Predicting Stability of Lift Slab Structures by Energy Method

The stability of a lift slab structure is vulnerable during some construction stages, even though the structure becomes perfectly safe when completed. Some stages of the construction can lead to instability, because of the way the lifted slabs are parked before they reach their final destination, where they are integrated with the columns. A formula is derived that can be applied to any construction stage and any configuration of parked slabs. The formula finds the critical load of a typical slab that might cause the structure to collapse during the construction of any specific stage. An example of one such collapse during a construction stage was the case of L'Ambiance Plaza in Bridgeport, Conn. The formula is easy to apply numerically and good enough to indicate whether a specific stage of construction is stable or not. Although the formula does not take into consideration the P-δ effect, it is conservative enough to offset its small influence.