Siefert Associates, LLC  has been selected by the contractor to aid in the construction of the foundations for the first major project of Columbia University Expansion.

 

The First Phase Contract for the Jerome L. Green Science Center includes the construction of over 150,000-square feet of watertight perimeter diaphragm slurry wall. Ninety-six load-bearing elements (barrettes) installed to depths of up to 240 feet support embedded steel columns weighing up to 35 tons each to facilitate a top-down construction sequence.

 

Siefert Associates, LLC has been instrumental in the engineering of crane layouts and rigging designs for slurry wall and drilled shaft rebar cage erection, design of equipment platforms, as well as obtaining permit approvals from the NYC DOB and MTA.

 

The project is divided into two main categories: slurry wall rebar cage erection and drilled shaft rebar cage erection. The rebar cages from both categories have been tilted, suspended vertically, lowered into the slurry wall / drilled shaft panel opening, supported temporarily over guide walls/slabs, and lowered to final elevation by means of mini-cages spliced to the structural cage (for most slurry wall / drilled shaft panels). More specifically, SALLC designed the rigging of the rebar cages in the vertical stage of erection including lifting channels mounted on the top of the rebar cage by means of wire rope clips. Next, SALLC designed the rigging for the upending stages for the rebar cages that were not upended by the tilt frame. The upending was either done by a single crane in a twin-hook operation (for shorter cages) or it was done by a tandem crane pick with the main crane in a twin-hook operation and assist crane in a single hook operation. Finally, the structural stability and integrity of the rebar cages were evaluated during all stages of the upending and erection.

 

While the rebar cage erection has been the bulk of the work, SALLC has designed a work platform for a Liebherr LTM 1220 or 1250 hydraulic crane on the west side of Phase 1 slurry wall foundation plan, in order to accommodate and assist in the top-down construction at the main excavation hole. Additionally, SALLC has evaluated the structural capacity of the future composite deck slab and supporting stringers to carry a Tadano 450XL-4 hydraulic crane servicing the secondary excavation hole with lighter lifts.