Effects of section slenderness and concrete strength on the cross‐sectional behaviour of lightweight concrete‐filled cold‐formed built‐up box sections

This paper concerns axial compressive behaviour of lightweight concrete‐filled cold‐formed built‐up box sections (CFBBS) at cross‐sectional level. A total of twenty‐four lightweight concrete‐filled CFBBS stub columns and their hollow counterparts—formed by nesting two asymmetric lipped channel sections front‐to‐front—were tested. The varying parameters in the present experimental study included three cross‐section slenderness (h/t) ranging from 75 to 125 and three concrete grades (f_c) with measured cylinder strengths varying from 33.5 to 55.6 MPa. The typical mechanical behaviour of the stub column tests was discussed in terms of load‐end shortening response. The parametric influences on the load‐end shortening response and ultimate compressive load were scrutinised.