Summary: |
Lift slab structures are built in a method, which makes them inherently vulnerableto static and dynamic instability during the construction stages. The columnscannot be laterally braced in the areas, where temporarily anchored slabs are to belifted to higher levels, because the bracing will make the lifting process of the slabsto higher level impossible. Thus the columns will stay long and slender above theanchored slabs until the shear walls are built at the lower levels, This situationrequires the checking of the whole structure above the shear walls for its stabilityagainst its own load. A formula was derived to help in checking the stability of suchstructures, based on the number of slabs, anchored temporarily at different levels,the distances between those anchored groups and the rigidity of the columns. Acomputer program was written to enable the construction process envision thecritical situation which may cause instability. |