compared with those obtained using the proposed equations from various design codes. The proposed equations from the following codes: American Code (AISC 360-22), Eurocode (EN 1994-1-1), Japanese code (AIJ), and Chinese Code (GB/T 51446-21) are conservative and give good agreement with the experimental results.