However, geotechnical and earthquake consulting engineer Robert Pyke has warned that it is “too early to tell” whether the latest fix to San Francisco's Millennium Tower has stopped its tilt. The Millennium Tower PPU design team expects the recovery to continue in the coming months and years. Speaking to Engineering News Record Hamburger said that as of the 19 June, “survey data reveals that settlement has indeed been arrested, as was the primary project objective, and in fact, the building has risen slightly out of the ground”. On 15 June, Shimmick began the final stage of load transfer, which consisted of raising all 18 piles to 1,000kips (4,448kN) each. It comes after the second stage of the load transfer was initiated on 10 June, which consisted of bringing the 12 piles along Fremont Street up to 500kips (2,224kN) each. The latest data shows that the PPU could finally be working, the engineers involved in the fix have claimed. The main contractor for the pile driving work is Legacy Foundations, a division of Shimmick Construction. The engineering upgrade was designed by Simpson Gumpertz and Heger consulting principal engineer Ronald Hamburger, who is the engineer of record for the fix, working on behalf of residential condominium association Millennium Tower. The original foundation is made up of a 3m thick reinforced concrete slab supported by 942 precast prestressed concrete piles extending approximately 24.3m below grade in the Colma Formation of dense clayey sand. The fix also involves extending the existing mat foundation to encompass the new piles. This has involved transferring a portion of the building’s weight from its existing foundation system onto 18 new perimeter piles socketed into bedrock. The US$100M (£79M) engineering “fix” devised to strengthen the building’s foundations along its north and west sides is a pile perimeter upgrade (PPU). The 58 storey luxury tower was tilting 736mm to the north west as measured from its roof in early June, since it was constructed in 2009. The Millennium Tower in the city centre appears to have recovered around 19mm of tilt to the west after the final stages of an engineering upgrade to stabilise it were applied to the building in June. The tilting building led to a class-action lawsuit between its residents and Millennium Partners, which was settled in 2018.The latest phase of work to stabilise San Francisco’s troubled Millennium Tower has reversed some of the tower’s tilt, according to monitoring data – but an expert has said it is “too early” to tell if the fix is working. It was designed by Handel Architects, engineered by DeSimone Consulting Engineers and constructed by Webcor Builders. The $350 million Millennium Tower was built by Mission Street Development, an affiliate of Millennium Partners, based in San Francisco. This summer, construction workers will restore the Muni lines, pour new sidewalks and plant new red maples, water gums and Brisbane boxes along Fremont and Mission streets. Millennium Tower Condo Association President Howard Dickstein said he is confident the “engineering upgrade will restore our building’s reputation and the value of condominiums while putting to rest any lingering questions about the tower’s stability.” The tower’s HOA has contracted with a surveyor to monitor the building’s performance. ![]() The work has been overseen by the Department of Building Inspection and an independent panel of experts hired by the city.
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