Henry Miller Theatre

When the 86-year old Henry Miller’s Theatre in Manhattan was demolished to make way for a new, 850- foot high skyscraper building, the Construction Manager, Tishman Construction Corporation, was faced with an unusual problem: the theatre’s original Palladian style, red brick façade was landmarked, and had to be preserved. Temporary scaffolding was planned to support the façade. However, during the period between demolition of the existing building and the planned new construction, the façade/scaffolding combination would be essentially free- standing and subject to wind loads. The Geotechnical Engineer, Mueser Rutledge Consulting Engineers, of New York, NY therefore recommended that the scaffolding be supported with minipiles.

DESIGN/BUILD SOLUTION
Site soils consisted of 10 feet of urban fill overlying sand and gravel. Weathered gneissic schist was encountered at approximately 25 feet below working grade. From com- pression and tension data provided by Mueser Rutledge, Moretrench determined that two, 30-ton capacity, rock- socketed minipiles tied into each of four strategic pile caps would meet the required retention criteria.

With a tight work zone alongside a busy, open street, allowing little room to maneuver heavy equipment and materials, safety awareness was as much a priority for the minipile crew as the technical execution of the work. At each pile cap location, rotary drilling techniques were used to seat 5-inch diameter outer casing on top of rock. The inner drill string was then advanced ahead of the casing using a down-the-hole hammer in order to drill out the 10-foot rock socket. Once the required depth was reached, the inner drill string was pulled, and a Grade 75 threadbar was installed for the full length of the pile and tremie grouted. After the grout had been allowed to cure, Moretrench conducted load tension tests on two piles to measure creep. Both tests resulted in movement that was well within the allowable limit. The pile caps were then poured, forming the structural connection between the underpinning elements and the scaffold.

Vibration monitoring performed by Mueser Rutledge during demolition of the existing building recorded negligible movement. The scaffolding support system and the aging façade remained solid, testifying to the quality of the
underpinning work.