Long‐Term Tieback Monitoring at Harvard Square

Abstract

Tiebacks are used extensively for temporary lateral support for exterior walls of the new underground Harvard Square transit station in Cambridge, Massachusetts. Although not required for permanent conditions, some tiebacks having construction load cell monitoring were left in place after construction was completed. These tiebacks consisted of regroutable, multistrand tendons having design capacities of 282 kips (1,250 kn). All tiebacks have been subjected to a 30-min hold test to verify capacity. After five years' time, the instrumented tiebacks are observed to be holding the design loads.