Constructed in 1939, with extra modifications accomplished within the Nineteen Sixties, a three-story concrete constructing in Houston’s Midtown was not structurally designed for enlargement. In 2017, Rice Administration Firm, stewards of the Rice College endowment, bought the remaining years of a 99-year lease of the constructing – what was a former Sears division retailer.
Throughout the proposal part, Rice Administration Firm determined to proceed with the steel-framed vertical enlargement of two tales in addition to a horizontal enlargement of the prevailing concrete construction on the decrease three ranges. This repurposed construction can be referred to as The Ion. The ultimate resolution concerned a extra important extent of demolition each on the constructing exterior and inside.
Repurposing current constructions, particularly these fabricated from concrete, has confirmed widespread of late as a way to cost-effectively develop artistic area, shorten building schedules, and scale back the impression on the setting. Whereas the previous two are well-known methods, the latter sometimes entails the discount of embodied carbon. Emissions related to extracting and putting in new supplies are decreased in addition to the quantity of waste produced throughout demolition.
The aim was to repurpose the prevailing construction right into a collaborative expertise innovation hub for Houston’s entrepreneurial, company, and tutorial communities.
Nevertheless, repurposing the stand-alone “concrete field” whereas sustaining its authentic character offered quite a few engineering challenges. “The unique constructing was a darkish field,” says Dennis Wittry, managing principal at Walter P Moore. “To make the constructing inviting to industrial tenants, bringing daylight into the area was important. The unique scope of labor anticipated utilizing punched home windows to herald nominal daylight into the area whereas minimizing demolition of the outside concrete partitions that have been serving because the primarily lateral system for the constructing.”
Rice Administration employed Walter P Moore because the structural engineer of document, three design and architectural corporations—James Carpenter Design Associates, SHoP Architects, and Gensler—whereas Gilbane served as the final contractor and Encore Concrete Building was the concrete contractor.
The design intent to repurpose the constructing was to strengthen or adapt the constructions in ways in which made it appear to be it was a part of the unique building. Subsequently, the horizontal and vertical expansions would serve totally different roles as soon as the constructing was repurposed. The horizontal concrete-related enlargement was a completion of the historic authentic construction. New openings within the current construction have been framed out by creating new concrete beams throughout the current slab, slightly than introducing new metal beams. This created an uncluttered look that complemented the unique construction.
“Conceptually and virtually, the horizontal enlargement made most design sense in concrete, the system of the unique construction,” says Anneli Rice, undertaking director at SHoP Architects.
As for the two-story vertical enlargement of the construction, the usage of metal framing minimized the rise in load on the prevailing construction. To help the added load required strengthening of the prevailing unfold footing foundations. Nevertheless, the prevailing columns didn’t require strengthening. Walter P Moore labored with a geotechnical engineer to find out that the prevailing soil was satisfactory to help the next stress than the foundations have been initially designed.
“This restricted the necessity to develop the unfold footings, however required their strengthening,” Wittry says. “To strengthen the unfold footings, the area between the highest of footing and prime of basement degree slab on grade was utilized. We drilled and epoxied dowels into the prevailing prime of footing to compositely join it to a brand new thickened part.”
In the meantime, the framing for the prevailing roof on the third degree didn’t have adequate load capability to function an occupied ground. In consequence, new metal overbuild framing was spanned between the prevailing columns. The brand new framing didn’t require fireproofing as a result of current concrete roof slab immediately under.
With a purpose to introduce daylight into the construction, multi-story openings have been minimize into the concrete partitions for a brand new curtainwall. Moreover, a shocking 26 by 92 ft mild effectively was constructed within the middle of the construction. Designed by James Carpenter Design Associates, the sunshine effectively makes the difference of the big floorplates into workspaces potential, offering important entry to sunlight and the outside.
“We needed the middle of the constructing to come back alive with mild and exercise, and this central quantity created a canvas for these areas to connect with the sky,” says Joseph Welker, studio director at James Carpenter Design Associates.
To create the sunshine effectively, 4 concrete columns have been demolished in the midst of the construction in addition to a big space of three current concrete slabs. The sunshine effectively minimize an angled slice out of the constructing to comply with the trail of mirrored mild from a skylight above. Nevertheless, it additionally left a cantilevering concrete slab situation of various lengths at every degree.
“To keep away from cracking of the prevailing slabs, they have been ‘overcut’ to the column edge to permit distribution of reinforcement primarily based on the brand new help circumstances,” Wittry says. “A building sequence was developed for the development of the sunshine effectively to keep away from overloading current components.”
The remaining concrete slabs have been hung at every degree by way of three-inch diameter hanger rods from new concrete switch girders that have been poured over the prevailing roof throughout the depth of the metal overbuild. The unique plan was to increase the hanger rods to the brand new roof and help them from the metal.
Nevertheless, Walter P Moore designed them to cease on the current roof degree, which freed the 2 new higher flooring from visible obstructions within the mild effectively.
Rice Administration Firm most well-liked to maintain the prevailing concrete structural parts in addition to the retrofitted structural concrete uncovered all through the constructing as a part of The Ion’s design. This included all columns and ground framing.
Every retrofitted space in The Ion contains current uncovered 9.5-in. concrete flat slab construction with 4.5-in. drop panels at every column. Walter P Moore’s structural design widened current concrete beams or forged new 4.5-in. deep beam stems doweled into the soffit of the prevailing slab the place current openings wanted to be infilled or current beams strengthened. By matching the depth of those beams to the prevailing drop panels, the beams seem as a part of the unique building.
Because of the in depth new openings for curtain wall within the exterior concrete partitions and the extra wind publicity as a result of two-story vertical enlargement, new concrete shear partitions have been launched on the concrete flooring of the constructing close to the stair and elevator cores. Metal braced frames have been used over prime of the concrete shear partitions, on the vertically expanded ground ranges.
The beams and shear partitions have been constructed utilizing self-consolidating concrete pumped by new holes created within the current slabs.
“Self-consolidating concrete was used within the concrete beams that have been added to the prevailing construction in addition to within the new shear partitions,” says Aaron Smith, undertaking supervisor at Encore Concrete Building. “In an current construction, when putting new concrete beams beneath an current ground plate, normal concrete with a 5-in. droop couldn’t be positioned from above. Self-consolidating concrete was used as a way to make sure high quality.”
To pour the self-consolidating concrete, massive core holes have been positioned roughly 10-ft aside by the prevailing slab and it was poured from the highest. Smaller holes roughly 0.5-in. in diameter have been drilled roughly 2 ft. aside between the bigger holes so air may escape and never turn out to be trapped between the brand new self-consolidating concrete and the prevailing slab and beams.
The Ion seamlessly built-in the unique artwork deco model of the construction, significantly on the ground-level storefront façade on the north facet. The addition of the glass curtainwall on the constructing’s south finish, and introduction of daylight by massive openings within the east and west concrete exterior partitions join the open inside to the encompassing streetscape. Giant, multistory exterior openings have been added for brand new home windows within the concrete partitions, in addition to the two-story vertical enlargement.
The Ion was designed to keep up the aesthetic of the northwest and northeast storefront corners, whereas vertically extending the curtainwall within the corners by 15 ft. It was a problem for the constructing workforce to realize this whereas concurrently sustaining the soundness of the areas, which supported the prevailing concrete façade and concrete roof framing.
“Sustaining the storefront aesthetic was extraordinarily tough from a building standpoint,” says Taliah McGowan, senior undertaking supervisor at Gilbane Constructing Firm. “To put in the curtainwall and keep the nook aesthetic, the prevailing concrete partitions wanted to be demolished and opened up.”
This required the prevailing concrete construction to be strengthened with a brand new metal construction, however the reshoring required to hold the prevailing roof beams—weighing upwards of 100,000 lbs. that have been beforehand supported by the concrete to be demolished—impeded the location of the brand new construction, in keeping with McGowan.
Shoring was put in within the middle portion of the wall so the outer places might be demolished. As soon as this was full, a portion of the brand new metal framing was put in to help the wall. After the middle shoring was eliminated, the rest of the demolition and metal set up occurred.
Throughout the transformation from a stand-alone division retailer right into a collaborative innovation expertise hub, The Ion offered the whole constructing workforce with a sequence of structural- and concrete-related challenges.
Repurposing of the 1939 concrete construction concerned demolition of current stairs, escalator, middle columns, and ground slab, and slicing new openings within the exterior partitions and ground slabs for brand new stairs and elevators, whereas infilling current stair and elevator openings. Reworking the unique division retailer in lieu of its full demolition and new construct minimized embodied carbon, offered a platform for progressive design and engineering, and created a very distinctive area to encourage “exterior the concrete field” improvements for a few years to come back.
In regards to the writer
Rachel Calafell, PE, is a principal and undertaking supervisor at Walter P Moore. She will be reached at [email protected]