Composite Mega Columns with multiple untied sections
Concrete sections reinforced by multiple encased rolled sections are a possible solution to realize mega columns of tall buildings. In comparison to concrete filled caissons, the advantages are less welding, less fabrication work, the use of simple splices well settled for decades in high-rise projects and possibility of simpler beam to column connections. All these characteristics, combined to the availability of huge rolled sections in steel which do not require pre-heating before welding, lead to another advantage: a high potential for reliable ductile behaviour.
Although codes and specifications do consider composite structural elements, they do not offer specific provisions on the design of composite sections with two or more encased steel sections. Following experimental campaigns and numerical validations, Simplified design approaches are proposed and described in this report in accordance with three codes: European, American and Chinese.