Stability of Large Reinforcing Column Cages during Temporary Construction Conditions

摘要

Reinforcing cages for large columns requires shoring during the fabrication and erection stages of construction before concrete is placed to form a permanent load-bearing structure. Many column-reinforcing cage collapses have occurred, resulting in injuries and fatalities because the cages were not properly supported in the temporary condition. Guying systems are commonly used to stabilize large reinforcing cages during construction to avoid such accidents. This paper presents a two-dimensional first-principle stability analysis of reinforcing cages that are either pinned or fixed at the base, and supported by one level of guy wires along the height of the cage. The effect of lowering guy-wire attachment points on the stability of cages is also included because this construction practice is reported to be used in some locales. Critical buckling-load diagrams are determined that account for the relative stiffness of the guy wires with respect to the reinforcing cages and the effect of pretensioning the guy wires. These diagrams are used to provide plausible explanations for validating or refuting current construction practices as far as guy-wire angle of inclination and pretensioning, and rebar cage-base support conditions are concerned.