By Luke Carothers
A major topic of discussion in the AEC industry is the potential of older, existing structures. Rather than accruing environmental debt through the demolition of such buildings, many firms are instead finding ways to repurpose them to serve the needs of a modern population. One such project is The Ion in Houston, Texas. The existing structure, which was not designed to accommodate expansion, was built in 1939 as a department store and was most recently occupied by Sears. In 2017, Rice Management Company bought out the remainder of Sears’ 99-year ground lease and began plans to renovate the space as a landmark for the coming Ion District.
Rice Management Company, who serve as stewards of the Rice University Endowment, recognized the declining interest in the building as a retail space and sought to transform it into a collaborative technology innovation hub for Houston’s entrepreneurial, corporate, and academic communities. Because the original structure was not designed for expansion, the plan to add an additional two stories of steel framing as well as horizontal expansions proved to be a difficult task. To help with this task, Rice Management Company enlisted the services of Walter P Moore as a structural engineer for the project.
Rice Management Company also tapped a number of other firms to help complete this project. Three architectural firms worked on the Ion project: SHoP Architects, James Carpenter Design Associates, and Gensler. Hines served as the development manager for the Rice Management Company, and Gilbane was the general contractor.
One of the biggest challenges facing these teams was compensating for the added load of two additional floors. While the plan was to expand the building vertically, it was clear that the existing roof on the building lacked strength to serve as a new floor. To give the roof the needed load capacity, it was overbuilt with new steel framing that spans from column to column. The project’s foundations were also strengthened to support the weight of the vertical expansion. To support this weight, the structure’s existing spread footings were thickened to increase their flexural capacity.
In addition to the added weight of two floors, the building’s vertical expansion also introduced a significant increase in wind load. This challenge was further compounded by openings cut in the exterior walls for added daylight, which previously served as the lateral system for the building. As such, a completely new lateral system had to be added to the building in the form of concrete shear walls through the existing structure. Rachel Calafell, Principal/Structures at Walter P Moore, is part of the team working on the project. According to Calafell, these shear walls had to be threaded through the structure by “coring holes through the existing slabs, doweling rebar through them, and pumping self-consolidating concrete through.”
Calafell describes the original structure as “a concrete box” with concrete columns, flat slab, and exterior walls. In addition, these concrete walls had very few openings to let in light due to previous use as a retail store. Despite the “concrete box” structural description, the original building was adorned with iconic corners on the northside and an art deco storefront. For many years, the building’s storefront served as an important cultural touchstone as families would gather around to window shop around Christmas.
One of the major focuses throughout the project was preserving the building to restore the original art deco architecture. When the building was originally constructed the concrete walls were exposed, but when the building was renovated in the 1960s, metal plating was installed on the exterior. These panels were removed during the current project to restore the exposed concrete exterior.
Another major focus of the project was to find ways to allow more light into the building. To help with this purpose, James Carpenter Design Associates were tasked with conceiving the new facade and interior light-volume. The first step in introducing light to the building was to create several multi-story openings in the exterior as well as a light well that slices through the center of the building, tracing the path of light inward. To accommodate the center light well, four columns had to be removed from the center of the building as well as a large extent of concrete slabs.
While the precise angle of the center light well maximizes light, it also means that the structural team had to contend with a different slab condition on each level. To solve this problem, Calafell and her team designed hanger rods to support the slabs, which were suspended from the overbuild section of the roof.
All these changes mean the new building, The Ion, can serve a wholly reinvisioned purpose as a center of innovation in a historically innovative area. Historically, Houston has been home to groundbreaking achievements in the fields of energy, space, and medicine. The Ion represents a significant reinvestment in the technology and infrastructure that lays the foundation for future achievements in these fields and others.
Luke Carothers is the Editor for Civil + Structural Engineer Media. If you want us to cover your project or want to feature your own article, he can be reached at firstname.lastname@example.org.