Circu‐Rectangular Bundled Tube Office Tower—A Case History

This paper documents the structural design and analysis as it evolved in the planning of the new Four Allen Center Tower in Houston, Texas. The 1,440,000 sq ft $\left(133\text{,}920m^2\right)$ tower consists of 50 levels above grade and two levels below grade. Aeroelastic wind tunnel models predicted that extreme dynamic oscillation of the tower may occur due to the configuration of existing tall buildings surrounding the site. Dynamic wind force resistance for the silver reflective glass structure was, provided by a four‐celled “bundled framed tube” system. The bundled tube frames are comprised of two‐story high “tree column” modules located at 15 ft (4.58 m) on centers around the building perimeter. The interior tubular cell partitions are framed by three “tree beam” diagonal truss frames quadsecting the tower's curvirectangular plan shape. The superstructure gravity and lateral loadings were transferred to the soil substratum through the medium of an 8 ft‐6 in. thick concrete foundation mat.