During lift-slab operations, load transfer to building columns cannot begin until which condition is satisfied?

During lift-slab operations, load transfer to building columns cannot begin until which condition is satisfied?

• A. Welds on column shear plates or weld blocks have cooled to air temperature
• B. Concrete has cured for 7 days
• C. Hydraulic jacks reach maximum pressure
• D. Temporary supports are removed and floor is swept clean

Answer: (A)

In lift-slab work, the connection between the slab and the columns must be fully ready to carry load before any load is shifted from temporary supports. That readiness comes from the welds on the column shear plates or weld blocks cooling to ambient temperature. The welding process introduces heat, and while the weld and surrounding heat-affected zone are still hot, their strength and dimensions aren’t at their final, stable values. Waiting for cooling ensures the weld metal has reached its designed strength and that any thermal distortion has settled, so the transfer of gravity load to the columns can occur safely without risking weld failure or misalignment. Other steps like curing time, jack pressure, or floor cleaning are important for the overall job, but they don’t determine the exact point at which load transfer to the columns should begin.

In lift-slab work, the connection between the slab and the columns must be fully ready to carry load before any load is shifted from temporary supports. That readiness comes from the welds on the column shear plates or weld blocks cooling to ambient temperature. The welding process introduces heat, and while the weld and surrounding heat-affected zone are still hot, their strength and dimensions aren’t at their final, stable values. Waiting for cooling ensures the weld metal has reached its designed strength and that any thermal distortion has settled, so the transfer of gravity load to the columns can occur safely without risking weld failure or misalignment. Other steps like curing time, jack pressure, or floor cleaning are important for the overall job, but they don’t determine the exact point at which load transfer to the columns should begin.