Cardno provided structural engineering services for this 1 million square foot speculative office building in Houston’s Central Business District. This 50-story building features a pyramid-shaped lobby with 110-foot clear vertical span, an urban green space sitting atop an integrated garage, with outdoor space wrapped around an interior terrace, also topped by accessible green space. A compact building core and floorplates are highly flexible and allow daylight deep into the interiors.
The tower’s geometry posed the biggest challenge for Cardno’s structural engineers. The north and south facades each have a vertical crease that appears to make them envelope the west façade. The west façade is narrowest at the bottom and expands up to level 12, where it then gradually contracts up to the roof level, appearing to absorb the “folds” of the adjacent two facades. This geometry created two planes of sloped columns. The first is on the west face of the building; the second is one bay east.
The north and south facades have mirror-image angles at the top, “fins” that extend 75 feet above the roof to screen the cooling towers. A separate structural truss system provides lateral support for the fins. With the fins, 609 Main reaches a height of 755 feet.
Below grade, there are two additional levels of parking and a 70-foot pedestrian tunnel that provides access under Main Street to the Houston underground pedestrian tunnel system. A 42,000-gallon tank is incorporated into the basement to collect rain and AC condensate for irrigation.