Since 1902, Turner Construction Company has charged a path for advancement in construction. At the turn of the century, the company pioneered the use of steel-reinforced concrete to create safer, stronger, and more efficient buildings. In the decades since, Turner has built a reputation for undertaking large, complex projects, fostering innovation, and embracing emerging technologies. One project that put Turner’s innovative spirit to the test was the Seattle Aquarium's $160 million Ocean Pavilion expansion. The project includes the creation of three large habitats with essentially no straight edges, including a main habitat consisting of 680 cubic yards of concrete and 355 tons of rebar. Turner Construction Company’s self-perform concrete team brought this complex project to life with a powerhouse of trade partners, technology, and innovative digital fabrication techniques. A Geometric and Logistical Challenge The unique build presented several challenges. The Aquarium is in the heart of downtown Seattle’s waterfront, which has been undergoing a multi-year redevelopment, including construction of an underground tunnel for Highway 99, demolition of Seattle's Alaskan Way Viaduct, and major revitalization of the surface streets and pedestrian corridors. The ongoing street revisions meant that a portion of the building's footprint on its West side would be in use for Alaskan Way before traffic could ultimately be shifted to the East side of the site. Traffic’s revised path would take it underneath the new pedestrian bridge, allowing pedestrians a new unimpeded walking path between the Pike Place Market and Seattle’s waterfront, and spectacular views of the Salish Sea from Ocean Pavilion’s public rooftop. Site constraints coupled with a small footprint required careful logistics planning to depict the multiple milestone phases of construction. The small footprint left little space for staging, and the geometry of the primary habitats meant that formwork coordination and prefabrication efforts would need to account for the numerous life support systems (LSS) and embedments prior to site delivery. With its extensive tech stack, Turner Construction Company was well- positioned to overcome these challenges by using a variety of hardware and software technology tools that contributed to the project's success. Model-based From Start to Finish While the project presented several challenges, one of the issues the Turner team managed was working from a contractual 3D model provided by the designer, LMN Architects, that represented the geometry of the primary habitats. "Because of the habitat’s complex geometry, the architect provided us with a model that could be used as the basis for Turner’s self-perform concrete detailing efforts. This collaborative detailing effort combined all the formwork, rebar, embedments, acrylic viewing windows, and mechanical systems into one model that could then be used to generate the necessary shop drawings and digitally fabricated formwork elements," said Sean
Beatty, Virtual Design and Construction (VDC) department manager at Turner Construction. The main habitat’s structure includes a two-foot-thick curved concrete wall with 355 tons of rebar and 680 cubic yards of concrete, or four times the rebar used on a typical core. Turner Construction’s VDC team used internally developed parametric modeling scripts to generate the rebar geometry necessary to understand the congestion and the constructability of the engineers reinforcing design. This 3D representation and visualization in context with the final habitat geometry, mechanical systems and formwork enabled revisions of the reinforcing that aided constructability while ensuring a monolithic pour of the main habitat without cold joints. SketchUp 3D modeling software was used throughout the process, beginning with a quality control model to understand overall project quantities through each design iteration. This included an accurate geolocated site model that combined drone imagery, adjacent buildings, underground utilities, and adjacent street revisions. Modeling the site from civil surveys and bringing in pre-made components from the 3D warehouse, as well as components they developed internally gave Turner an accurate representation of the site in its current state. With this, Turner Construction Company began planning the phased site logistics, which included excavation, fencing, trucking, formwork, and public protection at all project stages. They organized the model into layers, leveraging scenes and textures to differentiate between phases and collaborated with trade partners to determine precisely how things will be assembled and bundled for delivery. "The model was a powerful way to visualize logistics plans in 3D and convey them to the owner, the city and our trade partners,” said Beatty. “It gives us the flexibility to model things quickly, incorporate different model content and move it between platforms.” Turner and its trade partners produced various model content, which was imported into the structural BIM software to generate the consolidated self-perform concrete model and lift drawings. A plug-in for bi-directional data exchange ensured that any modifications made in other software could be synchronized back to the structural BIM software to maintain consistency in the geometry throughout design iterations and input from the design and trade partners. “The link streamlined the design-build process and empowered us to explore complex geometries and prepare models for fabrication with enhanced precision and efficiency,” said Beatty. “Reference models produced with a variety of software applications were continuously updated throughout the formwork and MEP coordination efforts, and this up-to-date data ensured that our final concrete geometry was accurate and could be conveyed to our field survey team for model-based layout,” he said. The integration of software and hardware made this process very efficient and accurate. The imported geometry served as the foundation for subsequent detailing and constructability analysis. Tekla Structures, structural BIM software, provided a comprehensive suite of analysis for creating accurate concrete elements, formwork, embed, rebar, and more. These
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Summer 2024 csengineermag.com
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