Developer/Owner

Stanford Carr Development, LLC

Architect

RMA Architects, Inc.

Contractor

Hawaiian Dredging Construction Company

Location

Honolulu, Hawaii

Background

Keauhou Place, a Stanford Carr Development (SCD) project for which BASE was structural engineer of record, includes a 400-ft., 388-unit residential tower and 35 townhomes. Located in the booming Kaka‘ako district of Honolulu, Keauhou Place is part of a nearly four acre, large city block that is split between two developers: Gerding Edlen (GE) on the east third of the site and SCD on the west two-thirds of the site. GE’s project includes mid-rise rental apartments and commercial space. The entire development will have direct access to a future HART rail station.

Client Benefits

BASE carefully examined each unique use of this mixed-use development to determine the most cost effective structural system for each separate area. The design intensive result involved melding multiple unique framing systems into one cohesive project.  Design options were discussed and coordinated throughout a design-assist process to maintain efficiency and constructability of the three different structural systems ultimately selected.  As a result of this thorough planning, the client received a project that seamlessly optimized and integrated several structural systems into a single mixed-use project.

The Science and Design of Structural Engineering

The different uses involved in Keauhou Place led to providing three unique structural systems. The tower structure uses post-tensioned flat plate construction to meet stringent height restrictions. The parking structure employs an efficient garage beam forming system with 60-ft. spans that both optimizes parking stall counts and improves vehicular access. The townhomes surround and visually screen the parking structure and use low-rise cold-formed steel construction.  Each structural system is economically tailored to meet specific requirements unique to its usage.

An additional challenge was the subdivision of the site between the two developers.  The optimal location of the high-rise tower is within the middle of the overall development, which in this case, also happens to coincide with a property line.   For various reasons, towers are rarely constructed directly against a property line. This condition for the Keauhou tower required thoughtful coordination and analysis of the tower’s foundations to minimize the need to cantilever heavily loaded tower columns away from the property line.

Subdivision of the site also impacted the location of the tower’s primary structural core (i.e. main shear resisting walls located at the elevator and entry lobby), which are required to be significantly offset from the building’s center of mass. The result is a layout where little, if any, of the tower’s building weight is supported by the core.  Although this situation may appear to have some advantages, natural building weight helps offset overturning forces on the cores imparted from lateral wind and seismic loads.  The structural design accounts for higher tension forces in these core walls and corresponding foundations for load cases where wind or seismic forces act in the direction away from the property line.  The tower slab systems were also designed and detailed to ensure that lateral loads imparted to the overall floor plates have an adequately robust load path to the offset tower core walls.