Lift slab construction
Lift slab construction is a method of constructing concrete buildings by casting the floor or roof slab on top of the previous slab and then raising the slab up with hydraulic jacks. This method of construction allows for a large portion of the work to be completed at ground level, negating the need to form floor work in place. The ability to create monolithic concrete slabs makes the lift slab construction technique useful in quickly creating structures with repetitive form work, like parking ramps.
History
This method of construction simultaneously began development in 1948 by both Philip N. Youtz of New York and Thomas B Slick of Texas. Although the first patent for lift slab construction was given to Slick in 1955, the method of construction is commonly referred to as the "Youtz-Slick Method". His patent called for a method that would allow for fabrication to be completed at the ground level, eliminate a large portion of the formwork, create uniform floors of concrete, and reduce the labor to be completed at an elevated level.Applications of lift slab construction
The method was first used at Trinity University in San Antonio, Texas during the construction of Northup Hall in 1952. Northrup Hall was the first full scale building erected using lift slab construction. Being such, the process drew a crowd of spectators, waiting to see if the structural integrity of the building would hold.Johnstone Hall, a Clemson University dormitory in Clemson, South Carolina, was erected using this method in 1954, as did Woodrow [Wilson High School |Woodrow Wilson High School] in the same year. Sections of Johnstone Hall were demolished in the mid-1990s to make way for new suite-style residence halls. Demolition of the remainder of Johnstone Hall, along several attached structures, was completed in 2024.
The building located at 2150 Shattuck Avenue in Berkeley, CA is one example of lift slab construction utilized in the Bay Area in the mid-twentieth century. Built in 1969, the First Savings Building utilizes lift slab construction to support the fourteen story height of the building. The building's structural system consists of a system of trusses from which the various concrete slab floors are hung. In turn, these trusses extend out from two reinforced concrete cores which provide the main structural support for the entirety of the building.
Lift slab construction was also involved in the L'Ambiance Plaza collapse in Bridgeport, Connecticut, in 1987, and resulted in a nationwide federal investigation into this construction technique in the United States, and Connecticut imposed a temporary moratorium on lift slab construction. The failure of the structure has been primarily attributed to instability with the steel columns that were meant to support the floors. Although other factors were involved in the collapse while under construction, it is the insufficient lateral bracing that ultimately caused the structural failure.
Northminster Car Park in Peterborough, England, built using the lift slab technique, was found to be unsafe and beyond economic repair in 2019.