Christchurch Justice and Emergency Services PrecinctNew Zealand 40 King StreetNew Zealand

United States

550 Allerton St

This project involved a new six-storey office building located in a densely populated area of Redwood City, California and incorporated an ambitious exposed structural-steel frame concept design. Located on a triangular site, with adjacent property, the building was designed primarily for earthquake resistance, with moment resisting frames and large steel members to prevent drift across the property under lateral loading. Aimed for the high-tech industry and to showcase sustainable design principles, it was desirable to expose the bare structural-steel frame elements and minimise applied, particularly for the secondary beams which spanned over 14 m.

Holmes Fire undertook a performance-based structural-fire engineering assessment of the building to determine the feasibility of achieving the required level of fire-resisting performance, without applied fire protection to the steel members. A major component of the assessment involved 3D thermal-structural finite element modelling of critical floor bays to ascertain the impact of a realistic fire on the steel frame as an entire interconnected structure. It was demonstrated that whilst large displacements of the floor system might occur, the overall building structure was capable of maintaining its required load carrying capacity during exposure to a severe fire event without collapse. Holmes fire’s services provided a level of assurance to the design team that enables an informed decision to be made on the future design development of the building.